sqlite 3.5.1 windows source

1 files changed, 2749 insertions, 0 deletions

diff --git a/libraries/sqlite/win32/os_unix.c b/libraries/sqlite/win32/os_unix.c
new file mode 100755
index 0000000..e95435e
--- /dev/null
+++ b/libraries/sqlite/win32/os_unix.c
@@ -0,0 +1,2749 @@
+/*
+** 2004 May 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains code that is specific to Unix systems.
+*/
+#include "sqliteInt.h"
+#if OS_UNIX              /* This file is used on unix only */
+
+/* #define SQLITE_ENABLE_LOCKING_STYLE 0 */
+
+/*
+** These #defines should enable >2GB file support on Posix if the
+** underlying operating system supports it.  If the OS lacks
+** large file support, these should be no-ops.
+**
+** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
+** on the compiler command line.  This is necessary if you are compiling
+** on a recent machine (ex: RedHat 7.2) but you want your code to work
+** on an older machine (ex: RedHat 6.0).  If you compile on RedHat 7.2
+** without this option, LFS is enable.  But LFS does not exist in the kernel
+** in RedHat 6.0, so the code won't work.  Hence, for maximum binary
+** portability you should omit LFS.
+*/
+#ifndef SQLITE_DISABLE_LFS
+# define _LARGE_FILE       1
+# ifndef _FILE_OFFSET_BITS
+#   define _FILE_OFFSET_BITS 64
+# endif
+# define _LARGEFILE_SOURCE 1
+#endif
+
+/*
+** standard include files.
+*/
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/time.h>
+#include <errno.h>
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+#include <sys/ioctl.h>
+#include <sys/param.h>
+#include <sys/mount.h>
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+/*
+** If we are to be thread-safe, include the pthreads header and define
+** the SQLITE_UNIX_THREADS macro.
+*/
+#if SQLITE_THREADSAFE
+# include <pthread.h>
+# define SQLITE_UNIX_THREADS 1
+#endif
+
+/*
+** Default permissions when creating a new file
+*/
+#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
+# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
+#endif
+
+/*
+** Maximum supported path-length.
+*/
+#define MAX_PATHNAME 512
+
+
+/*
+** The unixFile structure is subclass of sqlite3_file specific for the unix
+** protability layer.
+*/
+typedef struct unixFile unixFile;
+struct unixFile {
+  sqlite3_io_methods const *pMethod;  /* Always the first entry */
+#ifdef SQLITE_TEST
+  /* In test mode, increase the size of this structure a bit so that 
+  ** it is larger than the struct CrashFile defined in test6.c.
+  */
+  char aPadding[32];
+#endif
+  struct openCnt *pOpen;    /* Info about all open fd's on this inode */
+  struct lockInfo *pLock;   /* Info about locks on this inode */
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+  void *lockingContext;     /* Locking style specific state */
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+  int h;                    /* The file descriptor */
+  unsigned char locktype;   /* The type of lock held on this fd */
+  int dirfd;                /* File descriptor for the directory */
+#if SQLITE_THREADSAFE
+  pthread_t tid;            /* The thread that "owns" this unixFile */
+#endif
+};
+
+/*
+** Include code that is common to all os_*.c files
+*/
+#include "os_common.h"
+
+/*
+** Define various macros that are missing from some systems.
+*/
+#ifndef O_LARGEFILE
+# define O_LARGEFILE 0
+#endif
+#ifdef SQLITE_DISABLE_LFS
+# undef O_LARGEFILE
+# define O_LARGEFILE 0
+#endif
+#ifndef O_NOFOLLOW
+# define O_NOFOLLOW 0
+#endif
+#ifndef O_BINARY
+# define O_BINARY 0
+#endif
+
+/*
+** The DJGPP compiler environment looks mostly like Unix, but it
+** lacks the fcntl() system call.  So redefine fcntl() to be something
+** that always succeeds.  This means that locking does not occur under
+** DJGPP.  But it's DOS - what did you expect?
+*/
+#ifdef __DJGPP__
+# define fcntl(A,B,C) 0
+#endif
+
+/*
+** The threadid macro resolves to the thread-id or to 0.  Used for
+** testing and debugging only.
+*/
+#if SQLITE_THREADSAFE
+#define threadid pthread_self()
+#else
+#define threadid 0
+#endif
+
+/*
+** Set or check the unixFile.tid field.  This field is set when an unixFile
+** is first opened.  All subsequent uses of the unixFile verify that the
+** same thread is operating on the unixFile.  Some operating systems do
+** not allow locks to be overridden by other threads and that restriction
+** means that sqlite3* database handles cannot be moved from one thread
+** to another.  This logic makes sure a user does not try to do that
+** by mistake.
+**
+** Version 3.3.1 (2006-01-15):  unixFile can be moved from one thread to
+** another as long as we are running on a system that supports threads
+** overriding each others locks (which now the most common behavior)
+** or if no locks are held.  But the unixFile.pLock field needs to be
+** recomputed because its key includes the thread-id.  See the 
+** transferOwnership() function below for additional information
+*/
+#if SQLITE_THREADSAFE
+# define SET_THREADID(X)   (X)->tid = pthread_self()
+# define CHECK_THREADID(X) (threadsOverrideEachOthersLocks==0 && \
+                            !pthread_equal((X)->tid, pthread_self()))
+#else
+# define SET_THREADID(X)
+# define CHECK_THREADID(X) 0
+#endif
+
+/*
+** 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 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 that fstat() fills in)
+** and check for locks already existing on that inode.  When locks are
+** created or removed, we have to look at our own internal record of the
+** locks to see if another thread has previously set a lock on that same
+** inode.
+**
+** The sqlite3_file structure for POSIX is no longer just an integer file
+** descriptor.  It is now a structure that holds the integer file
+** descriptor and a pointer to a structure that describes the internal
+** locks on the corresponding inode.  There is one locking structure
+** per inode, so if the same inode is opened twice, both unixFile structures
+** point to the same locking structure.  The locking structure keeps
+** a reference count (so we will know when to delete it) and a "cnt"
+** field that tells us its internal lock status.  cnt==0 means the
+** file is unlocked.  cnt==-1 means the file has an exclusive lock.
+** cnt>0 means there are cnt shared locks on the file.
+**
+** Any attempt to lock or unlock a file first checks the locking
+** structure.  The fcntl() system call is only invoked to set a 
+** POSIX lock if the internal lock structure transitions between
+** a locked and an unlocked state.
+**
+** 2004-Jan-11:
+** More recent discoveries about POSIX advisory locks.  (The more
+** I discover, the more I realize the a POSIX advisory locks are
+** an abomination.)
+**
+** If you close a file descriptor that points to a file that has locks,
+** all locks on that file that are owned by the current process are
+** released.  To work around this problem, each unixFile structure contains
+** a pointer to an openCnt structure.  There is one openCnt structure
+** per open inode, which means that multiple unixFile can point to a single
+** openCnt.  When an attempt is made to close an unixFile, if there are
+** other unixFile open on the same inode that are holding locks, the call
+** to close() the file descriptor is deferred until all of the locks clear.
+** The openCnt structure keeps a list of file descriptors that need to
+** be closed and that list is walked (and cleared) when the last lock
+** clears.
+**
+** First, under Linux threads, because each thread has a separate
+** process ID, lock operations in one thread do not override locks
+** to the same file in other threads.  Linux threads behave like
+** separate processes in this respect.  But, if you close a file
+** descriptor in linux threads, all locks are cleared, even locks
+** on other threads and even though the other threads have different
+** process IDs.  Linux threads is inconsistent in this respect.
+** (I'm beginning to think that linux threads is an abomination too.)
+** The consequence of this all is that the hash table for the lockInfo
+** structure has to include the process id as part of its key because
+** locks in different threads are treated as distinct.  But the 
+** openCnt structure should not include the process id in its
+** key because close() clears lock on all threads, not just the current
+** thread.  Were it not for this goofiness in linux threads, we could
+** combine the lockInfo and openCnt structures into a single structure.
+**
+** 2004-Jun-28:
+** On some versions of linux, threads can override each others locks.
+** On others not.  Sometimes you can change the behavior on the same
+** system by setting the LD_ASSUME_KERNEL environment variable.  The
+** POSIX standard is silent as to which behavior is correct, as far
+** as I can tell, so other versions of unix might show the same
+** inconsistency.  There is no little doubt in my mind that posix
+** advisory locks and linux threads are profoundly broken.
+**
+** To work around the inconsistencies, we have to test at runtime 
+** whether or not threads can override each others locks.  This test
+** is run once, the first time any lock is attempted.  A static 
+** variable is set to record the results of this test for future
+** use.
+*/
+
+/*
+** An instance of the following structure serves as the key used
+** to locate a particular lockInfo structure given its inode.
+**
+** If threads cannot override each others locks, then we set the
+** lockKey.tid field to the thread ID.  If threads can override
+** each others locks then tid is always set to zero.  tid is omitted
+** if we compile without threading support.
+*/
+struct lockKey {
+  dev_t dev;       /* Device number */
+  ino_t ino;       /* Inode number */
+#if SQLITE_THREADSAFE
+  pthread_t tid;   /* Thread ID or zero if threads can override each other */
+#endif
+};
+
+/*
+** An instance of the following structure is allocated for each open
+** inode on each thread with a different process ID.  (Threads have
+** different process IDs on linux, but not on most other unixes.)
+**
+** A single inode can have multiple file descriptors, so each unixFile
+** structure contains a pointer to an instance of this object and this
+** object keeps a count of the number of unixFile pointing to it.
+*/
+struct lockInfo {
+  struct lockKey key;  /* The lookup key */
+  int cnt;             /* Number of SHARED locks held */
+  int locktype;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
+  int nRef;            /* Number of pointers to this structure */
+};
+
+/*
+** An instance of the following structure serves as the key used
+** to locate a particular openCnt structure given its inode.  This
+** is the same as the lockKey except that the thread ID is omitted.
+*/
+struct openKey {
+  dev_t dev;   /* Device number */
+  ino_t ino;   /* Inode number */
+};
+
+/*
+** An instance of the following structure is allocated for each open
+** inode.  This structure keeps track of the number of locks on that
+** inode.  If a close is attempted against an inode that is holding
+** locks, the close is deferred until all locks clear by adding the
+** file descriptor to be closed to the pending list.
+*/
+struct openCnt {
+  struct openKey key;   /* The lookup key */
+  int nRef;             /* Number of pointers to this structure */
+  int nLock;            /* Number of outstanding locks */
+  int nPending;         /* Number of pending close() operations */
+  int *aPending;        /* Malloced space holding fd's awaiting a close() */
+};
+
+/* 
+** These hash tables map inodes and file descriptors (really, lockKey and
+** openKey structures) into lockInfo and openCnt structures.  Access to 
+** these hash tables must be protected by a mutex.
+*/
+static Hash lockHash = {SQLITE_HASH_BINARY, 0, 0, 0, 0, 0};
+static Hash openHash = {SQLITE_HASH_BINARY, 0, 0, 0, 0, 0};
+
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+/*
+** The locking styles are associated with the different file locking
+** capabilities supported by different file systems.  
+**
+** POSIX locking style fully supports shared and exclusive byte-range locks 
+** ADP locking only supports exclusive byte-range locks
+** FLOCK only supports a single file-global exclusive lock
+** DOTLOCK isn't a true locking style, it refers to the use of a special
+**   file named the same as the database file with a '.lock' extension, this
+**   can be used on file systems that do not offer any reliable file locking
+** NO locking means that no locking will be attempted, this is only used for
+**   read-only file systems currently
+** UNSUPPORTED means that no locking will be attempted, this is only used for
+**   file systems that are known to be unsupported
+*/
+typedef enum {
+        posixLockingStyle = 0,       /* standard posix-advisory locks */
+        afpLockingStyle,             /* use afp locks */
+        flockLockingStyle,           /* use flock() */
+        dotlockLockingStyle,         /* use <file>.lock files */
+        noLockingStyle,              /* useful for read-only file system */
+        unsupportedLockingStyle      /* indicates unsupported file system */
+} sqlite3LockingStyle;
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+/*
+** Helper functions to obtain and relinquish the global mutex.
+*/
+static void enterMutex(){
+  sqlite3_mutex_enter(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+static void leaveMutex(){
+  sqlite3_mutex_leave(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+
+#if SQLITE_THREADSAFE
+/*
+** This variable records whether or not threads can override each others
+** locks.
+**
+**    0:  No.  Threads cannot override each others locks.
+**    1:  Yes.  Threads can override each others locks.
+**   -1:  We don't know yet.
+**
+** On some systems, we know at compile-time if threads can override each
+** others locks.  On those systems, the SQLITE_THREAD_OVERRIDE_LOCK macro
+** will be set appropriately.  On other systems, we have to check at
+** runtime.  On these latter systems, SQLTIE_THREAD_OVERRIDE_LOCK is
+** undefined.
+**
+** This variable normally has file scope only.  But during testing, we make
+** it a global so that the test code can change its value in order to verify
+** that the right stuff happens in either case.
+*/
+#ifndef SQLITE_THREAD_OVERRIDE_LOCK
+# define SQLITE_THREAD_OVERRIDE_LOCK -1
+#endif
+#ifdef SQLITE_TEST
+int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
+#else
+static int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
+#endif
+
+/*
+** This structure holds information passed into individual test
+** threads by the testThreadLockingBehavior() routine.
+*/
+struct threadTestData {
+  int fd;                /* File to be locked */
+  struct flock lock;     /* The locking operation */
+  int result;            /* Result of the locking operation */
+};
+
+#ifdef SQLITE_LOCK_TRACE
+/*
+** Print out information about all locking operations.
+**
+** This routine is used for troubleshooting locks on multithreaded
+** platforms.  Enable by compiling with the -DSQLITE_LOCK_TRACE
+** command-line option on the compiler.  This code is normally
+** turned off.
+*/
+static int lockTrace(int fd, int op, struct flock *p){
+  char *zOpName, *zType;
+  int s;
+  int savedErrno;
+  if( op==F_GETLK ){
+    zOpName = "GETLK";
+  }else if( op==F_SETLK ){
+    zOpName = "SETLK";
+  }else{
+    s = fcntl(fd, op, p);
+    sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
+    return s;
+  }
+  if( p->l_type==F_RDLCK ){
+    zType = "RDLCK";
+  }else if( p->l_type==F_WRLCK ){
+    zType = "WRLCK";
+  }else if( p->l_type==F_UNLCK ){
+    zType = "UNLCK";
+  }else{
+    assert( 0 );
+  }
+  assert( p->l_whence==SEEK_SET );
+  s = fcntl(fd, op, p);
+  savedErrno = errno;
+  sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
+     threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
+     (int)p->l_pid, s);
+  if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
+    struct flock l2;
+    l2 = *p;
+    fcntl(fd, F_GETLK, &l2);
+    if( l2.l_type==F_RDLCK ){
+      zType = "RDLCK";
+    }else if( l2.l_type==F_WRLCK ){
+      zType = "WRLCK";
+    }else if( l2.l_type==F_UNLCK ){
+      zType = "UNLCK";
+    }else{
+      assert( 0 );
+    }
+    sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
+       zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
+  }
+  errno = savedErrno;
+  return s;
+}
+#define fcntl lockTrace
+#endif /* SQLITE_LOCK_TRACE */
+
+/*
+** The testThreadLockingBehavior() routine launches two separate
+** threads on this routine.  This routine attempts to lock a file
+** descriptor then returns.  The success or failure of that attempt
+** allows the testThreadLockingBehavior() procedure to determine
+** whether or not threads can override each others locks.
+*/
+static void *threadLockingTest(void *pArg){
+  struct threadTestData *pData = (struct threadTestData*)pArg;
+  pData->result = fcntl(pData->fd, F_SETLK, &pData->lock);
+  return pArg;
+}
+
+/*
+** This procedure attempts to determine whether or not threads
+** can override each others locks then sets the 
+** threadsOverrideEachOthersLocks variable appropriately.
+*/
+static void testThreadLockingBehavior(int fd_orig){
+  int fd;
+  struct threadTestData d[2];
+  pthread_t t[2];
+
+  fd = dup(fd_orig);
+  if( fd<0 ) return;
+  memset(d, 0, sizeof(d));
+  d[0].fd = fd;
+  d[0].lock.l_type = F_RDLCK;
+  d[0].lock.l_len = 1;
+  d[0].lock.l_start = 0;
+  d[0].lock.l_whence = SEEK_SET;
+  d[1] = d[0];
+  d[1].lock.l_type = F_WRLCK;
+  pthread_create(&t[0], 0, threadLockingTest, &d[0]);
+  pthread_create(&t[1], 0, threadLockingTest, &d[1]);
+  pthread_join(t[0], 0);
+  pthread_join(t[1], 0);
+  close(fd);
+  threadsOverrideEachOthersLocks =  d[0].result==0 && d[1].result==0;
+}
+#endif /* SQLITE_THREADSAFE */
+
+/*
+** Release a lockInfo structure previously allocated by findLockInfo().
+*/
+static void releaseLockInfo(struct lockInfo *pLock){
+  if (pLock == NULL)
+    return;
+  pLock->nRef--;
+  if( pLock->nRef==0 ){
+    sqlite3HashInsert(&lockHash, &pLock->key, sizeof(pLock->key), 0);
+    sqlite3_free(pLock);
+  }
+}
+
+/*
+** Release a openCnt structure previously allocated by findLockInfo().
+*/
+static void releaseOpenCnt(struct openCnt *pOpen){
+  if (pOpen == NULL)
+    return;
+  pOpen->nRef--;
+  if( pOpen->nRef==0 ){
+    sqlite3HashInsert(&openHash, &pOpen->key, sizeof(pOpen->key), 0);
+    free(pOpen->aPending);
+    sqlite3_free(pOpen);
+  }
+}
+
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+/*
+** Tests a byte-range locking query to see if byte range locks are 
+** supported, if not we fall back to dotlockLockingStyle.
+*/
+static sqlite3LockingStyle sqlite3TestLockingStyle(
+  const char *filePath, 
+  int fd
+){
+  /* test byte-range lock using fcntl */
+  struct flock lockInfo;
+  
+  lockInfo.l_len = 1;
+  lockInfo.l_start = 0;
+  lockInfo.l_whence = SEEK_SET;
+  lockInfo.l_type = F_RDLCK;
+  
+  if( fcntl(fd, F_GETLK, &lockInfo)!=-1 ) {
+    return posixLockingStyle;
+  } 
+  
+  /* testing for flock can give false positives.  So if if the above test
+  ** fails, then we fall back to using dot-lock style locking.
+  */  
+  return dotlockLockingStyle;
+}
+
+/* 
+** Examines the f_fstypename entry in the statfs structure as returned by 
+** stat() for the file system hosting the database file, assigns the 
+** appropriate locking style based on it's value.  These values and 
+** assignments are based on Darwin/OSX behavior and have not been tested on 
+** other systems.
+*/
+static sqlite3LockingStyle sqlite3DetectLockingStyle(
+  const char *filePath, 
+  int fd
+){
+
+#ifdef SQLITE_FIXED_LOCKING_STYLE
+  return (sqlite3LockingStyle)SQLITE_FIXED_LOCKING_STYLE;
+#else
+  struct statfs fsInfo;
+
+  if (statfs(filePath, &fsInfo) == -1)
+    return sqlite3TestLockingStyle(filePath, fd);
+  
+  if (fsInfo.f_flags & MNT_RDONLY)
+    return noLockingStyle;
+  
+  if( (!strcmp(fsInfo.f_fstypename, "hfs")) ||
+    (!strcmp(fsInfo.f_fstypename, "ufs")) )
+                return posixLockingStyle;
+  
+  if(!strcmp(fsInfo.f_fstypename, "afpfs"))
+    return afpLockingStyle;
+  
+  if(!strcmp(fsInfo.f_fstypename, "nfs")) 
+    return sqlite3TestLockingStyle(filePath, fd);
+  
+  if(!strcmp(fsInfo.f_fstypename, "smbfs"))
+    return flockLockingStyle;
+  
+  if(!strcmp(fsInfo.f_fstypename, "msdos"))
+    return dotlockLockingStyle;
+  
+  if(!strcmp(fsInfo.f_fstypename, "webdav"))
+    return unsupportedLockingStyle;
+  
+  return sqlite3TestLockingStyle(filePath, fd);  
+#endif /* SQLITE_FIXED_LOCKING_STYLE */
+}
+
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+/*
+** Given a file descriptor, locate lockInfo and openCnt structures that
+** describes that file descriptor.  Create new ones if necessary.  The
+** return values might be uninitialized if an error occurs.
+**
+** Return the number of errors.
+*/
+static int findLockInfo(
+  int fd,                      /* The file descriptor used in the key */
+  struct lockInfo **ppLock,    /* Return the lockInfo structure here */
+  struct openCnt **ppOpen      /* Return the openCnt structure here */
+){
+  int rc;
+  struct lockKey key1;
+  struct openKey key2;
+  struct stat statbuf;
+  struct lockInfo *pLock;
+  struct openCnt *pOpen;
+  rc = fstat(fd, &statbuf);
+  if( rc!=0 ) return 1;
+
+  memset(&key1, 0, sizeof(key1));
+  key1.dev = statbuf.st_dev;
+  key1.ino = statbuf.st_ino;
+#if SQLITE_THREADSAFE
+  if( threadsOverrideEachOthersLocks<0 ){
+    testThreadLockingBehavior(fd);
+  }
+  key1.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self();
+#endif
+  memset(&key2, 0, sizeof(key2));
+  key2.dev = statbuf.st_dev;
+  key2.ino = statbuf.st_ino;
+  pLock = (struct lockInfo*)sqlite3HashFind(&lockHash, &key1, sizeof(key1));
+  if( pLock==0 ){
+    struct lockInfo *pOld;
+    pLock = sqlite3_malloc( sizeof(*pLock) );
+    if( pLock==0 ){
+      rc = 1;
+      goto exit_findlockinfo;
+    }
+    pLock->key = key1;
+    pLock->nRef = 1;
+    pLock->cnt = 0;
+    pLock->locktype = 0;
+    pOld = sqlite3HashInsert(&lockHash, &pLock->key, sizeof(key1), pLock);
+    if( pOld!=0 ){
+      assert( pOld==pLock );
+      sqlite3_free(pLock);
+      rc = 1;
+      goto exit_findlockinfo;
+    }
+  }else{
+    pLock->nRef++;
+  }
+  *ppLock = pLock;
+  if( ppOpen!=0 ){
+    pOpen = (struct openCnt*)sqlite3HashFind(&openHash, &key2, sizeof(key2));
+    if( pOpen==0 ){
+      struct openCnt *pOld;
+      pOpen = sqlite3_malloc( sizeof(*pOpen) );
+      if( pOpen==0 ){
+        releaseLockInfo(pLock);
+        rc = 1;
+        goto exit_findlockinfo;
+      }
+      pOpen->key = key2;
+      pOpen->nRef = 1;
+      pOpen->nLock = 0;
+      pOpen->nPending = 0;
+      pOpen->aPending = 0;
+      pOld = sqlite3HashInsert(&openHash, &pOpen->key, sizeof(key2), pOpen);
+      if( pOld!=0 ){
+        assert( pOld==pOpen );
+        sqlite3_free(pOpen);
+        releaseLockInfo(pLock);
+        rc = 1;
+        goto exit_findlockinfo;
+      }
+    }else{
+      pOpen->nRef++;
+    }
+    *ppOpen = pOpen;
+  }
+
+exit_findlockinfo:
+  return rc;
+}
+
+#ifdef SQLITE_DEBUG
+/*
+** Helper function for printing out trace information from debugging
+** binaries. This returns the string represetation of the supplied
+** integer lock-type.
+*/
+static const char *locktypeName(int locktype){
+  switch( locktype ){
+  case NO_LOCK: return "NONE";
+  case SHARED_LOCK: return "SHARED";
+  case RESERVED_LOCK: return "RESERVED";
+  case PENDING_LOCK: return "PENDING";
+  case EXCLUSIVE_LOCK: return "EXCLUSIVE";
+  }
+  return "ERROR";
+}
+#endif
+
+/*
+** If we are currently in a different thread than the thread that the
+** unixFile argument belongs to, then transfer ownership of the unixFile
+** over to the current thread.
+**
+** A unixFile is only owned by a thread on systems where one thread is
+** unable to override locks created by a different thread.  RedHat9 is
+** an example of such a system.
+**
+** Ownership transfer is only allowed if the unixFile is currently unlocked.
+** If the unixFile is locked and an ownership is wrong, then return
+** SQLITE_MISUSE.  SQLITE_OK is returned if everything works.
+*/
+#if SQLITE_THREADSAFE
+static int transferOwnership(unixFile *pFile){
+  int rc;
+  pthread_t hSelf;
+  if( threadsOverrideEachOthersLocks ){
+    /* Ownership transfers not needed on this system */
+    return SQLITE_OK;
+  }
+  hSelf = pthread_self();
+  if( pthread_equal(pFile->tid, hSelf) ){
+    /* We are still in the same thread */
+    OSTRACE1("No-transfer, same thread\n");
+    return SQLITE_OK;
+  }
+  if( pFile->locktype!=NO_LOCK ){
+    /* We cannot change ownership while we are holding a lock! */
+    return SQLITE_MISUSE;
+  }
+  OSTRACE4("Transfer ownership of %d from %d to %d\n",
+            pFile->h, pFile->tid, hSelf);
+  pFile->tid = hSelf;
+  if (pFile->pLock != NULL) {
+    releaseLockInfo(pFile->pLock);
+    rc = findLockInfo(pFile->h, &pFile->pLock, 0);
+    OSTRACE5("LOCK    %d is now %s(%s,%d)\n", pFile->h,
+           locktypeName(pFile->locktype),
+           locktypeName(pFile->pLock->locktype), pFile->pLock->cnt);
+    return rc;
+  } else {
+    return SQLITE_OK;
+  }
+}
+#else
+  /* On single-threaded builds, ownership transfer is a no-op */
+# define transferOwnership(X) SQLITE_OK
+#endif
+
+/*
+** Seek to the offset passed as the second argument, then read cnt 
+** bytes into pBuf. Return the number of bytes actually read.
+*/
+static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
+  int got;
+  i64 newOffset;
+  TIMER_START;
+#if defined(USE_PREAD)
+  got = pread(id->h, pBuf, cnt, offset);
+  SimulateIOError( got = -1 );
+#elif defined(USE_PREAD64)
+  got = pread64(id->h, pBuf, cnt, offset);
+  SimulateIOError( got = -1 );
+#else
+  newOffset = lseek(id->h, offset, SEEK_SET);
+  SimulateIOError( newOffset-- );
+  if( newOffset!=offset ){
+    return -1;
+  }
+  got = read(id->h, pBuf, cnt);
+#endif
+  TIMER_END;
+  OSTRACE5("READ    %-3d %5d %7lld %d\n", id->h, got, offset, TIMER_ELAPSED);
+  return got;
+}
+
+/*
+** Read data from a file into a buffer.  Return SQLITE_OK if all
+** bytes were read successfully and SQLITE_IOERR if anything goes
+** wrong.
+*/
+static int unixRead(
+  sqlite3_file *id, 
+  void *pBuf, 
+  int amt,
+  sqlite3_int64 offset
+){
+  int got;
+  assert( id );
+  got = seekAndRead((unixFile*)id, offset, pBuf, amt);
+  if( got==amt ){
+    return SQLITE_OK;
+  }else if( got<0 ){
+    return SQLITE_IOERR_READ;
+  }else{
+    memset(&((char*)pBuf)[got], 0, amt-got);
+    return SQLITE_IOERR_SHORT_READ;
+  }
+}
+
+/*
+** Seek to the offset in id->offset then read cnt bytes into pBuf.
+** Return the number of bytes actually read.  Update the offset.
+*/
+static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
+  int got;
+  i64 newOffset;
+  TIMER_START;
+#if defined(USE_PREAD)
+  got = pwrite(id->h, pBuf, cnt, offset);
+#elif defined(USE_PREAD64)
+  got = pwrite64(id->h, pBuf, cnt, offset);
+#else
+  newOffset = lseek(id->h, offset, SEEK_SET);
+  if( newOffset!=offset ){
+    return -1;
+  }
+  got = write(id->h, pBuf, cnt);
+#endif
+  TIMER_END;
+  OSTRACE5("WRITE   %-3d %5d %7lld %d\n", id->h, got, offset, TIMER_ELAPSED);
+  return got;
+}
+
+
+/*
+** Write data from a buffer into a file.  Return SQLITE_OK on success
+** or some other error code on failure.
+*/
+static int unixWrite(
+  sqlite3_file *id, 
+  const void *pBuf, 
+  int amt,
+  sqlite3_int64 offset 
+){
+  int wrote = 0;
+  assert( id );
+  assert( amt>0 );
+  while( amt>0 && (wrote = seekAndWrite((unixFile*)id, offset, pBuf, amt))>0 ){
+    amt -= wrote;
+    offset += wrote;
+    pBuf = &((char*)pBuf)[wrote];
+  }
+  SimulateIOError(( wrote=(-1), amt=1 ));
+  SimulateDiskfullError(( wrote=0, amt=1 ));
+  if( amt>0 ){
+    if( wrote<0 ){
+      return SQLITE_IOERR_WRITE;
+    }else{
+      return SQLITE_FULL;
+    }
+  }
+  return SQLITE_OK;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Count the number of fullsyncs and normal syncs.  This is used to test
+** that syncs and fullsyncs are 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.
+** Otherwise use fsync() in its place.
+*/
+#ifndef HAVE_FDATASYNC
+# define fdatasync fsync
+#endif
+
+/*
+** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not
+** the F_FULLFSYNC macro is defined.  F_FULLFSYNC is currently
+** only available on Mac OS X.  But that could change.
+*/
+#ifdef F_FULLFSYNC
+# define HAVE_FULLFSYNC 1
+#else
+# define HAVE_FULLFSYNC 0
+#endif
+
+
+/*
+** The fsync() system call does not work as advertised on many
+** unix systems.  The following procedure is an attempt to make
+** it work better.
+**
+** The SQLITE_NO_SYNC macro disables all fsync()s.  This is useful
+** for testing when we want to run through the test suite quickly.
+** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
+** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
+** or power failure will likely corrupt the database file.
+*/
+static int full_fsync(int fd, int fullSync, int dataOnly){
+  int rc;
+
+  /* Record the number of times that we do a normal fsync() and 
+  ** FULLSYNC.  This is used during testing to verify that this procedure
+  ** gets called with the correct arguments.
+  */
+#ifdef SQLITE_TEST
+  if( fullSync ) sqlite3_fullsync_count++;
+  sqlite3_sync_count++;
+#endif
+
+  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
+  ** no-op
+  */
+#ifdef SQLITE_NO_SYNC
+  rc = SQLITE_OK;
+#else
+
+#if 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);
+  }else{
+    rc = fsync(fd);
+  }
+#endif /* HAVE_FULLFSYNC */
+#endif /* defined(SQLITE_NO_SYNC) */
+
+  return rc;
+}
+
+/*
+** Make sure all writes to a particular file are committed to disk.
+**
+** If dataOnly==0 then both the file itself and its metadata (file
+** size, access time, etc) are synced.  If dataOnly!=0 then only the
+** file data is synced.
+**
+** Under Unix, also make sure that the directory entry for the file
+** has been created by fsync-ing the directory that contains the file.
+** If we do not do this and we encounter a power failure, the directory
+** entry for the journal might not exist after we reboot.  The next
+** SQLite to access the file will not know that the journal exists (because
+** the directory entry for the journal was never created) and the transaction
+** will not roll back - possibly leading to database corruption.
+*/
+static int unixSync(sqlite3_file *id, int flags){
+  int rc;
+  unixFile *pFile = (unixFile*)id;
+
+  int isDataOnly = (flags&SQLITE_SYNC_DATAONLY);
+  int isFullsync = (flags&0x0F)==SQLITE_SYNC_FULL;
+
+  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
+  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
+      || (flags&0x0F)==SQLITE_SYNC_FULL
+  );
+
+  assert( pFile );
+  OSTRACE2("SYNC    %-3d\n", pFile->h);
+  rc = full_fsync(pFile->h, isFullsync, isDataOnly);
+  SimulateIOError( rc=1 );
+  if( rc ){
+    return SQLITE_IOERR_FSYNC;
+  }
+  if( pFile->dirfd>=0 ){
+    OSTRACE4("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd,
+            HAVE_FULLFSYNC, isFullsync);
+#ifndef SQLITE_DISABLE_DIRSYNC
+    /* The directory sync is only attempted if full_fsync is
+    ** turned off or unavailable.  If a full_fsync occurred above,
+    ** then the directory sync is superfluous.
+    */
+    if( (!HAVE_FULLFSYNC || !isFullsync) && full_fsync(pFile->dirfd,0,0) ){
+       /*
+       ** We have received multiple reports of fsync() returning
+       ** errors when applied to directories on certain file systems.
+       ** A failed directory sync is not a big deal.  So it seems
+       ** better to ignore the error.  Ticket #1657
+       */
+       /* return SQLITE_IOERR; */
+    }
+#endif
+    close(pFile->dirfd);  /* Only need to sync once, so close the directory */
+    pFile->dirfd = -1;    /* when we are done. */
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Truncate an open file to a specified size
+*/
+static int unixTruncate(sqlite3_file *id, i64 nByte){
+  int rc;
+  assert( id );
+  rc = ftruncate(((unixFile*)id)->h, (off_t)nByte);
+  SimulateIOError( rc=1 );
+  if( rc ){
+    return SQLITE_IOERR_TRUNCATE;
+  }else{
+    return SQLITE_OK;
+  }
+}
+
+/*
+** Determine the current size of a file in bytes
+*/
+static int unixFileSize(sqlite3_file *id, i64 *pSize){
+  int rc;
+  struct stat buf;
+  assert( id );
+  rc = fstat(((unixFile*)id)->h, &buf);
+  SimulateIOError( rc=1 );
+  if( rc!=0 ){
+    return SQLITE_IOERR_FSTAT;
+  }
+  *pSize = buf.st_size;
+  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, return
+** non-zero.  If the file is unlocked or holds only SHARED locks, then
+** return zero.
+*/
+static int unixCheckReservedLock(sqlite3_file *id){
+  int r = 0;
+  unixFile *pFile = (unixFile*)id;
+
+  assert( pFile );
+  enterMutex(); /* Because pFile->pLock is shared across threads */
+
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->pLock->locktype>SHARED_LOCK ){
+    r = 1;
+  }
+
+  /* Otherwise see if some other process holds it.
+  */
+  if( !r ){
+    struct flock lock;
+    lock.l_whence = SEEK_SET;
+    lock.l_start = RESERVED_BYTE;
+    lock.l_len = 1;
+    lock.l_type = F_WRLCK;
+    fcntl(pFile->h, F_GETLK, &lock);
+    if( lock.l_type!=F_UNLCK ){
+      r = 1;
+    }
+  }
+  
+  leaveMutex();
+  OSTRACE3("TEST WR-LOCK %d %d\n", pFile->h, r);
+
+  return r;
+}
+
+/*
+** Lock the file with the lock specified by parameter locktype - one
+** of the following:
+**
+**     (1) SHARED_LOCK
+**     (2) RESERVED_LOCK
+**     (3) PENDING_LOCK
+**     (4) EXCLUSIVE_LOCK
+**
+** Sometimes when requesting one lock state, additional lock states
+** are inserted in between.  The locking might fail on one of the later
+** transitions leaving the lock state different from what it started but
+** still short of its goal.  The following chart shows the allowed
+** transitions and the inserted intermediate states:
+**
+**    UNLOCKED -> SHARED
+**    SHARED -> RESERVED
+**    SHARED -> (PENDING) -> EXCLUSIVE
+**    RESERVED -> (PENDING) -> EXCLUSIVE
+**    PENDING -> EXCLUSIVE
+**
+** This routine will only increase a lock.  Use the sqlite3OsUnlock()
+** routine to lower a locking level.
+*/
+static int unixLock(sqlite3_file *id, int locktype){
+  /* The following describes the implementation of the various locks and
+  ** lock transitions in terms of the POSIX advisory shared and exclusive
+  ** lock primitives (called read-locks and write-locks below, to avoid
+  ** confusion with SQLite lock names). The algorithms are complicated
+  ** slightly in order to be compatible with windows systems simultaneously
+  ** accessing the same database file, in case that is ever required.
+  **
+  ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
+  ** byte', each single bytes at well known offsets, and the 'shared byte
+  ** range', a range of 510 bytes at a well known offset.
+  **
+  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
+  ** byte'.  If this is successful, a random byte from the 'shared byte
+  ** range' is read-locked and the lock on the 'pending byte' released.
+  **
+  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
+  ** A RESERVED lock is implemented by grabbing a write-lock on the
+  ** 'reserved byte'. 
+  **
+  ** A process may only obtain a PENDING lock after it has obtained a
+  ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
+  ** on the 'pending byte'. This ensures that no new SHARED locks can be
+  ** obtained, but existing SHARED locks are allowed to persist. A process
+  ** does not have to obtain a RESERVED lock on the way to a PENDING lock.
+  ** This property is used by the algorithm for rolling back a journal file
+  ** after a crash.
+  **
+  ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
+  ** implemented by obtaining a write-lock on the entire 'shared byte
+  ** range'. Since all other locks require a read-lock on one of the bytes
+  ** within this range, this ensures that no other locks are held on the
+  ** database. 
+  **
+  ** The reason a single byte cannot be used instead of the 'shared byte
+  ** range' is that some versions of windows do not support read-locks. By
+  ** locking a random byte from a range, concurrent SHARED locks may exist
+  ** even if the locking primitive used is always a write-lock.
+  */
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  struct lockInfo *pLock = pFile->pLock;
+  struct flock lock;
+  int s;
+
+  assert( pFile );
+  OSTRACE7("LOCK    %d %s was %s(%s,%d) pid=%d\n", pFile->h,
+      locktypeName(locktype), locktypeName(pFile->locktype),
+      locktypeName(pLock->locktype), pLock->cnt , getpid());
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** unixFile, do nothing. Don't use the end_lock: exit path, as
+  ** enterMutex() hasn't been called yet.
+  */
+  if( pFile->locktype>=locktype ){
+    OSTRACE3("LOCK    %d %s ok (already held)\n", pFile->h,
+            locktypeName(locktype));
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct
+  */
+  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
+  assert( locktype!=PENDING_LOCK );
+  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+
+  /* This mutex is needed because pFile->pLock is shared across threads
+  */
+  enterMutex();
+
+  /* Make sure the current thread owns the pFile.
+  */
+  rc = transferOwnership(pFile);
+  if( rc!=SQLITE_OK ){
+    leaveMutex();
+    return rc;
+  }
+  pLock = pFile->pLock;
+
+  /* If some thread using this PID has a lock via a different unixFile*
+  ** handle that precludes the requested lock, return BUSY.
+  */
+  if( (pFile->locktype!=pLock->locktype && 
+          (pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK))
+  ){
+    rc = SQLITE_BUSY;
+    goto end_lock;
+  }
+
+  /* If a SHARED lock is requested, and some thread using this PID already
+  ** has a SHARED or RESERVED lock, then increment reference counts and
+  ** return SQLITE_OK.
+  */
+  if( locktype==SHARED_LOCK && 
+      (pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){
+    assert( locktype==SHARED_LOCK );
+    assert( pFile->locktype==0 );
+    assert( pLock->cnt>0 );
+    pFile->locktype = SHARED_LOCK;
+    pLock->cnt++;
+    pFile->pOpen->nLock++;
+    goto end_lock;
+  }
+
+  lock.l_len = 1L;
+
+  lock.l_whence = SEEK_SET;
+
+  /* A PENDING lock is needed before acquiring a SHARED lock and before
+  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
+  ** be released.
+  */
+  if( locktype==SHARED_LOCK 
+      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
+  ){
+    lock.l_type = (locktype==SHARED_LOCK?F_RDLCK:F_WRLCK);
+    lock.l_start = PENDING_BYTE;
+    s = fcntl(pFile->h, F_SETLK, &lock);
+    if( s==(-1) ){
+      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
+      goto end_lock;
+    }
+  }
+
+
+  /* If control gets to this point, then actually go ahead and make
+  ** operating system calls for the specified lock.
+  */
+  if( locktype==SHARED_LOCK ){
+    assert( pLock->cnt==0 );
+    assert( pLock->locktype==0 );
+
+    /* Now get the read-lock */
+    lock.l_start = SHARED_FIRST;
+    lock.l_len = SHARED_SIZE;
+    s = fcntl(pFile->h, F_SETLK, &lock);
+
+    /* Drop the temporary PENDING lock */
+    lock.l_start = PENDING_BYTE;
+    lock.l_len = 1L;
+    lock.l_type = F_UNLCK;
+    if( fcntl(pFile->h, F_SETLK, &lock)!=0 ){
+      rc = SQLITE_IOERR_UNLOCK;  /* This should never happen */
+      goto end_lock;
+    }
+    if( s==(-1) ){
+      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
+    }else{
+      pFile->locktype = SHARED_LOCK;
+      pFile->pOpen->nLock++;
+      pLock->cnt = 1;
+    }
+  }else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){
+    /* We are trying for an exclusive lock but another thread in this
+    ** same process is still holding a shared lock. */
+    rc = SQLITE_BUSY;
+  }else{
+    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
+    ** assumed that there is a SHARED or greater lock on the file
+    ** already.
+    */
+    assert( 0!=pFile->locktype );
+    lock.l_type = F_WRLCK;
+    switch( locktype ){
+      case RESERVED_LOCK:
+        lock.l_start = RESERVED_BYTE;
+        break;
+      case EXCLUSIVE_LOCK:
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = SHARED_SIZE;
+        break;
+      default:
+        assert(0);
+    }
+    s = fcntl(pFile->h, F_SETLK, &lock);
+    if( s==(-1) ){
+      rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
+    }
+  }
+  
+  if( rc==SQLITE_OK ){
+    pFile->locktype = locktype;
+    pLock->locktype = locktype;
+  }else if( locktype==EXCLUSIVE_LOCK ){
+    pFile->locktype = PENDING_LOCK;
+    pLock->locktype = PENDING_LOCK;
+  }
+
+end_lock:
+  leaveMutex();
+  OSTRACE4("LOCK    %d %s %s\n", pFile->h, locktypeName(locktype), 
+      rc==SQLITE_OK ? "ok" : "failed");
+  return rc;
+}
+
+/*
+** Lower the locking level on file descriptor pFile to locktype.  locktype
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int unixUnlock(sqlite3_file *id, int locktype){
+  struct lockInfo *pLock;
+  struct flock lock;
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+
+  assert( pFile );
+  OSTRACE7("UNLOCK  %d %d was %d(%d,%d) pid=%d\n", pFile->h, locktype,
+      pFile->locktype, pFile->pLock->locktype, pFile->pLock->cnt, getpid());
+
+  assert( locktype<=SHARED_LOCK );
+  if( pFile->locktype<=locktype ){
+    return SQLITE_OK;
+  }
+  if( CHECK_THREADID(pFile) ){
+    return SQLITE_MISUSE;
+  }
+  enterMutex();
+  pLock = pFile->pLock;
+  assert( pLock->cnt!=0 );
+  if( pFile->locktype>SHARED_LOCK ){
+    assert( pLock->locktype==pFile->locktype );
+    if( locktype==SHARED_LOCK ){
+      lock.l_type = F_RDLCK;
+      lock.l_whence = SEEK_SET;
+      lock.l_start = SHARED_FIRST;
+      lock.l_len = SHARED_SIZE;
+      if( fcntl(pFile->h, F_SETLK, &lock)==(-1) ){
+        /* This should never happen */
+        rc = SQLITE_IOERR_RDLOCK;
+      }
+    }
+    lock.l_type = F_UNLCK;
+    lock.l_whence = SEEK_SET;
+    lock.l_start = PENDING_BYTE;
+    lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
+    if( fcntl(pFile->h, F_SETLK, &lock)!=(-1) ){
+      pLock->locktype = SHARED_LOCK;
+    }else{
+      rc = SQLITE_IOERR_UNLOCK;  /* This should never happen */
+    }
+  }
+  if( locktype==NO_LOCK ){
+    struct openCnt *pOpen;
+
+    /* Decrement the shared lock counter.  Release the lock using an
+    ** OS call only when all threads in this same process have released
+    ** the lock.
+    */
+    pLock->cnt--;
+    if( pLock->cnt==0 ){
+      lock.l_type = F_UNLCK;
+      lock.l_whence = SEEK_SET;
+      lock.l_start = lock.l_len = 0L;
+      if( fcntl(pFile->h, F_SETLK, &lock)!=(-1) ){
+        pLock->locktype = NO_LOCK;
+      }else{
+        rc = SQLITE_IOERR_UNLOCK;  /* This should never happen */
+      }
+    }
+
+    /* Decrement the count of locks against this same file.  When the
+    ** count reaches zero, close any other file descriptors whose close
+    ** was deferred because of outstanding locks.
+    */
+    pOpen = pFile->pOpen;
+    pOpen->nLock--;
+    assert( pOpen->nLock>=0 );
+    if( pOpen->nLock==0 && pOpen->nPending>0 ){
+      int i;
+      for(i=0; i<pOpen->nPending; i++){
+        close(pOpen->aPending[i]);
+      }
+      free(pOpen->aPending);
+      pOpen->nPending = 0;
+      pOpen->aPending = 0;
+    }
+  }
+  leaveMutex();
+  pFile->locktype = locktype;
+  return rc;
+}
+
+/*
+** Close a file.
+*/
+static int unixClose(sqlite3_file *id){
+  unixFile *pFile = (unixFile *)id;
+  if( !pFile ) return SQLITE_OK;
+  unixUnlock(id, NO_LOCK);
+  if( pFile->dirfd>=0 ) close(pFile->dirfd);
+  pFile->dirfd = -1;
+  enterMutex();
+
+  if( pFile->pOpen->nLock ){
+    /* If there are outstanding locks, do not actually close the file just
+    ** yet because that would clear those locks.  Instead, add the file
+    ** descriptor to pOpen->aPending.  It will be automatically closed when
+    ** the last lock is cleared.
+    */
+    int *aNew;
+    struct openCnt *pOpen = pFile->pOpen;
+    aNew = realloc( pOpen->aPending, (pOpen->nPending+1)*sizeof(int) );
+    if( aNew==0 ){
+      /* If a malloc fails, just leak the file descriptor */
+    }else{
+      pOpen->aPending = aNew;
+      pOpen->aPending[pOpen->nPending] = pFile->h;
+      pOpen->nPending++;
+    }
+  }else{
+    /* There are no outstanding locks so we can close the file immediately */
+    close(pFile->h);
+  }
+  releaseLockInfo(pFile->pLock);
+  releaseOpenCnt(pFile->pOpen);
+
+  leaveMutex();
+  OSTRACE2("CLOSE   %-3d\n", pFile->h);
+  OpenCounter(-1);
+  memset(pFile, 0, sizeof(unixFile));
+  return SQLITE_OK;
+}
+
+
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+#pragma mark AFP Support
+
+/*
+ ** The afpLockingContext structure contains all afp lock specific state
+ */
+typedef struct afpLockingContext afpLockingContext;
+struct afpLockingContext {
+  unsigned long long sharedLockByte;
+  char *filePath;
+};
+
+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 0 on success, 1 on failure.  To match the behavior of the 
+** normal posix file locking (used in unixLock for example), we should 
+** provide 'richer' return codes - specifically to differentiate between
+** 'file busy' and 'file system error' results.
+*/
+static int _AFPFSSetLock(
+  const char *path, 
+  int fd, 
+  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 = fd;
+  OSTRACE5("AFPLOCK setting lock %s for %d in range %llx:%llx\n", 
+    (setLockFlag?"ON":"OFF"), fd, offset, length);
+  err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
+  if ( err==-1 ) {
+    OSTRACE4("AFPLOCK failed to fsctl() '%s' %d %s\n", path, errno, 
+      strerror(errno));
+    return 1; /* error */
+  } else {
+    return 0;
+  }
+}
+
+/*
+ ** 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, return
+ ** non-zero.  If the file is unlocked or holds only SHARED locks, then
+ ** return zero.
+ */
+static int afpUnixCheckReservedLock(sqlite3_file *id){
+  int r = 0;
+  unixFile *pFile = (unixFile*)id;
+  
+  assert( pFile ); 
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  
+  /* Check if a thread in this process holds such a lock */
+  if( pFile->locktype>SHARED_LOCK ){
+    r = 1;
+  }
+  
+  /* Otherwise see if some other process holds it.
+   */
+  if ( !r ) {
+    /* lock the byte */
+    int failed = _AFPFSSetLock(context->filePath, pFile->h, RESERVED_BYTE, 1,1);  
+    if (failed) {
+      /* if we failed to get the lock then someone else must have it */
+      r = 1;
+    } else {
+      /* if we succeeded in taking the reserved lock, unlock it to restore
+      ** the original state */
+      _AFPFSSetLock(context->filePath, pFile->h, RESERVED_BYTE, 1, 0);
+    }
+  }
+  OSTRACE3("TEST WR-LOCK %d %d\n", pFile->h, r);
+  
+  return r;
+}
+
+/* AFP-style locking following the behavior of unixLock, see the unixLock 
+** function comments for details of lock management. */
+static int afpUnixLock(sqlite3_file *id, int locktype)
+{
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  int gotPendingLock = 0;
+  
+  assert( pFile );
+  OSTRACE5("LOCK    %d %s was %s pid=%d\n", pFile->h,
+         locktypeName(locktype), locktypeName(pFile->locktype), getpid());  
+  /* If there is already a lock of this type or more restrictive on the
+    ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
+    ** enterMutex() hasn't been called yet.
+    */
+  if( pFile->locktype>=locktype ){
+    OSTRACE3("LOCK    %d %s ok (already held)\n", pFile->h,
+           locktypeName(locktype));
+    return SQLITE_OK;
+  }
+
+  /* Make sure the locking sequence is correct
+    */
+  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
+  assert( locktype!=PENDING_LOCK );
+  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+  
+  /* This mutex is needed because pFile->pLock is shared across threads
+    */
+  enterMutex();
+
+  /* Make sure the current thread owns the pFile.
+    */
+  rc = transferOwnership(pFile);
+  if( rc!=SQLITE_OK ){
+    leaveMutex();
+    return rc;
+  }
+    
+  /* A PENDING lock is needed before acquiring a SHARED lock and before
+    ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
+    ** be released.
+    */
+  if( locktype==SHARED_LOCK 
+      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
+      ){
+    int failed = _AFPFSSetLock(context->filePath, pFile->h, 
+      PENDING_BYTE, 1, 1);
+    if (failed) {
+      rc = SQLITE_BUSY;
+      goto afp_end_lock;
+    }
+  }
+  
+  /* If control gets to this point, then actually go ahead and make
+    ** operating system calls for the specified lock.
+    */
+  if( locktype==SHARED_LOCK ){
+    int lk, failed;
+    int tries = 0;
+    
+    /* Now get the read-lock */
+    /* note that the quality of the randomness doesn't matter that much */
+    lk = random(); 
+    context->sharedLockByte = (lk & 0x7fffffff)%(SHARED_SIZE - 1);
+    failed = _AFPFSSetLock(context->filePath, pFile->h, 
+      SHARED_FIRST+context->sharedLockByte, 1, 1);
+    
+    /* Drop the temporary PENDING lock */
+    if (_AFPFSSetLock(context->filePath, pFile->h, PENDING_BYTE, 1, 0)) {
+      rc = SQLITE_IOERR_UNLOCK;  /* This should never happen */
+      goto afp_end_lock;
+    }
+    
+    if( failed ){
+      rc = SQLITE_BUSY;
+    } else {
+      pFile->locktype = SHARED_LOCK;
+    }
+  }else{
+    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
+    ** assumed that there is a SHARED or greater lock on the file
+    ** already.
+    */
+    int failed = 0;
+    assert( 0!=pFile->locktype );
+    if (locktype >= RESERVED_LOCK && pFile->locktype < RESERVED_LOCK) {
+        /* Acquire a RESERVED lock */
+        failed = _AFPFSSetLock(context->filePath, pFile->h, 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  afpUnixUnlock
+      */
+      if (!_AFPFSSetLock(context->filePath, pFile->h, SHARED_FIRST +
+                         context->sharedLockByte, 1, 0)) {
+        /* now attemmpt to get the exclusive lock range */
+        failed = _AFPFSSetLock(context->filePath, pFile->h, SHARED_FIRST, 
+                               SHARED_SIZE, 1);
+        if (failed && _AFPFSSetLock(context->filePath, pFile->h, SHARED_FIRST +
+                                    context->sharedLockByte, 1, 1)) {
+          rc = SQLITE_IOERR_RDLOCK; /* this should never happen */
+        }
+      } else {
+        /* */
+        rc = SQLITE_IOERR_UNLOCK; /* this should never happen */
+      }
+    }
+    if( failed && rc == SQLITE_OK){
+      rc = SQLITE_BUSY;
+    }
+  }
+  
+  if( rc==SQLITE_OK ){
+    pFile->locktype = locktype;
+  }else if( locktype==EXCLUSIVE_LOCK ){
+    pFile->locktype = PENDING_LOCK;
+  }
+  
+afp_end_lock:
+    leaveMutex();
+  OSTRACE4("LOCK    %d %s %s\n", pFile->h, locktypeName(locktype), 
+         rc==SQLITE_OK ? "ok" : "failed");
+  return rc;
+}
+
+/*
+ ** Lower the locking level on file descriptor pFile to locktype.  locktype
+ ** must be either NO_LOCK or SHARED_LOCK.
+ **
+ ** If the locking level of the file descriptor is already at or below
+ ** the requested locking level, this routine is a no-op.
+ */
+static int afpUnixUnlock(sqlite3_file *id, int locktype) {
+  struct flock lock;
+  int rc = SQLITE_OK;
+  unixFile *pFile = (unixFile*)id;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+
+  assert( pFile );
+  OSTRACE5("UNLOCK  %d %d was %d pid=%d\n", pFile->h, locktype,
+         pFile->locktype, getpid());
+  
+  assert( locktype<=SHARED_LOCK );
+  if( pFile->locktype<=locktype ){
+    return SQLITE_OK;
+  }
+  if( CHECK_THREADID(pFile) ){
+    return SQLITE_MISUSE;
+  }
+  enterMutex();
+  if( pFile->locktype>SHARED_LOCK ){
+    if( locktype==SHARED_LOCK ){
+      int failed = 0;
+
+      /* unlock the exclusive range - then re-establish the shared lock */
+      if (pFile->locktype==EXCLUSIVE_LOCK) {
+        failed = _AFPFSSetLock(context->filePath, pFile->h, SHARED_FIRST, 
+                                 SHARED_SIZE, 0);
+        if (!failed) {
+          /* successfully removed the exclusive lock */
+          if (_AFPFSSetLock(context->filePath, pFile->h, SHARED_FIRST+
+                            context->sharedLockByte, 1, 1)) {
+            /* failed to re-establish our shared lock */
+            rc = SQLITE_IOERR_RDLOCK; /* This should never happen */
+          }
+        } else {
+          /* This should never happen - failed to unlock the exclusive range */
+          rc = SQLITE_IOERR_UNLOCK;
+        } 
+      }
+    }
+    if (rc == SQLITE_OK && pFile->locktype>=PENDING_LOCK) {
+      if (_AFPFSSetLock(context->filePath, pFile->h, PENDING_BYTE, 1, 0)){
+        /* failed to release the pending lock */
+        rc = SQLITE_IOERR_UNLOCK; /* This should never happen */
+      }
+    } 
+    if (rc == SQLITE_OK && pFile->locktype>=RESERVED_LOCK) {
+      if (_AFPFSSetLock(context->filePath, pFile->h, RESERVED_BYTE, 1, 0)) {
+        /* failed to release the reserved lock */
+        rc = SQLITE_IOERR_UNLOCK;  /* This should never happen */
+      }
+    } 
+  }
+  if( locktype==NO_LOCK ){
+    int failed = _AFPFSSetLock(context->filePath, pFile->h, 
+                               SHARED_FIRST + context->sharedLockByte, 1, 0);
+    if (failed) {
+      rc = SQLITE_IOERR_UNLOCK;  /* This should never happen */
+    }
+  }
+  if (rc == SQLITE_OK)
+    pFile->locktype = locktype;
+  leaveMutex();
+  return rc;
+}
+
+/*
+ ** Close a file & cleanup AFP specific locking context 
+ */
+static int afpUnixClose(sqlite3_file *id) {
+  unixFile *pFile = (unixFile*)pId;
+
+  if( !pFile ) return SQLITE_OK;
+  afpUnixUnlock(*pId, NO_LOCK);
+  /* free the AFP locking structure */
+  if (pFile->lockingContext != NULL) {
+    if (((afpLockingContext *)pFile->lockingContext)->filePath != NULL)
+      sqlite3_free(((afpLockingContext*)pFile->lockingContext)->filePath);
+    sqlite3_free(pFile->lockingContext);
+  }
+
+  if( pFile->dirfd>=0 ) close(pFile->dirfd);
+  pFile->dirfd = -1;
+  close(pFile->h);
+  OSTRACE2("CLOSE   %-3d\n", pFile->h);
+  OpenCounter(-1);
+  return SQLITE_OK;
+}
+
+
+#pragma mark flock() style locking
+
+/*
+ ** The flockLockingContext is not used
+ */
+typedef void flockLockingContext;
+
+static int flockUnixCheckReservedLock(sqlite3_file *id) {
+  unixFile *pFile = (unixFile*)id;
+  
+  if (pFile->locktype == RESERVED_LOCK) {
+    return 1; /* already have a reserved lock */
+  } else {
+    /* attempt to get the lock */
+    int rc = flock(pFile->h, LOCK_EX | LOCK_NB);
+    if (!rc) {
+      /* got the lock, unlock it */
+      flock(pFile->h, LOCK_UN);
+      return 0;  /* no one has it reserved */
+    }
+    return 1; /* someone else might have it reserved */
+  }
+}
+
+static int flockUnixLock(sqlite3_file *id, int locktype) {
+  unixFile *pFile = (unixFile*)id;
+  
+  /* if we already have a lock, it is exclusive.  
+  ** Just adjust level and punt on outta here. */
+  if (pFile->locktype > NO_LOCK) {
+    pFile->locktype = locktype;
+    return SQLITE_OK;
+  }
+  
+  /* grab an exclusive lock */
+  int rc = flock(pFile->h, LOCK_EX | LOCK_NB);
+  if (rc) {
+    /* didn't get, must be busy */
+    return SQLITE_BUSY;
+  } else {
+    /* got it, set the type and return ok */
+    pFile->locktype = locktype;
+    return SQLITE_OK;
+  }
+}
+
+static int flockUnixUnlock(sqlite3_file *id, int locktype) {
+  unixFile *pFile = (unixFile*)id;
+  
+  assert( locktype<=SHARED_LOCK );
+  
+  /* no-op if possible */
+  if( pFile->locktype==locktype ){
+    return SQLITE_OK;
+  }
+  
+  /* shared can just be set because we always have an exclusive */
+  if (locktype==SHARED_LOCK) {
+    pFile->locktype = locktype;
+    return SQLITE_OK;
+  }
+  
+  /* no, really, unlock. */
+  int rc = flock(pFile->h, LOCK_UN);
+  if (rc)
+    return SQLITE_IOERR_UNLOCK;
+  else {
+    pFile->locktype = NO_LOCK;
+    return SQLITE_OK;
+  }
+}
+
+/*
+ ** Close a file.
+ */
+static int flockUnixClose(sqlite3_file *pId) {
+  unixFile *pFile = (unixFile*)*pId;
+  
+  if( !pFile ) return SQLITE_OK;
+  flockUnixUnlock(*pId, NO_LOCK);
+  
+  if( pFile->dirfd>=0 ) close(pFile->dirfd);
+  pFile->dirfd = -1;
+  enterMutex();
+  
+  close(pFile->h);  
+  leaveMutex();
+  OSTRACE2("CLOSE   %-3d\n", pFile->h);
+  OpenCounter(-1);
+  return SQLITE_OK;
+}
+
+#pragma mark Old-School .lock file based locking
+
+/*
+ ** The dotlockLockingContext structure contains all dotlock (.lock) lock
+ ** specific state
+ */
+typedef struct dotlockLockingContext dotlockLockingContext;
+struct dotlockLockingContext {
+  char *lockPath;
+};
+
+
+static int dotlockUnixCheckReservedLock(sqlite3_file *id) {
+  unixFile *pFile = (unixFile*)id;
+  dotlockLockingContext *context = 
+    (dotlockLockingContext *) pFile->lockingContext;
+  
+  if (pFile->locktype == RESERVED_LOCK) {
+    return 1; /* already have a reserved lock */
+  } else {
+    struct stat statBuf;
+    if (lstat(context->lockPath,&statBuf) == 0)
+      /* file exists, someone else has the lock */
+      return 1;
+    else
+      /* file does not exist, we could have it if we want it */
+      return 0;
+  }
+}
+
+static int dotlockUnixLock(sqlite3_file *id, int locktype) {
+  unixFile *pFile = (unixFile*)id;
+  dotlockLockingContext *context = 
+    (dotlockLockingContext *) pFile->lockingContext;
+  
+  /* if we already have a lock, it is exclusive.  
+  ** Just adjust level and punt on outta here. */
+  if (pFile->locktype > NO_LOCK) {
+    pFile->locktype = locktype;
+    
+    /* Always update the timestamp on the old file */
+    utimes(context->lockPath,NULL);
+    return SQLITE_OK;
+  }
+  
+  /* check to see if lock file already exists */
+  struct stat statBuf;
+  if (lstat(context->lockPath,&statBuf) == 0){
+    return SQLITE_BUSY; /* it does, busy */
+  }
+  
+  /* grab an exclusive lock */
+  int fd = open(context->lockPath,O_RDONLY|O_CREAT|O_EXCL,0600);
+  if (fd < 0) {
+    /* failed to open/create the file, someone else may have stolen the lock */
+    return SQLITE_BUSY; 
+  }
+  close(fd);
+  
+  /* got it, set the type and return ok */
+  pFile->locktype = locktype;
+  return SQLITE_OK;
+}
+
+static int dotlockUnixUnlock(sqlite3_file *id, int locktype) {
+  unixFile *pFile = (unixFile*)id;
+  dotlockLockingContext *context = 
+    (dotlockLockingContext *) pFile->lockingContext;
+  
+  assert( locktype<=SHARED_LOCK );
+  
+  /* no-op if possible */
+  if( pFile->locktype==locktype ){
+    return SQLITE_OK;
+  }
+  
+  /* shared can just be set because we always have an exclusive */
+  if (locktype==SHARED_LOCK) {
+    pFile->locktype = locktype;
+    return SQLITE_OK;
+  }
+  
+  /* no, really, unlock. */
+  unlink(context->lockPath);
+  pFile->locktype = NO_LOCK;
+  return SQLITE_OK;
+}
+
+/*
+ ** Close a file.
+ */
+static int dotlockUnixClose(sqlite3_file *id) {
+  unixFile *pFile = (unixFile*)id;
+  
+  if( !pFile ) return SQLITE_OK;
+  dotlockUnixUnlock(*pId, NO_LOCK);
+  /* free the dotlock locking structure */
+  if (pFile->lockingContext != NULL) {
+    if (((dotlockLockingContext *)pFile->lockingContext)->lockPath != NULL)
+      sqlite3_free( ( (dotlockLockingContext *)
+        pFile->lockingContext)->lockPath);
+    sqlite3_free(pFile->lockingContext);
+  }
+  
+  if( pFile->dirfd>=0 ) close(pFile->dirfd);
+  pFile->dirfd = -1;
+  enterMutex();
+  
+  close(pFile->h);
+  
+  leaveMutex();
+  OSTRACE2("CLOSE   %-3d\n", pFile->h);
+  OpenCounter(-1);
+  return SQLITE_OK;
+}
+
+
+#pragma mark No locking
+
+/*
+ ** The nolockLockingContext is void
+ */
+typedef void nolockLockingContext;
+
+static int nolockUnixCheckReservedLock(sqlite3_file *id) {
+  return 0;
+}
+
+static int nolockUnixLock(sqlite3_file *id, int locktype) {
+  return SQLITE_OK;
+}
+
+static int nolockUnixUnlock(sqlite3_file *id, int locktype) {
+  return SQLITE_OK;
+}
+
+/*
+ ** Close a file.
+ */
+static int nolockUnixClose(sqlite3_file *id) {
+  unixFile *pFile = (unixFile*)id;
+  
+  if( !pFile ) return SQLITE_OK;
+  if( pFile->dirfd>=0 ) close(pFile->dirfd);
+  pFile->dirfd = -1;
+  enterMutex();
+  
+  close(pFile->h);
+  
+  leaveMutex();
+  OSTRACE2("CLOSE   %-3d\n", pFile->h);
+  OpenCounter(-1);
+  return SQLITE_OK;
+}
+
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+
+/*
+** Information and control of an open file handle.
+*/
+static int unixFileControl(sqlite3_file *id, int op, void *pArg){
+  switch( op ){
+    case SQLITE_FCNTL_LOCKSTATE: {
+      *(int*)pArg = ((unixFile*)id)->locktype;
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_ERROR;
+}
+
+/*
+** Return the sector size in bytes of the underlying block device for
+** the specified file. This is almost always 512 bytes, but may be
+** larger for some devices.
+**
+** SQLite code assumes this function cannot fail. It also assumes that
+** if two files are created in the same file-system directory (i.e.
+** a database and it's journal file) that the sector size will be the
+** same for both.
+*/
+static int unixSectorSize(sqlite3_file *id){
+  return SQLITE_DEFAULT_SECTOR_SIZE;
+}
+
+/*
+** Return the device characteristics for the file. This is always 0.
+*/
+static int unixDeviceCharacteristics(sqlite3_file *id){
+  return 0;
+}
+
+/*
+** This vector defines all the methods that can operate on an sqlite3_file
+** for unix.
+*/
+static const sqlite3_io_methods sqlite3UnixIoMethod = {
+  1,                        /* iVersion */
+  unixClose,
+  unixRead,
+  unixWrite,
+  unixTruncate,
+  unixSync,
+  unixFileSize,
+  unixLock,
+  unixUnlock,
+  unixCheckReservedLock,
+  unixFileControl,
+  unixSectorSize,
+  unixDeviceCharacteristics
+};
+
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+/*
+** This vector defines all the methods that can operate on an sqlite3_file
+** for unix with AFP style file locking.
+*/
+static const sqlite3_io_methods sqlite3AFPLockingUnixIoMethod = {
+  1,                        /* iVersion */
+  unixClose,
+  unixRead,
+  unixWrite,
+  unixTruncate,
+  unixSync,
+  unixFileSize,
+  afpUnixLock,
+  afpUnixUnlock,
+  afpUnixCheckReservedLock,
+  unixFileControl,
+  unixSectorSize,
+  unixDeviceCharacteristics
+};
+
+/*
+** This vector defines all the methods that can operate on an sqlite3_file
+** for unix with flock() style file locking.
+*/
+static const sqlite3_io_methods sqlite3FlockLockingUnixIoMethod = {
+  1,                        /* iVersion */
+  flockUnixClose,
+  unixRead,
+  unixWrite,
+  unixTruncate,
+  unixSync,
+  unixFileSize,
+  flockUnixLock,
+  flockUnixUnlock,
+  flockUnixCheckReservedLock,
+  unixFileControl,
+  unixSectorSize,
+  unixDeviceCharacteristics
+};
+
+/*
+** This vector defines all the methods that can operate on an sqlite3_file
+** for unix with dotlock style file locking.
+*/
+static const sqlite3_io_methods sqlite3DotlockLockingUnixIoMethod = {
+  1,                        /* iVersion */
+  dotlockUnixClose,
+  unixRead,
+  unixWrite,
+  unixTruncate,
+  unixSync,
+  unixFileSize,
+  dotlockUnixLock,
+  dotlockUnixUnlock,
+  dotlockUnixCheckReservedLock,
+  unixFileControl,
+  unixSectorSize,
+  unixDeviceCharacteristics
+};
+
+/*
+** This vector defines all the methods that can operate on an sqlite3_file
+** for unix with dotlock style file locking.
+*/
+static const sqlite3_io_methods sqlite3NolockLockingUnixIoMethod = {
+  1,                        /* iVersion */
+  nolockUnixClose,
+  unixRead,
+  unixWrite,
+  unixTruncate,
+  unixSync,
+  unixFileSize,
+  nolockUnixLock,
+  nolockUnixUnlock,
+  nolockUnixCheckReservedLock,
+  unixFileControl,
+  unixSectorSize,
+  unixDeviceCharacteristics
+};
+
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+/*
+** Allocate memory for a new unixFile and initialize that unixFile.
+** Write a pointer to the new unixFile into *pId.
+** If we run out of memory, close the file and return an error.
+*/
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+/* 
+** When locking extensions are enabled, the filepath and locking style 
+** are needed to determine the unixFile pMethod to use for locking operations.
+** The locking-style specific lockingContext data structure is created 
+** and assigned here also.
+*/
+static int fillInUnixFile(
+  int h,                  /* Open file descriptor of file being opened */
+  int dirfd,              /* Directory file descriptor */
+  sqlite3_file *pId,      /* Write completed initialization here */
+  const char *zFilename,  /* Name of the file being opened */
+){
+  sqlite3LockingStyle lockingStyle;
+  unixFile *pNew = (unixFile *)pId;
+  int rc;
+
+  memset(pNew, 0, sizeof(unixFile));
+  lockingStyle = sqlite3DetectLockingStyle(zFilename, h);
+  if ( lockingStyle == posixLockingStyle ) {
+    enterMutex();
+    rc = findLockInfo(h, &pNew->pLock, &pNew->pOpen);
+    leaveMutex();
+    if( rc ){
+      close(h);
+      unlink(zFilename);
+      return SQLITE_NOMEM;
+    }
+  } else {
+    /*  pLock and pOpen are only used for posix advisory locking */
+    pNew->pLock = NULL;
+    pNew->pOpen = NULL;
+  }
+  pNew->dirfd = -1;
+  pNew->h = h;
+  SET_THREADID(pNew);
+  pNew = sqlite3_malloc( sizeof(unixFile) );
+  if( pNew==0 ){
+    close(h);
+    enterMutex();
+    releaseLockInfo(pNew->pLock);
+    releaseOpenCnt(pNew->pOpen);
+    leaveMutex();
+    return SQLITE_NOMEM;
+  }else{
+    switch(lockingStyle) {
+      case afpLockingStyle: {
+        /* afp locking uses the file path so it needs to be included in
+        ** the afpLockingContext */
+        int nFilename;
+        pNew->pMethod = &sqlite3AFPLockingUnixIoMethod;
+        pNew->lockingContext = 
+          sqlite3_malloc(sizeof(afpLockingContext));
+        nFilename = strlen(zFilename)+1;
+        ((afpLockingContext *)pNew->lockingContext)->filePath = 
+          sqlite3_malloc(nFilename);
+        memcpy(((afpLockingContext *)pNew->lockingContext)->filePath, 
+               zFilename, nFilename);
+        srandomdev();
+        break;
+      }
+      case flockLockingStyle:
+        /* flock locking doesn't need additional lockingContext information */
+        pNew->pMethod = &sqlite3FlockLockingUnixIoMethod;
+        break;
+      case dotlockLockingStyle: {
+        /* dotlock locking uses the file path so it needs to be included in
+         ** the dotlockLockingContext */
+        int nFilename;
+        pNew->pMethod = &sqlite3DotlockLockingUnixIoMethod;
+        pNew->lockingContext = sqlite3_malloc(
+          sizeof(dotlockLockingContext));
+        nFilename = strlen(zFilename) + 6;
+        ((dotlockLockingContext *)pNew->lockingContext)->lockPath = 
+            sqlite3_malloc( nFilename );
+        sqlite3_snprintf(nFilename, 
+                ((dotlockLockingContext *)pNew->lockingContext)->lockPath, 
+                "%s.lock", zFilename);
+        break;
+      }
+      case posixLockingStyle:
+        /* posix locking doesn't need additional lockingContext information */
+        pNew->pMethod = &sqlite3UnixIoMethod;
+        break;
+      case noLockingStyle:
+      case unsupportedLockingStyle:
+      default: 
+        pNew->pMethod = &sqlite3NolockLockingUnixIoMethod;
+    }
+    OpenCounter(+1);
+    return SQLITE_OK;
+  }
+}
+#else /* SQLITE_ENABLE_LOCKING_STYLE */
+static int fillInUnixFile(
+  int h,                 /* Open file descriptor on file being opened */
+  int dirfd,
+  sqlite3_file *pId,     /* Write to the unixFile structure here */
+  const char *zFilename  /* Name of the file being opened */
+){
+  unixFile *pNew = (unixFile *)pId;
+  int rc;
+
+#ifdef FD_CLOEXEC
+  fcntl(h, F_SETFD, fcntl(h, F_GETFD, 0) | FD_CLOEXEC);
+#endif
+
+  enterMutex();
+  rc = findLockInfo(h, &pNew->pLock, &pNew->pOpen);
+  leaveMutex();
+  if( rc ){
+    close(h);
+    return SQLITE_NOMEM;
+  }
+
+  OSTRACE3("OPEN    %-3d %s\n", h, zFilename);
+  pNew->dirfd = -1;
+  pNew->h = h;
+  pNew->dirfd = dirfd;
+  SET_THREADID(pNew);
+
+  pNew->pMethod = &sqlite3UnixIoMethod;
+  OpenCounter(+1);
+  return SQLITE_OK;
+}
+#endif /* SQLITE_ENABLE_LOCKING_STYLE */
+
+/*
+** Open a file descriptor to the directory containing file zFilename.
+** If successful, *pFd is set to the opened file descriptor and
+** SQLITE_OK is returned. If an error occurs, either SQLITE_NOMEM
+** or SQLITE_CANTOPEN is returned and *pFd is set to an undefined
+** value.
+**
+** If SQLITE_OK is returned, the caller is responsible for closing
+** the file descriptor *pFd using close().
+*/
+static int openDirectory(const char *zFilename, int *pFd){
+  int ii;
+  int fd = -1;
+  char zDirname[MAX_PATHNAME+1];
+
+  sqlite3_snprintf(MAX_PATHNAME, zDirname, "%s", zFilename);
+  for(ii=strlen(zDirname); ii>=0 && zDirname[ii]!='/'; ii--);
+  if( ii>0 ){
+    zDirname[ii] = '\0';
+    fd = open(zDirname, O_RDONLY|O_BINARY, 0);
+    if( fd>=0 ){
+#ifdef FD_CLOEXEC
+      fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
+#endif
+      OSTRACE3("OPENDIR %-3d %s\n", fd, zDirname);
+    }
+  }
+  *pFd = fd;
+  return (fd>=0?SQLITE_OK:SQLITE_CANTOPEN);
+}
+
+/*
+** Open the file zPath.
+** 
+** Previously, the SQLite OS layer used three functions in place of this
+** one:
+**
+**     sqlite3OsOpenReadWrite();
+**     sqlite3OsOpenReadOnly();
+**     sqlite3OsOpenExclusive();
+**
+** These calls correspond to the following combinations of flags:
+**
+**     ReadWrite() ->     (READWRITE | CREATE)
+**     ReadOnly()  ->     (READONLY) 
+**     OpenExclusive() -> (READWRITE | CREATE | EXCLUSIVE)
+**
+** The old OpenExclusive() accepted a boolean argument - "delFlag". If
+** true, the file was configured to be automatically deleted when the
+** file handle closed. To achieve the same effect using this new 
+** interface, add the DELETEONCLOSE flag to those specified above for 
+** OpenExclusive().
+*/
+static int unixOpen(
+  sqlite3_vfs *pVfs, 
+  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 oflags = 0;                /* Flags to pass to open() */
+  int eType = flags&0xFFFFFF00;  /* Type of file to open */
+
+  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
+  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
+  int isCreate     = (flags & SQLITE_OPEN_CREATE);
+  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
+  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+
+  /* If creating a master or main-file journal, this function will open
+  ** a file-descriptor on the directory too. The first time unixSync()
+  ** is called the directory file descriptor will be fsync()ed and close()d.
+  */
+  int isOpenDirectory = (isCreate && 
+      (eType==SQLITE_OPEN_MASTER_JOURNAL || eType==SQLITE_OPEN_MAIN_JOURNAL)
+  );
+
+  /* Check the following statements are true: 
+  **
+  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and 
+  **   (b) if CREATE is set, then READWRITE must also be set, and
+  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
+  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
+  */
+  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
+  assert(isCreate==0 || isReadWrite);
+  assert(isExclusive==0 || isCreate);
+  assert(isDelete==0 || isCreate);
+
+
+  /* The main DB, main journal, and master journal are never automatically
+  ** deleted
+  */
+  assert( eType!=SQLITE_OPEN_MAIN_DB || !isDelete );
+  assert( eType!=SQLITE_OPEN_MAIN_JOURNAL || !isDelete );
+  assert( eType!=SQLITE_OPEN_MASTER_JOURNAL || !isDelete );
+
+  /* Assert that the upper layer has set one of the "file-type" flags. */
+  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB 
+       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL 
+       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_MASTER_JOURNAL 
+       || eType==SQLITE_OPEN_TRANSIENT_DB
+  );
+
+  if( isReadonly )  oflags |= O_RDONLY;
+  if( isReadWrite ) oflags |= O_RDWR;
+  if( isCreate )    oflags |= O_CREAT;
+  if( isExclusive ) oflags |= (O_EXCL|O_NOFOLLOW);
+  oflags |= (O_LARGEFILE|O_BINARY);
+
+  memset(pFile, 0, sizeof(unixFile));
+  fd = open(zPath, oflags, isDelete?0600:SQLITE_DEFAULT_FILE_PERMISSIONS);
+  if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){
+    /* Failed to open the file for read/write access. Try read-only. */
+    flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
+    flags |= SQLITE_OPEN_READONLY;
+    return unixOpen(pVfs, zPath, pFile, flags, pOutFlags);
+  }
+  if( fd<0 ){
+    return SQLITE_CANTOPEN;
+  }
+  if( isDelete ){
+    unlink(zPath);
+  }
+  if( pOutFlags ){
+    *pOutFlags = flags;
+  }
+
+  assert(fd!=0);
+  if( isOpenDirectory ){
+    int rc = openDirectory(zPath, &dirfd);
+    if( rc!=SQLITE_OK ){
+      close(fd);
+      return rc;
+    }
+  }
+  return fillInUnixFile(fd, dirfd, pFile, zPath);
+}
+
+/*
+** Delete the file at zPath. If the dirSync argument is true, fsync()
+** the directory after deleting the file.
+*/
+static int unixDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int rc = SQLITE_OK;
+  SimulateIOError(return SQLITE_IOERR_DELETE);
+  unlink(zPath);
+  if( dirSync ){
+    int fd;
+    rc = openDirectory(zPath, &fd);
+    if( rc==SQLITE_OK ){
+      if( fsync(fd) ){
+        rc = SQLITE_IOERR_DIR_FSYNC;
+      }
+      close(fd);
+    }
+  }
+  return rc;
+}
+
+/*
+** Test the existance of or access permissions of file zPath. The
+** test performed depends on the value of flags:
+**
+**     SQLITE_ACCESS_EXISTS: Return 1 if the file exists
+**     SQLITE_ACCESS_READWRITE: Return 1 if the file is read and writable.
+**     SQLITE_ACCESS_READONLY: Return 1 if the file is readable.
+**
+** Otherwise return 0.
+*/
+static int unixAccess(sqlite3_vfs *pVfs, const char *zPath, int flags){
+  int amode = 0;
+  switch( flags ){
+    case SQLITE_ACCESS_EXISTS:
+      amode = F_OK;
+      break;
+    case SQLITE_ACCESS_READWRITE:
+      amode = W_OK|R_OK;
+      break;
+    case SQLITE_ACCESS_READ:
+      amode = R_OK;
+      break;
+
+    default:
+      assert(!"Invalid flags argument");
+  }
+  return (access(zPath, amode)==0);
+}
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be allocated
+** by the calling process and must be big enough to hold at least
+** pVfs->mxPathname bytes.
+*/
+static int unixGetTempname(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+  static const char *azDirs[] = {
+     0,
+     "/var/tmp",
+     "/usr/tmp",
+     "/tmp",
+     ".",
+  };
+  static const unsigned char zChars[] =
+    "abcdefghijklmnopqrstuvwxyz"
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    "0123456789";
+  int i, j;
+  struct stat buf;
+  const char *zDir = ".";
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. 
+  */
+  SimulateIOError( return SQLITE_ERROR );
+
+  azDirs[0] = sqlite3_temp_directory;
+  for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++){
+    if( azDirs[i]==0 ) continue;
+    if( stat(azDirs[i], &buf) ) continue;
+    if( !S_ISDIR(buf.st_mode) ) continue;
+    if( access(azDirs[i], 07) ) continue;
+    zDir = azDirs[i];
+    break;
+  }
+  do{
+    assert( pVfs->mxPathname==MAX_PATHNAME );
+    assert( nBuf>=MAX_PATHNAME );
+    sqlite3_snprintf(MAX_PATHNAME-17, zBuf, "%s/"SQLITE_TEMP_FILE_PREFIX, zDir);
+    j = strlen(zBuf);
+    sqlite3Randomness(15, &zBuf[j]);
+    for(i=0; i<15; i++, j++){
+      zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
+    }
+    zBuf[j] = 0;
+  }while( access(zBuf,0)==0 );
+  return SQLITE_OK;
+}
+
+
+/*
+** Turn a relative pathname into a full pathname. The relative path
+** is stored as a nul-terminated string in the buffer pointed to by
+** zPath. 
+**
+** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes 
+** (in this case, MAX_PATHNAME bytes). The full-path is written to
+** this buffer before returning.
+*/
+static int unixFullPathname(
+  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zPath,            /* Possibly relative input path */
+  int nOut,                     /* Size of output buffer in bytes */
+  char *zOut                    /* Output buffer */
+){
+
+  /* It's odd to simulate an io-error here, but really this is just
+  ** using the io-error infrastructure to test that SQLite handles this
+  ** function failing. This function could fail if, for example, the
+  ** current working directly has been unlinked.
+  */
+  SimulateIOError( return SQLITE_ERROR );
+
+  assert( pVfs->mxPathname==MAX_PATHNAME );
+  zOut[MAX_PATHNAME-1] = '\0';
+  if( zPath[0]=='/' ){
+    sqlite3_snprintf(MAX_PATHNAME, zOut, "%s", zPath);
+  }else{
+    int nCwd;
+    if( getcwd(zOut, MAX_PATHNAME-1)==0 ){
+      return SQLITE_CANTOPEN;
+    }
+    nCwd = strlen(zOut);
+    sqlite3_snprintf(MAX_PATHNAME-nCwd, &zOut[nCwd], "/%s", zPath);
+  }
+  return SQLITE_OK;
+
+#if 0
+  /*
+  ** Remove "/./" path elements and convert "/A/./" path elements
+  ** to just "/".
+  */
+  if( zFull ){
+    int i, j;
+    for(i=j=0; zFull[i]; i++){
+      if( zFull[i]=='/' ){
+        if( zFull[i+1]=='/' ) continue;
+        if( zFull[i+1]=='.' && zFull[i+2]=='/' ){
+          i += 1;
+          continue;
+        }
+        if( zFull[i+1]=='.' && zFull[i+2]=='.' && zFull[i+3]=='/' ){
+          while( j>0 && zFull[j-1]!='/' ){ j--; }
+          i += 3;
+          continue;
+        }
+      }
+      zFull[j++] = zFull[i];
+    }
+    zFull[j] = 0;
+  }
+#endif
+}
+
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Interfaces for opening a shared library, finding entry points
+** within the shared library, and closing the shared library.
+*/
+#include <dlfcn.h>
+static void *unixDlOpen(sqlite3_vfs *pVfs, const char *zFilename){
+  return dlopen(zFilename, RTLD_NOW | RTLD_GLOBAL);
+}
+
+/*
+** SQLite calls this function immediately after a call to unixDlSym() or
+** unixDlOpen() fails (returns a null pointer). If a more detailed error
+** message is available, it is written to zBufOut. If no error message
+** is available, zBufOut is left unmodified and SQLite uses a default
+** error message.
+*/
+static void unixDlError(sqlite3_vfs *pVfs, int nBuf, char *zBufOut){
+  char *zErr;
+  enterMutex();
+  zErr = dlerror();
+  if( zErr ){
+    sqlite3_snprintf(nBuf, zBufOut, "%s", zErr);
+  }
+  leaveMutex();
+}
+static void *unixDlSym(sqlite3_vfs *pVfs, void *pHandle, const char *zSymbol){
+  return dlsym(pHandle, zSymbol);
+}
+static void unixDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  dlclose(pHandle);
+}
+#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
+  #define unixDlOpen  0
+  #define unixDlError 0
+  #define unixDlSym   0
+  #define unixDlClose 0
+#endif
+
+/*
+** Write nBuf bytes of random data to the supplied buffer zBuf.
+*/
+static int unixRandomness(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+
+  assert(nBuf>=(sizeof(time_t)+sizeof(int)));
+
+  /* We have to initialize zBuf to prevent valgrind from reporting
+  ** errors.  The reports issued by valgrind are incorrect - we would
+  ** prefer that the randomness be increased by making use of the
+  ** uninitialized space in zBuf - but valgrind errors tend to worry
+  ** some users.  Rather than argue, it seems easier just to initialize
+  ** the whole array and silence valgrind, even if that means less randomness
+  ** in the random seed.
+  **
+  ** When testing, initializing zBuf[] to zero is all we do.  That means
+  ** that we always use the same random number sequence.  This makes the
+  ** tests repeatable.
+  */
+  memset(zBuf, 0, nBuf);
+#if !defined(SQLITE_TEST)
+  {
+    int pid, fd;
+    fd = open("/dev/urandom", O_RDONLY);
+    if( fd<0 ){
+      time_t t;
+      time(&t);
+      memcpy(zBuf, &t, sizeof(t));
+      pid = getpid();
+      memcpy(&zBuf[sizeof(t)], &pid, sizeof(pid));
+    }else{
+      read(fd, zBuf, nBuf);
+      close(fd);
+    }
+  }
+#endif
+  return SQLITE_OK;
+}
+
+
+/*
+** Sleep for a little while.  Return the amount of time slept.
+** The argument is the number of microseconds we want to sleep.
+** The return value is the number of microseconds of sleep actually
+** requested from the underlying operating system, a number which
+** might be greater than or equal to the argument, but not less
+** than the argument.
+*/
+static int unixSleep(sqlite3_vfs *pVfs, int microseconds){
+#if defined(HAVE_USLEEP) && HAVE_USLEEP
+  usleep(microseconds);
+  return microseconds;
+#else
+  int seconds = (microseconds+999999)/1000000;
+  sleep(seconds);
+  return seconds*1000000;
+#endif
+}
+
+/*
+** 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.
+*/
+static int unixCurrentTime(sqlite3_vfs *pVfs, double *prNow){
+#ifdef NO_GETTOD
+  time_t t;
+  time(&t);
+  *prNow = t/86400.0 + 2440587.5;
+#else
+  struct timeval sNow;
+  gettimeofday(&sNow, 0);
+  *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_usec/86400000000.0;
+#endif
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *prNow = sqlite3_current_time/86400.0 + 2440587.5;
+  }
+#endif
+  return 0;
+}
+
+/*
+** Return a pointer to the sqlite3DefaultVfs structure.   We use
+** a function rather than give the structure global scope because
+** some compilers (MSVC) do not allow forward declarations of
+** initialized structures.
+*/
+sqlite3_vfs *sqlite3OsDefaultVfs(void){
+  static sqlite3_vfs unixVfs = {
+    1,                  /* iVersion */
+    sizeof(unixFile),   /* szOsFile */
+    MAX_PATHNAME,       /* mxPathname */
+    0,                  /* pNext */
+    "unix",             /* zName */
+    0,                  /* pAppData */
+  
+    unixOpen,           /* xOpen */
+    unixDelete,         /* xDelete */
+    unixAccess,         /* xAccess */
+    unixGetTempname,    /* xGetTempName */
+    unixFullPathname,   /* xFullPathname */
+    unixDlOpen,         /* xDlOpen */
+    unixDlError,        /* xDlError */
+    unixDlSym,          /* xDlSym */
+    unixDlClose,        /* xDlClose */
+    unixRandomness,     /* xRandomness */
+    unixSleep,          /* xSleep */
+    unixCurrentTime     /* xCurrentTime */
+  };
+  
+  return &unixVfs;
+}
+ 
+#endif /* OS_UNIX */