SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that is specific to Unix systems.
**
** $Id: os_unix.c,v 1.213 2008/11/19 11:35:40 danielk1977 Exp $
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX              /* This file is used on unix only */

/*
** If SQLITE_ENABLE_LOCKING_STYLE is defined and is non-zero, then several
** alternative locking implementations are provided:

#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 defined(__RTP__) || defined(_WRS_KERNEL)
#define lstat stat
#include <semaphore.h>
#include <limits.h>
#else
#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

  int h;                    /* The file descriptor */
  unsigned char locktype;   /* The type of lock held on this fd */
  int dirfd;                /* File descriptor for the directory */
#if SQLITE_THREADSAFE
  pthread_t tid;            /* The thread that "owns" this unixFile */
#endif
  int lastErrno;            /* The unix errno from the last I/O error */
#if defined(__RTP__) || defined(_WRS_KERNEL)
  int isDelete;             /* Delete on close if true */
  char *zRealpath;
#endif
};

/*
** Include code that is common to all os_*.c files

** If threads cannot override each others locks, then we set the
** lockKey.tid field to the thread ID.  If threads can override
** each others locks then tid is always set to zero.  tid is omitted
** if we compile without threading support.
*/
struct lockKey {
  dev_t dev;       /* Device number */
#if defined(__RTP__) || defined(_WRS_KERNEL)
  void *rnam;      /* Realname since inode unusable */
#else
  ino_t ino;       /* Inode number */
#endif
#if SQLITE_THREADSAFE
  pthread_t tid;   /* Thread ID or zero if threads can override each other */
#endif

/*
** An instance of the following structure serves as the key used
** to locate a particular openCnt structure given its inode.  This
** is the same as the lockKey except that the thread ID is omitted.
*/
struct openKey {
  dev_t dev;   /* Device number */
#if defined(__RTP__) || defined(_WRS_KERNEL)
  void *rnam;  /* Realname since inode unusable */
#else
  ino_t ino;   /* Inode number */
#endif
};

/*
** 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.
*/
struct openCnt {
  struct openKey key;   /* The lookup key */
  int nRef;             /* Number of pointers to this structure */
  int nLock;            /* Number of outstanding locks */
  int nPending;         /* Number of pending close() operations */
  int *aPending;        /* Malloced space holding fd's awaiting a close() */
#if defined(__RTP__) || defined(_WRS_KERNEL)
  sem_t *pSem;          /* Named POSIX semaphore */
  char aSemName[MAX_PATHNAME+1];   /* Name of that semaphore */
#endif
  struct openCnt *pNext, *pPrev;   /* List of all openCnt objects */
};

/*
** List of all lockInfo and openCnt objects.  This used to be a hash
** table.  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 oo a simple linked list will suffice.
*/
static struct lockInfo *lockList = 0;
static struct openCnt *openList = 0;

#if defined(__RTP__) || defined(_WRS_KERNEL)
/*
** This hash table is used to bind the canonical file name to a
** unixFile structure and use the hash key (= canonical name)
** instead of the Inode number of the file to find the matching
** lockInfo and openCnt structures. It also helps to make the
** name of the semaphore when LOCKING_STYLE_NAMEDSEM is used
** for the file.

      }
      sqlite3_free(pOpen->aPending);
      sqlite3_free(pOpen);
    }
  }
}

#if defined(__RTP__) || defined(_WRS_KERNEL)
/*
** Implementation of a realpath() like function for vxWorks
** to determine canonical path name from given name. It does
** not support symlinks. Neither does it handle volume prefixes.
*/
char *
vxrealpath(const char *pathname, int dostat)

  lockInfo.l_whence = SEEK_SET;
  lockInfo.l_type = F_RDLCK;
  if( fcntl(fd, F_GETLK, &lockInfo)!=-1 ) {
    return LOCKING_STYLE_POSIX;
  }
  
  /* Testing for flock() can give false positives.  So if if the above 
  ** test fails, then we fall back to using dot-file style locking.

  */
#if defined(__RTP__) || defined(_WRS_KERNEL)  
  return LOCKING_STYLE_NAMEDSEM;
#else
  return LOCKING_STYLE_DOTFILE;
#endif
}
#endif

/* 
** If SQLITE_ENABLE_LOCKING_STYLE is defined, this function Examines the 
** f_fstypename entry in the statfs structure as returned by stat() for 
** the file system hosting the database file and selects  the appropriate
** locking style based on its value.  These values and assignments are 
** based on Darwin/OSX behavior and have not been thoroughly tested on 
** other systems.
**
** If SQLITE_ENABLE_LOCKING_STYLE is not defined, this function always
** returns LOCKING_STYLE_POSIX.
*/
#if SQLITE_ENABLE_LOCKING_STYLE
static int detectLockingStyle(
  sqlite3_vfs *pVfs,
  const char *filePath, 
  int fd
){
#if defined(__RTP__) || defined(_WRS_KERNEL)
  if( !filePath ){
    return LOCKING_STYLE_NONE;
  }
  if( pVfs->pAppData ){
    return SQLITE_PTR_TO_INT(pVfs->pAppData);
  }
  if (access(filePath, 0) != -1){

        return aMap[i].eLockingStyle;
      }
    }
  }

  /* Default case. Handles, amongst others, "nfs". */
  return testLockingStyle(fd);  
#endif /* if defined(__RTP__) || defined(_WRS_KERNEL) */
  return LOCKING_STYLE_POSIX;
}
#else
  #define detectLockingStyle(x,y,z) LOCKING_STYLE_POSIX
#endif /* ifdef SQLITE_ENABLE_LOCKING_STYLE */

/*
** Given a file descriptor, locate lockInfo and openCnt structures that
** describes that file descriptor.  Create new ones if necessary.  The
** return values might be uninitialized if an error occurs.
**
** Return an appropriate error code.
*/
static int findLockInfo(
  int fd,                      /* The file descriptor used in the key */
#if defined(__RTP__) || defined(_WRS_KERNEL)
  void *rnam,                  /* vxWorks realname */
#endif
  struct lockInfo **ppLock,    /* Return the lockInfo structure here */
  struct openCnt **ppOpen      /* Return the openCnt structure here */
){
  int rc;
  struct lockKey key1;

    if( rc!=0 ){
      return SQLITE_IOERR;
    }
  }

  memset(&key1, 0, sizeof(key1));
  key1.dev = statbuf.st_dev;
#if defined(__RTP__) || defined(_WRS_KERNEL)
  key1.rnam = rnam;
#else
  key1.ino = statbuf.st_ino;
#endif
#if SQLITE_THREADSAFE
  if( threadsOverrideEachOthersLocks<0 ){
    testThreadLockingBehavior(fd);
  }
  key1.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self();
#endif
  memset(&key2, 0, sizeof(key2));
  key2.dev = statbuf.st_dev;
#if defined(__RTP__) || defined(_WRS_KERNEL)
  key2.rnam = rnam;
#else
  key2.ino = statbuf.st_ino;
#endif
  pLock = lockList;
  while( pLock && memcmp(&key1, &pLock->key, sizeof(key1)) ){
    pLock = pLock->pNext;

      pOpen->nLock = 0;
      pOpen->nPending = 0;
      pOpen->aPending = 0;
      pOpen->pNext = openList;
      pOpen->pPrev = 0;
      if( openList ) openList->pPrev = pOpen;
      openList = pOpen;
#if defined(__RTP__) || defined(_WRS_KERNEL)
      pOpen->pSem = NULL;
      pOpen->aSemName[0] = '\0';
#endif
    }else{
      pOpen->nRef++;
    }
    *ppOpen = pOpen;

    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);
#if defined(__RTP__) || defined(_WRS_KERNEL)
    rc = findLockInfo(pFile->h, pFile->zRealpath, &pFile->pLock, 0);
#else
    rc = findLockInfo(pFile->h, &pFile->pLock, 0);
#endif
    OSTRACE5("LOCK    %d is now %s(%s,%d)\n", pFile->h,
           locktypeName(pFile->locktype),
           locktypeName(pFile->pLock->locktype), pFile->pLock->cnt);

  if( pFile ){
    if( pFile->dirfd>=0 ){
      close(pFile->dirfd);
    }
    if( pFile->h>=0 ){
      close(pFile->h);
    }
#if defined(__RTP__) || defined(_WRS_KERNEL)
    if( pFile->isDelete && pFile->zRealpath ){
      unlink(pFile->zRealpath);
    }
    if( pFile->zRealpath ){
      HashElem *pElem;
      int n = strlen(pFile->zRealpath) + 1;
      pElem = sqlite3HashFindElem(&nameHash, pFile->zRealpath, n);

  }
  return SQLITE_OK;
}


#if SQLITE_ENABLE_LOCKING_STYLE

#if !defined(__RTP__) && !defined(_WRS_KERNEL)
#pragma mark AFP Support

/*
 ** The afpLockingContext structure contains all afp lock specific state
 */
typedef struct afpLockingContext afpLockingContext;
struct afpLockingContext {

static int flockClose(sqlite3_file *id) {
  if( id ){
    flockUnlock(id, NO_LOCK);
  }
  return closeUnixFile(id);
}

#endif /* !defined(__RTP__) && !defined(_WRS_KERNEL) */

#pragma mark Old-School .lock file based locking

/* Dotlock-style reserved lock checking following the behavior of 
** unixCheckReservedLock, see the unixCheckReservedLock function comments */
static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) {
  int rc = SQLITE_OK;

  char *zLockFile = (char *)pFile->lockingContext;
  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;
#if !defined(__RTP__) && !defined(_WRS_KERNEL)    
    /* Always update the timestamp on the old file */
    utimes(zLockFile, NULL);
#endif
    rc = SQLITE_OK;
    goto dotlock_end_lock;
  }
  

  return SQLITE_OK;
}

/*
 ** Close a file.
 */
static int dotlockClose(sqlite3_file *id) {
#if defined(__RTP__) || defined(_WRS_KERNEL)
  int rc;
#endif
  if( id ){
    unixFile *pFile = (unixFile*)id;
    dotlockUnlock(id, NO_LOCK);
    sqlite3_free(pFile->lockingContext);
  }
#if defined(__RTP__) || defined(_WRS_KERNEL)
  enterMutex();
  rc = closeUnixFile(id);
  leaveMutex();
  return rc;
#else
  return closeUnixFile(id);
#endif
}

#if defined(__RTP__) || defined(_WRS_KERNEL)

#pragma mark POSIX/vxWorks named semaphore based locking

/* Namedsem-style reserved lock checking following the behavior of 
** unixCheckReservedLock, see the unixCheckReservedLock function comments */
static int namedsemCheckReservedLock(sqlite3_file *id, int *pResOut) {
  int rc = SQLITE_OK;

    releaseOpenCnt(pFile->pOpen);
    closeUnixFile(id);
    leaveMutex();
  }
  return SQLITE_OK;
}

#endif /* defined(__RTP__) || defined(_WRS_KERNEL) */

#endif /* SQLITE_ENABLE_LOCKING_STYLE */

/*
** The nolockLockingContext is void
*/
typedef void nolockLockingContext;

    unixDeviceCharacteristics   /* xDeviceCapabilities */                \
  }
  static sqlite3_io_methods aIoMethod[] = {
    IOMETHODS(unixClose, unixLock, unixUnlock, unixCheckReservedLock) 
   ,IOMETHODS(nolockClose, nolockLock, nolockUnlock, nolockCheckReservedLock)
#if SQLITE_ENABLE_LOCKING_STYLE
   ,IOMETHODS(dotlockClose, dotlockLock, dotlockUnlock,dotlockCheckReservedLock)
#if defined(__RTP__) || defined(_WRS_KERNEL)
   ,IOMETHODS(nolockClose, nolockLock, nolockUnlock, nolockCheckReservedLock)
   ,IOMETHODS(nolockClose, nolockLock, nolockUnlock, nolockCheckReservedLock)
   ,IOMETHODS(namedsemClose, namedsemLock, namedsemUnlock, namedsemCheckReservedLock)
#else
   ,IOMETHODS(flockClose, flockLock, flockUnlock, flockCheckReservedLock)
   ,IOMETHODS(afpClose, afpLock, afpUnlock, afpCheckReservedLock)
   ,IOMETHODS(nolockClose, nolockLock, nolockUnlock, nolockCheckReservedLock)

  assert( pNew->pOpen==NULL );

  OSTRACE3("OPEN    %-3d %s\n", h, zFilename);    
  pNew->h = h;
  pNew->dirfd = dirfd;
  SET_THREADID(pNew);

#if defined(__RTP__) || defined(_WRS_KERNEL)
  {
    HashElem *pElem;
    char *zRealname = vxrealpath(zFilename, 1);
    int n;
    pNew->zRealpath = 0;
    if( !zRealname ){
      rc = SQLITE_NOMEM;

    eLockingStyle = detectLockingStyle(pVfs, zFilename, h);
  }

  switch( eLockingStyle ){

    case LOCKING_STYLE_POSIX: {
      enterMutex();
#if defined(__RTP__) || defined(_WRS_KERNEL)
      rc = findLockInfo(h, pNew->zRealpath, &pNew->pLock, &pNew->pOpen);
#else
      rc = findLockInfo(h, &pNew->pLock, &pNew->pOpen);
#endif
      leaveMutex();
      break;
    }

#if SQLITE_ENABLE_LOCKING_STYLE

#if !defined(__RTP__) && !defined(_WRS_KERNEL)
    case LOCKING_STYLE_AFP: {
      /* 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 ){

      }else{
        sqlite3_snprintf(nFilename, zLockFile, "%s.lock", zFilename);
      }
      pNew->lockingContext = zLockFile;
      break;
    }

#if defined(__RTP__) || defined(_WRS_KERNEL)
    case LOCKING_STYLE_NAMEDSEM: {
      /* Named semaphore locking uses the file path so it needs to be
      ** included in the namedsemLockingContext
      */
      enterMutex();
      rc = findLockInfo(h, pNew->zRealpath, &pNew->pLock, &pNew->pOpen);
      if( (rc==SQLITE_OK) && (pNew->pOpen->pSem==NULL) ){

        }
      }
      leaveMutex();
      break;
    }
#endif

#if !defined(__RTP__) && !defined(_WRS_KERNEL)
    case LOCKING_STYLE_FLOCK: 
#endif
    case LOCKING_STYLE_NONE: 
      break;
#endif
  }
  
  pNew->lastErrno = 0;
#if defined(__RTP__) || defined(_WRS_KERNEL)
  if( rc!=SQLITE_OK ){
    unlink(zFilename);
    isDelete = 0;
  }
  pNew->isDelete = isDelete;
#endif
  if( rc!=SQLITE_OK ){

    flags |= SQLITE_OPEN_READONLY;
    return unixOpen(pVfs, zPath, pFile, flags, pOutFlags);
  }
  if( fd<0 ){
    return SQLITE_CANTOPEN;
  }
  if( isDelete ){
#if defined(__RTP__) || defined(_WRS_KERNEL)
    zPath = zName;
#else
    unlink(zName);
#endif
  }
  if( pOutFlags ){
    *pOutFlags = flags;

  SimulateIOError(return SQLITE_IOERR_DELETE);
  unlink(zPath);
#ifndef SQLITE_DISABLE_DIRSYNC
  if( dirSync ){
    int fd;
    rc = openDirectory(zPath, &fd);
    if( rc==SQLITE_OK ){
#if defined(__RTP__) || defined(_WRS_KERNEL)
      if( fsync(fd)==-1 )
#else
      if( fsync(fd) )
#endif
      {
        rc = SQLITE_IOERR_DIR_FSYNC;
      }

  ** function failing. This function could fail if, for example, the
  ** current working directly has been unlinked.
  */
  SimulateIOError( return SQLITE_ERROR );

  assert( pVfs->mxPathname==MAX_PATHNAME );

#if defined(__RTP__) || defined(_WRS_KERNEL)
  {
    char *zRealname = vxrealpath(zPath, 0);
    zOut[0] = '\0';
    if( !zRealname ){
      return SQLITE_CANTOPEN;
    }
    sqlite3_snprintf(nOut, zOut, "%s", zRealname);

** 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 defined(__RTP__) || defined(_WRS_KERNEL)
  struct timespec sp;

  sp.tv_sec = microseconds / 1000000;
  sp.tv_nsec = (microseconds % 1000000) * 1000;
  nanosleep(&sp, NULL);
  return microseconds;
#elif defined(HAVE_USLEEP) && HAVE_USLEEP

/*
** 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(__RTP__) || defined(_WRS_KERNEL)
  struct timespec sNow;
  clock_gettime(CLOCK_REALTIME, &sNow);
  *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_nsec/86400000000000.0;
#elif defined(NO_GETTOD)
  time_t t;
  time(&t);
  *prNow = t/86400.0 + 2440587.5;

    UNIXVFS("unix-none",    LOCKING_STYLE_NONE),
    UNIXVFS("unix-namedsem",LOCKING_STYLE_NAMEDSEM),
  };
  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
    sqlite3_vfs_register(&aVfs[i], 0);
  }
#endif
#if defined(__RTP__) || defined(_WRS_KERNEL)
  sqlite3HashInit(&nameHash, 1);
#endif
  sqlite3_vfs_register(&unixVfs, 1);
  return SQLITE_OK; 
}

/*