SQLite

#endif
#if OS_WIN
# include <winbase.h>
#endif


#if OS_UNIX
/*
** Here is the dirt on POSIX advisory locks:  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 be 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.
**
** Bummer.  If you ask me, this is broken.  Badly broken.  It 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 the stat() 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.
**
** The OsFile 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 OsFile 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.
*/

/*
** An instance of the following structure serves as the key used
** to locate a particular lockInfo structure given its inode. 
*/
struct inodeKey {
  dev_t dev;   /* Device number */
  ino_t ino;   /* Inode number */
};

/*
** An instance of the following structure is allocated for each inode.
** A single inode can have multiple file descriptors, so each OsFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of OsFiles pointing to it.
*/
struct lockInfo {
  struct inodeKey key;  /* The lookup key */
  int cnt;              /* 0: unlocked.  -1: write lock.  >=1: read lock */
  int nRef;             /* Number of pointers to this structure */
};

/* 
** This hash table maps inodes (in the form of inodeKey structures) into
** pointers to lockInfo structures.
*/
static Hash lockHash = { SQLITE_HASH_BINARY, 0, 0, 0, 0, 0 };

/*
** Given a file descriptor, locate a lockInfo structure that describes
** that file descriptor.  Create a new one if necessary.  NULL might
** be returned if malloc() fails.
*/
static struct lockInfo *findLockInfo(int fd){
  int rc;
  struct inodeKey key;
  struct stat statbuf;
  struct lockInfo *pInfo;
  rc = fstat(fd, &statbuf);
  if( rc!=0 ) return 0;
  key.dev = statbuf.st_dev;
  key.ino = statbuf.st_ino;
  pInfo = (struct lockInfo*)sqliteHashFind(&lockHash, &key, sizeof(key));
  if( pInfo==0 ){
    pInfo = sqliteMalloc( sizeof(*pInfo) );
    if( pInfo==0 ) return 0;
    pInfo->key = key;
    pInfo->nRef = 1;
    pInfo->cnt = 0;
    sqliteHashInsert(&lockHash, &pInfo->key, sizeof(key), pInfo);
  }else{
    pInfo->nRef++;
  }
  return pInfo;
}

/*
** Release a lockInfo structure previously allocated by findLockInfo().
*/
static void releaseLockInfo(struct lockInfo *pInfo){
  pInfo->nRef--;
  if( pInfo->nRef==0 ){
    sqliteHashInsert(&lockHash, &pInfo->key, sizeof(pInfo->key), 0);
    sqliteFree(pInfo);
  }
}
#endif  /** POSIX advisory lock work-around **/


/*
** Delete the named file
*/
int sqliteOsDelete(const char *zFilename){
#if OS_UNIX

#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests for temporary tables and indices.
#
# $Id: temptable.test,v 1.3 2001/10/09 12:39:24 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Create an alternative connection to the database
#
do_test temptable-1.0 {

  execsql {
    SELECT y FROM t2 WHERE x=1;
  }
} {2}
do_test temptable-5.9 {
  execsql {SELECT y FROM t2 WHERE x=9}
} {8}

db2 close

finish_test

proc chng {date desc} {
  puts "<DT><B>$date</B></DT>"
  puts "<DD><P><UL>$desc</UL></P></DD>"
}

chng {2001 Oct 9 (2.0.2)} {
<li>Fix two bugs in the locking protocol.  (One was masking the other.)</li>
<li>Removed some unused "#include <unistd.h>" that were causing problems
    for VC++.</li>
<li>Fixed <b>sqlite.h</b> so that it is usable from C++</li>
<li>Added the FULL_COLUMN_NAMES pragma.  When set to "ON", the names of
    columns are reported back as TABLE.COLUMN instead of just COLUMN.</li>
<li>Added the TABLE_INFO() and INDEX_INFO() pragmas to help support the
    ODBC interface.</li>