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Overview
Comment:Continue with the cleanup of os_unix.c. (CVS 5969)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 215d36ea89078036fb66b5154f054613b735dab3
User & Date: drh 2008-12-03 19:34:47
Context
2008-12-03
21:26
Make os_unix compile with SQLITE_ENABLE_PROXY_LOCKING (CVS 5970) check-in: 3efedac6 user: aswift tags: trunk
19:34
Continue with the cleanup of os_unix.c. (CVS 5969) check-in: 215d36ea user: drh tags: trunk
2008-11-29
22:49
Fully initialize the unused bytes of the buffer that will become the journal file header, in order to silence a complaint from valgrind. (CVS 5968) check-in: 2822cbb9 user: drh tags: trunk
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** 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 current set of divisions is as follows:
**
**   *  General-purpose declarations and utility functions.
**   *  Unique file ID logic used by VxWorks.
**   *  Various locking primitive implementations:
**      + 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)
**      + for proxy 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.
**   *  VFS method implementations.
**   *  Definitions of sqlite3_vfs objects for all locking methods
**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
**
** $Id: os_unix.c,v 1.224 2008/11/29 02:20:27 drh Exp $
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX              /* This file is used on unix only */

/*
** This module implements the following locking styles:

**
**   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),
................................................................................
/****************** End of the dot-file lock implementation *******************
******************************************************************************/

/******************************************************************************
************************** Begin flock Locking ********************************
**
** Use the flock() system call to do file locking.







**
** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off or if
** compiling for VXWORKS.
*/
#if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS

/* flock-style reserved lock checking following the behavior of 
 ** unixCheckReservedLock, see the unixCheckReservedLock function comments */




static int flockCheckReservedLock(sqlite3_file *id, int *pResOut){
  int rc = SQLITE_OK;
  int reserved = 0;
  unixFile *pFile = (unixFile*)id;
  
  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
  
................................................................................
    reserved=1;
  }
#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
  *pResOut = reserved;
  return rc;
}






























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.  
................................................................................
  if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
    rc = SQLITE_BUSY;
  }
#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
  return rc;
}









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 );
................................................................................
/******************* End of the flock lock implementation *********************
******************************************************************************/

/******************************************************************************
************************ Begin Named Semaphore Locking ************************
**
** Named semaphore locking is only supported on VxWorks.





*/
#if OS_VXWORKS

/* Namedsem-style reserved lock checking following the behavior of 
** unixCheckReservedLock, see the unixCheckReservedLock function comments */




static int semCheckReservedLock(sqlite3_file *id, int *pResOut) {
  int rc = SQLITE_OK;
  int reserved = 0;
  unixFile *pFile = (unixFile*)id;

  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
  
................................................................................
  }
  OSTRACE4("TEST WR-LOCK %d %d %d\n", pFile->h, rc, reserved);

  *pResOut = reserved;
  return rc;
}






























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.  
................................................................................
  /* got it, set the type and return ok */
  pFile->locktype = locktype;

 sem_end_lock:
  return rc;
}








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,
................................................................................
#if defined(__DARWIN__) && 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;
};

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)

/* 



 ** Return SQLITE_OK on success, SQLITE_BUSY on failure.
 */
static int _AFPFSSetLock(
  const char *path, 
  unixFile *pFile, 
  unsigned long long offset, 
  unsigned long long length, 
  int setLockFlag

){
  struct ByteRangeLockPB2       pb;
  int                     err;

  
  pb.unLockFlag = setLockFlag ? 0 : 1;
  pb.startEndFlag = 0;
  pb.offset = offset;
  pb.length = length; 
  pb.fd = pFile->h;
  //SimulateIOErrorBenign(1);
................................................................................
    }
    return rc;
  } else {
    return SQLITE_OK;
  }
}

/* AFP-style reserved lock checking following the behavior of 
** unixCheckReservedLock, see the unixCheckReservedLock function comments */




static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
  int rc = SQLITE_OK;
  int reserved = 0;
  unixFile *pFile = (unixFile*)id;
  
  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
  
................................................................................
    reserved = 1;
  }
  
  /* Otherwise see if some other process holds it.
   */
  if( !reserved ){
    /* lock the RESERVED byte */
    int lrc = _AFPFSSetLock(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 = _AFPFSSetLock(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;
}

/* AFP-style locking following the behavior of unixLock, see the unixLock 
** function comments for details of lock management. */






















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,
................................................................................
  ** 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 = _AFPFSSetLock(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
................................................................................
  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 = _AFPFSSetLock(context->dbPath, pFile, 
          SHARED_FIRST+context->sharedByte, 1, 1);
    if( IS_LOCK_ERROR(lrc1) ){
      lrc1Errno = pFile->lastErrno;
    }
    /* Drop the temporary PENDING lock */
    lrc2 = _AFPFSSetLock(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;
................................................................................
    ** 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 = _AFPFSSetLock(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 = _AFPFSSetLock(context->dbPath, pFile, SHARED_FIRST +
                         context->sharedByte, 1, 0)) ){
        int failed2 = SQLITE_OK;
        /* now attemmpt to get the exclusive lock range */
        failed = _AFPFSSetLock(context->dbPath, pFile, SHARED_FIRST, 
                               SHARED_SIZE, 1);
        if( failed && (failed2 = _AFPFSSetLock(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;
................................................................................
  if( CHECK_THREADID(pFile) ){
    return SQLITE_MISUSE;
  }
  unixEnterMutex();
  if( pFile->locktype>SHARED_LOCK ){
    
    if( pFile->locktype==EXCLUSIVE_LOCK ){
      rc = _AFPFSSetLock(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 = _AFPFSSetLock(pCtx->dbPath, pFile, sharedLockByte, 1, 1);
      }
    }
    if( rc==SQLITE_OK && pFile->locktype>=PENDING_LOCK ){
      rc = _AFPFSSetLock(pCtx->dbPath, pFile, PENDING_BYTE, 1, 0);
    } 
    if( rc==SQLITE_OK && pFile->locktype>=RESERVED_LOCK ){
      rc = _AFPFSSetLock(pCtx->dbPath, pFile, RESERVED_BYTE, 1, 0);
    }
  }else if( locktype==NO_LOCK ){
    /* clear the shared lock */
    int sharedLockByte = SHARED_FIRST+pCtx->sharedByte;
    rc = _AFPFSSetLock(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 );
................................................................................
*/

/*
** Proxy locking is only available on MacOSX 
*/
#if defined(__DARWIN__) && SQLITE_ENABLE_LOCKING_STYLE



static int getDbPathForUnixFile(unixFile *pFile, char *dbPath);
static int getLockPath(const char *dbPath, char *lPath, size_t maxLen);
static int createProxyUnixFile(const char *path, unixFile **ppFile);
static int fillInUnixFile(sqlite3_vfs *pVfs, int h, int dirfd, sqlite3_file *pId, const char *zFilename, int noLock, int isDelete);
static int takeConch(unixFile *pFile);
static int releaseConch(unixFile *pFile);
static int unixRandomness(sqlite3_vfs *pVfs, int nBuf, char *zBuf);






#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;
  char *conchFilePath;
  unixFile *lockProxy;
  char *lockProxyPath;
  char *dbPath;
  int conchHeld;
  void *oldLockingContext; /* preserve the original locking context for close */


  sqlite3_io_methods const *pOldMethod; /* ditto pMethod */
};


static int proxyCheckReservedLock(sqlite3_file *id, int *pResOut) {
  unixFile *pFile = (unixFile*)id;
  int rc = takeConch(pFile);
  if( rc==SQLITE_OK ){
    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
    unixFile *proxy = pCtx->lockProxy;
    return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
  }
  return rc;
}

static int proxyLock(sqlite3_file *id, int locktype) {
  unixFile *pFile = (unixFile*)id;
  int rc = takeConch(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;
}

static int proxyUnlock(sqlite3_file *id, int locktype) {
  unixFile *pFile = (unixFile*)id;
  int rc = takeConch(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.
 */
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);
    }
    if( conchFile ){
      if( pCtx->conchHeld ){
        rc = releaseConch(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;
}

/* 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 genHostID(char *pHostID){
  int pid, fd, i, len;
  unsigned char *key = (unsigned char *)pHostID;
  
  memset(key, 0, HOSTIDLEN);
  len = 0;
  fd = open("/dev/urandom", O_RDONLY);
  if( fd>=0 ){
................................................................................
    }
  }
#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 int getHostIDPath(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 getHostID(char *pHostID, int *pError){
  int fd;
  char path[MAXPATHLEN]; 
  size_t len;
	int rc=SQLITE_OK;

  getHostIDPath(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 */
................................................................................
    }
    close(fd); /* silently leak the fd if it fails */
    OSTRACE3("GETHOSTID  read %s pid=%d\n", pHostID, getpid());
    return rc;
  }else{
    int i;
    /* we're creating the host ID file (use a random string of bytes) */
    genHostID(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;
  }
}





















































































/* 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 takeConch(unixFile *pFile){
  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
  
  if( pCtx->conchHeld>0 ){
    return SQLITE_OK;
  }else{
    unixFile *conchFile = pCtx->conchFile;
    char testValue[CONCHLEN];
................................................................................
    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 = getHostID(testValue, &pError);
			if( rc&SQLITE_IOERR==SQLITE_IOERR ){
				pFile->lastErrno = pError;
			}
      if( pCtx->lockProxyPath ){
        strlcpy(&testValue[HOSTIDLEN], pCtx->lockProxyPath, MAXPATHLEN);
      }
    }
    if( rc!=SQLITE_OK ){
      goto end_takeconch;
    }
................................................................................
      ** 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 ){
      getLockPath(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);
................................................................................
      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? takeConch 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 = createProxyUnixFile(path, &pCtx->lockProxy);
    }
    if( rc==SQLITE_OK ){
      pCtx->conchHeld = 1;

      if( tLockPath ){
        pCtx->lockProxyPath = sqlite3DbStrDup(0, tLockPath);
        if( pCtx->lockProxy->pMethod == &afpIoMethods ){
................................................................................
    } else {
      conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
    }
    OSTRACE3("TAKECONCH  %d %s\n", conchFile->h, rc==SQLITE_OK?"ok":"failed");
    return rc;
  }
}
  



static int releaseConch(unixFile *pFile){




  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
  int rc;
  unixFile *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;
}












static int getConchPathFromDBPath(char *dbPath, char **pConchPath){
  int i;

  int len = strlen(dbPath);
  char *conchPath;

  


  conchPath = (char *)sqlite3_malloc(len + 8);
  if( conchPath==0 ){
    return SQLITE_NOMEM;
  }
  strlcpy(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++;
  }
  conchPath[i+1]='\0';
  strlcat(conchPath, "-conch", len + 8);
  *pConchPath = conchPath;
  return SQLITE_OK;
}





static int getLockPath(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
  {
    char utdir[MAXPATHLEN];
    
    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 */
      int err = errno;
#  ifdef SQLITE_DEBUG
      if( err!=EEXIST ){
        fprintf(stderr, "getLockPath: 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 = 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;
}

/* 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 taken = 0;
................................................................................
    }
    sqlite3_free(oldPath);
    pCtx->lockProxyPath = sqlite3DbStrDup(0, path);
  }
  
  return rc;
}






























/*
** 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 transformUnixFileForLockProxy(unixFile *pFile, const char *path) {
  proxyLockingContext *pCtx;
  char dbPath[MAXPATHLEN];
  char *lockPath=NULL;
  int rc = SQLITE_OK;
  
  if( pFile->locktype!=NO_LOCK ){
    return SQLITE_BUSY;
  }
  getDbPathForUnixFile(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,
................................................................................

  pCtx = sqlite3_malloc( sizeof(*pCtx) );
  if( pCtx==0 ){
    return SQLITE_NOMEM;
  }
  memset(pCtx, 0, sizeof(*pCtx));

  rc = getConchPathFromDBPath(dbPath, &pCtx->conchFilePath);
  if( rc==SQLITE_OK ){
    rc = createProxyUnixFile(pCtx->conchFilePath, &pCtx->conchFile);
  }  
  if( rc==SQLITE_OK && lockPath ){
    pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
  }

end_transform_file:
  if( rc==SQLITE_OK ){
................................................................................
    }
    sqlite3_free(pCtx->conchFilePath); 
    sqlite3_free(pCtx);
  }
  OSTRACE3("TRANSPROXY  %d %s\n", pFile->h,
           (rc==SQLITE_OK ? "ok" : "failed"));
  return rc;
} 

static int createProxyUnixFile(const char *path, unixFile **ppFile) {

  int fd;
  int dirfd = -1;











  unixFile *pNew;

  int rc = SQLITE_OK;




  fd = open(path, O_RDWR | O_CREAT, SQLITE_DEFAULT_FILE_PERMISSIONS);
  if( fd<0 ){
    return SQLITE_CANTOPEN;
  }
  
  pNew = (unixFile *)sqlite3_malloc(sizeof(unixFile));
  if( pNew==NULL ){



























    rc = SQLITE_NOMEM;
    goto end_create_proxy;




  }
  memset(pNew, 0, sizeof(unixFile));

  
  rc = fillInUnixFile(NULL, fd, dirfd, (sqlite3_file*)pNew, path, 0, 0);












  if( rc==SQLITE_OK ){
    *ppFile = pNew;

















    return SQLITE_OK;
  }
end_create_proxy:    
  close(fd); /* silently leak fd if error, we're already in error */





  sqlite3_free(pNew);





  return rc;
}


















#endif /* defined(__DARWIN__) && 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.
................................................................................
  }
  return SQLITE_OK;
}

#ifdef SQLITE_TEST
/*
** Count the number of fullsyncs and normal syncs.  This is used to test
** that syncs and fullsyncs are occuring at the right times.
*/
int sqlite3_sync_count = 0;
int sqlite3_fullsync_count = 0;
#endif

/*
** Use the fdatasync() API only if the HAVE_FDATASYNC macro is defined.
................................................................................
#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 
  if( dataOnly ){
    rc = fdatasync(fd);
    if( OS_VXWORKS && rc==-1 && errno==ENOTSUP ){
      rc = fsync(fd);
................................................................................
      return SQLITE_OK;
    }
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__DARWIN__)
    case SQLITE_GET_LOCKPROXYFILE: {
      unixFile *pFile = (unixFile*)id;
      if( pFile->pMethod == &proxyIoMethods ){
        proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
        takeConch(pFile);
        if( pCtx->lockProxyPath ){
          *(const char **)pArg = pCtx->lockProxyPath;
        }else{
          *(const char **)pArg = ":auto: (not held)";
        }
      } else {
        *(const char **)pArg = NULL;
................................................................................
        }else{
          /* turn on proxy file locking */
          rc = transformUnixFileForLockProxy(pFile, proxyPath);
        }
      }
      return rc;
    }
#endif
  }
  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
................................................................................
/*
** Here ends the implementation of all sqlite3_file methods.
**
********************** End sqlite3_file Methods *******************************
******************************************************************************/

/*













** 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.
................................................................................
  proxyCheckReservedLock    /* xCheckReservedLock method */
);
#endif


#if defined(__DARWIN__) && SQLITE_ENABLE_LOCKING_STYLE
/* 
** This procedure attempts to determine the best locking strategy for
** the given database file.  It then returns the sqlite3_io_methods
** object that implements that strategy.
**
** This is for MacOSX only.
*/
static const sqlite3_io_methods *autolockIoFinder(
  const char *filePath,    /* name of the database file */
  int fd                   /* file descriptor open on the database file */
){
  static const struct Mapping {
    const char *zFilesystem;
    const sqlite3_io_methods *pMethods;
  } aMap[] = {
    { "hfs",    &posixIoMethods },
    { "ufs",    &posixIoMethods },
    { "afpfs",  &afpIoMethods },
#ifdef SQLITE_ENABLE_AFP_LOCKING_SMB
    { "smbfs",  &afpIoMethods },
#else
................................................................................
    { 0, 0 }
  };
  int i;
  struct statfs fsInfo;
  struct flock lockInfo;

  if( !filePath ){


    return &nolockIoMethods;
  }
  if( statfs(filePath, &fsInfo) != -1 ){
    if( fsInfo.f_flags & MNT_RDONLY ){
      return &nolockIoMethods;
    }
    for(i=0; aMap[i].zFilesystem; i++){
................................................................................
  }else{
    pNew->pMethod = pLockingStyle;
    OpenCounter(+1);
  }
  return rc;
}

#if SQLITE_ENABLE_LOCKING_STYLE
static int getDbPathForUnixFile(unixFile *pFile, char *dbPath){
#if defined(__DARWIN__)
  if( pFile->pMethod == &afpIoMethods ){
    /* afp style keeps a reference to the db path in the filePath field 
    ** of the struct */
    assert( 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;
}
#endif

/*
** 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.
**
................................................................................
** 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, 
  const char *zPath, 
  sqlite3_file *pFile,
  int flags,
  int *pOutFlags
){
  int fd = 0;                    /* 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;

  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
  int isCreate     = (flags & SQLITE_OPEN_CREATE);
................................................................................
  return fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete);
}

/*
** Delete the file at zPath. If the dirSync argument is true, fsync()
** the directory after deleting the file.
*/
static int unixDelete(sqlite3_vfs *NotUsed, const char *zPath, int dirSync){




  int rc = SQLITE_OK;
  UNUSED_PARAMETER(NotUsed);
  SimulateIOError(return SQLITE_IOERR_DELETE);
  unlink(zPath);
#ifndef SQLITE_DISABLE_DIRSYNC
  if( dirSync ){
    int fd;
................................................................................
**     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, 
  const char *zPath, 
  int flags, 
  int *pResOut
){
  int amode = 0;
  UNUSED_PARAMETER(NotUsed);
  SimulateIOError( return SQLITE_IOERR_ACCESS; );
  switch( flags ){
    case SQLITE_ACCESS_EXISTS:
      amode = F_OK;
................................................................................
  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 directly has been unlinked.
  */
  SimulateIOError( return SQLITE_ERROR );

  assert( pVfs->mxPathname==MAX_PATHNAME );
  UNUSED_PARAMETER(pVfs);

  zOut[nOut-1] = '\0';
................................................................................
  sleep(seconds);
  return seconds*1000000;
#endif
  UNUSED_PARAMETER(NotUsed);
}

/*
** The following variable, if set to a non-zero value, becomes the result

** returned from sqlite3OsCurrentTime().  This is used for testing.
*/
#ifdef SQLITE_TEST
int sqlite3_current_time = 0;
#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.
*/
................................................................................
    *prNow = sqlite3_current_time/86400.0 + 2440587.5;
  }
#endif
  UNUSED_PARAMETER(NotUsed);
  return 0;
}








static int unixGetLastError(sqlite3_vfs *NotUsed, int NotUsed2, char *NotUsed3){
  UNUSED_PARAMETER(NotUsed);
  UNUSED_PARAMETER(NotUsed2);
  UNUSED_PARAMETER(NotUsed3);
  return 0;
}

................................................................................
/*
** 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.





*/
int sqlite3_os_init(void){ 
  /* Macro to define the static contents of an sqlite3_vfs structure for
  ** the unix backend. The two parameters are the values to use for
  ** the sqlite3_vfs.zName and sqlite3_vfs.pAppData fields, respectively.








  ** 





  */
  #define UNIXVFS(VFSNAME, FINDER) {                        \
    1,                    /* iVersion */                    \
    sizeof(unixFile),     /* szOsFile */                    \
    MAX_PATHNAME,         /* mxPathname */                  \
    0,                    /* pNext */                       \
    VFSNAME,              /* zName */                       \
................................................................................
    unixDlClose,          /* xDlClose */                    \
    unixRandomness,       /* xRandomness */                 \
    unixSleep,            /* xSleep */                      \
    unixCurrentTime,      /* xCurrentTime */                \
    unixGetLastError      /* xGetLastError */               \
  }

  unsigned int i;







  static sqlite3_vfs aVfs[] = {
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__DARWIN__)
    UNIXVFS("unix",          autolockIoFinder ),
#else
    UNIXVFS("unix",          posixIoFinder ),
#endif
    UNIXVFS("unix-none",     nolockIoFinder ),
................................................................................
    UNIXVFS("unix-flock",    flockIoFinder ),
#endif
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__DARWIN__)
    UNIXVFS("unix-afp",      afpIoFinder ),
    UNIXVFS("unix-proxy",    proxyIoFinder ),
#endif
  };



  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. This is a no-op for unix.




*/
int sqlite3_os_end(void){ 
  return SQLITE_OK; 
}
 
#endif /* SQLITE_OS_UNIX */







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** 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:
**      + 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)
**      + for proxy 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.
**   *  Definitions of sqlite3_vfs objects for all locking methods
**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
**
** $Id: os_unix.c,v 1.225 2008/12/03 19:34:47 drh Exp $
*/
#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),
................................................................................
/****************** 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; );
  
................................................................................
    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.  
................................................................................
  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 );
................................................................................
/******************* 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; );
  
................................................................................
  }
  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.  
................................................................................
  /* 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,
................................................................................
#if defined(__DARWIN__) && 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;
  //SimulateIOErrorBenign(1);
................................................................................
    }
    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; );
  
................................................................................
    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,
................................................................................
  ** 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
................................................................................
  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;
................................................................................
    ** 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;
................................................................................
  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 );
................................................................................
*/

/*
** Proxy locking is only available on MacOSX 
*/
#if defined(__DARWIN__) && SQLITE_ENABLE_LOCKING_STYLE


/*
** Forward reference
*/
static int fillInUnixFile(
  sqlite3_vfs *pVfs,
  int h,
  int dirfd,
  sqlite3_file *pId,
  const char *zFilename,
  int noLock,
  int isDelete
);


#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, i, len;
  unsigned char *key = (unsigned char *)pHostID;
  
  memset(key, 0, HOSTIDLEN);
  len = 0;
  fd = open("/dev/urandom", O_RDONLY);
  if( fd>=0 ){
................................................................................
    }
  }
#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 int 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 */
................................................................................
    }
    close(fd); /* silently leak the fd if it fails */
    OSTRACE3("GETHOSTID  read %s pid=%d\n", pHostID, getpid());
    return rc;
  }else{
    int i;
    /* 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
  {
    char utdir[MAXPATHLEN];
    
    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 */
      int err = errno;
#  ifdef SQLITE_DEBUG
      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 = 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) {
  int fd;
  int dirfd = -1;
  unixFile *pNew;
  int rc = SQLITE_OK;

  fd = open(path, O_RDWR | O_CREAT, SQLITE_DEFAULT_FILE_PERMISSIONS);
  if( fd<0 ){
    return SQLITE_CANTOPEN;
  }
  
  pNew = (unixFile *)sqlite3_malloc(sizeof(unixFile));
  if( pNew==NULL ){
    rc = SQLITE_NOMEM;
    goto end_create_proxy;
  }
  memset(pNew, 0, sizeof(unixFile));
  
  rc = fillInUnixFile(NULL, fd, dirfd, (sqlite3_file*)pNew, path, 0, 0);
  if( rc==SQLITE_OK ){
    *ppFile = pNew;
    return SQLITE_OK;
  }
end_create_proxy:    
  close(fd); /* silently leak fd if error, we're already in error */
  sqlite3_free(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];
................................................................................
    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&SQLITE_IOERR==SQLITE_IOERR ){
        pFile->lastErrno = pError;
      }
      if( pCtx->lockProxyPath ){
        strlcpy(&testValue[HOSTIDLEN], pCtx->lockProxyPath, MAXPATHLEN);
      }
    }
    if( rc!=SQLITE_OK ){
      goto end_takeconch;
    }
................................................................................
      ** 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);
................................................................................
      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 ){
................................................................................
    } 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 = 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( 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 taken = 0;
................................................................................
    }
    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(__DARWIN__)
  if( pFile->pMethod == &afpIoMethods ){
    /* afp style keeps a reference to the db path in the filePath field 
    ** of the struct */
    assert( 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 transformUnixFileForLockProxy(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,
................................................................................

  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);
  }

end_transform_file:
  if( rc==SQLITE_OK ){
................................................................................
    }
    sqlite3_free(pCtx->conchFilePath); 
    sqlite3_free(pCtx);
  }
  OSTRACE3("TRANSPROXY  %d %s\n", pFile->h,
           (rc==SQLITE_OK ? "ok" : "failed"));
  return rc;
}


/*
** 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(__DARWIN__) && 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.
................................................................................
  }
  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

/*
** Use the fdatasync() API only if the HAVE_FDATASYNC macro is defined.
................................................................................
#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 
  if( dataOnly ){
    rc = fdatasync(fd);
    if( OS_VXWORKS && rc==-1 && errno==ENOTSUP ){
      rc = fsync(fd);
................................................................................
      return SQLITE_OK;
    }
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__DARWIN__)
    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;
................................................................................
        }else{
          /* turn on proxy file locking */
          rc = transformUnixFileForLockProxy(pFile, proxyPath);
        }
      }
      return rc;
    }
#endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__DARWIN__) */
  }
  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
................................................................................
/*
** 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.
**
**
** 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.
................................................................................
  proxyCheckReservedLock    /* xCheckReservedLock method */
);
#endif


#if defined(__DARWIN__) && 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 *autolockIoFinder(
  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
................................................................................
    { 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++){
................................................................................
  }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.
**
................................................................................
** 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 */
){
  int fd = 0;                    /* 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;

  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
  int isCreate     = (flags & SQLITE_OPEN_CREATE);
................................................................................
  return fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete);
}

/*
** 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;
................................................................................
**     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;
................................................................................
  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';
................................................................................
  sleep(seconds);
  return seconds*1000000;
#endif
  UNUSED_PARAMETER(NotUsed);
}

/*
** 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.
*/
................................................................................
    *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;
}

................................................................................
/*
** 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 "finder"
  ** function.  The FINDER parameter to this macro is the name of 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 */                       \
................................................................................
    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 && defined(__DARWIN__)
    UNIXVFS("unix",          autolockIoFinder ),
#else
    UNIXVFS("unix",          posixIoFinder ),
#endif
    UNIXVFS("unix-none",     nolockIoFinder ),
................................................................................
    UNIXVFS("unix-flock",    flockIoFinder ),
#endif
#if SQLITE_ENABLE_LOCKING_STYLE && defined(__DARWIN__)
    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 */