/*
** 2004 May 22
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains the VFS implementation for unix-like operating systems
** include Linux, MacOSX, *BSD, QNX, VxWorks, AIX, HPUX, and others.
**
** There are actually several different VFS implementations in this file.
** The differences are in the way that file locking is done. The default
** implementation uses Posix Advisory Locks. Alternative implementations
** use flock(), dot-files, various proprietary locking schemas, or simply
** skip locking all together.
**
** This source file is organized into divisions where the logic for various
** subfunctions is contained within the appropriate division. PLEASE
** KEEP THE STRUCTURE OF THIS FILE INTACT. New code should be placed
** in the correct division and should be clearly labeled.
**
** The layout of divisions is as follows:
**
** * General-purpose declarations and utility functions.
** * Unique file ID logic used by VxWorks.
** * Various locking primitive implementations (all except proxy locking):
** + for Posix Advisory Locks
** + for no-op locks
** + for dot-file locks
** + for flock() locking
** + for named semaphore locks (VxWorks only)
** + for AFP filesystem locks (MacOSX only)
** * sqlite3_file methods not associated with locking.
** * Definitions of sqlite3_io_methods objects for all locking
** methods plus "finder" functions for each locking method.
** * sqlite3_vfs method implementations.
** * Locking primitives for the proxy uber-locking-method. (MacOSX only)
** * Definitions of sqlite3_vfs objects for all locking methods
** plus implementations of sqlite3_os_init() and sqlite3_os_end().
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX /* This file is used on unix only */
/*
** There are various methods for file locking used for concurrency
** control:
**
** 1. POSIX locking (the default),
** 2. No locking,
** 3. Dot-file locking,
** 4. flock() locking,
** 5. AFP locking (OSX only),
** 6. Named POSIX semaphores (VXWorks only),
** 7. proxy locking. (OSX only)
**
** Styles 4, 5, and 7 are only available of SQLITE_ENABLE_LOCKING_STYLE
** is defined to 1. The SQLITE_ENABLE_LOCKING_STYLE also enables automatic
** selection of the appropriate locking style based on the filesystem
** where the database is located.
*/
#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
# if defined(__APPLE__)
# define SQLITE_ENABLE_LOCKING_STYLE 1
# else
# define SQLITE_ENABLE_LOCKING_STYLE 0
# endif
#endif
/*
** Define the OS_VXWORKS pre-processor macro to 1 if building on
** vxworks, or 0 otherwise.
*/
#ifndef OS_VXWORKS
# if defined(__RTP__) || defined(_WRS_KERNEL)
# define OS_VXWORKS 1
# else
# define OS_VXWORKS 0
# endif
#endif
/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it. If the OS lacks
** large file support, these should be no-ops.
**
** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
** on the compiler command line. This is necessary if you are compiling
** on a recent machine (ex: RedHat 7.2) but you want your code to work
** on an older machine (ex: RedHat 6.0). If you compile on RedHat 7.2
** without this option, LFS is enable. But LFS does not exist in the kernel
** in RedHat 6.0, so the code won't work. Hence, for maximum binary
** portability you should omit LFS.
**
** The previous paragraph was written in 2005. (This paragraph is written
** on 2008-11-28.) These days, all Linux kernels support large files, so
** you should probably leave LFS enabled. But some embedded platforms might
** lack LFS in which case the SQLITE_DISABLE_LFS macro might still be useful.
*/
#ifndef SQLITE_DISABLE_LFS
# define _LARGE_FILE 1
# ifndef _FILE_OFFSET_BITS
# define _FILE_OFFSET_BITS 64
# endif
# define _LARGEFILE_SOURCE 1
#endif
/*
** standard include files.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>
#include <errno.h>
#if SQLITE_ENABLE_LOCKING_STYLE
# include <sys/ioctl.h>
# if OS_VXWORKS
# include <semaphore.h>
# include <limits.h>
# else
# include <sys/file.h>
# include <sys/param.h>
# include <sys/mount.h>
# endif
#endif /* SQLITE_ENABLE_LOCKING_STYLE */
/*
** If we are to be thread-safe, include the pthreads header and define
** the SQLITE_UNIX_THREADS macro.
*/
#if SQLITE_THREADSAFE
# include <pthread.h>
# define SQLITE_UNIX_THREADS 1
#endif
/*
** Default permissions when creating a new file
*/
#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
#endif
/*
** Default permissions when creating auto proxy dir
*/
#ifndef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
# define SQLITE_DEFAULT_PROXYDIR_PERMISSIONS 0755
#endif
/*
** Maximum supported path-length.
*/
#define MAX_PATHNAME 512
/*
** Only set the lastErrno if the error code is a real error and not
** a normal expected return code of SQLITE_BUSY or SQLITE_OK
*/
#define IS_LOCK_ERROR(x) ((x != SQLITE_OK) && (x != SQLITE_BUSY))
/*
** Sometimes, after a file handle is closed by SQLite, the file descriptor
** cannot be closed immediately. In these cases, instances of the following
** structure are used to store the file descriptor while waiting for an
** opportunity to either close or reuse it.
*/
typedef struct UnixUnusedFd UnixUnusedFd;
struct UnixUnusedFd {
int fd; /* File descriptor to close */
int flags; /* Flags this file descriptor was opened with */
UnixUnusedFd *pNext; /* Next unused file descriptor on same file */
};
/*
** The unixFile structure is subclass of sqlite3_file specific to the unix
** VFS implementations.
*/
typedef struct unixFile unixFile;
struct unixFile {
sqlite3_io_methods const *pMethod; /* Always the first entry */
struct unixOpenCnt *pOpen; /* Info about all open fd's on this inode */
struct unixLockInfo *pLock; /* Info about locks on this inode */
int h; /* The file descriptor */
int dirfd; /* File descriptor for the directory */
unsigned char locktype; /* The type of lock held on this fd */
int lastErrno; /* The unix errno from the last I/O error */
void *lockingContext; /* Locking style specific state */
UnixUnusedFd *pUnused; /* Pre-allocated UnixUnusedFd */
#if SQLITE_ENABLE_LOCKING_STYLE
int openFlags; /* The flags specified at open() */
#endif
#if SQLITE_THREADSAFE && defined(__linux__)
pthread_t tid; /* The thread that "owns" this unixFile */
#endif
#if OS_VXWORKS
int isDelete; /* Delete on close if true */
struct vxworksFileId *pId; /* Unique file ID */
#endif
#ifndef NDEBUG
/* The next group of variables are used to track whether or not the
** transaction counter in bytes 24-27 of database files are updated
** whenever any part of the database changes. An assertion fault will
** occur if a file is updated without also updating the transaction
** counter. This test is made to avoid new problems similar to the
** one described by ticket #3584.
*/
unsigned char transCntrChng; /* True if the transaction counter changed */
unsigned char dbUpdate; /* True if any part of database file changed */
unsigned char inNormalWrite; /* True if in a normal write operation */
#endif
#ifdef SQLITE_TEST
/* In test mode, increase the size of this structure a bit so that
** it is larger than the struct CrashFile defined in test6.c.
*/
char aPadding[32];
#endif
};
/*
** Include code that is common to all os_*.c files
*/
#include "os_common.h"
/*
** Define various macros that are missing from some systems.
*/
#ifndef O_LARGEFILE
# define O_LARGEFILE 0
#endif
#ifdef SQLITE_DISABLE_LFS
# undef O_LARGEFILE
# define O_LARGEFILE 0
#endif
#ifndef O_NOFOLLOW
# define O_NOFOLLOW 0
#endif
#ifndef O_BINARY
# define O_BINARY 0
#endif
/*
** The DJGPP compiler environment looks mostly like Unix, but it
** lacks the fcntl() system call. So redefine fcntl() to be something
** that always succeeds. This means that locking does not occur under
** DJGPP. But it is DOS - what did you expect?
*/
#ifdef __DJGPP__
# define fcntl(A,B,C) 0
#endif
/*
** The threadid macro resolves to the thread-id or to 0. Used for
** testing and debugging only.
*/
#if SQLITE_THREADSAFE
#define threadid pthread_self()
#else
#define threadid 0
#endif
/*
** Helper functions to obtain and relinquish the global mutex. The
** global mutex is used to protect the unixOpenCnt, unixLockInfo and
** vxworksFileId objects used by this file, all of which may be
** shared by multiple threads.
**
** Function unixMutexHeld() is used to assert() that the global mutex
** is held when required. This function is only used as part of assert()
** statements. e.g.
**
** unixEnterMutex()
** assert( unixMutexHeld() );
** unixEnterLeave()
*/
static void unixEnterMutex(void){
sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
static void unixLeaveMutex(void){
sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
#ifdef SQLITE_DEBUG
static int unixMutexHeld(void) {
return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
#endif
#ifdef SQLITE_DEBUG
/*
** Helper function for printing out trace information from debugging
** binaries. This returns the string represetation of the supplied
** integer lock-type.
*/
static const char *locktypeName(int locktype){
switch( locktype ){
case NO_LOCK: return "NONE";
case SHARED_LOCK: return "SHARED";
case RESERVED_LOCK: return "RESERVED";
case PENDING_LOCK: return "PENDING";
case EXCLUSIVE_LOCK: return "EXCLUSIVE";
}
return "ERROR";
}
#endif
#ifdef SQLITE_LOCK_TRACE
/*
** Print out information about all locking operations.
**
** This routine is used for troubleshooting locks on multithreaded
** platforms. Enable by compiling with the -DSQLITE_LOCK_TRACE
** command-line option on the compiler. This code is normally
** turned off.
*/
static int lockTrace(int fd, int op, struct flock *p){
char *zOpName, *zType;
int s;
int savedErrno;
if( op==F_GETLK ){
zOpName = "GETLK";
}else if( op==F_SETLK ){
zOpName = "SETLK";
}else{
s = fcntl(fd, op, p);
sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
return s;
}
if( p->l_type==F_RDLCK ){
zType = "RDLCK";
}else if( p->l_type==F_WRLCK ){
zType = "WRLCK";
}else if( p->l_type==F_UNLCK ){
zType = "UNLCK";
}else{
assert( 0 );
}
assert( p->l_whence==SEEK_SET );
s = fcntl(fd, op, p);
savedErrno = errno;
sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
(int)p->l_pid, s);
if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
struct flock l2;
l2 = *p;
fcntl(fd, F_GETLK, &l2);
if( l2.l_type==F_RDLCK ){
zType = "RDLCK";
}else if( l2.l_type==F_WRLCK ){
zType = "WRLCK";
}else if( l2.l_type==F_UNLCK ){
zType = "UNLCK";
}else{
assert( 0 );
}
sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
}
errno = savedErrno;
return s;
}
#define fcntl lockTrace
#endif /* SQLITE_LOCK_TRACE */
/*
** This routine translates a standard POSIX errno code into something
** useful to the clients of the sqlite3 functions. Specifically, it is
** intended to translate a variety of "try again" errors into SQLITE_BUSY
** and a variety of "please close the file descriptor NOW" errors into
** SQLITE_IOERR
**
** Errors during initialization of locks, or file system support for locks,
** should handle ENOLCK, ENOTSUP, EOPNOTSUPP separately.
*/
static int sqliteErrorFromPosixError(int posixError, int sqliteIOErr) {
switch (posixError) {
case 0:
return SQLITE_OK;
case EAGAIN:
case ETIMEDOUT:
case EBUSY:
case EINTR:
case ENOLCK:
/* random NFS retry error, unless during file system support
* introspection, in which it actually means what it says */
return SQLITE_BUSY;
case EACCES:
/* EACCES is like EAGAIN during locking operations, but not any other time*/
if( (sqliteIOErr == SQLITE_IOERR_LOCK) ||
(sqliteIOErr == SQLITE_IOERR_UNLOCK) ||
(sqliteIOErr == SQLITE_IOERR_RDLOCK) ||
(sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) ){
return SQLITE_BUSY;
}
/* else fall through */
case EPERM:
return SQLITE_PERM;
case EDEADLK:
return SQLITE_IOERR_BLOCKED;
#if EOPNOTSUPP!=ENOTSUP
case EOPNOTSUPP:
/* something went terribly awry, unless during file system support
* introspection, in which it actually means what it says */
#endif
#ifdef ENOTSUP
case ENOTSUP:
/* invalid fd, unless during file system support introspection, in which
* it actually means what it says */
#endif
case EIO:
case EBADF:
case EINVAL:
case ENOTCONN:
case ENODEV:
case ENXIO:
case ENOENT:
case ESTALE:
case ENOSYS:
/* these should force the client to close the file and reconnect */
default:
return sqliteIOErr;
}
}
/******************************************************************************
****************** Begin Unique File ID Utility Used By VxWorks ***************
**
** On most versions of unix, we can get a unique ID for a file by concatenating
** the device number and the inode number. But this does not work on VxWorks.
** On VxWorks, a unique file id must be based on the canonical filename.
**
** A pointer to an instance of the following structure can be used as a
** unique file ID in VxWorks. Each instance of this structure contains
** a copy of the canonical filename. There is also a reference count.
** The structure is reclaimed when the number of pointers to it drops to
** zero.
**
** There are never very many files open at one time and lookups are not
** a performance-critical path, so it is sufficient to put these
** structures on a linked list.
*/
struct vxworksFileId {
struct vxworksFileId *pNext; /* Next in a list of them all */
int nRef; /* Number of references to this one */
int nName; /* Length of the zCanonicalName[] string */
char *zCanonicalName; /* Canonical filename */
};
#if OS_VXWORKS
/*
** All unique filenames are held on a linked list headed by this
** variable:
*/
static struct vxworksFileId *vxworksFileList = 0;
/*
** Simplify a filename into its canonical form
** by making the following changes:
**
** * removing any trailing and duplicate /
** * convert /./ into just /
** * convert /A/../ where A is any simple name into just /
**
** Changes are made in-place. Return the new name length.
**
** The original filename is in z[0..n-1]. Return the number of
** characters in the simplified name.
*/
static int vxworksSimplifyName(char *z, int n){
int i, j;
while( n>1 && z[n-1]=='/' ){ n--; }
for(i=j=0; i<n; i++){
if( z[i]=='/' ){
if( z[i+1]=='/' ) continue;
if( z[i+1]=='.' && i+2<n && z[i+2]=='/' ){
i += 1;
continue;
}
if( z[i+1]=='.' && i+3<n && z[i+2]=='.' && z[i+3]=='/' ){
while( j>0 && z[j-1]!='/' ){ j--; }
if( j>0 ){ j--; }
i += 2;
continue;
}
}
z[j++] = z[i];
}
z[j] = 0;
return j;
}
/*
** Find a unique file ID for the given absolute pathname. Return
** a pointer to the vxworksFileId object. This pointer is the unique
** file ID.
**
** The nRef field of the vxworksFileId object is incremented before
** the object is returned. A new vxworksFileId object is created
** and added to the global list if necessary.
**
** If a memory allocation error occurs, return NULL.
*/
static struct vxworksFileId *vxworksFindFileId(const char *zAbsoluteName){
struct vxworksFileId *pNew; /* search key and new file ID */
struct vxworksFileId *pCandidate; /* For looping over existing file IDs */
int n; /* Length of zAbsoluteName string */
assert( zAbsoluteName[0]=='/' );
n = (int)strlen(zAbsoluteName);
pNew = sqlite3_malloc( sizeof(*pNew) + (n+1) );
if( pNew==0 ) return 0;
pNew->zCanonicalName = (char*)&pNew[1];
memcpy(pNew->zCanonicalName, zAbsoluteName, n+1);
n = vxworksSimplifyName(pNew->zCanonicalName, n);
/* Search for an existing entry that matching the canonical name.
** If found, increment the reference count and return a pointer to
** the existing file ID.
*/
unixEnterMutex();
for(pCandidate=vxworksFileList; pCandidate; pCandidate=pCandidate->pNext){
if( pCandidate->nName==n
&& memcmp(pCandidate->zCanonicalName, pNew->zCanonicalName, n)==0
){
sqlite3_free(pNew);
pCandidate->nRef++;
unixLeaveMutex();
return pCandidate;
}
}
/* No match was found. We will make a new file ID */
pNew->nRef = 1;
pNew->nName = n;
pNew->pNext = vxworksFileList;
vxworksFileList = pNew;
unixLeaveMutex();
return pNew;
}
/*
** Decrement the reference count on a vxworksFileId object. Free
** the object when the reference count reaches zero.
*/
static void vxworksReleaseFileId(struct vxworksFileId *pId){
unixEnterMutex();
assert( pId->nRef>0 );
pId->nRef--;
if( pId->nRef==0 ){
struct vxworksFileId **pp;
for(pp=&vxworksFileList; *pp && *pp!=pId; pp = &((*pp)->pNext)){}
assert( *pp==pId );
*pp = pId->pNext;
sqlite3_free(pId);
}
unixLeaveMutex();
}
#endif /* OS_VXWORKS */
/*************** End of Unique File ID Utility Used By VxWorks ****************
******************************************************************************/
/******************************************************************************
*************************** Posix Advisory Locking ****************************
**
** POSIX advisory locks are broken by design. ANSI STD 1003.1 (1996)
** section 6.5.2.2 lines 483 through 490 specify that when a process
** sets or clears a lock, that operation overrides any prior locks set
** by the same process. It does not explicitly say so, but this implies
** that it overrides locks set by the same process using a different
** file descriptor. Consider this test case:
**
** int fd1 = open("./file1", O_RDWR|O_CREAT, 0644);
** int fd2 = open("./file2", O_RDWR|O_CREAT, 0644);
**
** Suppose ./file1 and ./file2 are really the same file (because
** one is a hard or symbolic link to the other) then if you set
** an exclusive lock on fd1, then try to get an exclusive lock
** on fd2, it works. I would have expected the second lock to
** fail since there was already a lock on the file due to fd1.
** But not so. Since both locks came from the same process, the
** second overrides the first, even though they were on different
** file descriptors opened on different file names.
**
** This means that we cannot use POSIX locks to synchronize file access
** among competing threads of the same process. POSIX locks will work fine
** to synchronize access for threads in separate processes, but not
** threads within the same process.
**
** To work around the problem, SQLite has to manage file locks internally
** on its own. Whenever a new database is opened, we have to find the
** specific inode of the database file (the inode is determined by the
** st_dev and st_ino fields of the stat structure that fstat() fills in)
** and check for locks already existing on that inode. When locks are
** created or removed, we have to look at our own internal record of the
** locks to see if another thread has previously set a lock on that same
** inode.
**
** (Aside: The use of inode numbers as unique IDs does not work on VxWorks.
** For VxWorks, we have to use the alternative unique ID system based on
** canonical filename and implemented in the previous division.)
**
** The sqlite3_file structure for POSIX is no longer just an integer file
** descriptor. It is now a structure that holds the integer file
** descriptor and a pointer to a structure that describes the internal
** locks on the corresponding inode. There is one locking structure
** per inode, so if the same inode is opened twice, both unixFile structures
** point to the same locking structure. The locking structure keeps
** a reference count (so we will know when to delete it) and a "cnt"
** field that tells us its internal lock status. cnt==0 means the
** file is unlocked. cnt==-1 means the file has an exclusive lock.
** cnt>0 means there are cnt shared locks on the file.
**
** Any attempt to lock or unlock a file first checks the locking
** structure. The fcntl() system call is only invoked to set a
** POSIX lock if the internal lock structure transitions between
** a locked and an unlocked state.
**
** But wait: there are yet more problems with POSIX advisory locks.
**
** If you close a file descriptor that points to a file that has locks,
** all locks on that file that are owned by the current process are
** released. To work around this problem, each unixFile structure contains
** a pointer to an unixOpenCnt structure. There is one unixOpenCnt structure
** per open inode, which means that multiple unixFile can point to a single
** unixOpenCnt. When an attempt is made to close an unixFile, if there are
** other unixFile open on the same inode that are holding locks, the call
** to close() the file descriptor is deferred until all of the locks clear.
** The unixOpenCnt structure keeps a list of file descriptors that need to
** be closed and that list is walked (and cleared) when the last lock
** clears.
**
** Yet another problem: LinuxThreads do not play well with posix locks.
**
** Many older versions of linux use the LinuxThreads library which is
** not posix compliant. Under LinuxThreads, a lock created by thread
** A cannot be modified or overridden by a different thread B.
** Only thread A can modify the lock. Locking behavior is correct
** if the appliation uses the newer Native Posix Thread Library (NPTL)
** on linux - with NPTL a lock created by thread A can override locks
** in thread B. But there is no way to know at compile-time which
** threading library is being used. So there is no way to know at
** compile-time whether or not thread A can override locks on thread B.
** We have to do a run-time check to discover the behavior of the
** current process.
**
** On systems where thread A is unable to modify locks created by
** thread B, we have to keep track of which thread created each
** lock. Hence there is an extra field in the key to the unixLockInfo
** structure to record this information. And on those systems it
** is illegal to begin a transaction in one thread and finish it
** in another. For this latter restriction, there is no work-around.
** It is a limitation of LinuxThreads.
*/
/*
** Set or check the unixFile.tid field. This field is set when an unixFile
** is first opened. All subsequent uses of the unixFile verify that the
** same thread is operating on the unixFile. Some operating systems do
** not allow locks to be overridden by other threads and that restriction
** means that sqlite3* database handles cannot be moved from one thread
** to another while locks are held.
**
** Version 3.3.1 (2006-01-15): unixFile can be moved from one thread to
** another as long as we are running on a system that supports threads
** overriding each others locks (which is now the most common behavior)
** or if no locks are held. But the unixFile.pLock field needs to be
** recomputed because its key includes the thread-id. See the
** transferOwnership() function below for additional information
*/
#if SQLITE_THREADSAFE && defined(__linux__)
# define SET_THREADID(X) (X)->tid = pthread_self()
# define CHECK_THREADID(X) (threadsOverrideEachOthersLocks==0 && \
!pthread_equal((X)->tid, pthread_self()))
#else
# define SET_THREADID(X)
# define CHECK_THREADID(X) 0
#endif
/*
** An instance of the following structure serves as the key used
** to locate a particular unixOpenCnt structure given its inode. This
** is the same as the unixLockKey except that the thread ID is omitted.
*/
struct unixFileId {
dev_t dev; /* Device number */
#if OS_VXWORKS
struct vxworksFileId *pId; /* Unique file ID for vxworks. */
#else
ino_t ino; /* Inode number */
#endif
};
/*
** An instance of the following structure serves as the key used
** to locate a particular unixLockInfo structure given its inode.
**
** If threads cannot override each others locks (LinuxThreads), then we
** set the unixLockKey.tid field to the thread ID. If threads can override
** each others locks (Posix and NPTL) then tid is always set to zero.
** tid is omitted if we compile without threading support or on an OS
** other than linux.
*/
struct unixLockKey {
struct unixFileId fid; /* Unique identifier for the file */
#if SQLITE_THREADSAFE && defined(__linux__)
pthread_t tid; /* Thread ID of lock owner. Zero if not using LinuxThreads */
#endif
};
/*
** An instance of the following structure is allocated for each open
** inode. Or, on LinuxThreads, there is one of these structures for
** each inode opened by each thread.
**
** A single inode can have multiple file descriptors, so each unixFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of unixFile pointing to it.
*/
struct unixLockInfo {
struct unixLockKey lockKey; /* The lookup key */
int cnt; /* Number of SHARED locks held */
int locktype; /* One of SHARED_LOCK, RESERVED_LOCK etc. */
int nRef; /* Number of pointers to this structure */
struct unixLockInfo *pNext; /* List of all unixLockInfo objects */
struct unixLockInfo *pPrev; /* .... doubly linked */
};
/*
** An instance of the following structure is allocated for each open
** inode. This structure keeps track of the number of locks on that
** inode. If a close is attempted against an inode that is holding
** locks, the close is deferred until all locks clear by adding the
** file descriptor to be closed to the pending list.
**
** TODO: Consider changing this so that there is only a single file
** descriptor for each open file, even when it is opened multiple times.
** The close() system call would only occur when the last database
** using the file closes.
*/
struct unixOpenCnt {
struct unixFileId fileId; /* The lookup key */
int nRef; /* Number of pointers to this structure */
int nLock; /* Number of outstanding locks */
UnixUnusedFd *pUnused; /* Unused file descriptors to close */
#if OS_VXWORKS
sem_t *pSem; /* Named POSIX semaphore */
char aSemName[MAX_PATHNAME+1]; /* Name of that semaphore */
#endif
struct unixOpenCnt *pNext, *pPrev; /* List of all unixOpenCnt objects */
};
/*
** Lists of all unixLockInfo and unixOpenCnt objects. These used to be hash
** tables. But the number of objects is rarely more than a dozen and
** never exceeds a few thousand. And lookup is not on a critical
** path so a simple linked list will suffice.
*/
static struct unixLockInfo *lockList = 0;
static struct unixOpenCnt *openList = 0;
/*
** This variable remembers whether or not threads can override each others
** locks.
**
** 0: No. Threads cannot override each others locks. (LinuxThreads)
** 1: Yes. Threads can override each others locks. (Posix & NLPT)
** -1: We don't know yet.
**
** On some systems, we know at compile-time if threads can override each
** others locks. On those systems, the SQLITE_THREAD_OVERRIDE_LOCK macro
** will be set appropriately. On other systems, we have to check at
** runtime. On these latter systems, SQLTIE_THREAD_OVERRIDE_LOCK is
** undefined.
**
** This variable normally has file scope only. But during testing, we make
** it a global so that the test code can change its value in order to verify
** that the right stuff happens in either case.
*/
#if SQLITE_THREADSAFE && defined(__linux__)
# ifndef SQLITE_THREAD_OVERRIDE_LOCK
# define SQLITE_THREAD_OVERRIDE_LOCK -1
# endif
# ifdef SQLITE_TEST
int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
# else
static int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
# endif
#endif
/*
** This structure holds information passed into individual test
** threads by the testThreadLockingBehavior() routine.
*/
struct threadTestData {
int fd; /* File to be locked */
struct flock lock; /* The locking operation */
int result; /* Result of the locking operation */
};
#if SQLITE_THREADSAFE && defined(__linux__)
/*
** This function is used as the main routine for a thread launched by
** testThreadLockingBehavior(). It tests whether the shared-lock obtained
** by the main thread in testThreadLockingBehavior() conflicts with a
** hypothetical write-lock obtained by this thread on the same file.
**
** The write-lock is not actually acquired, as this is not possible if
** the file is open in read-only mode (see ticket #3472).
*/
static void *threadLockingTest(void *pArg){
struct threadTestData *pData = (struct threadTestData*)pArg;
pData->result = fcntl(pData->fd, F_GETLK, &pData->lock);
return pArg;
}
#endif /* SQLITE_THREADSAFE && defined(__linux__) */
#if SQLITE_THREADSAFE && defined(__linux__)
/*
** This procedure attempts to determine whether or not threads
** can override each others locks then sets the
** threadsOverrideEachOthersLocks variable appropriately.
*/
static void testThreadLockingBehavior(int fd_orig){
int fd;
int rc;
struct threadTestData d;
struct flock l;
pthread_t t;
fd = dup(fd_orig);
if( fd<0 ) return;
memset(&l, 0, sizeof(l));
l.l_type = F_RDLCK;
l.l_len = 1;
l.l_start = 0;
l.l_whence = SEEK_SET;
rc = fcntl(fd_orig, F_SETLK, &l);
if( rc!=0 ) return;
memset(&d, 0, sizeof(d));
d.fd = fd;
d.lock = l;
d.lock.l_type = F_WRLCK;
if( pthread_create(&t, 0, threadLockingTest, &d)==0 ){
pthread_join(t, 0);
}
close(fd);
if( d.result!=0 ) return;
threadsOverrideEachOthersLocks = (d.lock.l_type==F_UNLCK);
}
#endif /* SQLITE_THREADSAFE && defined(__linux__) */
/*
** Release a unixLockInfo structure previously allocated by findLockInfo().
**
** The mutex entered using the unixEnterMutex() function must be held
** when this function is called.
*/
static void releaseLockInfo(struct unixLockInfo *pLock){
assert( unixMutexHeld() );
if( pLock ){
pLock->nRef--;
if( pLock->nRef==0 ){
if( pLock->pPrev ){
assert( pLock->pPrev->pNext==pLock );
pLock->pPrev->pNext = pLock->pNext;
}else{
assert( lockList==pLock );
lockList = pLock->pNext;
}
if( pLock->pNext ){
assert( pLock->pNext->pPrev==pLock );
pLock->pNext->pPrev = pLock->pPrev;
}
sqlite3_free(pLock);
}
}
}
/*
** Release a unixOpenCnt structure previously allocated by findLockInfo().
**
** The mutex entered using the unixEnterMutex() function must be held
** when this function is called.
*/
static void releaseOpenCnt(struct unixOpenCnt *pOpen){
assert( unixMutexHeld() );
if( pOpen ){
pOpen->nRef--;
if( pOpen->nRef==0 ){
if( pOpen->pPrev ){
assert( pOpen->pPrev->pNext==pOpen );
pOpen->pPrev->pNext = pOpen->pNext;
}else{
assert( openList==pOpen );
openList = pOpen->pNext;
}
if( pOpen->pNext ){
assert( pOpen->pNext->pPrev==pOpen );
pOpen->pNext->pPrev = pOpen->pPrev;
}
assert( !pOpen->pUnused );
sqlite3_free(pOpen);
}
}
}
/*
** Given a file descriptor, locate unixLockInfo and unixOpenCnt structures that
** describes that file descriptor. Create new ones if necessary. The
** return values might be uninitialized if an error occurs.
**
** The mutex entered using the unixEnterMutex() function must be held
** when this function is called.
**
** Return an appropriate error code.
*/
static int findLockInfo(
unixFile *pFile, /* Unix file with file desc used in the key */
struct unixLockInfo **ppLock, /* Return the unixLockInfo structure here */
struct unixOpenCnt **ppOpen /* Return the unixOpenCnt structure here */
){
int rc; /* System call return code */
int fd; /* The file descriptor for pFile */
struct unixLockKey lockKey; /* Lookup key for the unixLockInfo structure */
struct unixFileId fileId; /* Lookup key for the unixOpenCnt struct */
struct stat statbuf; /* Low-level file information */
struct unixLockInfo *pLock = 0;/* Candidate unixLockInfo object */
struct unixOpenCnt *pOpen; /* Candidate unixOpenCnt object */
assert( unixMutexHeld() );
/* Get low-level information about the file that we can used to
** create a unique name for the file.
*/
fd = pFile->h;
rc = fstat(fd, &statbuf);
if( rc!=0 ){
pFile->lastErrno = errno;
#ifdef EOVERFLOW
if( pFile->lastErrno==EOVERFLOW ) return SQLITE_NOLFS;
#endif
return SQLITE_IOERR;
}
#ifdef __APPLE__
/* On OS X on an msdos filesystem, the inode number is reported
** incorrectly for zero-size files. See ticket #3260. To work
** around this problem (we consider it a bug in OS X, not SQLite)
** we always increase the file size to 1 by writing a single byte
** prior to accessing the inode number. The one byte written is
** an ASCII 'S' character which also happens to be the first byte
** in the header of every SQLite database. In this way, if there
** is a race condition such that another thread has already populated
** the first page of the database, no damage is done.
*/
if( statbuf.st_size==0 ){
rc = write(fd, "S", 1);
if( rc!=1 ){
return SQLITE_IOERR;
}
rc = fstat(fd, &statbuf);
if( rc!=0 ){
pFile->lastErrno = errno;
return SQLITE_IOERR;
}
}
#endif
memset(&lockKey, 0, sizeof(lockKey));
lockKey.fid.dev = statbuf.st_dev;
#if OS_VXWORKS
lockKey.fid.pId = pFile->pId;
#else
lockKey.fid.ino = statbuf.st_ino;
#endif
#if SQLITE_THREADSAFE && defined(__linux__)
if( threadsOverrideEachOthersLocks<0 ){
testThreadLockingBehavior(fd);
}
lockKey.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self();
#endif
fileId = lockKey.fid;
if( ppLock!=0 ){
pLock = lockList;
while( pLock && memcmp(&lockKey, &pLock->lockKey, sizeof(lockKey)) ){
pLock = pLock->pNext;
}
if( pLock==0 ){
pLock = sqlite3_malloc( sizeof(*pLock) );
if( pLock==0 ){
rc = SQLITE_NOMEM;
goto exit_findlockinfo;
}
pLock->lockKey = lockKey;
pLock->nRef = 1;
pLock->cnt = 0;
pLock->locktype = 0;
pLock->pNext = lockList;
pLock->pPrev = 0;
if( lockList ) lockList->pPrev = pLock;
lockList = pLock;
}else{
pLock->nRef++;
}
*ppLock = pLock;
}
if( ppOpen!=0 ){
pOpen = openList;
while( pOpen && memcmp(&fileId, &pOpen->fileId, sizeof(fileId)) ){
pOpen = pOpen->pNext;
}
if( pOpen==0 ){
pOpen = sqlite3_malloc( sizeof(*pOpen) );
if( pOpen==0 ){
releaseLockInfo(pLock);
rc = SQLITE_NOMEM;
goto exit_findlockinfo;
}
memset(pOpen, 0, sizeof(*pOpen));
pOpen->fileId = fileId;
pOpen->nRef = 1;
pOpen->pNext = openList;
if( openList ) openList->pPrev = pOpen;
openList = pOpen;
}else{
pOpen->nRef++;
}
*ppOpen = pOpen;
}
exit_findlockinfo:
return rc;
}
/*
** If we are currently in a different thread than the thread that the
** unixFile argument belongs to, then transfer ownership of the unixFile
** over to the current thread.
**
** A unixFile is only owned by a thread on systems that use LinuxThreads.
**
** Ownership transfer is only allowed if the unixFile is currently unlocked.
** If the unixFile is locked and an ownership is wrong, then return
** SQLITE_MISUSE. SQLITE_OK is returned if everything works.
*/
#if SQLITE_THREADSAFE && defined(__linux__)
static int transferOwnership(unixFile *pFile){
int rc;
pthread_t hSelf;
if( threadsOverrideEachOthersLocks ){
/* Ownership transfers not needed on this system */
return SQLITE_OK;
}
hSelf = pthread_self();
if( pthread_equal(pFile->tid, hSelf) ){
/* We are still in the same thread */
OSTRACE1("No-transfer, same thread\n");
return SQLITE_OK;
}
if( pFile->locktype!=NO_LOCK ){
/* We cannot change ownership while we are holding a lock! */
return SQLITE_MISUSE;
}
OSTRACE4("Transfer ownership of %d from %d to %d\n",
pFile->h, pFile->tid, hSelf);
pFile->tid = hSelf;
if (pFile->pLock != NULL) {
releaseLockInfo(pFile->pLock);
rc = findLockInfo(pFile, &pFile->pLock, 0);
OSTRACE5("LOCK %d is now %s(%s,%d)\n", pFile->h,
locktypeName(pFile->locktype),
locktypeName(pFile->pLock->locktype), pFile->pLock->cnt);
return rc;
} else {
return SQLITE_OK;
}
}
#else /* if not SQLITE_THREADSAFE */
/* On single-threaded builds, ownership transfer is a no-op */
# define transferOwnership(X) SQLITE_OK
#endif /* SQLITE_THREADSAFE */
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, set *pResOut
** to a non-zero value otherwise *pResOut is set to zero. The return value
** is set to SQLITE_OK unless an I/O error occurs during lock checking.
*/
static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
int rc = SQLITE_OK;
int reserved = 0;
unixFile *pFile = (unixFile*)id;
SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
assert( pFile );
unixEnterMutex(); /* Because pFile->pLock is shared across threads */
/* Check if a thread in this process holds such a lock */
if( pFile->pLock->locktype>SHARED_LOCK ){
reserved = 1;
}
/* Otherwise see if some other process holds it.
*/
#ifndef __DJGPP__
if( !reserved ){
struct flock lock;
lock.l_whence = SEEK_SET;
lock.l_start = RESERVED_BYTE;
lock.l_len = 1;
lock.l_type = F_WRLCK;
if (-1 == fcntl(pFile->h, F_GETLK, &lock)) {
int tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK);
pFile->lastErrno = tErrno;
} else if( lock.l_type!=F_UNLCK ){
reserved = 1;
}
}
#endif
unixLeaveMutex();
OSTRACE4("TEST WR-LOCK %d %d %d\n", pFile->h, rc, reserved);
*pResOut = reserved;
return rc;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** This routine will only increase a lock. Use the sqlite3OsUnlock()
** routine to lower a locking level.
*/
static int unixLock(sqlite3_file *id, int locktype){
/* The following describes the implementation of the various locks and
** lock transitions in terms of the POSIX advisory shared and exclusive
** lock primitives (called read-locks and write-locks below, to avoid
** confusion with SQLite lock names). The algorithms are complicated
** slightly in order to be compatible with windows systems simultaneously
** accessing the same database file, in case that is ever required.
**
** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
** byte', each single bytes at well known offsets, and the 'shared byte
** range', a range of 510 bytes at a well known offset.
**
** To obtain a SHARED lock, a read-lock is obtained on the 'pending
** byte'. If this is successful, a random byte from the 'shared byte
** range' is read-locked and the lock on the 'pending byte' released.
**
** A process may only obtain a RESERVED lock after it has a SHARED lock.
** A RESERVED lock is implemented by grabbing a write-lock on the
** 'reserved byte'.
**
** A process may only obtain a PENDING lock after it has obtained a
** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
** on the 'pending byte'. This ensures that no new SHARED locks can be
** obtained, but existing SHARED locks are allowed to persist. A process
** does not have to obtain a RESERVED lock on the way to a PENDING lock.
** This property is used by the algorithm for rolling back a journal file
** after a crash.
**
** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
** implemented by obtaining a write-lock on the entire 'shared byte
** range'. Since all other locks require a read-lock on one of the bytes
** within this range, this ensures that no other locks are held on the
** database.
**
** The reason a single byte cannot be used instead of the 'shared byte
** range' is that some versions of windows do not support read-locks. By
** locking a random byte from a range, concurrent SHARED locks may exist
** even if the locking primitive used is always a write-lock.
*/
int rc = SQLITE_OK;
unixFile *pFile = (unixFile*)id;
struct unixLockInfo *pLock = pFile->pLock;
struct flock lock;
int s;
assert( pFile );
OSTRACE7("LOCK %d %s was %s(%s,%d) pid=%d\n", pFile->h,
locktypeName(locktype), locktypeName(pFile->locktype),
locktypeName(pLock->locktype), pLock->cnt , getpid());
/* If there is already a lock of this type or more restrictive on the
** unixFile, do nothing. Don't use the end_lock: exit path, as
** unixEnterMutex() hasn't been called yet.
*/
if( pFile->locktype>=locktype ){
OSTRACE3("LOCK %d %s ok (already held)\n", pFile->h,
locktypeName(locktype));
return SQLITE_OK;
}
/* Make sure the locking sequence is correct
*/
assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
assert( locktype!=PENDING_LOCK );
assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
/* This mutex is needed because pFile->pLock is shared across threads
*/
unixEnterMutex();
/* Make sure the current thread owns the pFile.
*/
rc = transferOwnership(pFile);
if( rc!=SQLITE_OK ){
unixLeaveMutex();
return rc;
}
pLock = pFile->pLock;
/* If some thread using this PID has a lock via a different unixFile*
** handle that precludes the requested lock, return BUSY.
*/
if( (pFile->locktype!=pLock->locktype &&
(pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK))
){
rc = SQLITE_BUSY;
goto end_lock;
}
/* If a SHARED lock is requested, and some thread using this PID already
** has a SHARED or RESERVED lock, then increment reference counts and
** return SQLITE_OK.
*/
if( locktype==SHARED_LOCK &&
(pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){
assert( locktype==SHARED_LOCK );
assert( pFile->locktype==0 );
assert( pLock->cnt>0 );
pFile->locktype = SHARED_LOCK;
pLock->cnt++;
pFile->pOpen->nLock++;
goto end_lock;
}
lock.l_len = 1L;
lock.l_whence = SEEK_SET;
/* A PENDING lock is needed before acquiring a SHARED lock and before
** acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will
** be released.
*/
if( locktype==SHARED_LOCK
|| (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
){
lock.l_type = (locktype==SHARED_LOCK?F_RDLCK:F_WRLCK);
lock.l_start = PENDING_BYTE;
s = fcntl(pFile->h, F_SETLK, &lock);
if( s==(-1) ){
int tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
goto end_lock;
}
}
/* If control gets to this point, then actually go ahead and make
** operating system calls for the specified lock.
*/
if( locktype==SHARED_LOCK ){
int tErrno = 0;
assert( pLock->cnt==0 );
assert( pLock->locktype==0 );
/* Now get the read-lock */
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
if( (s = fcntl(pFile->h, F_SETLK, &lock))==(-1) ){
tErrno = errno;
}
/* Drop the temporary PENDING lock */
lock.l_start = PENDING_BYTE;
lock.l_len = 1L;
lock.l_type = F_UNLCK;
if( fcntl(pFile->h, F_SETLK, &lock)!=0 ){
if( s != -1 ){
/* This could happen with a network mount */
tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
goto end_lock;
}
}
if( s==(-1) ){
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
}else{
pFile->locktype = SHARED_LOCK;
pFile->pOpen->nLock++;
pLock->cnt = 1;
}
}else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){
/* We are trying for an exclusive lock but another thread in this
** same process is still holding a shared lock. */
rc = SQLITE_BUSY;
}else{
/* The request was for a RESERVED or EXCLUSIVE lock. It is
** assumed that there is a SHARED or greater lock on the file
** already.
*/
assert( 0!=pFile->locktype );
lock.l_type = F_WRLCK;
switch( locktype ){
case RESERVED_LOCK:
lock.l_start = RESERVED_BYTE;
break;
case EXCLUSIVE_LOCK:
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
break;
default:
assert(0);
}
s = fcntl(pFile->h, F_SETLK, &lock);
if( s==(-1) ){
int tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
}
}
#ifndef NDEBUG
/* Set up the transaction-counter change checking flags when
** transitioning from a SHARED to a RESERVED lock. The change
** from SHARED to RESERVED marks the beginning of a normal
** write operation (not a hot journal rollback).
*/
if( rc==SQLITE_OK
&& pFile->locktype<=SHARED_LOCK
&& locktype==RESERVED_LOCK
){
pFile->transCntrChng = 0;
pFile->dbUpdate = 0;
pFile->inNormalWrite = 1;
}
#endif
if( rc==SQLITE_OK ){
pFile->locktype = locktype;
pLock->locktype = locktype;
}else if( locktype==EXCLUSIVE_LOCK ){
pFile->locktype = PENDING_LOCK;
pLock->locktype = PENDING_LOCK;
}
end_lock:
unixLeaveMutex();
OSTRACE4("LOCK %d %s %s\n", pFile->h, locktypeName(locktype),
rc==SQLITE_OK ? "ok" : "failed");
return rc;
}
/*
** Close all file descriptors accumuated in the unixOpenCnt->pUnused list.
** If all such file descriptors are closed without error, the list is
** cleared and SQLITE_OK returned.
**
** Otherwise, if an error occurs, then successfully closed file descriptor
** entries are removed from the list, and SQLITE_IOERR_CLOSE returned.
** not deleted and SQLITE_IOERR_CLOSE returned.
*/
static int closePendingFds(unixFile *pFile){
int rc = SQLITE_OK;
struct unixOpenCnt *pOpen = pFile->pOpen;
UnixUnusedFd *pError = 0;
UnixUnusedFd *p;
UnixUnusedFd *pNext;
for(p=pOpen->pUnused; p; p=pNext){
pNext = p->pNext;
if( close(p->fd) ){
pFile->lastErrno = errno;
rc = SQLITE_IOERR_CLOSE;
p->pNext = pError;
pError = p;
}else{
sqlite3_free(p);
}
}
pOpen->pUnused = pError;
return rc;
}
/*
** Add the file descriptor used by file handle pFile to the corresponding
** pUnused list.
*/
static void setPendingFd(unixFile *pFile){
struct unixOpenCnt *pOpen = pFile->pOpen;
UnixUnusedFd *p = pFile->pUnused;
p->pNext = pOpen->pUnused;
pOpen->pUnused = p;
pFile->h = -1;
pFile->pUnused = 0;
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
*/
static int unixUnlock(sqlite3_file *id, int locktype){
struct unixLockInfo *pLock;
struct flock lock;
int rc = SQLITE_OK;
unixFile *pFile = (unixFile*)id;
int h;
assert( pFile );
OSTRACE7("UNLOCK %d %d was %d(%d,%d) pid=%d\n", pFile->h, locktype,
pFile->locktype, pFile->pLock->locktype, pFile->pLock->cnt, getpid());
assert( locktype<=SHARED_LOCK );
if( pFile->locktype<=locktype ){
return SQLITE_OK;
}
if( CHECK_THREADID(pFile) ){
return SQLITE_MISUSE;
}
unixEnterMutex();
h = pFile->h;
pLock = pFile->pLock;
assert( pLock->cnt!=0 );
if( pFile->locktype>SHARED_LOCK ){
assert( pLock->locktype==pFile->locktype );
SimulateIOErrorBenign(1);
SimulateIOError( h=(-1) )
SimulateIOErrorBenign(0);
#ifndef NDEBUG
/* When reducing a lock such that other processes can start
** reading the database file again, make sure that the
** transaction counter was updated if any part of the database
** file changed. If the transaction counter is not updated,
** other connections to the same file might not realize that
** the file has changed and hence might not know to flush their
** cache. The use of a stale cache can lead to database corruption.
*/
assert( pFile->inNormalWrite==0
|| pFile->dbUpdate==0
|| pFile->transCntrChng==1 );
pFile->inNormalWrite = 0;
#endif
if( locktype==SHARED_LOCK ){
lock.l_type = F_RDLCK;
lock.l_whence = SEEK_SET;
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
if( fcntl(h, F_SETLK, &lock)==(-1) ){
int tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
goto end_unlock;
}
}
lock.l_type = F_UNLCK;
lock.l_whence = SEEK_SET;
lock.l_start = PENDING_BYTE;
lock.l_len = 2L; assert( PENDING_BYTE+1==RESERVED_BYTE );
if( fcntl(h, F_SETLK, &lock)!=(-1) ){
pLock->locktype = SHARED_LOCK;
}else{
int tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
goto end_unlock;
}
}
if( locktype==NO_LOCK ){
struct unixOpenCnt *pOpen;
/* Decrement the shared lock counter. Release the lock using an
** OS call only when all threads in this same process have released
** the lock.
*/
pLock->cnt--;
if( pLock->cnt==0 ){
lock.l_type = F_UNLCK;
lock.l_whence = SEEK_SET;
lock.l_start = lock.l_len = 0L;
SimulateIOErrorBenign(1);
SimulateIOError( h=(-1) )
SimulateIOErrorBenign(0);
if( fcntl(h, F_SETLK, &lock)!=(-1) ){
pLock->locktype = NO_LOCK;
}else{
int tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
pLock->locktype = NO_LOCK;
pFile->locktype = NO_LOCK;
}
}
/* Decrement the count of locks against this same file. When the
** count reaches zero, close any other file descriptors whose close
** was deferred because of outstanding locks.
*/
pOpen = pFile->pOpen;
pOpen->nLock--;
assert( pOpen->nLock>=0 );
if( pOpen->nLock==0 ){
int rc2 = closePendingFds(pFile);
if( rc==SQLITE_OK ){
rc = rc2;
}
}
}
end_unlock:
unixLeaveMutex();
if( rc==SQLITE_OK ) pFile->locktype = locktype;
return rc;
}
/*
** This function performs the parts of the "close file" operation
** common to all locking schemes. It closes the directory and file
** handles, if they are valid, and sets all fields of the unixFile
** structure to 0.
**
** It is *not* necessary to hold the mutex when this routine is called,
** even on VxWorks. A mutex will be acquired on VxWorks by the
** vxworksReleaseFileId() routine.
*/
static int closeUnixFile(sqlite3_file *id){
unixFile *pFile = (unixFile*)id;
if( pFile ){
if( pFile->dirfd>=0 ){
int err = close(pFile->dirfd);
if( err ){
pFile->lastErrno = errno;
return SQLITE_IOERR_DIR_CLOSE;
}else{
pFile->dirfd=-1;
}
}
if( pFile->h>=0 ){
int err = close(pFile->h);
if( err ){
pFile->lastErrno = errno;
return SQLITE_IOERR_CLOSE;
}
}
#if OS_VXWORKS
if( pFile->pId ){
if( pFile->isDelete ){
unlink(pFile->pId->zCanonicalName);
}
vxworksReleaseFileId(pFile->pId);
pFile->pId = 0;
}
#endif
OSTRACE2("CLOSE %-3d\n", pFile->h);
OpenCounter(-1);
sqlite3_free(pFile->pUnused);
memset(pFile, 0, sizeof(unixFile));
}
return SQLITE_OK;
}
/*
** Close a file.
*/
static int unixClose(sqlite3_file *id){
int rc = SQLITE_OK;
if( id ){
unixFile *pFile = (unixFile *)id;
unixUnlock(id, NO_LOCK);
unixEnterMutex();
if( pFile->pOpen && pFile->pOpen->nLock ){
/* If there are outstanding locks, do not actually close the file just
** yet because that would clear those locks. Instead, add the file
** descriptor to pOpen->pUnused list. It will be automatically closed
** when the last lock is cleared.
*/
setPendingFd(pFile);
}
releaseLockInfo(pFile->pLock);
releaseOpenCnt(pFile->pOpen);
rc = closeUnixFile(id);
unixLeaveMutex();
}
return rc;
}
/************** End of the posix advisory lock implementation *****************
******************************************************************************/
/******************************************************************************
****************************** No-op Locking **********************************
**
** Of the various locking implementations available, this is by far the
** simplest: locking is ignored. No attempt is made to lock the database
** file for reading or writing.
**
** This locking mode is appropriate for use on read-only databases
** (ex: databases that are burned into CD-ROM, for example.) It can
** also be used if the application employs some external mechanism to
** prevent simultaneous access of the same database by two or more
** database connections. But there is a serious risk of database
** corruption if this locking mode is used in situations where multiple
** database connections are accessing the same database file at the same
** time and one or more of those connections are writing.
*/
static int nolockCheckReservedLock(sqlite3_file *NotUsed, int *pResOut){
UNUSED_PARAMETER(NotUsed);
*pResOut = 0;
return SQLITE_OK;
}
static int nolockLock(sqlite3_file *NotUsed, int NotUsed2){
UNUSED_PARAMETER2(NotUsed, NotUsed2);
return SQLITE_OK;
}
static int nolockUnlock(sqlite3_file *NotUsed, int NotUsed2){
UNUSED_PARAMETER2(NotUsed, NotUsed2);
return SQLITE_OK;
}
/*
** Close the file.
*/
static int nolockClose(sqlite3_file *id) {
return closeUnixFile(id);
}
/******************* End of the no-op lock implementation *********************
******************************************************************************/
/******************************************************************************
************************* Begin dot-file Locking ******************************
**
** The dotfile locking implementation uses the existing of separate lock
** files in order to control access to the database. This works on just
** about every filesystem imaginable. But there are serious downsides:
**
** (1) There is zero concurrency. A single reader blocks all other
** connections from reading or writing the database.
**
** (2) An application crash or power loss can leave stale lock files
** sitting around that need to be cleared manually.
**
** Nevertheless, a dotlock is an appropriate locking mode for use if no
** other locking strategy is available.
**
** Dotfile locking works by creating a file in the same directory as the
** database and with the same name but with a ".lock" extension added.
** The existance of a lock file implies an EXCLUSIVE lock. All other lock
** types (SHARED, RESERVED, PENDING) are mapped into EXCLUSIVE.
*/
/*
** The file suffix added to the data base filename in order to create the
** lock file.
*/
#define DOTLOCK_SUFFIX ".lock"
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, set *pResOut
** to a non-zero value otherwise *pResOut is set to zero. The return value
** is set to SQLITE_OK unless an I/O error occurs during lock checking.
**
** In dotfile locking, either a lock exists or it does not. So in this
** variation of CheckReservedLock(), *pResOut is set to true if any lock
** is held on the file and false if the file is unlocked.
*/
static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) {
int rc = SQLITE_OK;
int reserved = 0;
unixFile *pFile = (unixFile*)id;
SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
assert( pFile );
/* Check if a thread in this process holds such a lock */
if( pFile->locktype>SHARED_LOCK ){
/* Either this connection or some other connection in the same process
** holds a lock on the file. No need to check further. */
reserved = 1;
}else{
/* The lock is held if and only if the lockfile exists */
const char *zLockFile = (const char*)pFile->lockingContext;
reserved = access(zLockFile, 0)==0;
}
OSTRACE4("TEST WR-LOCK %d %d %d\n", pFile->h, rc, reserved);
*pResOut = reserved;
return rc;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** This routine will only increase a lock. Use the sqlite3OsUnlock()
** routine to lower a locking level.
**
** With dotfile locking, we really only support state (4): EXCLUSIVE.
** But we track the other locking levels internally.
*/
static int dotlockLock(sqlite3_file *id, int locktype) {
unixFile *pFile = (unixFile*)id;
int fd;
char *zLockFile = (char *)pFile->lockingContext;
int rc = SQLITE_OK;
/* If we have any lock, then the lock file already exists. All we have
** to do is adjust our internal record of the lock level.
*/
if( pFile->locktype > NO_LOCK ){
pFile->locktype = locktype;
#if !OS_VXWORKS
/* Always update the timestamp on the old file */
utimes(zLockFile, NULL);
#endif
return SQLITE_OK;
}
/* grab an exclusive lock */
fd = open(zLockFile,O_RDONLY|O_CREAT|O_EXCL,0600);
if( fd<0 ){
/* failed to open/create the file, someone else may have stolen the lock */
int tErrno = errno;
if( EEXIST == tErrno ){
rc = SQLITE_BUSY;
} else {
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
}
return rc;
}
if( close(fd) ){
pFile->lastErrno = errno;
rc = SQLITE_IOERR_CLOSE;
}
/* got it, set the type and return ok */
pFile->locktype = locktype;
return rc;
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
**
** When the locking level reaches NO_LOCK, delete the lock file.
*/
static int dotlockUnlock(sqlite3_file *id, int locktype) {
unixFile *pFile = (unixFile*)id;
char *zLockFile = (char *)pFile->lockingContext;
assert( pFile );
OSTRACE5("UNLOCK %d %d was %d pid=%d\n", pFile->h, locktype,
pFile->locktype, getpid());
assert( locktype<=SHARED_LOCK );
/* no-op if possible */
if( pFile->locktype==locktype ){
return SQLITE_OK;
}
/* To downgrade to shared, simply update our internal notion of the
** lock state. No need to mess with the file on disk.
*/
if( locktype==SHARED_LOCK ){
pFile->locktype = SHARED_LOCK;
return SQLITE_OK;
}
/* To fully unlock the database, delete the lock file */
assert( locktype==NO_LOCK );
if( unlink(zLockFile) ){
int rc = 0;
int tErrno = errno;
if( ENOENT != tErrno ){
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
}
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
return rc;
}
pFile->locktype = NO_LOCK;
return SQLITE_OK;
}
/*
** Close a file. Make sure the lock has been released before closing.
*/
static int dotlockClose(sqlite3_file *id) {
int rc;
if( id ){
unixFile *pFile = (unixFile*)id;
dotlockUnlock(id, NO_LOCK);
sqlite3_free(pFile->lockingContext);
}
rc = closeUnixFile(id);
return rc;
}
/****************** End of the dot-file lock implementation *******************
******************************************************************************/
/******************************************************************************
************************** Begin flock Locking ********************************
**
** Use the flock() system call to do file locking.
**
** flock() locking is like dot-file locking in that the various
** fine-grain locking levels supported by SQLite are collapsed into
** a single exclusive lock. In other words, SHARED, RESERVED, and
** PENDING locks are the same thing as an EXCLUSIVE lock. SQLite
** still works when you do this, but concurrency is reduced since
** only a single process can be reading the database at a time.
**
** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off or if
** compiling for VXWORKS.
*/
#if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, set *pResOut
** to a non-zero value otherwise *pResOut is set to zero. The return value
** is set to SQLITE_OK unless an I/O error occurs during lock checking.
*/
static int flockCheckReservedLock(sqlite3_file *id, int *pResOut){
int rc = SQLITE_OK;
int reserved = 0;
unixFile *pFile = (unixFile*)id;
SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
assert( pFile );
/* Check if a thread in this process holds such a lock */
if( pFile->locktype>SHARED_LOCK ){
reserved = 1;
}
/* Otherwise see if some other process holds it. */
if( !reserved ){
/* attempt to get the lock */
int lrc = flock(pFile->h, LOCK_EX | LOCK_NB);
if( !lrc ){
/* got the lock, unlock it */
lrc = flock(pFile->h, LOCK_UN);
if ( lrc ) {
int tErrno = errno;
/* unlock failed with an error */
lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
if( IS_LOCK_ERROR(lrc) ){
pFile->lastErrno = tErrno;
rc = lrc;
}
}
} else {
int tErrno = errno;
reserved = 1;
/* someone else might have it reserved */
lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
if( IS_LOCK_ERROR(lrc) ){
pFile->lastErrno = tErrno;
rc = lrc;
}
}
}
OSTRACE4("TEST WR-LOCK %d %d %d\n", pFile->h, rc, reserved);
#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
rc = SQLITE_OK;
reserved=1;
}
#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
*pResOut = reserved;
return rc;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** flock() only really support EXCLUSIVE locks. We track intermediate
** lock states in the sqlite3_file structure, but all locks SHARED or
** above are really EXCLUSIVE locks and exclude all other processes from
** access the file.
**
** This routine will only increase a lock. Use the sqlite3OsUnlock()
** routine to lower a locking level.
*/
static int flockLock(sqlite3_file *id, int locktype) {
int rc = SQLITE_OK;
unixFile *pFile = (unixFile*)id;
assert( pFile );
/* if we already have a lock, it is exclusive.
** Just adjust level and punt on outta here. */
if (pFile->locktype > NO_LOCK) {
pFile->locktype = locktype;
return SQLITE_OK;
}
/* grab an exclusive lock */
if (flock(pFile->h, LOCK_EX | LOCK_NB)) {
int tErrno = errno;
/* didn't get, must be busy */
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
} else {
/* got it, set the type and return ok */
pFile->locktype = locktype;
}
OSTRACE4("LOCK %d %s %s\n", pFile->h, locktypeName(locktype),
rc==SQLITE_OK ? "ok" : "failed");
#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
rc = SQLITE_BUSY;
}
#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
return rc;
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
*/
static int flockUnlock(sqlite3_file *id, int locktype) {
unixFile *pFile = (unixFile*)id;
assert( pFile );
OSTRACE5("UNLOCK %d %d was %d pid=%d\n", pFile->h, locktype,
pFile->locktype, getpid());
assert( locktype<=SHARED_LOCK );
/* no-op if possible */
if( pFile->locktype==locktype ){
return SQLITE_OK;
}
/* shared can just be set because we always have an exclusive */
if (locktype==SHARED_LOCK) {
pFile->locktype = locktype;
return SQLITE_OK;
}
/* no, really, unlock. */
int rc = flock(pFile->h, LOCK_UN);
if (rc) {
int r, tErrno = errno;
r = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
if( IS_LOCK_ERROR(r) ){
pFile->lastErrno = tErrno;
}
#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
if( (r & SQLITE_IOERR) == SQLITE_IOERR ){
r = SQLITE_BUSY;
}
#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
return r;
} else {
pFile->locktype = NO_LOCK;
return SQLITE_OK;
}
}
/*
** Close a file.
*/
static int flockClose(sqlite3_file *id) {
if( id ){
flockUnlock(id, NO_LOCK);
}
return closeUnixFile(id);
}
#endif /* SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORK */
/******************* End of the flock lock implementation *********************
******************************************************************************/
/******************************************************************************
************************ Begin Named Semaphore Locking ************************
**
** Named semaphore locking is only supported on VxWorks.
**
** Semaphore locking is like dot-lock and flock in that it really only
** supports EXCLUSIVE locking. Only a single process can read or write
** the database file at a time. This reduces potential concurrency, but
** makes the lock implementation much easier.
*/
#if OS_VXWORKS
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, set *pResOut
** to a non-zero value otherwise *pResOut is set to zero. The return value
** is set to SQLITE_OK unless an I/O error occurs during lock checking.
*/
static int semCheckReservedLock(sqlite3_file *id, int *pResOut) {
int rc = SQLITE_OK;
int reserved = 0;
unixFile *pFile = (unixFile*)id;
SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
assert( pFile );
/* Check if a thread in this process holds such a lock */
if( pFile->locktype>SHARED_LOCK ){
reserved = 1;
}
/* Otherwise see if some other process holds it. */
if( !reserved ){
sem_t *pSem = pFile->pOpen->pSem;
struct stat statBuf;
if( sem_trywait(pSem)==-1 ){
int tErrno = errno;
if( EAGAIN != tErrno ){
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK);
pFile->lastErrno = tErrno;
} else {
/* someone else has the lock when we are in NO_LOCK */
reserved = (pFile->locktype < SHARED_LOCK);
}
}else{
/* we could have it if we want it */
sem_post(pSem);
}
}
OSTRACE4("TEST WR-LOCK %d %d %d\n", pFile->h, rc, reserved);
*pResOut = reserved;
return rc;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** Semaphore locks only really support EXCLUSIVE locks. We track intermediate
** lock states in the sqlite3_file structure, but all locks SHARED or
** above are really EXCLUSIVE locks and exclude all other processes from
** access the file.
**
** This routine will only increase a lock. Use the sqlite3OsUnlock()
** routine to lower a locking level.
*/
static int semLock(sqlite3_file *id, int locktype) {
unixFile *pFile = (unixFile*)id;
int fd;
sem_t *pSem = pFile->pOpen->pSem;
int rc = SQLITE_OK;
/* if we already have a lock, it is exclusive.
** Just adjust level and punt on outta here. */
if (pFile->locktype > NO_LOCK) {
pFile->locktype = locktype;
rc = SQLITE_OK;
goto sem_end_lock;
}
/* lock semaphore now but bail out when already locked. */
if( sem_trywait(pSem)==-1 ){
rc = SQLITE_BUSY;
goto sem_end_lock;
}
/* got it, set the type and return ok */
pFile->locktype = locktype;
sem_end_lock:
return rc;
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
*/
static int semUnlock(sqlite3_file *id, int locktype) {
unixFile *pFile = (unixFile*)id;
sem_t *pSem = pFile->pOpen->pSem;
assert( pFile );
assert( pSem );
OSTRACE5("UNLOCK %d %d was %d pid=%d\n", pFile->h, locktype,
pFile->locktype, getpid());
assert( locktype<=SHARED_LOCK );
/* no-op if possible */
if( pFile->locktype==locktype ){
return SQLITE_OK;
}
/* shared can just be set because we always have an exclusive */
if (locktype==SHARED_LOCK) {
pFile->locktype = locktype;
return SQLITE_OK;
}
/* no, really unlock. */
if ( sem_post(pSem)==-1 ) {
int rc, tErrno = errno;
rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
return rc;
}
pFile->locktype = NO_LOCK;
return SQLITE_OK;
}
/*
** Close a file.
*/
static int semClose(sqlite3_file *id) {
if( id ){
unixFile *pFile = (unixFile*)id;
semUnlock(id, NO_LOCK);
assert( pFile );
unixEnterMutex();
releaseLockInfo(pFile->pLock);
releaseOpenCnt(pFile->pOpen);
unixLeaveMutex();
closeUnixFile(id);
}
return SQLITE_OK;
}
#endif /* OS_VXWORKS */
/*
** Named semaphore locking is only available on VxWorks.
**
*************** End of the named semaphore lock implementation ****************
******************************************************************************/
/******************************************************************************
*************************** Begin AFP Locking *********************************
**
** AFP is the Apple Filing Protocol. AFP is a network filesystem found
** on Apple Macintosh computers - both OS9 and OSX.
**
** Third-party implementations of AFP are available. But this code here
** only works on OSX.
*/
#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
/*
** The afpLockingContext structure contains all afp lock specific state
*/
typedef struct afpLockingContext afpLockingContext;
struct afpLockingContext {
unsigned long long sharedByte;
const char *dbPath; /* Name of the open file */
};
struct ByteRangeLockPB2
{
unsigned long long offset; /* offset to first byte to lock */
unsigned long long length; /* nbr of bytes to lock */
unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
unsigned char unLockFlag; /* 1 = unlock, 0 = lock */
unsigned char startEndFlag; /* 1=rel to end of fork, 0=rel to start */
int fd; /* file desc to assoc this lock with */
};
#define afpfsByteRangeLock2FSCTL _IOWR('z', 23, struct ByteRangeLockPB2)
/*
** This is a utility for setting or clearing a bit-range lock on an
** AFP filesystem.
**
** Return SQLITE_OK on success, SQLITE_BUSY on failure.
*/
static int afpSetLock(
const char *path, /* Name of the file to be locked or unlocked */
unixFile *pFile, /* Open file descriptor on path */
unsigned long long offset, /* First byte to be locked */
unsigned long long length, /* Number of bytes to lock */
int setLockFlag /* True to set lock. False to clear lock */
){
struct ByteRangeLockPB2 pb;
int err;
pb.unLockFlag = setLockFlag ? 0 : 1;
pb.startEndFlag = 0;
pb.offset = offset;
pb.length = length;
pb.fd = pFile->h;
OSTRACE6("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n",
(setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""),
offset, length);
err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
if ( err==-1 ) {
int rc;
int tErrno = errno;
OSTRACE4("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
path, tErrno, strerror(tErrno));
#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
rc = SQLITE_BUSY;
#else
rc = sqliteErrorFromPosixError(tErrno,
setLockFlag ? SQLITE_IOERR_LOCK : SQLITE_IOERR_UNLOCK);
#endif /* SQLITE_IGNORE_AFP_LOCK_ERRORS */
if( IS_LOCK_ERROR(rc) ){
pFile->lastErrno = tErrno;
}
return rc;
} else {
return SQLITE_OK;
}
}
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, set *pResOut
** to a non-zero value otherwise *pResOut is set to zero. The return value
** is set to SQLITE_OK unless an I/O error occurs during lock checking.
*/
static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
int rc = SQLITE_OK;
int reserved = 0;
unixFile *pFile = (unixFile*)id;
SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
assert( pFile );
afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
/* Check if a thread in this process holds such a lock */
if( pFile->locktype>SHARED_LOCK ){
reserved = 1;
}
/* Otherwise see if some other process holds it.
*/
if( !reserved ){
/* lock the RESERVED byte */
int lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
if( SQLITE_OK==lrc ){
/* if we succeeded in taking the reserved lock, unlock it to restore
** the original state */
lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
} else {
/* if we failed to get the lock then someone else must have it */
reserved = 1;
}
if( IS_LOCK_ERROR(lrc) ){
rc=lrc;
}
}
OSTRACE4("TEST WR-LOCK %d %d %d\n", pFile->h, rc, reserved);
*pResOut = reserved;
return rc;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** This routine will only increase a lock. Use the sqlite3OsUnlock()
** routine to lower a locking level.
*/
static int afpLock(sqlite3_file *id, int locktype){
int rc = SQLITE_OK;
unixFile *pFile = (unixFile*)id;
afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
assert( pFile );
OSTRACE5("LOCK %d %s was %s pid=%d\n", pFile->h,
locktypeName(locktype), locktypeName(pFile->locktype), getpid());
/* If there is already a lock of this type or more restrictive on the
** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
** unixEnterMutex() hasn't been called yet.
*/
if( pFile->locktype>=locktype ){
OSTRACE3("LOCK %d %s ok (already held)\n", pFile->h,
locktypeName(locktype));
return SQLITE_OK;
}
/* Make sure the locking sequence is correct
*/
assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
assert( locktype!=PENDING_LOCK );
assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
/* This mutex is needed because pFile->pLock is shared across threads
*/
unixEnterMutex();
/* Make sure the current thread owns the pFile.
*/
rc = transferOwnership(pFile);
if( rc!=SQLITE_OK ){
unixLeaveMutex();
return rc;
}
/* A PENDING lock is needed before acquiring a SHARED lock and before
** acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will
** be released.
*/
if( locktype==SHARED_LOCK
|| (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
){
int failed;
failed = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 1);
if (failed) {
rc = failed;
goto afp_end_lock;
}
}
/* If control gets to this point, then actually go ahead and make
** operating system calls for the specified lock.
*/
if( locktype==SHARED_LOCK ){
int lk, lrc1, lrc2, lrc1Errno;
/* Now get the read-lock SHARED_LOCK */
/* note that the quality of the randomness doesn't matter that much */
lk = random();
context->sharedByte = (lk & 0x7fffffff)%(SHARED_SIZE - 1);
lrc1 = afpSetLock(context->dbPath, pFile,
SHARED_FIRST+context->sharedByte, 1, 1);
if( IS_LOCK_ERROR(lrc1) ){
lrc1Errno = pFile->lastErrno;
}
/* Drop the temporary PENDING lock */
lrc2 = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
if( IS_LOCK_ERROR(lrc1) ) {
pFile->lastErrno = lrc1Errno;
rc = lrc1;
goto afp_end_lock;
} else if( IS_LOCK_ERROR(lrc2) ){
rc = lrc2;
goto afp_end_lock;
} else if( lrc1 != SQLITE_OK ) {
rc = lrc1;
} else {
pFile->locktype = SHARED_LOCK;
pFile->pOpen->nLock++;
}
}else{
/* The request was for a RESERVED or EXCLUSIVE lock. It is
** assumed that there is a SHARED or greater lock on the file
** already.
*/
int failed = 0;
assert( 0!=pFile->locktype );
if (locktype >= RESERVED_LOCK && pFile->locktype < RESERVED_LOCK) {
/* Acquire a RESERVED lock */
failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
}
if (!failed && locktype == EXCLUSIVE_LOCK) {
/* Acquire an EXCLUSIVE lock */
/* Remove the shared lock before trying the range. we'll need to
** reestablish the shared lock if we can't get the afpUnlock
*/
if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST +
context->sharedByte, 1, 0)) ){
int failed2 = SQLITE_OK;
/* now attemmpt to get the exclusive lock range */
failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST,
SHARED_SIZE, 1);
if( failed && (failed2 = afpSetLock(context->dbPath, pFile,
SHARED_FIRST + context->sharedByte, 1, 1)) ){
/* Can't reestablish the shared lock. Sqlite can't deal, this is
** a critical I/O error
*/
rc = ((failed & SQLITE_IOERR) == SQLITE_IOERR) ? failed2 :
SQLITE_IOERR_LOCK;
goto afp_end_lock;
}
}else{
rc = failed;
}
}
if( failed ){
rc = failed;
}
}
if( rc==SQLITE_OK ){
pFile->locktype = locktype;
}else if( locktype==EXCLUSIVE_LOCK ){
pFile->locktype = PENDING_LOCK;
}
afp_end_lock:
unixLeaveMutex();
OSTRACE4("LOCK %d %s %s\n", pFile->h, locktypeName(locktype),
rc==SQLITE_OK ? "ok" : "failed");
return rc;
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
*/
static int afpUnlock(sqlite3_file *id, int locktype) {
int rc = SQLITE_OK;
unixFile *pFile = (unixFile*)id;
afpLockingContext *pCtx = (afpLockingContext *) pFile->lockingContext;
assert( pFile );
OSTRACE5("UNLOCK %d %d was %d pid=%d\n", pFile->h, locktype,
pFile->locktype, getpid());
assert( locktype<=SHARED_LOCK );
if( pFile->locktype<=locktype ){
return SQLITE_OK;
}
if( CHECK_THREADID(pFile) ){
return SQLITE_MISUSE;
}
unixEnterMutex();
if( pFile->locktype>SHARED_LOCK ){
if( pFile->locktype==EXCLUSIVE_LOCK ){
rc = afpSetLock(pCtx->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
if( rc==SQLITE_OK && locktype==SHARED_LOCK ){
/* only re-establish the shared lock if necessary */
int sharedLockByte = SHARED_FIRST+pCtx->sharedByte;
rc = afpSetLock(pCtx->dbPath, pFile, sharedLockByte, 1, 1);
}
}
if( rc==SQLITE_OK && pFile->locktype>=PENDING_LOCK ){
rc = afpSetLock(pCtx->dbPath, pFile, PENDING_BYTE, 1, 0);
}
if( rc==SQLITE_OK && pFile->locktype>=RESERVED_LOCK ){
rc = afpSetLock(pCtx->dbPath, pFile, RESERVED_BYTE, 1, 0);
}
}else if( locktype==NO_LOCK ){
/* clear the shared lock */
int sharedLockByte = SHARED_FIRST+pCtx->sharedByte;
rc = afpSetLock(pCtx->dbPath, pFile, sharedLockByte, 1, 0);
}
if( rc==SQLITE_OK ){
if( locktype==NO_LOCK ){
struct unixOpenCnt *pOpen = pFile->pOpen;
pOpen->nLock--;
assert( pOpen->nLock>=0 );
if( pOpen->nLock==0 ){
rc = closePendingFds(pFile);
}
}
}
unixLeaveMutex();
if( rc==SQLITE_OK ){
pFile->locktype = locktype;
}
return rc;
}
/*
** Close a file & cleanup AFP specific locking context
*/
static int afpClose(sqlite3_file *id) {
if( id ){
unixFile *pFile = (unixFile*)id;
afpUnlock(id, NO_LOCK);
unixEnterMutex();
if( pFile->pOpen && pFile->pOpen->nLock ){
/* If there are outstanding locks, do not actually close the file just
** yet because that would clear those locks. Instead, add the file
** descriptor to pOpen->aPending. It will be automatically closed when
** the last lock is cleared.
*/
setPendingFd(pFile);
}
releaseOpenCnt(pFile->pOpen);
sqlite3_free(pFile->lockingContext);
closeUnixFile(id);
unixLeaveMutex();
}
return SQLITE_OK;
}
#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
/*
** The code above is the AFP lock implementation. The code is specific
** to MacOSX and does not work on other unix platforms. No alternative
** is available. If you don't compile for a mac, then the "unix-afp"
** VFS is not available.
**
********************* End of the AFP lock implementation **********************
******************************************************************************/
/******************************************************************************
**************** Non-locking sqlite3_file methods *****************************
**
** The next division contains implementations for all methods of the
** sqlite3_file object other than the locking methods. The locking
** methods were defined in divisions above (one locking method per
** division). Those methods that are common to all locking modes
** are gather together into this division.
*/
/*
** Seek to the offset passed as the second argument, then read cnt
** bytes into pBuf. Return the number of bytes actually read.
**
** NB: If you define USE_PREAD or USE_PREAD64, then it might also
** be necessary to define _XOPEN_SOURCE to be 500. This varies from
** one system to another. Since SQLite does not define USE_PREAD
** any any form by default, we will not attempt to define _XOPEN_SOURCE.
** See tickets #2741 and #2681.
**
** To avoid stomping the errno value on a failed read the lastErrno value
** is set before returning.
*/
static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
int got;
i64 newOffset;
TIMER_START;
#if defined(USE_PREAD)
got = pread(id->h, pBuf, cnt, offset);
SimulateIOError( got = -1 );
#elif defined(USE_PREAD64)
got = pread64(id->h, pBuf, cnt, offset);
SimulateIOError( got = -1 );
#else
newOffset = lseek(id->h, offset, SEEK_SET);
SimulateIOError( newOffset-- );
if( newOffset!=offset ){
if( newOffset == -1 ){
((unixFile*)id)->lastErrno = errno;
}else{
((unixFile*)id)->lastErrno = 0;
}
return -1;
}
got = read(id->h, pBuf, cnt);
#endif
TIMER_END;
if( got<0 ){
((unixFile*)id)->lastErrno = errno;
}
OSTRACE5("READ %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED);
return got;
}
/*
** Read data from a file into a buffer. Return SQLITE_OK if all
** bytes were read successfully and SQLITE_IOERR if anything goes
** wrong.
*/
static int unixRead(
sqlite3_file *id,
void *pBuf,
int amt,
sqlite3_int64 offset
){
unixFile *pFile = (unixFile *)id;
int got;
assert( id );
/* If this is a database file (not a journal, master-journal or temp
** file), the bytes in the locking range should never be read or written. */
assert( pFile->pUnused==0
|| offset>=PENDING_BYTE+512
|| offset+amt<=PENDING_BYTE
);
got = seekAndRead(pFile, offset, pBuf, amt);
if( got==amt ){
return SQLITE_OK;
}else if( got<0 ){
/* lastErrno set by seekAndRead */
return SQLITE_IOERR_READ;
}else{
pFile->lastErrno = 0; /* not a system error */
/* Unread parts of the buffer must be zero-filled */
memset(&((char*)pBuf)[got], 0, amt-got);
return SQLITE_IOERR_SHORT_READ;
}
}
/*
** Seek to the offset in id->offset then read cnt bytes into pBuf.
** Return the number of bytes actually read. Update the offset.
**
** To avoid stomping the errno value on a failed write the lastErrno value
** is set before returning.
*/
static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
int got;
i64 newOffset;
TIMER_START;
#if defined(USE_PREAD)
got = pwrite(id->h, pBuf, cnt, offset);
#elif defined(USE_PREAD64)
got = pwrite64(id->h, pBuf, cnt, offset);
#else
newOffset = lseek(id->h, offset, SEEK_SET);
if( newOffset!=offset ){
if( newOffset == -1 ){
((unixFile*)id)->lastErrno = errno;
}else{
((unixFile*)id)->lastErrno = 0;
}
return -1;
}
got = write(id->h, pBuf, cnt);
#endif
TIMER_END;
if( got<0 ){
((unixFile*)id)->lastErrno = errno;
}
OSTRACE5("WRITE %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED);
return got;
}
/*
** Write data from a buffer into a file. Return SQLITE_OK on success
** or some other error code on failure.
*/
static int unixWrite(
sqlite3_file *id,
const void *pBuf,
int amt,
sqlite3_int64 offset
){
unixFile *pFile = (unixFile*)id;
int wrote = 0;
assert( id );
assert( amt>0 );
/* If this is a database file (not a journal, master-journal or temp
** file), the bytes in the locking range should never be read or written. */
assert( pFile->pUnused==0
|| offset>=PENDING_BYTE+512
|| offset+amt<=PENDING_BYTE
);
#ifndef NDEBUG
/* If we are doing a normal write to a database file (as opposed to
** doing a hot-journal rollback or a write to some file other than a
** normal database file) then record the fact that the database
** has changed. If the transaction counter is modified, record that
** fact too.
*/
if( pFile->inNormalWrite ){
pFile->dbUpdate = 1; /* The database has been modified */
if( offset<=24 && offset+amt>=27 ){
int rc;
char oldCntr[4];
SimulateIOErrorBenign(1);
rc = seekAndRead(pFile, 24, oldCntr, 4);
SimulateIOErrorBenign(0);
if( rc!=4 || memcmp(oldCntr, &((char*)pBuf)[24-offset], 4)!=0 ){
pFile->transCntrChng = 1; /* The transaction counter has changed */
}
}
}
#endif
while( amt>0 && (wrote = seekAndWrite(pFile, offset, pBuf, amt))>0 ){
amt -= wrote;
offset += wrote;
pBuf = &((char*)pBuf)[wrote];
}
SimulateIOError(( wrote=(-1), amt=1 ));
SimulateDiskfullError(( wrote=0, amt=1 ));
if( amt>0 ){
if( wrote<0 ){
/* lastErrno set by seekAndWrite */
return SQLITE_IOERR_WRITE;
}else{
pFile->lastErrno = 0; /* not a system error */
return SQLITE_FULL;
}
}
return SQLITE_OK;
}
#ifdef SQLITE_TEST
/*
** Count the number of fullsyncs and normal syncs. This is used to test
** that syncs and fullsyncs are occurring at the right times.
*/
int sqlite3_sync_count = 0;
int sqlite3_fullsync_count = 0;
#endif
/*
** We do not trust systems to provide a working fdatasync(). Some do.
** Others do no. To be safe, we will stick with the (slower) fsync().
** If you know that your system does support fdatasync() correctly,
** then simply compile with -Dfdatasync=fdatasync
*/
#if !defined(fdatasync) && !defined(__linux__)
# define fdatasync fsync
#endif
/*
** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not
** the F_FULLFSYNC macro is defined. F_FULLFSYNC is currently
** only available on Mac OS X. But that could change.
*/
#ifdef F_FULLFSYNC
# define HAVE_FULLFSYNC 1
#else
# define HAVE_FULLFSYNC 0
#endif
/*
** The fsync() system call does not work as advertised on many
** unix systems. The following procedure is an attempt to make
** it work better.
**
** The SQLITE_NO_SYNC macro disables all fsync()s. This is useful
** for testing when we want to run through the test suite quickly.
** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
** or power failure will likely corrupt the database file.
**
** SQLite sets the dataOnly flag if the size of the file is unchanged.
** The idea behind dataOnly is that it should only write the file content
** to disk, not the inode. We only set dataOnly if the file size is
** unchanged since the file size is part of the inode. However,
** Ted Ts'o tells us that fdatasync() will also write the inode if the
** file size has changed. The only real difference between fdatasync()
** and fsync(), Ted tells us, is that fdatasync() will not flush the
** inode if the mtime or owner or other inode attributes have changed.
** We only care about the file size, not the other file attributes, so
** as far as SQLite is concerned, an fdatasync() is always adequate.
** So, we always use fdatasync() if it is available, regardless of
** the value of the dataOnly flag.
*/
static int full_fsync(int fd, int fullSync, int dataOnly){
int rc;
/* The following "ifdef/elif/else/" block has the same structure as
** the one below. It is replicated here solely to avoid cluttering
** up the real code with the UNUSED_PARAMETER() macros.
*/
#ifdef SQLITE_NO_SYNC
UNUSED_PARAMETER(fd);
UNUSED_PARAMETER(fullSync);
UNUSED_PARAMETER(dataOnly);
#elif HAVE_FULLFSYNC
UNUSED_PARAMETER(dataOnly);
#else
UNUSED_PARAMETER(fullSync);
UNUSED_PARAMETER(dataOnly);
#endif
/* Record the number of times that we do a normal fsync() and
** FULLSYNC. This is used during testing to verify that this procedure
** gets called with the correct arguments.
*/
#ifdef SQLITE_TEST
if( fullSync ) sqlite3_fullsync_count++;
sqlite3_sync_count++;
#endif
/* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
** no-op
*/
#ifdef SQLITE_NO_SYNC
rc = SQLITE_OK;
#elif HAVE_FULLFSYNC
if( fullSync ){
rc = fcntl(fd, F_FULLFSYNC, 0);
}else{
rc = 1;
}
/* If the FULLFSYNC failed, fall back to attempting an fsync().
** It shouldn't be possible for fullfsync to fail on the local
** file system (on OSX), so failure indicates that FULLFSYNC
** isn't supported for this file system. So, attempt an fsync
** and (for now) ignore the overhead of a superfluous fcntl call.
** It'd be better to detect fullfsync support once and avoid
** the fcntl call every time sync is called.
*/
if( rc ) rc = fsync(fd);
#else
rc = fdatasync(fd);
#if OS_VXWORKS
if( rc==-1 && errno==ENOTSUP ){
rc = fsync(fd);
}
#endif /* OS_VXWORKS */
#endif /* ifdef SQLITE_NO_SYNC elif HAVE_FULLFSYNC */
if( OS_VXWORKS && rc!= -1 ){
rc = 0;
}
return rc;
}
/*
** Make sure all writes to a particular file are committed to disk.
**
** If dataOnly==0 then both the file itself and its metadata (file
** size, access time, etc) are synced. If dataOnly!=0 then only the
** file data is synced.
**
** Under Unix, also make sure that the directory entry for the file
** has been created by fsync-ing the directory that contains the file.
** If we do not do this and we encounter a power failure, the directory
** entry for the journal might not exist after we reboot. The next
** SQLite to access the file will not know that the journal exists (because
** the directory entry for the journal was never created) and the transaction
** will not roll back - possibly leading to database corruption.
*/
static int unixSync(sqlite3_file *id, int flags){
int rc;
unixFile *pFile = (unixFile*)id;
int isDataOnly = (flags&SQLITE_SYNC_DATAONLY);
int isFullsync = (flags&0x0F)==SQLITE_SYNC_FULL;
/* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
assert((flags&0x0F)==SQLITE_SYNC_NORMAL
|| (flags&0x0F)==SQLITE_SYNC_FULL
);
/* Unix cannot, but some systems may return SQLITE_FULL from here. This
** line is to test that doing so does not cause any problems.
*/
SimulateDiskfullError( return SQLITE_FULL );
assert( pFile );
OSTRACE2("SYNC %-3d\n", pFile->h);
rc = full_fsync(pFile->h, isFullsync, isDataOnly);
SimulateIOError( rc=1 );
if( rc ){
pFile->lastErrno = errno;
return SQLITE_IOERR_FSYNC;
}
if( pFile->dirfd>=0 ){
int err;
OSTRACE4("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd,
HAVE_FULLFSYNC, isFullsync);
#ifndef SQLITE_DISABLE_DIRSYNC
/* The directory sync is only attempted if full_fsync is
** turned off or unavailable. If a full_fsync occurred above,
** then the directory sync is superfluous.
*/
if( (!HAVE_FULLFSYNC || !isFullsync) && full_fsync(pFile->dirfd,0,0) ){
/*
** We have received multiple reports of fsync() returning
** errors when applied to directories on certain file systems.
** A failed directory sync is not a big deal. So it seems
** better to ignore the error. Ticket #1657
*/
/* pFile->lastErrno = errno; */
/* return SQLITE_IOERR; */
}
#endif
err = close(pFile->dirfd); /* Only need to sync once, so close the */
if( err==0 ){ /* directory when we are done */
pFile->dirfd = -1;
}else{
pFile->lastErrno = errno;
rc = SQLITE_IOERR_DIR_CLOSE;
}
}
return rc;
}
/*
** Truncate an open file to a specified size
*/
static int unixTruncate(sqlite3_file *id, i64 nByte){
int rc;
assert( id );
SimulateIOError( return SQLITE_IOERR_TRUNCATE );
rc = ftruncate(((unixFile*)id)->h, (off_t)nByte);
if( rc ){
((unixFile*)id)->lastErrno = errno;
return SQLITE_IOERR_TRUNCATE;
}else{
return SQLITE_OK;
}
}
/*
** Determine the current size of a file in bytes
*/
static int unixFileSize(sqlite3_file *id, i64 *pSize){
int rc;
struct stat buf;
assert( id );
rc = fstat(((unixFile*)id)->h, &buf);
SimulateIOError( rc=1 );
if( rc!=0 ){
((unixFile*)id)->lastErrno = errno;
return SQLITE_IOERR_FSTAT;
}
*pSize = buf.st_size;
/* When opening a zero-size database, the findLockInfo() procedure
** writes a single byte into that file in order to work around a bug
** in the OS-X msdos filesystem. In order to avoid problems with upper
** layers, we need to report this file size as zero even though it is
** really 1. Ticket #3260.
*/
if( *pSize==1 ) *pSize = 0;
return SQLITE_OK;
}
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
/*
** Handler for proxy-locking file-control verbs. Defined below in the
** proxying locking division.
*/
static int proxyFileControl(sqlite3_file*,int,void*);
#endif
/*
** Information and control of an open file handle.
*/
static int unixFileControl(sqlite3_file *id, int op, void *pArg){
switch( op ){
case SQLITE_FCNTL_LOCKSTATE: {
*(int*)pArg = ((unixFile*)id)->locktype;
return SQLITE_OK;
}
case SQLITE_LAST_ERRNO: {
*(int*)pArg = ((unixFile*)id)->lastErrno;
return SQLITE_OK;
}
#ifndef NDEBUG
/* The pager calls this method to signal that it has done
** a rollback and that the database is therefore unchanged and
** it hence it is OK for the transaction change counter to be
** unchanged.
*/
case SQLITE_FCNTL_DB_UNCHANGED: {
((unixFile*)id)->dbUpdate = 0;
return SQLITE_OK;
}
#endif
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
case SQLITE_SET_LOCKPROXYFILE:
case SQLITE_GET_LOCKPROXYFILE: {
return proxyFileControl(id,op,pArg);
}
#endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) */
}
return SQLITE_ERROR;
}
/*
** Return the sector size in bytes of the underlying block device for
** the specified file. This is almost always 512 bytes, but may be
** larger for some devices.
**
** SQLite code assumes this function cannot fail. It also assumes that
** if two files are created in the same file-system directory (i.e.
** a database and its journal file) that the sector size will be the
** same for both.
*/
static int unixSectorSize(sqlite3_file *NotUsed){
UNUSED_PARAMETER(NotUsed);
return SQLITE_DEFAULT_SECTOR_SIZE;
}
/*
** Return the device characteristics for the file. This is always 0 for unix.
*/
static int unixDeviceCharacteristics(sqlite3_file *NotUsed){
UNUSED_PARAMETER(NotUsed);
return 0;
}
/*
** Here ends the implementation of all sqlite3_file methods.
**
********************** End sqlite3_file Methods *******************************
******************************************************************************/
/*
** This division contains definitions of sqlite3_io_methods objects that
** implement various file locking strategies. It also contains definitions
** of "finder" functions. A finder-function is used to locate the appropriate
** sqlite3_io_methods object for a particular database file. The pAppData
** field of the sqlite3_vfs VFS objects are initialized to be pointers to
** the correct finder-function for that VFS.
**
** Most finder functions return a pointer to a fixed sqlite3_io_methods
** object. The only interesting finder-function is autolockIoFinder, which
** looks at the filesystem type and tries to guess the best locking
** strategy from that.
**
** For finder-funtion F, two objects are created:
**
** (1) The real finder-function named "FImpt()".
**
** (2) A constant pointer to this function named just "F".
**
**
** A pointer to the F pointer is used as the pAppData value for VFS
** objects. We have to do this instead of letting pAppData point
** directly at the finder-function since C90 rules prevent a void*
** from be cast into a function pointer.
**
**
** Each instance of this macro generates two objects:
**
** * A constant sqlite3_io_methods object call METHOD that has locking
** methods CLOSE, LOCK, UNLOCK, CKRESLOCK.
**
** * An I/O method finder function called FINDER that returns a pointer
** to the METHOD object in the previous bullet.
*/
#define IOMETHODS(FINDER, METHOD, CLOSE, LOCK, UNLOCK, CKLOCK) \
static const sqlite3_io_methods METHOD = { \
1, /* iVersion */ \
CLOSE, /* xClose */ \
unixRead, /* xRead */ \
unixWrite, /* xWrite */ \
unixTruncate, /* xTruncate */ \
unixSync, /* xSync */ \
unixFileSize, /* xFileSize */ \
LOCK, /* xLock */ \
UNLOCK, /* xUnlock */ \
CKLOCK, /* xCheckReservedLock */ \
unixFileControl, /* xFileControl */ \
unixSectorSize, /* xSectorSize */ \
unixDeviceCharacteristics /* xDeviceCapabilities */ \
}; \
static const sqlite3_io_methods *FINDER##Impl(const char *z, int h){ \
UNUSED_PARAMETER(z); UNUSED_PARAMETER(h); \
return &METHOD; \
} \
static const sqlite3_io_methods *(*const FINDER)(const char*,int) \
= FINDER##Impl;
/*
** Here are all of the sqlite3_io_methods objects for each of the
** locking strategies. Functions that return pointers to these methods
** are also created.
*/
IOMETHODS(
posixIoFinder, /* Finder function name */
posixIoMethods, /* sqlite3_io_methods object name */
unixClose, /* xClose method */
unixLock, /* xLock method */
unixUnlock, /* xUnlock method */
unixCheckReservedLock /* xCheckReservedLock method */
)
IOMETHODS(
nolockIoFinder, /* Finder function name */
nolockIoMethods, /* sqlite3_io_methods object name */
nolockClose, /* xClose method */
nolockLock, /* xLock method */
nolockUnlock, /* xUnlock method */
nolockCheckReservedLock /* xCheckReservedLock method */
)
IOMETHODS(
dotlockIoFinder, /* Finder function name */
dotlockIoMethods, /* sqlite3_io_methods object name */
dotlockClose, /* xClose method */
dotlockLock, /* xLock method */
dotlockUnlock, /* xUnlock method */
dotlockCheckReservedLock /* xCheckReservedLock method */
)
#if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS
IOMETHODS(
flockIoFinder, /* Finder function name */
flockIoMethods, /* sqlite3_io_methods object name */
flockClose, /* xClose method */
flockLock, /* xLock method */
flockUnlock, /* xUnlock method */
flockCheckReservedLock /* xCheckReservedLock method */
)
#endif
#if OS_VXWORKS
IOMETHODS(
semIoFinder, /* Finder function name */
semIoMethods, /* sqlite3_io_methods object name */
semClose, /* xClose method */
semLock, /* xLock method */
semUnlock, /* xUnlock method */
semCheckReservedLock /* xCheckReservedLock method */
)
#endif
#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
IOMETHODS(
afpIoFinder, /* Finder function name */
afpIoMethods, /* sqlite3_io_methods object name */
afpClose, /* xClose method */
afpLock, /* xLock method */
afpUnlock, /* xUnlock method */
afpCheckReservedLock /* xCheckReservedLock method */
)
#endif
/*
** The proxy locking method is a "super-method" in the sense that it
** opens secondary file descriptors for the conch and lock files and
** it uses proxy, dot-file, AFP, and flock() locking methods on those
** secondary files. For this reason, the division that implements
** proxy locking is located much further down in the file. But we need
** to go ahead and define the sqlite3_io_methods and finder function
** for proxy locking here. So we forward declare the I/O methods.
*/
#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
static int proxyClose(sqlite3_file*);
static int proxyLock(sqlite3_file*, int);
static int proxyUnlock(sqlite3_file*, int);
static int proxyCheckReservedLock(sqlite3_file*, int*);
IOMETHODS(
proxyIoFinder, /* Finder function name */
proxyIoMethods, /* sqlite3_io_methods object name */
proxyClose, /* xClose method */
proxyLock, /* xLock method */
proxyUnlock, /* xUnlock method */
proxyCheckReservedLock /* xCheckReservedLock method */
)
#endif
#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
/*
** This "finder" function attempts to determine the best locking strategy
** for the database file "filePath". It then returns the sqlite3_io_methods
** object that implements that strategy.
**
** This is for MacOSX only.
*/
static const sqlite3_io_methods *autolockIoFinderImpl(
const char *filePath, /* name of the database file */
int fd /* file descriptor open on the database file */
){
static const struct Mapping {
const char *zFilesystem; /* Filesystem type name */
const sqlite3_io_methods *pMethods; /* Appropriate locking method */
} aMap[] = {
{ "hfs", &posixIoMethods },
{ "ufs", &posixIoMethods },
{ "afpfs", &afpIoMethods },
#ifdef SQLITE_ENABLE_AFP_LOCKING_SMB
{ "smbfs", &afpIoMethods },
#else
{ "smbfs", &flockIoMethods },
#endif
{ "webdav", &nolockIoMethods },
{ 0, 0 }
};
int i;
struct statfs fsInfo;
struct flock lockInfo;
if( !filePath ){
/* If filePath==NULL that means we are dealing with a transient file
** that does not need to be locked. */
return &nolockIoMethods;
}
if( statfs(filePath, &fsInfo) != -1 ){
if( fsInfo.f_flags & MNT_RDONLY ){
return &nolockIoMethods;
}
for(i=0; aMap[i].zFilesystem; i++){
if( strcmp(fsInfo.f_fstypename, aMap[i].zFilesystem)==0 ){
return aMap[i].pMethods;
}
}
}
/* Default case. Handles, amongst others, "nfs".
** Test byte-range lock using fcntl(). If the call succeeds,
** assume that the file-system supports POSIX style locks.
*/
lockInfo.l_len = 1;
lockInfo.l_start = 0;
lockInfo.l_whence = SEEK_SET;
lockInfo.l_type = F_RDLCK;
if( fcntl(fd, F_GETLK, &lockInfo)!=-1 ) {
return &posixIoMethods;
}else{
return &dotlockIoMethods;
}
}
static const sqlite3_io_methods *(*const autolockIoFinder)(const char*,int)
= autolockIoFinderImpl;
#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
#if OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE
/*
** This "finder" function attempts to determine the best locking strategy
** for the database file "filePath". It then returns the sqlite3_io_methods
** object that implements that strategy.
**
** This is for VXWorks only.
*/
static const sqlite3_io_methods *autolockIoFinderImpl(
const char *filePath, /* name of the database file */
int fd /* file descriptor open on the database file */
){
struct flock lockInfo;
if( !filePath ){
/* If filePath==NULL that means we are dealing with a transient file
** that does not need to be locked. */
return &nolockIoMethods;
}
/* Test if fcntl() is supported and use POSIX style locks.
** Otherwise fall back to the named semaphore method.
*/
lockInfo.l_len = 1;
lockInfo.l_start = 0;
lockInfo.l_whence = SEEK_SET;
lockInfo.l_type = F_RDLCK;
if( fcntl(fd, F_GETLK, &lockInfo)!=-1 ) {
return &posixIoMethods;
}else{
return &semIoMethods;
}
}
static const sqlite3_io_methods *(*const autolockIoFinder)(const char*,int)
= autolockIoFinderImpl;
#endif /* OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE */
/*
** An abstract type for a pointer to a IO method finder function:
*/
typedef const sqlite3_io_methods *(*finder_type)(const char*,int);
/****************************************************************************
**************************** sqlite3_vfs methods ****************************
**
** This division contains the implementation of methods on the
** sqlite3_vfs object.
*/
/*
** Initialize the contents of the unixFile structure pointed to by pId.
*/
static int fillInUnixFile(
sqlite3_vfs *pVfs, /* Pointer to vfs object */
int h, /* Open file descriptor of file being opened */
int dirfd, /* Directory file descriptor */
sqlite3_file *pId, /* Write to the unixFile structure here */
const char *zFilename, /* Name of the file being opened */
int noLock, /* Omit locking if true */
int isDelete /* Delete on close if true */
){
const sqlite3_io_methods *pLockingStyle;
unixFile *pNew = (unixFile *)pId;
int rc = SQLITE_OK;
assert( pNew->pLock==NULL );
assert( pNew->pOpen==NULL );
/* Parameter isDelete is only used on vxworks. Express this explicitly
** here to prevent compiler warnings about unused parameters.
*/
UNUSED_PARAMETER(isDelete);
OSTRACE3("OPEN %-3d %s\n", h, zFilename);
pNew->h = h;
pNew->dirfd = dirfd;
SET_THREADID(pNew);
#if OS_VXWORKS
pNew->pId = vxworksFindFileId(zFilename);
if( pNew->pId==0 ){
noLock = 1;
rc = SQLITE_NOMEM;
}
#endif
if( noLock ){
pLockingStyle = &nolockIoMethods;
}else{
pLockingStyle = (**(finder_type*)pVfs->pAppData)(zFilename, h);
#if SQLITE_ENABLE_LOCKING_STYLE
/* Cache zFilename in the locking context (AFP and dotlock override) for
** proxyLock activation is possible (remote proxy is based on db name)
** zFilename remains valid until file is closed, to support */
pNew->lockingContext = (void*)zFilename;
#endif
}
if( pLockingStyle == &posixIoMethods ){
unixEnterMutex();
rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen);
if( rc!=SQLITE_OK ){
/* If an error occured in findLockInfo(), close the file descriptor
** immediately, before releasing the mutex. findLockInfo() may fail
** in two scenarios:
**
** (a) A call to fstat() failed.
** (b) A malloc failed.
**
** Scenario (b) may only occur if the process is holding no other
** file descriptors open on the same file. If there were other file
** descriptors on this file, then no malloc would be required by
** findLockInfo(). If this is the case, it is quite safe to close
** handle h - as it is guaranteed that no posix locks will be released
** by doing so.
**
** If scenario (a) caused the error then things are not so safe. The
** implicit assumption here is that if fstat() fails, things are in
** such bad shape that dropping a lock or two doesn't matter much.
*/
close(h);
h = -1;
}
unixLeaveMutex();
}
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
else if( pLockingStyle == &afpIoMethods ){
/* AFP locking uses the file path so it needs to be included in
** the afpLockingContext.
*/
afpLockingContext *pCtx;
pNew->lockingContext = pCtx = sqlite3_malloc( sizeof(*pCtx) );
if( pCtx==0 ){
rc = SQLITE_NOMEM;
}else{
/* NB: zFilename exists and remains valid until the file is closed
** according to requirement F11141. So we do not need to make a
** copy of the filename. */
pCtx->dbPath = zFilename;
srandomdev();
unixEnterMutex();
rc = findLockInfo(pNew, NULL, &pNew->pOpen);
unixLeaveMutex();
}
}
#endif
else if( pLockingStyle == &dotlockIoMethods ){
/* Dotfile locking uses the file path so it needs to be included in
** the dotlockLockingContext
*/
char *zLockFile;
int nFilename;
nFilename = (int)strlen(zFilename) + 6;
zLockFile = (char *)sqlite3_malloc(nFilename);
if( zLockFile==0 ){
rc = SQLITE_NOMEM;
}else{
sqlite3_snprintf(nFilename, zLockFile, "%s" DOTLOCK_SUFFIX, zFilename);
}
pNew->lockingContext = zLockFile;
}
#if OS_VXWORKS
else if( pLockingStyle == &semIoMethods ){
/* Named semaphore locking uses the file path so it needs to be
** included in the semLockingContext
*/
unixEnterMutex();
rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen);
if( (rc==SQLITE_OK) && (pNew->pOpen->pSem==NULL) ){
char *zSemName = pNew->pOpen->aSemName;
int n;
sqlite3_snprintf(MAX_PATHNAME, zSemName, "%s.sem",
pNew->pId->zCanonicalName);
for( n=0; zSemName[n]; n++ )
if( zSemName[n]=='/' ) zSemName[n] = '_';
pNew->pOpen->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
if( pNew->pOpen->pSem == SEM_FAILED ){
rc = SQLITE_NOMEM;
pNew->pOpen->aSemName[0] = '\0';
}
}
unixLeaveMutex();
}
#endif
pNew->lastErrno = 0;
#if OS_VXWORKS
if( rc!=SQLITE_OK ){
unlink(zFilename);
isDelete = 0;
}
pNew->isDelete = isDelete;
#endif
if( rc!=SQLITE_OK ){
if( dirfd>=0 ) close(dirfd); /* silent leak if fail, already in error */
if( h>=0 ) close(h);
}else{
pNew->pMethod = pLockingStyle;
OpenCounter(+1);
}
return rc;
}
/*
** Open a file descriptor to the directory containing file zFilename.
** If successful, *pFd is set to the opened file descriptor and
** SQLITE_OK is returned. If an error occurs, either SQLITE_NOMEM
** or SQLITE_CANTOPEN is returned and *pFd is set to an undefined
** value.
**
** If SQLITE_OK is returned, the caller is responsible for closing
** the file descriptor *pFd using close().
*/
static int openDirectory(const char *zFilename, int *pFd){
int ii;
int fd = -1;
char zDirname[MAX_PATHNAME+1];
sqlite3_snprintf(MAX_PATHNAME, zDirname, "%s", zFilename);
for(ii=(int)strlen(zDirname); ii>1 && zDirname[ii]!='/'; ii--);
if( ii>0 ){
zDirname[ii] = '\0';
fd = open(zDirname, O_RDONLY|O_BINARY, 0);
if( fd>=0 ){
#ifdef FD_CLOEXEC
fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
#endif
OSTRACE3("OPENDIR %-3d %s\n", fd, zDirname);
}
}
*pFd = fd;
return (fd>=0?SQLITE_OK:SQLITE_CANTOPEN);
}
/*
** Create a temporary file name in zBuf. zBuf must be allocated
** by the calling process and must be big enough to hold at least
** pVfs->mxPathname bytes.
*/
static int getTempname(int nBuf, char *zBuf){
static const char *azDirs[] = {
0,
0,
"/var/tmp",
"/usr/tmp",
"/tmp",
".",
};
static const unsigned char zChars[] =
"abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"0123456789";
unsigned int i, j;
struct stat buf;
const char *zDir = ".";
/* It's odd to simulate an io-error here, but really this is just
** using the io-error infrastructure to test that SQLite handles this
** function failing.
*/
SimulateIOError( return SQLITE_IOERR );
azDirs[0] = sqlite3_temp_directory;
if (NULL == azDirs[1]) {
azDirs[1] = getenv("TMPDIR");
}
for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++){
if( azDirs[i]==0 ) continue;
if( stat(azDirs[i], &buf) ) continue;
if( !S_ISDIR(buf.st_mode) ) continue;
if( access(azDirs[i], 07) ) continue;
zDir = azDirs[i];
break;
}
/* Check that the output buffer is large enough for the temporary file
** name. If it is not, return SQLITE_ERROR.
*/
if( (strlen(zDir) + strlen(SQLITE_TEMP_FILE_PREFIX) + 17) >= (size_t)nBuf ){
return SQLITE_ERROR;
}
do{
sqlite3_snprintf(nBuf-17, zBuf, "%s/"SQLITE_TEMP_FILE_PREFIX, zDir);
j = (int)strlen(zBuf);
sqlite3_randomness(15, &zBuf[j]);
for(i=0; i<15; i++, j++){
zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
}
zBuf[j] = 0;
}while( access(zBuf,0)==0 );
return SQLITE_OK;
}
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
/*
** Routine to transform a unixFile into a proxy-locking unixFile.
** Implementation in the proxy-lock division, but used by unixOpen()
** if SQLITE_PREFER_PROXY_LOCKING is defined.
*/
static int proxyTransformUnixFile(unixFile*, const char*);
#endif
/*
** Search for an unused file descriptor that was opened on the database
** file (not a journal or master-journal file) identified by pathname
** zPath with SQLITE_OPEN_XXX flags matching those passed as the second
** argument to this function.
**
** Such a file descriptor may exist if a database connection was closed
** but the associated file descriptor could not be closed because some
** other file descriptor open on the same file is holding a file-lock.
** Refer to comments in the unixClose() function and the lengthy comment
** describing "Posix Advisory Locking" at the start of this file for
** further details. Also, ticket #4018.
**
** If a suitable file descriptor is found, then it is returned. If no
** such file descriptor is located, -1 is returned.
*/
static UnixUnusedFd *findReusableFd(const char *zPath, int flags){
UnixUnusedFd *pUnused = 0;
/* Do not search for an unused file descriptor on vxworks. Not because
** vxworks would not benefit from the change (it might, we're not sure),
** but because no way to test it is currently available. It is better
** not to risk breaking vxworks support for the sake of such an obscure
** feature. */
#if !OS_VXWORKS
struct stat sStat; /* Results of stat() call */
/* A stat() call may fail for various reasons. If this happens, it is
** almost certain that an open() call on the same path will also fail.
** For this reason, if an error occurs in the stat() call here, it is
** ignored and -1 is returned. The caller will try to open a new file
** descriptor on the same path, fail, and return an error to SQLite.
**
** Even if a subsequent open() call does succeed, the consequences of
** not searching for a resusable file descriptor are not dire. */
if( 0==stat(zPath, &sStat) ){
struct unixOpenCnt *pO;
struct unixFileId id;
id.dev = sStat.st_dev;
id.ino = sStat.st_ino;
unixEnterMutex();
for(pO=openList; pO && memcmp(&id, &pO->fileId, sizeof(id)); pO=pO->pNext);
if( pO ){
UnixUnusedFd **pp;
for(pp=&pO->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
pUnused = *pp;
if( pUnused ){
*pp = pUnused->pNext;
}
}
unixLeaveMutex();
}
#endif /* if !OS_VXWORKS */
return pUnused;
}
/*
** Open the file zPath.
**
** Previously, the SQLite OS layer used three functions in place of this
** one:
**
** sqlite3OsOpenReadWrite();
** sqlite3OsOpenReadOnly();
** sqlite3OsOpenExclusive();
**
** These calls correspond to the following combinations of flags:
**
** ReadWrite() -> (READWRITE | CREATE)
** ReadOnly() -> (READONLY)
** OpenExclusive() -> (READWRITE | CREATE | EXCLUSIVE)
**
** The old OpenExclusive() accepted a boolean argument - "delFlag". If
** true, the file was configured to be automatically deleted when the
** file handle closed. To achieve the same effect using this new
** interface, add the DELETEONCLOSE flag to those specified above for
** OpenExclusive().
*/
static int unixOpen(
sqlite3_vfs *pVfs, /* The VFS for which this is the xOpen method */
const char *zPath, /* Pathname of file to be opened */
sqlite3_file *pFile, /* The file descriptor to be filled in */
int flags, /* Input flags to control the opening */
int *pOutFlags /* Output flags returned to SQLite core */
){
unixFile *p = (unixFile *)pFile;
int fd = -1; /* File descriptor returned by open() */
int dirfd = -1; /* Directory file descriptor */
int openFlags = 0; /* Flags to pass to open() */
int eType = flags&0xFFFFFF00; /* Type of file to open */
int noLock; /* True to omit locking primitives */
int rc = SQLITE_OK; /* Function Return Code */
int isExclusive = (flags & SQLITE_OPEN_EXCLUSIVE);
int isDelete = (flags & SQLITE_OPEN_DELETEONCLOSE);
int isCreate = (flags & SQLITE_OPEN_CREATE);
int isReadonly = (flags & SQLITE_OPEN_READONLY);
int isReadWrite = (flags & SQLITE_OPEN_READWRITE);
/* If creating a master or main-file journal, this function will open
** a file-descriptor on the directory too. The first time unixSync()
** is called the directory file descriptor will be fsync()ed and close()d.
*/
int isOpenDirectory = (isCreate &&
(eType==SQLITE_OPEN_MASTER_JOURNAL || eType==SQLITE_OPEN_MAIN_JOURNAL)
);
/* If argument zPath is a NULL pointer, this function is required to open
** a temporary file. Use this buffer to store the file name in.
*/
char zTmpname[MAX_PATHNAME+1];
const char *zName = zPath;
/* Check the following statements are true:
**
** (a) Exactly one of the READWRITE and READONLY flags must be set, and
** (b) if CREATE is set, then READWRITE must also be set, and
** (c) if EXCLUSIVE is set, then CREATE must also be set.
** (d) if DELETEONCLOSE is set, then CREATE must also be set.
*/
assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
assert(isCreate==0 || isReadWrite);
assert(isExclusive==0 || isCreate);
assert(isDelete==0 || isCreate);
/* The main DB, main journal, and master journal are never automatically
** deleted. Nor are they ever temporary files. */
assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL );
/* Assert that the upper layer has set one of the "file-type" flags. */
assert( eType==SQLITE_OPEN_MAIN_DB || eType==SQLITE_OPEN_TEMP_DB
|| eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL
|| eType==SQLITE_OPEN_SUBJOURNAL || eType==SQLITE_OPEN_MASTER_JOURNAL
|| eType==SQLITE_OPEN_TRANSIENT_DB
);
memset(p, 0, sizeof(unixFile));
if( eType==SQLITE_OPEN_MAIN_DB ){
UnixUnusedFd *pUnused;
pUnused = findReusableFd(zName, flags);
if( pUnused ){
fd = pUnused->fd;
}else{
pUnused = sqlite3_malloc(sizeof(*pUnused));
if( !pUnused ){
return SQLITE_NOMEM;
}
}
p->pUnused = pUnused;
}else if( !zName ){
/* If zName is NULL, the upper layer is requesting a temp file. */
assert(isDelete && !isOpenDirectory);
rc = getTempname(MAX_PATHNAME+1, zTmpname);
if( rc!=SQLITE_OK ){
return rc;
}
zName = zTmpname;
}
/* Determine the value of the flags parameter passed to POSIX function
** open(). These must be calculated even if open() is not called, as
** they may be stored as part of the file handle and used by the
** 'conch file' locking functions later on. */
if( isReadonly ) openFlags |= O_RDONLY;
if( isReadWrite ) openFlags |= O_RDWR;
if( isCreate ) openFlags |= O_CREAT;
if( isExclusive ) openFlags |= (O_EXCL|O_NOFOLLOW);
openFlags |= (O_LARGEFILE|O_BINARY);
if( fd<0 ){
mode_t openMode = (isDelete?0600:SQLITE_DEFAULT_FILE_PERMISSIONS);
fd = open(zName, openFlags, openMode);
OSTRACE4("OPENX %-3d %s 0%o\n", fd, zName, openFlags);
if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){
/* Failed to open the file for read/write access. Try read-only. */
flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
openFlags &= ~(O_RDWR|O_CREAT);
flags |= SQLITE_OPEN_READONLY;
openFlags |= O_RDONLY;
fd = open(zName, openFlags, openMode);
}
if( fd<0 ){
rc = SQLITE_CANTOPEN;
goto open_finished;
}
}
assert( fd>=0 );
if( pOutFlags ){
*pOutFlags = flags;
}
if( p->pUnused ){
p->pUnused->fd = fd;
p->pUnused->flags = flags;
}
if( isDelete ){
#if OS_VXWORKS
zPath = zName;
#else
unlink(zName);
#endif
}
#if SQLITE_ENABLE_LOCKING_STYLE
else{
p->openFlags = openFlags;
}
#endif
if( isOpenDirectory ){
rc = openDirectory(zPath, &dirfd);
if( rc!=SQLITE_OK ){
/* It is safe to close fd at this point, because it is guaranteed not
** to be open on a database file. If it were open on a database file,
** it would not be safe to close as this would release any locks held
** on the file by this process. */
assert( eType!=SQLITE_OPEN_MAIN_DB );
close(fd); /* silently leak if fail, already in error */
goto open_finished;
}
}
#ifdef FD_CLOEXEC
fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
#endif
noLock = eType!=SQLITE_OPEN_MAIN_DB;
#if SQLITE_PREFER_PROXY_LOCKING
if( zPath!=NULL && !noLock && pVfs->xOpen ){
char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
int useProxy = 0;
/* SQLITE_FORCE_PROXY_LOCKING==1 means force always use proxy, 0 means
** never use proxy, NULL means use proxy for non-local files only. */
if( envforce!=NULL ){
useProxy = atoi(envforce)>0;
}else{
struct statfs fsInfo;
if( statfs(zPath, &fsInfo) == -1 ){
/* In theory, the close(fd) call is sub-optimal. If the file opened
** with fd is a database file, and there are other connections open
** on that file that are currently holding advisory locks on it,
** then the call to close() will cancel those locks. In practice,
** we're assuming that statfs() doesn't fail very often. At least
** not while other file descriptors opened by the same process on
** the same file are working. */
p->lastErrno = errno;
if( dirfd>=0 ){
close(dirfd); /* silently leak if fail, in error */
}
close(fd); /* silently leak if fail, in error */
rc = SQLITE_IOERR_ACCESS;
goto open_finished;
}
useProxy = !(fsInfo.f_flags&MNT_LOCAL);
}
if( useProxy ){
rc = fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete);
if( rc==SQLITE_OK ){
rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:");
}
goto open_finished;
}
}
#endif
rc = fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete);
open_finished:
if( rc!=SQLITE_OK ){
sqlite3_free(p->pUnused);
}
return rc;
}
/*
** Delete the file at zPath. If the dirSync argument is true, fsync()
** the directory after deleting the file.
*/
static int unixDelete(
sqlite3_vfs *NotUsed, /* VFS containing this as the xDelete method */
const char *zPath, /* Name of file to be deleted */
int dirSync /* If true, fsync() directory after deleting file */
){
int rc = SQLITE_OK;
UNUSED_PARAMETER(NotUsed);
SimulateIOError(return SQLITE_IOERR_DELETE);
unlink(zPath);
#ifndef SQLITE_DISABLE_DIRSYNC
if( dirSync ){
int fd;
rc = openDirectory(zPath, &fd);
if( rc==SQLITE_OK ){
#if OS_VXWORKS
if( fsync(fd)==-1 )
#else
if( fsync(fd) )
#endif
{
rc = SQLITE_IOERR_DIR_FSYNC;
}
if( close(fd)&&!rc ){
rc = SQLITE_IOERR_DIR_CLOSE;
}
}
}
#endif
return rc;
}
/*
** Test the existance of or access permissions of file zPath. The
** test performed depends on the value of flags:
**
** SQLITE_ACCESS_EXISTS: Return 1 if the file exists
** SQLITE_ACCESS_READWRITE: Return 1 if the file is read and writable.
** SQLITE_ACCESS_READONLY: Return 1 if the file is readable.
**
** Otherwise return 0.
*/
static int unixAccess(
sqlite3_vfs *NotUsed, /* The VFS containing this xAccess method */
const char *zPath, /* Path of the file to examine */
int flags, /* What do we want to learn about the zPath file? */
int *pResOut /* Write result boolean here */
){
int amode = 0;
UNUSED_PARAMETER(NotUsed);
SimulateIOError( return SQLITE_IOERR_ACCESS; );
switch( flags ){
case SQLITE_ACCESS_EXISTS:
amode = F_OK;
break;
case SQLITE_ACCESS_READWRITE:
amode = W_OK|R_OK;
break;
case SQLITE_ACCESS_READ:
amode = R_OK;
break;
default:
assert(!"Invalid flags argument");
}
*pResOut = (access(zPath, amode)==0);
return SQLITE_OK;
}
/*
** Turn a relative pathname into a full pathname. The relative path
** is stored as a nul-terminated string in the buffer pointed to by
** zPath.
**
** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes
** (in this case, MAX_PATHNAME bytes). The full-path is written to
** this buffer before returning.
*/
static int unixFullPathname(
sqlite3_vfs *pVfs, /* Pointer to vfs object */
const char *zPath, /* Possibly relative input path */
int nOut, /* Size of output buffer in bytes */
char *zOut /* Output buffer */
){
/* It's odd to simulate an io-error here, but really this is just
** using the io-error infrastructure to test that SQLite handles this
** function failing. This function could fail if, for example, the
** current working directory has been unlinked.
*/
SimulateIOError( return SQLITE_ERROR );
assert( pVfs->mxPathname==MAX_PATHNAME );
UNUSED_PARAMETER(pVfs);
zOut[nOut-1] = '\0';
if( zPath[0]=='/' ){
sqlite3_snprintf(nOut, zOut, "%s", zPath);
}else{
int nCwd;
if( getcwd(zOut, nOut-1)==0 ){
return SQLITE_CANTOPEN;
}
nCwd = (int)strlen(zOut);
sqlite3_snprintf(nOut-nCwd, &zOut[nCwd], "/%s", zPath);
}
return SQLITE_OK;
}
#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Interfaces for opening a shared library, finding entry points
** within the shared library, and closing the shared library.
*/
#include <dlfcn.h>
static void *unixDlOpen(sqlite3_vfs *NotUsed, const char *zFilename){
UNUSED_PARAMETER(NotUsed);
return dlopen(zFilename, RTLD_NOW | RTLD_GLOBAL);
}
/*
** SQLite calls this function immediately after a call to unixDlSym() or
** unixDlOpen() fails (returns a null pointer). If a more detailed error
** message is available, it is written to zBufOut. If no error message
** is available, zBufOut is left unmodified and SQLite uses a default
** error message.
*/
static void unixDlError(sqlite3_vfs *NotUsed, int nBuf, char *zBufOut){
char *zErr;
UNUSED_PARAMETER(NotUsed);
unixEnterMutex();
zErr = dlerror();
if( zErr ){
sqlite3_snprintf(nBuf, zBufOut, "%s", zErr);
}
unixLeaveMutex();
}
static void (*unixDlSym(sqlite3_vfs *NotUsed, void *p, const char*zSym))(void){
/*
** GCC with -pedantic-errors says that C90 does not allow a void* to be
** cast into a pointer to a function. And yet the library dlsym() routine
** returns a void* which is really a pointer to a function. So how do we
** use dlsym() with -pedantic-errors?
**
** Variable x below is defined to be a pointer to a function taking
** parameters void* and const char* and returning a pointer to a function.
** We initialize x by assigning it a pointer to the dlsym() function.
** (That assignment requires a cast.) Then we call the function that
** x points to.
**
** This work-around is unlikely to work correctly on any system where
** you really cannot cast a function pointer into void*. But then, on the
** other hand, dlsym() will not work on such a system either, so we have
** not really lost anything.
*/
void (*(*x)(void*,const char*))(void);
UNUSED_PARAMETER(NotUsed);
x = (void(*(*)(void*,const char*))(void))dlsym;
return (*x)(p, zSym);
}
static void unixDlClose(sqlite3_vfs *NotUsed, void *pHandle){
UNUSED_PARAMETER(NotUsed);
dlclose(pHandle);
}
#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
#define unixDlOpen 0
#define unixDlError 0
#define unixDlSym 0
#define unixDlClose 0
#endif
/*
** Write nBuf bytes of random data to the supplied buffer zBuf.
*/
static int unixRandomness(sqlite3_vfs *NotUsed, int nBuf, char *zBuf){
UNUSED_PARAMETER(NotUsed);
assert((size_t)nBuf>=(sizeof(time_t)+sizeof(int)));
/* We have to initialize zBuf to prevent valgrind from reporting
** errors. The reports issued by valgrind are incorrect - we would
** prefer that the randomness be increased by making use of the
** uninitialized space in zBuf - but valgrind errors tend to worry
** some users. Rather than argue, it seems easier just to initialize
** the whole array and silence valgrind, even if that means less randomness
** in the random seed.
**
** When testing, initializing zBuf[] to zero is all we do. That means
** that we always use the same random number sequence. This makes the
** tests repeatable.
*/
memset(zBuf, 0, nBuf);
#if !defined(SQLITE_TEST)
{
int pid, fd;
fd = open("/dev/urandom", O_RDONLY);
if( fd<0 ){
time_t t;
time(&t);
memcpy(zBuf, &t, sizeof(t));
pid = getpid();
memcpy(&zBuf[sizeof(t)], &pid, sizeof(pid));
assert( sizeof(t)+sizeof(pid)<=(size_t)nBuf );
nBuf = sizeof(t) + sizeof(pid);
}else{
nBuf = read(fd, zBuf, nBuf);
close(fd);
}
}
#endif
return nBuf;
}
/*
** Sleep for a little while. Return the amount of time slept.
** The argument is the number of microseconds we want to sleep.
** The return value is the number of microseconds of sleep actually
** requested from the underlying operating system, a number which
** might be greater than or equal to the argument, but not less
** than the argument.
*/
static int unixSleep(sqlite3_vfs *NotUsed, int microseconds){
#if OS_VXWORKS
struct timespec sp;
sp.tv_sec = microseconds / 1000000;
sp.tv_nsec = (microseconds % 1000000) * 1000;
nanosleep(&sp, NULL);
UNUSED_PARAMETER(NotUsed);
return microseconds;
#elif defined(HAVE_USLEEP) && HAVE_USLEEP
usleep(microseconds);
UNUSED_PARAMETER(NotUsed);
return microseconds;
#else
int seconds = (microseconds+999999)/1000000;
sleep(seconds);
UNUSED_PARAMETER(NotUsed);
return seconds*1000000;
#endif
}
/*
** The following variable, if set to a non-zero value, is interpreted as
** the number of seconds since 1970 and is used to set the result of
** sqlite3OsCurrentTime() during testing.
*/
#ifdef SQLITE_TEST
int sqlite3_current_time = 0; /* Fake system time in seconds since 1970. */
#endif
/*
** Find the current time (in Universal Coordinated Time). Write the
** current time and date as a Julian Day number into *prNow and
** return 0. Return 1 if the time and date cannot be found.
*/
static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){
#if defined(SQLITE_OMIT_FLOATING_POINT)
time_t t;
time(&t);
*prNow = (((sqlite3_int64)t)/8640 + 24405875)/10;
#elif defined(NO_GETTOD)
time_t t;
time(&t);
*prNow = t/86400.0 + 2440587.5;
#elif OS_VXWORKS
struct timespec sNow;
clock_gettime(CLOCK_REALTIME, &sNow);
*prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_nsec/86400000000000.0;
#else
struct timeval sNow;
gettimeofday(&sNow, 0);
*prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_usec/86400000000.0;
#endif
#ifdef SQLITE_TEST
if( sqlite3_current_time ){
*prNow = sqlite3_current_time/86400.0 + 2440587.5;
}
#endif
UNUSED_PARAMETER(NotUsed);
return 0;
}
/*
** We added the xGetLastError() method with the intention of providing
** better low-level error messages when operating-system problems come up
** during SQLite operation. But so far, none of that has been implemented
** in the core. So this routine is never called. For now, it is merely
** a place-holder.
*/
static int unixGetLastError(sqlite3_vfs *NotUsed, int NotUsed2, char *NotUsed3){
UNUSED_PARAMETER(NotUsed);
UNUSED_PARAMETER(NotUsed2);
UNUSED_PARAMETER(NotUsed3);
return 0;
}
/*
************************ End of sqlite3_vfs methods ***************************
******************************************************************************/
/******************************************************************************
************************** Begin Proxy Locking ********************************
**
** Proxy locking is a "uber-locking-method" in this sense: It uses the
** other locking methods on secondary lock files. Proxy locking is a
** meta-layer over top of the primitive locking implemented above. For
** this reason, the division that implements of proxy locking is deferred
** until late in the file (here) after all of the other I/O methods have
** been defined - so that the primitive locking methods are available
** as services to help with the implementation of proxy locking.
**
****
**
** The default locking schemes in SQLite use byte-range locks on the
** database file to coordinate safe, concurrent access by multiple readers
** and writers [http://sqlite.org/lockingv3.html]. The five file locking
** states (UNLOCKED, PENDING, SHARED, RESERVED, EXCLUSIVE) are implemented
** as POSIX read & write locks over fixed set of locations (via fsctl),
** on AFP and SMB only exclusive byte-range locks are available via fsctl
** with _IOWR('z', 23, struct ByteRangeLockPB2) to track the same 5 states.
** To simulate a F_RDLCK on the shared range, on AFP a randomly selected
** address in the shared range is taken for a SHARED lock, the entire
** shared range is taken for an EXCLUSIVE lock):
**
** PENDING_BYTE 0x40000000
** RESERVED_BYTE 0x40000001
** SHARED_RANGE 0x40000002 -> 0x40000200
**
** This works well on the local file system, but shows a nearly 100x
** slowdown in read performance on AFP because the AFP client disables
** the read cache when byte-range locks are present. Enabling the read
** cache exposes a cache coherency problem that is present on all OS X
** supported network file systems. NFS and AFP both observe the
** close-to-open semantics for ensuring cache coherency
** [http://nfs.sourceforge.net/#faq_a8], which does not effectively
** address the requirements for concurrent database access by multiple
** readers and writers
** [http://www.nabble.com/SQLite-on-NFS-cache-coherency-td15655701.html].
**
** To address the performance and cache coherency issues, proxy file locking
** changes the way database access is controlled by limiting access to a
** single host at a time and moving file locks off of the database file
** and onto a proxy file on the local file system.
**
**
** Using proxy locks
** -----------------
**
** C APIs
**
** sqlite3_file_control(db, dbname, SQLITE_SET_LOCKPROXYFILE,
** <proxy_path> | ":auto:");
** sqlite3_file_control(db, dbname, SQLITE_GET_LOCKPROXYFILE, &<proxy_path>);
**
**
** SQL pragmas
**
** PRAGMA [database.]lock_proxy_file=<proxy_path> | :auto:
** PRAGMA [database.]lock_proxy_file
**
** Specifying ":auto:" means that if there is a conch file with a matching
** host ID in it, the proxy path in the conch file will be used, otherwise
** a proxy path based on the user's temp dir
** (via confstr(_CS_DARWIN_USER_TEMP_DIR,...)) will be used and the
** actual proxy file name is generated from the name and path of the
** database file. For example:
**
** For database path "/Users/me/foo.db"
** The lock path will be "<tmpdir>/sqliteplocks/_Users_me_foo.db:auto:")
**
** Once a lock proxy is configured for a database connection, it can not
** be removed, however it may be switched to a different proxy path via
** the above APIs (assuming the conch file is not being held by another
** connection or process).
**
**
** How proxy locking works
** -----------------------
**
** Proxy file locking relies primarily on two new supporting files:
**
** * conch file to limit access to the database file to a single host
** at a time
**
** * proxy file to act as a proxy for the advisory locks normally
** taken on the database
**
** The conch file - to use a proxy file, sqlite must first "hold the conch"
** by taking an sqlite-style shared lock on the conch file, reading the
** contents and comparing the host's unique host ID (see below) and lock
** proxy path against the values stored in the conch. The conch file is
** stored in the same directory as the database file and the file name
** is patterned after the database file name as ".<databasename>-conch".
** If the conch file does not exist, or it's contents do not match the
** host ID and/or proxy path, then the lock is escalated to an exclusive
** lock and the conch file contents is updated with the host ID and proxy
** path and the lock is downgraded to a shared lock again. If the conch
** is held by another process (with a shared lock), the exclusive lock
** will fail and SQLITE_BUSY is returned.
**
** The proxy file - a single-byte file used for all advisory file locks
** normally taken on the database file. This allows for safe sharing
** of the database file for multiple readers and writers on the same
** host (the conch ensures that they all use the same local lock file).
**
** There is a third file - the host ID file - used as a persistent record
** of a unique identifier for the host, a 128-byte unique host id file
** in the path defined by the HOSTIDPATH macro (default value is
** /Library/Caches/.com.apple.sqliteConchHostId).
**
** Requesting the lock proxy does not immediately take the conch, it is
** only taken when the first request to lock database file is made.
** This matches the semantics of the traditional locking behavior, where
** opening a connection to a database file does not take a lock on it.
** The shared lock and an open file descriptor are maintained until
** the connection to the database is closed.
**
** The proxy file and the lock file are never deleted so they only need
** to be created the first time they are used.
**
** Configuration options
** ---------------------
**
** SQLITE_PREFER_PROXY_LOCKING
**
** Database files accessed on non-local file systems are
** automatically configured for proxy locking, lock files are
** named automatically using the same logic as
** PRAGMA lock_proxy_file=":auto:"
**
** SQLITE_PROXY_DEBUG
**
** Enables the logging of error messages during host id file
** retrieval and creation
**
** HOSTIDPATH
**
** Overrides the default host ID file path location
**
** LOCKPROXYDIR
**
** Overrides the default directory used for lock proxy files that
** are named automatically via the ":auto:" setting
**
** SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
**
** Permissions to use when creating a directory for storing the
** lock proxy files, only used when LOCKPROXYDIR is not set.
**
**
** As mentioned above, when compiled with SQLITE_PREFER_PROXY_LOCKING,
** setting the environment variable SQLITE_FORCE_PROXY_LOCKING to 1 will
** force proxy locking to be used for every database file opened, and 0
** will force automatic proxy locking to be disabled for all database
** files (explicity calling the SQLITE_SET_LOCKPROXYFILE pragma or
** sqlite_file_control API is not affected by SQLITE_FORCE_PROXY_LOCKING).
*/
/*
** Proxy locking is only available on MacOSX
*/
#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
#ifdef SQLITE_TEST
/* simulate multiple hosts by creating unique hostid file paths */
int sqlite3_hostid_num = 0;
#endif
/*
** The proxyLockingContext has the path and file structures for the remote
** and local proxy files in it
*/
typedef struct proxyLockingContext proxyLockingContext;
struct proxyLockingContext {
unixFile *conchFile; /* Open conch file */
char *conchFilePath; /* Name of the conch file */
unixFile *lockProxy; /* Open proxy lock file */
char *lockProxyPath; /* Name of the proxy lock file */
char *dbPath; /* Name of the open file */
int conchHeld; /* True if the conch is currently held */
void *oldLockingContext; /* Original lockingcontext to restore on close */
sqlite3_io_methods const *pOldMethod; /* Original I/O methods for close */
};
/* HOSTIDLEN and CONCHLEN both include space for the string
** terminating nul
*/
#define HOSTIDLEN 128
#define CONCHLEN (MAXPATHLEN+HOSTIDLEN+1)
#ifndef HOSTIDPATH
# define HOSTIDPATH "/Library/Caches/.com.apple.sqliteConchHostId"
#endif
/* basically a copy of unixRandomness with different
** test behavior built in */
static int proxyGenerateHostID(char *pHostID){
int pid, fd, len;
unsigned char *key = (unsigned char *)pHostID;
memset(key, 0, HOSTIDLEN);
len = 0;
fd = open("/dev/urandom", O_RDONLY);
if( fd>=0 ){
len = read(fd, key, HOSTIDLEN);
close(fd); /* silently leak the fd if it fails */
}
if( len < HOSTIDLEN ){
time_t t;
time(&t);
memcpy(key, &t, sizeof(t));
pid = getpid();
memcpy(&key[sizeof(t)], &pid, sizeof(pid));
}
#ifdef MAKE_PRETTY_HOSTID
{
int i;
/* filter the bytes into printable ascii characters and NUL terminate */
key[(HOSTIDLEN-1)] = 0x00;
for( i=0; i<(HOSTIDLEN-1); i++ ){
unsigned char pa = key[i]&0x7F;
if( pa<0x20 ){
key[i] = (key[i]&0x80 == 0x80) ? pa+0x40 : pa+0x20;
}else if( pa==0x7F ){
key[i] = (key[i]&0x80 == 0x80) ? pa=0x20 : pa+0x7E;
}
}
}
#endif
return SQLITE_OK;
}
/* writes the host id path to path, path should be an pre-allocated buffer
** with enough space for a path
*/
static void proxyGetHostIDPath(char *path, size_t len){
strlcpy(path, HOSTIDPATH, len);
#ifdef SQLITE_TEST
if( sqlite3_hostid_num>0 ){
char suffix[2] = "1";
suffix[0] = suffix[0] + sqlite3_hostid_num;
strlcat(path, suffix, len);
}
#endif
OSTRACE3("GETHOSTIDPATH %s pid=%d\n", path, getpid());
}
/* get the host ID from a sqlite hostid file stored in the
** user-specific tmp directory, create the ID if it's not there already
*/
static int proxyGetHostID(char *pHostID, int *pError){
int fd;
char path[MAXPATHLEN];
size_t len;
int rc=SQLITE_OK;
proxyGetHostIDPath(path, MAXPATHLEN);
/* try to create the host ID file, if it already exists read the contents */
fd = open(path, O_CREAT|O_WRONLY|O_EXCL, 0644);
if( fd<0 ){
int err=errno;
if( err!=EEXIST ){
#ifdef SQLITE_PROXY_DEBUG /* set the sqlite error message instead */
fprintf(stderr, "sqlite error creating host ID file %s: %s\n",
path, strerror(err));
#endif
return SQLITE_PERM;
}
/* couldn't create the file, read it instead */
fd = open(path, O_RDONLY|O_EXCL);
if( fd<0 ){
#ifdef SQLITE_PROXY_DEBUG /* set the sqlite error message instead */
int err = errno;
fprintf(stderr, "sqlite error opening host ID file %s: %s\n",
path, strerror(err));
#endif
return SQLITE_PERM;
}
len = pread(fd, pHostID, HOSTIDLEN, 0);
if( len<0 ){
*pError = errno;
rc = SQLITE_IOERR_READ;
}else if( len<HOSTIDLEN ){
*pError = 0;
rc = SQLITE_IOERR_SHORT_READ;
}
close(fd); /* silently leak the fd if it fails */
OSTRACE3("GETHOSTID read %s pid=%d\n", pHostID, getpid());
return rc;
}else{
/* we're creating the host ID file (use a random string of bytes) */
proxyGenerateHostID(pHostID);
len = pwrite(fd, pHostID, HOSTIDLEN, 0);
if( len<0 ){
*pError = errno;
rc = SQLITE_IOERR_WRITE;
}else if( len<HOSTIDLEN ){
*pError = 0;
rc = SQLITE_IOERR_WRITE;
}
close(fd); /* silently leak the fd if it fails */
OSTRACE3("GETHOSTID wrote %s pid=%d\n", pHostID, getpid());
return rc;
}
}
static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
int len;
int dbLen;
int i;
#ifdef LOCKPROXYDIR
len = strlcpy(lPath, LOCKPROXYDIR, maxLen);
#else
# ifdef _CS_DARWIN_USER_TEMP_DIR
{
confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen);
len = strlcat(lPath, "sqliteplocks", maxLen);
if( mkdir(lPath, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
/* if mkdir fails, handle as lock file creation failure */
# ifdef SQLITE_DEBUG
int err = errno;
if( err!=EEXIST ){
fprintf(stderr, "proxyGetLockPath: mkdir(%s,0%o) error %d %s\n", lPath,
SQLITE_DEFAULT_PROXYDIR_PERMISSIONS, err, strerror(err));
}
# endif
}else{
OSTRACE3("GETLOCKPATH mkdir %s pid=%d\n", lPath, getpid());
}
}
# else
len = strlcpy(lPath, "/tmp/", maxLen);
# endif
#endif
if( lPath[len-1]!='/' ){
len = strlcat(lPath, "/", maxLen);
}
/* transform the db path to a unique cache name */
dbLen = (int)strlen(dbPath);
for( i=0; i<dbLen && (i+len+7)<maxLen; i++){
char c = dbPath[i];
lPath[i+len] = (c=='/')?'_':c;
}
lPath[i+len]='\0';
strlcat(lPath, ":auto:", maxLen);
return SQLITE_OK;
}
/*
** Create a new VFS file descriptor (stored in memory obtained from
** sqlite3_malloc) and open the file named "path" in the file descriptor.
**
** The caller is responsible not only for closing the file descriptor
** but also for freeing the memory associated with the file descriptor.
*/
static int proxyCreateUnixFile(const char *path, unixFile **ppFile) {
unixFile *pNew;
int flags = SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE;
int rc = SQLITE_OK;
sqlite3_vfs dummyVfs;
pNew = (unixFile *)sqlite3_malloc(sizeof(unixFile));
if( !pNew ){
return SQLITE_NOMEM;
}
memset(pNew, 0, sizeof(unixFile));
/* Call unixOpen() to open the proxy file. The flags passed to unixOpen()
** suggest that the file being opened is a "main database". This is
** necessary as other file types do not necessarily support locking. It
** is better to use unixOpen() instead of opening the file directly with
** open(), as unixOpen() sets up the various mechanisms required to
** make sure a call to close() does not cause the system to discard
** POSIX locks prematurely.
**
** It is important that the xOpen member of the VFS object passed to
** unixOpen() is NULL. This tells unixOpen() may try to open a proxy-file
** for the proxy-file (creating a potential infinite loop).
*/
dummyVfs.pAppData = (void*)&autolockIoFinder;
dummyVfs.xOpen = 0;
rc = unixOpen(&dummyVfs, path, (sqlite3_file *)pNew, flags, &flags);
if( rc==SQLITE_OK && (flags&SQLITE_OPEN_READONLY) ){
pNew->pMethod->xClose((sqlite3_file *)pNew);
rc = SQLITE_CANTOPEN;
}
if( rc!=SQLITE_OK ){
sqlite3_free(pNew);
pNew = 0;
}
*ppFile = pNew;
return rc;
}
/* takes the conch by taking a shared lock and read the contents conch, if
** lockPath is non-NULL, the host ID and lock file path must match. A NULL
** lockPath means that the lockPath in the conch file will be used if the
** host IDs match, or a new lock path will be generated automatically
** and written to the conch file.
*/
static int proxyTakeConch(unixFile *pFile){
proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
if( pCtx->conchHeld>0 ){
return SQLITE_OK;
}else{
unixFile *conchFile = pCtx->conchFile;
char testValue[CONCHLEN];
char conchValue[CONCHLEN];
char lockPath[MAXPATHLEN];
char *tLockPath = NULL;
int rc = SQLITE_OK;
int readRc = SQLITE_OK;
int syncPerms = 0;
OSTRACE4("TAKECONCH %d for %s pid=%d\n", conchFile->h,
(pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid());
rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);
if( rc==SQLITE_OK ){
int pError = 0;
memset(testValue, 0, CONCHLEN); /* conch is fixed size */
rc = proxyGetHostID(testValue, &pError);
if( (rc&0xff)==SQLITE_IOERR ){
pFile->lastErrno = pError;
}
if( pCtx->lockProxyPath ){
strlcpy(&testValue[HOSTIDLEN], pCtx->lockProxyPath, MAXPATHLEN);
}
}
if( rc!=SQLITE_OK ){
goto end_takeconch;
}
readRc = unixRead((sqlite3_file *)conchFile, conchValue, CONCHLEN, 0);
if( readRc!=SQLITE_IOERR_SHORT_READ ){
if( readRc!=SQLITE_OK ){
if( (rc&0xff)==SQLITE_IOERR ){
pFile->lastErrno = conchFile->lastErrno;
}
rc = readRc;
goto end_takeconch;
}
/* if the conch has data compare the contents */
if( !pCtx->lockProxyPath ){
/* for auto-named local lock file, just check the host ID and we'll
** use the local lock file path that's already in there */
if( !memcmp(testValue, conchValue, HOSTIDLEN) ){
tLockPath = (char *)&conchValue[HOSTIDLEN];
goto end_takeconch;
}
}else{
/* we've got the conch if conchValue matches our path and host ID */
if( !memcmp(testValue, conchValue, CONCHLEN) ){
goto end_takeconch;
}
}
}else{
/* a short read means we're "creating" the conch (even though it could
** have been user-intervention), if we acquire the exclusive lock,
** we'll try to match the current on-disk permissions of the database
*/
syncPerms = 1;
}
/* either conch was emtpy or didn't match */
if( !pCtx->lockProxyPath ){
proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN);
tLockPath = lockPath;
strlcpy(&testValue[HOSTIDLEN], lockPath, MAXPATHLEN);
}
/* update conch with host and path (this will fail if other process
** has a shared lock already) */
rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, EXCLUSIVE_LOCK);
if( rc==SQLITE_OK ){
rc = unixWrite((sqlite3_file *)conchFile, testValue, CONCHLEN, 0);
if( rc==SQLITE_OK && syncPerms ){
struct stat buf;
int err = fstat(pFile->h, &buf);
if( err==0 ){
/* try to match the database file permissions, ignore failure */
#ifndef SQLITE_PROXY_DEBUG
fchmod(conchFile->h, buf.st_mode);
#else
if( fchmod(conchFile->h, buf.st_mode)!=0 ){
int code = errno;
fprintf(stderr, "fchmod %o FAILED with %d %s\n",
buf.st_mode, code, strerror(code));
} else {
fprintf(stderr, "fchmod %o SUCCEDED\n",buf.st_mode);
}
}else{
int code = errno;
fprintf(stderr, "STAT FAILED[%d] with %d %s\n",
err, code, strerror(code));
#endif
}
}
}
conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
end_takeconch:
OSTRACE2("TRANSPROXY: CLOSE %d\n", pFile->h);
if( rc==SQLITE_OK && pFile->openFlags ){
if( pFile->h>=0 ){
#ifdef STRICT_CLOSE_ERROR
if( close(pFile->h) ){
pFile->lastErrno = errno;
return SQLITE_IOERR_CLOSE;
}
#else
close(pFile->h); /* silently leak fd if fail */
#endif
}
pFile->h = -1;
int fd = open(pCtx->dbPath, pFile->openFlags,
SQLITE_DEFAULT_FILE_PERMISSIONS);
OSTRACE2("TRANSPROXY: OPEN %d\n", fd);
if( fd>=0 ){
pFile->h = fd;
}else{
rc=SQLITE_CANTOPEN; /* SQLITE_BUSY? proxyTakeConch called
during locking */
}
}
if( rc==SQLITE_OK && !pCtx->lockProxy ){
char *path = tLockPath ? tLockPath : pCtx->lockProxyPath;
/* ACS: Need to make a copy of path sometimes */
rc = proxyCreateUnixFile(path, &pCtx->lockProxy);
}
if( rc==SQLITE_OK ){
pCtx->conchHeld = 1;
if( tLockPath ){
pCtx->lockProxyPath = sqlite3DbStrDup(0, tLockPath);
if( pCtx->lockProxy->pMethod == &afpIoMethods ){
((afpLockingContext *)pCtx->lockProxy->lockingContext)->dbPath =
pCtx->lockProxyPath;
}
}
} else {
conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
}
OSTRACE3("TAKECONCH %d %s\n", conchFile->h, rc==SQLITE_OK?"ok":"failed");
return rc;
}
}
/*
** If pFile holds a lock on a conch file, then release that lock.
*/
static int proxyReleaseConch(unixFile *pFile){
int rc; /* Subroutine return code */
proxyLockingContext *pCtx; /* The locking context for the proxy lock */
unixFile *conchFile; /* Name of the conch file */
pCtx = (proxyLockingContext *)pFile->lockingContext;
conchFile = pCtx->conchFile;
OSTRACE4("RELEASECONCH %d for %s pid=%d\n", conchFile->h,
(pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"),
getpid());
pCtx->conchHeld = 0;
rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
OSTRACE3("RELEASECONCH %d %s\n", conchFile->h,
(rc==SQLITE_OK ? "ok" : "failed"));
return rc;
}
/*
** Given the name of a database file, compute the name of its conch file.
** Store the conch filename in memory obtained from sqlite3_malloc().
** Make *pConchPath point to the new name. Return SQLITE_OK on success
** or SQLITE_NOMEM if unable to obtain memory.
**
** The caller is responsible for ensuring that the allocated memory
** space is eventually freed.
**
** *pConchPath is set to NULL if a memory allocation error occurs.
*/
static int proxyCreateConchPathname(char *dbPath, char **pConchPath){
int i; /* Loop counter */
int len = (int)strlen(dbPath); /* Length of database filename - dbPath */
char *conchPath; /* buffer in which to construct conch name */
/* Allocate space for the conch filename and initialize the name to
** the name of the original database file. */
*pConchPath = conchPath = (char *)sqlite3_malloc(len + 8);
if( conchPath==0 ){
return SQLITE_NOMEM;
}
memcpy(conchPath, dbPath, len+1);
/* now insert a "." before the last / character */
for( i=(len-1); i>=0; i-- ){
if( conchPath[i]=='/' ){
i++;
break;
}
}
conchPath[i]='.';
while ( i<len ){
conchPath[i+1]=dbPath[i];
i++;
}
/* append the "-conch" suffix to the file */
memcpy(&conchPath[i+1], "-conch", 7);
assert( (int)strlen(conchPath) == len+7 );
return SQLITE_OK;
}
/* Takes a fully configured proxy locking-style unix file and switches
** the local lock file path
*/
static int switchLockProxyPath(unixFile *pFile, const char *path) {
proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
char *oldPath = pCtx->lockProxyPath;
int rc = SQLITE_OK;
if( pFile->locktype!=NO_LOCK ){
return SQLITE_BUSY;
}
/* nothing to do if the path is NULL, :auto: or matches the existing path */
if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ||
(oldPath && !strncmp(oldPath, path, MAXPATHLEN)) ){
return SQLITE_OK;
}else{
unixFile *lockProxy = pCtx->lockProxy;
pCtx->lockProxy=NULL;
pCtx->conchHeld = 0;
if( lockProxy!=NULL ){
rc=lockProxy->pMethod->xClose((sqlite3_file *)lockProxy);
if( rc ) return rc;
sqlite3_free(lockProxy);
}
sqlite3_free(oldPath);
pCtx->lockProxyPath = sqlite3DbStrDup(0, path);
}
return rc;
}
/*
** pFile is a file that has been opened by a prior xOpen call. dbPath
** is a string buffer at least MAXPATHLEN+1 characters in size.
**
** This routine find the filename associated with pFile and writes it
** int dbPath.
*/
static int proxyGetDbPathForUnixFile(unixFile *pFile, char *dbPath){
#if defined(__APPLE__)
if( pFile->pMethod == &afpIoMethods ){
/* afp style keeps a reference to the db path in the filePath field
** of the struct */
assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
strcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath);
}else
#endif
if( pFile->pMethod == &dotlockIoMethods ){
/* dot lock style uses the locking context to store the dot lock
** file path */
int len = strlen((char *)pFile->lockingContext) - strlen(DOTLOCK_SUFFIX);
memcpy(dbPath, (char *)pFile->lockingContext, len + 1);
}else{
/* all other styles use the locking context to store the db file path */
assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
strcpy(dbPath, (char *)pFile->lockingContext);
}
return SQLITE_OK;
}
/*
** Takes an already filled in unix file and alters it so all file locking
** will be performed on the local proxy lock file. The following fields
** are preserved in the locking context so that they can be restored and
** the unix structure properly cleaned up at close time:
** ->lockingContext
** ->pMethod
*/
static int proxyTransformUnixFile(unixFile *pFile, const char *path) {
proxyLockingContext *pCtx;
char dbPath[MAXPATHLEN+1]; /* Name of the database file */
char *lockPath=NULL;
int rc = SQLITE_OK;
if( pFile->locktype!=NO_LOCK ){
return SQLITE_BUSY;
}
proxyGetDbPathForUnixFile(pFile, dbPath);
if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ){
lockPath=NULL;
}else{
lockPath=(char *)path;
}
OSTRACE4("TRANSPROXY %d for %s pid=%d\n", pFile->h,
(lockPath ? lockPath : ":auto:"), getpid());
pCtx = sqlite3_malloc( sizeof(*pCtx) );
if( pCtx==0 ){
return SQLITE_NOMEM;
}
memset(pCtx, 0, sizeof(*pCtx));
rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath);
if( rc==SQLITE_OK ){
rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile);
}
if( rc==SQLITE_OK && lockPath ){
pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
}
if( rc==SQLITE_OK ){
/* all memory is allocated, proxys are created and assigned,
** switch the locking context and pMethod then return.
*/
pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
pCtx->oldLockingContext = pFile->lockingContext;
pFile->lockingContext = pCtx;
pCtx->pOldMethod = pFile->pMethod;
pFile->pMethod = &proxyIoMethods;
}else{
if( pCtx->conchFile ){
rc = pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
if( rc ) return rc;
sqlite3_free(pCtx->conchFile);
}
sqlite3_free(pCtx->conchFilePath);
sqlite3_free(pCtx);
}
OSTRACE3("TRANSPROXY %d %s\n", pFile->h,
(rc==SQLITE_OK ? "ok" : "failed"));
return rc;
}
/*
** This routine handles sqlite3_file_control() calls that are specific
** to proxy locking.
*/
static int proxyFileControl(sqlite3_file *id, int op, void *pArg){
switch( op ){
case SQLITE_GET_LOCKPROXYFILE: {
unixFile *pFile = (unixFile*)id;
if( pFile->pMethod == &proxyIoMethods ){
proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
proxyTakeConch(pFile);
if( pCtx->lockProxyPath ){
*(const char **)pArg = pCtx->lockProxyPath;
}else{
*(const char **)pArg = ":auto: (not held)";
}
} else {
*(const char **)pArg = NULL;
}
return SQLITE_OK;
}
case SQLITE_SET_LOCKPROXYFILE: {
unixFile *pFile = (unixFile*)id;
int rc = SQLITE_OK;
int isProxyStyle = (pFile->pMethod == &proxyIoMethods);
if( pArg==NULL || (const char *)pArg==0 ){
if( isProxyStyle ){
/* turn off proxy locking - not supported */
rc = SQLITE_ERROR /*SQLITE_PROTOCOL? SQLITE_MISUSE?*/;
}else{
/* turn off proxy locking - already off - NOOP */
rc = SQLITE_OK;
}
}else{
const char *proxyPath = (const char *)pArg;
if( isProxyStyle ){
proxyLockingContext *pCtx =
(proxyLockingContext*)pFile->lockingContext;
if( !strcmp(pArg, ":auto:")
|| (pCtx->lockProxyPath &&
!strncmp(pCtx->lockProxyPath, proxyPath, MAXPATHLEN))
){
rc = SQLITE_OK;
}else{
rc = switchLockProxyPath(pFile, proxyPath);
}
}else{
/* turn on proxy file locking */
rc = proxyTransformUnixFile(pFile, proxyPath);
}
}
return rc;
}
default: {
assert( 0 ); /* The call assures that only valid opcodes are sent */
}
}
/*NOTREACHED*/
return SQLITE_ERROR;
}
/*
** Within this division (the proxying locking implementation) the procedures
** above this point are all utilities. The lock-related methods of the
** proxy-locking sqlite3_io_method object follow.
*/
/*
** This routine checks if there is a RESERVED lock held on the specified
** file by this or any other process. If such a lock is held, set *pResOut
** to a non-zero value otherwise *pResOut is set to zero. The return value
** is set to SQLITE_OK unless an I/O error occurs during lock checking.
*/
static int proxyCheckReservedLock(sqlite3_file *id, int *pResOut) {
unixFile *pFile = (unixFile*)id;
int rc = proxyTakeConch(pFile);
if( rc==SQLITE_OK ){
proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
unixFile *proxy = pCtx->lockProxy;
return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
}
return rc;
}
/*
** Lock the file with the lock specified by parameter locktype - one
** of the following:
**
** (1) SHARED_LOCK
** (2) RESERVED_LOCK
** (3) PENDING_LOCK
** (4) EXCLUSIVE_LOCK
**
** Sometimes when requesting one lock state, additional lock states
** are inserted in between. The locking might fail on one of the later
** transitions leaving the lock state different from what it started but
** still short of its goal. The following chart shows the allowed
** transitions and the inserted intermediate states:
**
** UNLOCKED -> SHARED
** SHARED -> RESERVED
** SHARED -> (PENDING) -> EXCLUSIVE
** RESERVED -> (PENDING) -> EXCLUSIVE
** PENDING -> EXCLUSIVE
**
** This routine will only increase a lock. Use the sqlite3OsUnlock()
** routine to lower a locking level.
*/
static int proxyLock(sqlite3_file *id, int locktype) {
unixFile *pFile = (unixFile*)id;
int rc = proxyTakeConch(pFile);
if( rc==SQLITE_OK ){
proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
unixFile *proxy = pCtx->lockProxy;
rc = proxy->pMethod->xLock((sqlite3_file*)proxy, locktype);
pFile->locktype = proxy->locktype;
}
return rc;
}
/*
** Lower the locking level on file descriptor pFile to locktype. locktype
** must be either NO_LOCK or SHARED_LOCK.
**
** If the locking level of the file descriptor is already at or below
** the requested locking level, this routine is a no-op.
*/
static int proxyUnlock(sqlite3_file *id, int locktype) {
unixFile *pFile = (unixFile*)id;
int rc = proxyTakeConch(pFile);
if( rc==SQLITE_OK ){
proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
unixFile *proxy = pCtx->lockProxy;
rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, locktype);
pFile->locktype = proxy->locktype;
}
return rc;
}
/*
** Close a file that uses proxy locks.
*/
static int proxyClose(sqlite3_file *id) {
if( id ){
unixFile *pFile = (unixFile*)id;
proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
unixFile *lockProxy = pCtx->lockProxy;
unixFile *conchFile = pCtx->conchFile;
int rc = SQLITE_OK;
if( lockProxy ){
rc = lockProxy->pMethod->xUnlock((sqlite3_file*)lockProxy, NO_LOCK);
if( rc ) return rc;
rc = lockProxy->pMethod->xClose((sqlite3_file*)lockProxy);
if( rc ) return rc;
sqlite3_free(lockProxy);
pCtx->lockProxy = 0;
}
if( conchFile ){
if( pCtx->conchHeld ){
rc = proxyReleaseConch(pFile);
if( rc ) return rc;
}
rc = conchFile->pMethod->xClose((sqlite3_file*)conchFile);
if( rc ) return rc;
sqlite3_free(conchFile);
}
sqlite3_free(pCtx->lockProxyPath);
sqlite3_free(pCtx->conchFilePath);
sqlite3_free(pCtx->dbPath);
/* restore the original locking context and pMethod then close it */
pFile->lockingContext = pCtx->oldLockingContext;
pFile->pMethod = pCtx->pOldMethod;
sqlite3_free(pCtx);
return pFile->pMethod->xClose(id);
}
return SQLITE_OK;
}
#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
/*
** The proxy locking style is intended for use with AFP filesystems.
** And since AFP is only supported on MacOSX, the proxy locking is also
** restricted to MacOSX.
**
**
******************* End of the proxy lock implementation **********************
******************************************************************************/
/*
** Initialize the operating system interface.
**
** This routine registers all VFS implementations for unix-like operating
** systems. This routine, and the sqlite3_os_end() routine that follows,
** should be the only routines in this file that are visible from other
** files.
**
** This routine is called once during SQLite initialization and by a
** single thread. The memory allocation and mutex subsystems have not
** necessarily been initialized when this routine is called, and so they
** should not be used.
*/
int sqlite3_os_init(void){
/*
** The following macro defines an initializer for an sqlite3_vfs object.
** The name of the VFS is NAME. The pAppData is a pointer to a pointer
** to the "finder" function. (pAppData is a pointer to a pointer because
** silly C90 rules prohibit a void* from being cast to a function pointer
** and so we have to go through the intermediate pointer to avoid problems
** when compiling with -pedantic-errors on GCC.)
**
** The FINDER parameter to this macro is the name of the pointer to the
** finder-function. The finder-function returns a pointer to the
** sqlite_io_methods object that implements the desired locking
** behaviors. See the division above that contains the IOMETHODS
** macro for addition information on finder-functions.
**
** Most finders simply return a pointer to a fixed sqlite3_io_methods
** object. But the "autolockIoFinder" available on MacOSX does a little
** more than that; it looks at the filesystem type that hosts the
** database file and tries to choose an locking method appropriate for
** that filesystem time.
*/
#define UNIXVFS(VFSNAME, FINDER) { \
1, /* iVersion */ \
sizeof(unixFile), /* szOsFile */ \
MAX_PATHNAME, /* mxPathname */ \
0, /* pNext */ \
VFSNAME, /* zName */ \
(void*)&FINDER, /* pAppData */ \
unixOpen, /* xOpen */ \
unixDelete, /* xDelete */ \
unixAccess, /* xAccess */ \
unixFullPathname, /* xFullPathname */ \
unixDlOpen, /* xDlOpen */ \
unixDlError, /* xDlError */ \
unixDlSym, /* xDlSym */ \
unixDlClose, /* xDlClose */ \
unixRandomness, /* xRandomness */ \
unixSleep, /* xSleep */ \
unixCurrentTime, /* xCurrentTime */ \
unixGetLastError /* xGetLastError */ \
}
/*
** All default VFSes for unix are contained in the following array.
**
** Note that the sqlite3_vfs.pNext field of the VFS object is modified
** by the SQLite core when the VFS is registered. So the following
** array cannot be const.
*/
static sqlite3_vfs aVfs[] = {
#if SQLITE_ENABLE_LOCKING_STYLE && (OS_VXWORKS || defined(__APPLE__))
UNIXVFS("unix", autolockIoFinder ),
#else
UNIXVFS("unix", posixIoFinder ),
#endif
UNIXVFS("unix-none", nolockIoFinder ),
UNIXVFS("unix-dotfile", dotlockIoFinder ),
#if OS_VXWORKS
UNIXVFS("unix-namedsem", semIoFinder ),
#endif
#if SQLITE_ENABLE_LOCKING_STYLE
UNIXVFS("unix-posix", posixIoFinder ),
#if !OS_VXWORKS
UNIXVFS("unix-flock", flockIoFinder ),
#endif
#endif
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
UNIXVFS("unix-afp", afpIoFinder ),
UNIXVFS("unix-proxy", proxyIoFinder ),
#endif
};
unsigned int i; /* Loop counter */
/* Register all VFSes defined in the aVfs[] array */
for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
sqlite3_vfs_register(&aVfs[i], i==0);
}
return SQLITE_OK;
}
/*
** Shutdown the operating system interface.
**
** Some operating systems might need to do some cleanup in this routine,
** to release dynamically allocated objects. But not on unix.
** This routine is a no-op for unix.
*/
int sqlite3_os_end(void){
return SQLITE_OK;
}
#endif /* SQLITE_OS_UNIX */