try out unqlite

1 files changed, 940 insertions, 0 deletions

diff --git a/common/unqlite/os_win.c b/common/unqlite/os_win.c
new file mode 100644
index 0000000..c1e0821
--- /dev/null
+++ b/common/unqlite/os_win.c
@@ -0,0 +1,940 @@
+/*
+ * Symisc unQLite: An Embeddable NoSQL (Post Modern) Database Engine.
+ * Copyright (C) 2012-2013, Symisc Systems http://unqlite.org/
+ * Version 1.1.6
+ * For information on licensing, redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES
+ * please contact Symisc Systems via:
+ *       legal@symisc.net
+ *       licensing@symisc.net
+ *       contact@symisc.net
+ * or visit:
+ *      http://unqlite.org/licensing.html
+ */
+ /* $SymiscID: os_win.c v1.2 Win7 2012-11-10 12:10 devel <chm@symisc.net> $ */
+#ifndef UNQLITE_AMALGAMATION
+#include "unqliteInt.h"
+#endif
+/* Omit the whole layer from the build if compiling for platforms other than Windows */
+#ifdef __WINNT__
+/* This file contains code that is specific to windows. (Mostly SQLite3 source tree) */
+#include <Windows.h>
+/*
+** Some microsoft compilers lack this definition.
+*/
+#ifndef INVALID_FILE_ATTRIBUTES
+# define INVALID_FILE_ATTRIBUTES ((DWORD)-1) 
+#endif
+/*
+** WinCE lacks native support for file locking so we have to fake it
+** with some code of our own.
+*/
+#ifdef __WIN_CE__
+typedef struct winceLock {
+  int nReaders;       /* Number of reader locks obtained */
+  BOOL bPending;      /* Indicates a pending lock has been obtained */
+  BOOL bReserved;     /* Indicates a reserved lock has been obtained */
+  BOOL bExclusive;    /* Indicates an exclusive lock has been obtained */
+} winceLock;
+#define AreFileApisANSI() 1
+#define FormatMessageW(a,b,c,d,e,f,g) 0
+#endif
+
+/*
+** The winFile structure is a subclass of unqlite_file* specific to the win32
+** portability layer.
+*/
+typedef struct winFile winFile;
+struct winFile {
+  const unqlite_io_methods *pMethod; /*** Must be first ***/
+  unqlite_vfs *pVfs;      /* The VFS used to open this file */
+  HANDLE h;               /* Handle for accessing the file */
+  sxu8 locktype;          /* Type of lock currently held on this file */
+  short sharedLockByte;   /* Randomly chosen byte used as a shared lock */
+  DWORD lastErrno;        /* The Windows errno from the last I/O error */
+  DWORD sectorSize;       /* Sector size of the device file is on */
+  int szChunk;            /* Chunk size */
+#ifdef __WIN_CE__
+  WCHAR *zDeleteOnClose;  /* Name of file to delete when closing */
+  HANDLE hMutex;          /* Mutex used to control access to shared lock */  
+  HANDLE hShared;         /* Shared memory segment used for locking */
+  winceLock local;        /* Locks obtained by this instance of winFile */
+  winceLock *shared;      /* Global shared lock memory for the file  */
+#endif
+};
+/*
+** Convert a UTF-8 string to microsoft unicode (UTF-16?). 
+**
+** Space to hold the returned string is obtained from HeapAlloc().
+*/
+static WCHAR *utf8ToUnicode(const char *zFilename){
+  int nChar;
+  WCHAR *zWideFilename;
+
+  nChar = MultiByteToWideChar(CP_UTF8, 0, zFilename, -1, 0, 0);
+  zWideFilename = (WCHAR *)HeapAlloc(GetProcessHeap(),0,nChar*sizeof(zWideFilename[0]) );
+  if( zWideFilename==0 ){
+    return 0;
+  }
+  nChar = MultiByteToWideChar(CP_UTF8, 0, zFilename, -1, zWideFilename, nChar);
+  if( nChar==0 ){
+    HeapFree(GetProcessHeap(),0,zWideFilename);
+    zWideFilename = 0;
+  }
+  return zWideFilename;
+}
+
+/*
+** Convert microsoft unicode to UTF-8.  Space to hold the returned string is
+** obtained from malloc().
+*/
+static char *unicodeToUtf8(const WCHAR *zWideFilename){
+  int nByte;
+  char *zFilename;
+
+  nByte = WideCharToMultiByte(CP_UTF8, 0, zWideFilename, -1, 0, 0, 0, 0);
+  zFilename = (char *)HeapAlloc(GetProcessHeap(),0,nByte );
+  if( zFilename==0 ){
+    return 0;
+  }
+  nByte = WideCharToMultiByte(CP_UTF8, 0, zWideFilename, -1, zFilename, nByte,
+                              0, 0);
+  if( nByte == 0 ){
+    HeapFree(GetProcessHeap(),0,zFilename);
+    zFilename = 0;
+  }
+  return zFilename;
+}
+
+/*
+** Convert an ansi string to microsoft unicode, based on the
+** current codepage settings for file apis.
+** 
+** Space to hold the returned string is obtained
+** from malloc.
+*/
+static WCHAR *mbcsToUnicode(const char *zFilename){
+  int nByte;
+  WCHAR *zMbcsFilename;
+  int codepage = AreFileApisANSI() ? CP_ACP : CP_OEMCP;
+
+  nByte = MultiByteToWideChar(codepage, 0, zFilename, -1, 0,0)*sizeof(WCHAR);
+  zMbcsFilename = (WCHAR *)HeapAlloc(GetProcessHeap(),0,nByte*sizeof(zMbcsFilename[0]) );
+  if( zMbcsFilename==0 ){
+    return 0;
+  }
+  nByte = MultiByteToWideChar(codepage, 0, zFilename, -1, zMbcsFilename, nByte);
+  if( nByte==0 ){
+    HeapFree(GetProcessHeap(),0,zMbcsFilename);
+    zMbcsFilename = 0;
+  }
+  return zMbcsFilename;
+}
+/*
+** Convert multibyte character string to UTF-8.  Space to hold the
+** returned string is obtained from malloc().
+*/
+char *unqlite_win32_mbcs_to_utf8(const char *zFilename){
+  char *zFilenameUtf8;
+  WCHAR *zTmpWide;
+
+  zTmpWide = mbcsToUnicode(zFilename);
+  if( zTmpWide==0 ){
+    return 0;
+  }
+  zFilenameUtf8 = unicodeToUtf8(zTmpWide);
+  HeapFree(GetProcessHeap(),0,zTmpWide);
+  return zFilenameUtf8;
+}
+/*
+** Some microsoft compilers lack this definition.
+*/
+#ifndef INVALID_SET_FILE_POINTER
+# define INVALID_SET_FILE_POINTER ((DWORD)-1)
+#endif
+
+/*
+** Move the current position of the file handle passed as the first 
+** argument to offset iOffset within the file. If successful, return 0. 
+** Otherwise, set pFile->lastErrno and return non-zero.
+*/
+static int seekWinFile(winFile *pFile, unqlite_int64 iOffset){
+  LONG upperBits;                 /* Most sig. 32 bits of new offset */
+  LONG lowerBits;                 /* Least sig. 32 bits of new offset */
+  DWORD dwRet;                    /* Value returned by SetFilePointer() */
+
+  upperBits = (LONG)((iOffset>>32) & 0x7fffffff);
+  lowerBits = (LONG)(iOffset & 0xffffffff);
+
+  /* API oddity: If successful, SetFilePointer() returns a dword 
+  ** containing the lower 32-bits of the new file-offset. Or, if it fails,
+  ** it returns INVALID_SET_FILE_POINTER. However according to MSDN, 
+  ** INVALID_SET_FILE_POINTER may also be a valid new offset. So to determine 
+  ** whether an error has actually occured, it is also necessary to call 
+  ** GetLastError().
+  */
+  dwRet = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
+  if( (dwRet==INVALID_SET_FILE_POINTER && GetLastError()!=NO_ERROR) ){
+    pFile->lastErrno = GetLastError();
+    return 1;
+  }
+  return 0;
+}
+/*
+** Close a file.
+**
+** It is reported that an attempt to close a handle might sometimes
+** fail.  This is a very unreasonable result, but windows is notorious
+** for being unreasonable so I do not doubt that it might happen.  If
+** the close fails, we pause for 100 milliseconds and try again.  As
+** many as MX_CLOSE_ATTEMPT attempts to close the handle are made before
+** giving up and returning an error.
+*/
+#define MX_CLOSE_ATTEMPT 3
+static int winClose(unqlite_file *id)
+{
+  int rc, cnt = 0;
+  winFile *pFile = (winFile*)id;
+  do{
+    rc = CloseHandle(pFile->h);
+  }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (Sleep(100), 1) );
+
+  return rc ? UNQLITE_OK : UNQLITE_IOERR;
+}
+/*
+** Read data from a file into a buffer.  Return UNQLITE_OK if all
+** bytes were read successfully and UNQLITE_IOERR if anything goes
+** wrong.
+*/
+static int winRead(
+  unqlite_file *id,          /* File to read from */
+  void *pBuf,                /* Write content into this buffer */
+  unqlite_int64 amt,        /* Number of bytes to read */
+  unqlite_int64 offset       /* Begin reading at this offset */
+){
+  winFile *pFile = (winFile*)id;  /* file handle */
+  DWORD nRead;                    /* Number of bytes actually read from file */
+
+  if( seekWinFile(pFile, offset) ){
+    return UNQLITE_FULL;
+  }
+  if( !ReadFile(pFile->h, pBuf, (DWORD)amt, &nRead, 0) ){
+    pFile->lastErrno = GetLastError();
+    return UNQLITE_IOERR;
+  }
+  if( nRead<(DWORD)amt ){
+    /* Unread parts of the buffer must be zero-filled */
+    SyZero(&((char*)pBuf)[nRead],(sxu32)(amt-nRead));
+    return UNQLITE_IOERR;
+  }
+
+  return UNQLITE_OK;
+}
+
+/*
+** Write data from a buffer into a file.  Return UNQLITE_OK on success
+** or some other error code on failure.
+*/
+static int winWrite(
+  unqlite_file *id,               /* File to write into */
+  const void *pBuf,               /* The bytes to be written */
+  unqlite_int64 amt,                        /* Number of bytes to write */
+  unqlite_int64 offset            /* Offset into the file to begin writing at */
+){
+  int rc;                         /* True if error has occured, else false */
+  winFile *pFile = (winFile*)id;  /* File handle */
+
+  rc = seekWinFile(pFile, offset);
+  if( rc==0 ){
+    sxu8 *aRem = (sxu8 *)pBuf;        /* Data yet to be written */
+    unqlite_int64 nRem = amt;         /* Number of bytes yet to be written */
+    DWORD nWrite;                 /* Bytes written by each WriteFile() call */
+
+    while( nRem>0 && WriteFile(pFile->h, aRem, (DWORD)nRem, &nWrite, 0) && nWrite>0 ){
+      aRem += nWrite;
+      nRem -= nWrite;
+    }
+    if( nRem>0 ){
+      pFile->lastErrno = GetLastError();
+      rc = 1;
+    }
+  }
+  if( rc ){
+    if( pFile->lastErrno==ERROR_HANDLE_DISK_FULL ){
+      return UNQLITE_FULL;
+    }
+    return UNQLITE_IOERR;
+  }
+  return UNQLITE_OK;
+}
+
+/*
+** Truncate an open file to a specified size
+*/
+static int winTruncate(unqlite_file *id, unqlite_int64 nByte){
+  winFile *pFile = (winFile*)id;  /* File handle object */
+  int rc = UNQLITE_OK;             /* Return code for this function */
+
+
+  /* If the user has configured a chunk-size for this file, truncate the
+  ** file so that it consists of an integer number of chunks (i.e. the
+  ** actual file size after the operation may be larger than the requested
+  ** size).
+  */
+  if( pFile->szChunk ){
+    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
+  }
+
+  /* SetEndOfFile() returns non-zero when successful, or zero when it fails. */
+  if( seekWinFile(pFile, nByte) ){
+    rc = UNQLITE_IOERR;
+  }else if( 0==SetEndOfFile(pFile->h) ){
+    pFile->lastErrno = GetLastError();
+    rc = UNQLITE_IOERR;
+  }
+  return rc;
+}
+/*
+** Make sure all writes to a particular file are committed to disk.
+*/
+static int winSync(unqlite_file *id, int flags){
+  winFile *pFile = (winFile*)id;
+  SXUNUSED(flags); /* MSVC warning */
+  if( FlushFileBuffers(pFile->h) ){
+    return UNQLITE_OK;
+  }else{
+    pFile->lastErrno = GetLastError();
+    return UNQLITE_IOERR;
+  }
+}
+/*
+** Determine the current size of a file in bytes
+*/
+static int winFileSize(unqlite_file *id, unqlite_int64 *pSize){
+  DWORD upperBits;
+  DWORD lowerBits;
+  winFile *pFile = (winFile*)id;
+  DWORD error;
+  lowerBits = GetFileSize(pFile->h, &upperBits);
+  if(   (lowerBits == INVALID_FILE_SIZE)
+     && ((error = GetLastError()) != NO_ERROR) )
+  {
+    pFile->lastErrno = error;
+    return UNQLITE_IOERR;
+  }
+  *pSize = (((unqlite_int64)upperBits)<<32) + lowerBits;
+  return UNQLITE_OK;
+}
+/*
+** LOCKFILE_FAIL_IMMEDIATELY is undefined on some Windows systems.
+*/
+#ifndef LOCKFILE_FAIL_IMMEDIATELY
+# define LOCKFILE_FAIL_IMMEDIATELY 1
+#endif
+
+/*
+** Acquire a reader lock.
+*/
+static int getReadLock(winFile *pFile){
+  int res;
+  OVERLAPPED ovlp;
+  ovlp.Offset = SHARED_FIRST;
+  ovlp.OffsetHigh = 0;
+  ovlp.hEvent = 0;
+  res = LockFileEx(pFile->h, LOCKFILE_FAIL_IMMEDIATELY,0, SHARED_SIZE, 0, &ovlp);
+  if( res == 0 ){
+    pFile->lastErrno = GetLastError();
+  }
+  return res;
+}
+/*
+** Undo a readlock
+*/
+static int unlockReadLock(winFile *pFile){
+  int res;
+  res = UnlockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+  if( res == 0 ){
+    pFile->lastErrno = GetLastError();
+  }
+  return res;
+}
+/*
+** 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.  The winUnlock() routine
+** erases all locks at once and returns us immediately to locking level 0.
+** It is not possible to lower the locking level one step at a time.  You
+** must go straight to locking level 0.
+*/
+static int winLock(unqlite_file *id, int locktype){
+  int rc = UNQLITE_OK;    /* Return code from subroutines */
+  int res = 1;           /* Result of a windows lock call */
+  int newLocktype;       /* Set pFile->locktype to this value before exiting */
+  int gotPendingLock = 0;/* True if we acquired a PENDING lock this time */
+  winFile *pFile = (winFile*)id;
+  DWORD error = NO_ERROR;
+
+  /* If there is already a lock of this type or more restrictive on the
+  ** OsFile, do nothing.
+  */
+  if( pFile->locktype>=locktype ){
+    return UNQLITE_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 );
+  */
+  /* Lock the PENDING_LOCK byte if we need to acquire a PENDING lock or
+  ** a SHARED lock.  If we are acquiring a SHARED lock, the acquisition of
+  ** the PENDING_LOCK byte is temporary.
+  */
+  newLocktype = pFile->locktype;
+  if(   (pFile->locktype==NO_LOCK)
+     || (   (locktype==EXCLUSIVE_LOCK)
+         && (pFile->locktype==RESERVED_LOCK))
+  ){
+    int cnt = 3;
+    while( cnt-->0 && (res = LockFile(pFile->h, PENDING_BYTE, 0, 1, 0))==0 ){
+      /* Try 3 times to get the pending lock.  The pending lock might be
+      ** held by another reader process who will release it momentarily.
+          */
+      Sleep(1);
+    }
+    gotPendingLock = res;
+    if( !res ){
+      error = GetLastError();
+    }
+  }
+
+  /* Acquire a shared lock
+  */
+  if( locktype==SHARED_LOCK && res ){
+   /* assert( pFile->locktype==NO_LOCK ); */
+    res = getReadLock(pFile);
+    if( res ){
+      newLocktype = SHARED_LOCK;
+    }else{
+      error = GetLastError();
+    }
+  }
+
+  /* Acquire a RESERVED lock
+  */
+  if( locktype==RESERVED_LOCK && res ){
+    /* assert( pFile->locktype==SHARED_LOCK ); */
+    res = LockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+    if( res ){
+      newLocktype = RESERVED_LOCK;
+    }else{
+      error = GetLastError();
+    }
+  }
+
+  /* Acquire a PENDING lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res ){
+    newLocktype = PENDING_LOCK;
+    gotPendingLock = 0;
+  }
+
+  /* Acquire an EXCLUSIVE lock
+  */
+  if( locktype==EXCLUSIVE_LOCK && res ){
+    /* assert( pFile->locktype>=SHARED_LOCK ); */
+    res = unlockReadLock(pFile);
+    res = LockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+    if( res ){
+      newLocktype = EXCLUSIVE_LOCK;
+    }else{
+      error = GetLastError();
+      getReadLock(pFile);
+    }
+  }
+
+  /* If we are holding a PENDING lock that ought to be released, then
+  ** release it now.
+  */
+  if( gotPendingLock && locktype==SHARED_LOCK ){
+    UnlockFile(pFile->h, PENDING_BYTE, 0, 1, 0);
+  }
+
+  /* Update the state of the lock has held in the file descriptor then
+  ** return the appropriate result code.
+  */
+  if( res ){
+    rc = UNQLITE_OK;
+  }else{
+    pFile->lastErrno = error;
+    rc = UNQLITE_BUSY;
+  }
+  pFile->locktype = (sxu8)newLocktype;
+  return rc;
+}
+/*
+** 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, otherwise zero.
+*/
+static int winCheckReservedLock(unqlite_file *id, int *pResOut){
+  int rc;
+  winFile *pFile = (winFile*)id;
+  if( pFile->locktype>=RESERVED_LOCK ){
+    rc = 1;
+  }else{
+    rc = LockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+    if( rc ){
+      UnlockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+    }
+    rc = !rc;
+  }
+  *pResOut = rc;
+  return UNQLITE_OK;
+}
+/*
+** Lower the locking level on file descriptor id 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.
+**
+** It is not possible for this routine to fail if the second argument
+** is NO_LOCK.  If the second argument is SHARED_LOCK then this routine
+** might return UNQLITE_IOERR;
+*/
+static int winUnlock(unqlite_file *id, int locktype){
+  int type;
+  winFile *pFile = (winFile*)id;
+  int rc = UNQLITE_OK;
+
+  type = pFile->locktype;
+  if( type>=EXCLUSIVE_LOCK ){
+    UnlockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
+    if( locktype==SHARED_LOCK && !getReadLock(pFile) ){
+      /* This should never happen.  We should always be able to
+      ** reacquire the read lock */
+      rc = UNQLITE_IOERR;
+    }
+  }
+  if( type>=RESERVED_LOCK ){
+    UnlockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
+  }
+  if( locktype==NO_LOCK && type>=SHARED_LOCK ){
+    unlockReadLock(pFile);
+  }
+  if( type>=PENDING_LOCK ){
+    UnlockFile(pFile->h, PENDING_BYTE, 0, 1, 0);
+  }
+  pFile->locktype = (sxu8)locktype;
+  return rc;
+}
+/*
+** 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.
+**
+*/
+static int winSectorSize(unqlite_file *id){
+  return (int)(((winFile*)id)->sectorSize);
+}
+/*
+** This vector defines all the methods that can operate on an
+** unqlite_file for Windows systems.
+*/
+static const unqlite_io_methods winIoMethod = {
+  1,                              /* iVersion */
+  winClose,                       /* xClose */
+  winRead,                        /* xRead */
+  winWrite,                       /* xWrite */
+  winTruncate,                    /* xTruncate */
+  winSync,                        /* xSync */
+  winFileSize,                    /* xFileSize */
+  winLock,                        /* xLock */
+  winUnlock,                      /* xUnlock */
+  winCheckReservedLock,           /* xCheckReservedLock */
+  winSectorSize,                  /* xSectorSize */
+};
+/*
+ * Windows VFS Methods.
+ */
+/*
+** Convert a UTF-8 filename into whatever form the underlying
+** operating system wants filenames in.  Space to hold the result
+** is obtained from malloc and must be freed by the calling
+** function.
+*/
+static void *convertUtf8Filename(const char *zFilename)
+{
+  void *zConverted;
+  zConverted = utf8ToUnicode(zFilename);
+  /* caller will handle out of memory */
+  return zConverted;
+}
+/*
+** Delete the named file.
+**
+** Note that windows does not allow a file to be deleted if some other
+** process has it open.  Sometimes a virus scanner or indexing program
+** will open a journal file shortly after it is created in order to do
+** whatever it does.  While this other process is holding the
+** file open, we will be unable to delete it.  To work around this
+** problem, we delay 100 milliseconds and try to delete again.  Up
+** to MX_DELETION_ATTEMPTs deletion attempts are run before giving
+** up and returning an error.
+*/
+#define MX_DELETION_ATTEMPTS 5
+static int winDelete(
+  unqlite_vfs *pVfs,          /* Not used on win32 */
+  const char *zFilename,      /* Name of file to delete */
+  int syncDir                 /* Not used on win32 */
+){
+  int cnt = 0;
+  DWORD rc;
+  DWORD error = 0;
+  void *zConverted;
+  zConverted = convertUtf8Filename(zFilename);
+  if( zConverted==0 ){
+           SXUNUSED(pVfs);
+           SXUNUSED(syncDir);
+    return UNQLITE_NOMEM;
+  }
+  do{
+          DeleteFileW((LPCWSTR)zConverted);
+  }while(   (   ((rc = GetFileAttributesW((LPCWSTR)zConverted)) != INVALID_FILE_ATTRIBUTES)
+          || ((error = GetLastError()) == ERROR_ACCESS_DENIED))
+          && (++cnt < MX_DELETION_ATTEMPTS)
+          && (Sleep(100), 1)
+          );
+        HeapFree(GetProcessHeap(),0,zConverted);
+ 
+  return (   (rc == INVALID_FILE_ATTRIBUTES) 
+          && (error == ERROR_FILE_NOT_FOUND)) ? UNQLITE_OK : UNQLITE_IOERR;
+}
+/*
+** Check the existance and status of a file.
+*/
+static int winAccess(
+  unqlite_vfs *pVfs,         /* Not used  */
+  const char *zFilename,     /* Name of file to check */
+  int flags,                 /* Type of test to make on this file */
+  int *pResOut               /* OUT: Result */
+){
+  WIN32_FILE_ATTRIBUTE_DATA sAttrData;
+  DWORD attr;
+  int rc = 0;
+  void *zConverted;
+  SXUNUSED(pVfs);
+
+  zConverted = convertUtf8Filename(zFilename);
+  if( zConverted==0 ){
+    return UNQLITE_NOMEM;
+  }
+  SyZero(&sAttrData,sizeof(sAttrData));
+  if( GetFileAttributesExW((WCHAR*)zConverted,
+          GetFileExInfoStandard, 
+          &sAttrData) ){
+      /* For an UNQLITE_ACCESS_EXISTS query, treat a zero-length file
+      ** as if it does not exist.
+      */
+      if(    flags==UNQLITE_ACCESS_EXISTS
+          && sAttrData.nFileSizeHigh==0 
+          && sAttrData.nFileSizeLow==0 ){
+        attr = INVALID_FILE_ATTRIBUTES;
+      }else{
+        attr = sAttrData.dwFileAttributes;
+      }
+    }else{
+      if( GetLastError()!=ERROR_FILE_NOT_FOUND ){
+        HeapFree(GetProcessHeap(),0,zConverted);
+        return UNQLITE_IOERR;
+      }else{
+        attr = INVALID_FILE_ATTRIBUTES;
+      }
+    }
+  HeapFree(GetProcessHeap(),0,zConverted);
+  switch( flags ){
+     case UNQLITE_ACCESS_READWRITE:
+      rc = (attr & FILE_ATTRIBUTE_READONLY)==0;
+      break;
+    case UNQLITE_ACCESS_READ:
+    case UNQLITE_ACCESS_EXISTS:
+        default:
+      rc = attr!=INVALID_FILE_ATTRIBUTES;
+      break;
+  }
+  *pResOut = rc;
+  return UNQLITE_OK;
+}
+/*
+** Turn a relative pathname into a full pathname.  Write the full
+** pathname into zOut[].  zOut[] will be at least pVfs->mxPathname
+** bytes in size.
+*/
+static int winFullPathname(
+  unqlite_vfs *pVfs,            /* Pointer to vfs object */
+  const char *zRelative,        /* Possibly relative input path */
+  int nFull,                    /* Size of output buffer in bytes */
+  char *zFull                   /* Output buffer */
+){
+  int nByte;
+  void *zConverted;
+  WCHAR *zTemp;
+  char *zOut;
+  SXUNUSED(nFull);
+  zConverted = convertUtf8Filename(zRelative);
+  if( zConverted == 0 ){
+          return UNQLITE_NOMEM;
+  }
+  nByte = GetFullPathNameW((WCHAR*)zConverted, 0, 0, 0) + 3;
+  zTemp = (WCHAR *)HeapAlloc(GetProcessHeap(),0,nByte*sizeof(zTemp[0]) );
+  if( zTemp==0 ){
+          HeapFree(GetProcessHeap(),0,zConverted);
+          return UNQLITE_NOMEM;
+  }
+  GetFullPathNameW((WCHAR*)zConverted, nByte, zTemp, 0);
+  HeapFree(GetProcessHeap(),0,zConverted);
+  zOut = unicodeToUtf8(zTemp);
+  HeapFree(GetProcessHeap(),0,zTemp);
+  if( zOut == 0 ){
+    return UNQLITE_NOMEM;
+  }
+  Systrcpy(zFull,(sxu32)pVfs->mxPathname,zOut,0);
+  HeapFree(GetProcessHeap(),0,zOut);
+  return UNQLITE_OK;
+}
+/*
+** Get the sector size of the device used to store
+** file.
+*/
+static int getSectorSize(
+    unqlite_vfs *pVfs,
+    const char *zRelative     /* UTF-8 file name */
+){
+  DWORD bytesPerSector = UNQLITE_DEFAULT_SECTOR_SIZE;
+  char zFullpath[MAX_PATH+1];
+  int rc;
+  DWORD dwRet = 0;
+  DWORD dwDummy;
+  /*
+  ** We need to get the full path name of the file
+  ** to get the drive letter to look up the sector
+  ** size.
+  */
+  rc = winFullPathname(pVfs, zRelative, MAX_PATH, zFullpath);
+  if( rc == UNQLITE_OK )
+  {
+    void *zConverted = convertUtf8Filename(zFullpath);
+    if( zConverted ){
+        /* trim path to just drive reference */
+        WCHAR *p = (WCHAR *)zConverted;
+        for(;*p;p++){
+          if( *p == '\\' ){
+            *p = '\0';
+            break;
+          }
+        }
+        dwRet = GetDiskFreeSpaceW((WCHAR*)zConverted,
+                                  &dwDummy,
+                                  &bytesPerSector,
+                                  &dwDummy,
+                                  &dwDummy);
+                 HeapFree(GetProcessHeap(),0,zConverted);
+        }
+    if( !dwRet ){
+      bytesPerSector = UNQLITE_DEFAULT_SECTOR_SIZE;
+    }
+  }
+  return (int) bytesPerSector; 
+}
+/*
+** Sleep for a little while.  Return the amount of time slept.
+*/
+static int winSleep(unqlite_vfs *pVfs, int microsec){
+  Sleep((microsec+999)/1000);
+  SXUNUSED(pVfs);
+  return ((microsec+999)/1000)*1000;
+}
+/*
+ * Export the current system time.
+ */
+static int winCurrentTime(unqlite_vfs *pVfs,Sytm *pOut)
+{
+        SYSTEMTIME sSys;
+        SXUNUSED(pVfs);
+        GetSystemTime(&sSys);
+        SYSTEMTIME_TO_SYTM(&sSys,pOut);
+        return UNQLITE_OK;
+}
+/*
+** The idea is that this function works like a combination of
+** GetLastError() and FormatMessage() on windows (or errno and
+** strerror_r() on unix). After an error is returned by an OS
+** function, UnQLite calls this function with zBuf pointing to
+** a buffer of nBuf bytes. The OS layer should populate the
+** buffer with a nul-terminated UTF-8 encoded error message
+** describing the last IO error to have occurred within the calling
+** thread.
+**
+** If the error message is too large for the supplied buffer,
+** it should be truncated. The return value of xGetLastError
+** is zero if the error message fits in the buffer, or non-zero
+** otherwise (if the message was truncated). If non-zero is returned,
+** then it is not necessary to include the nul-terminator character
+** in the output buffer.
+*/
+static int winGetLastError(unqlite_vfs *pVfs, int nBuf, char *zBuf)
+{
+  /* FormatMessage returns 0 on failure.  Otherwise it
+  ** returns the number of TCHARs written to the output
+  ** buffer, excluding the terminating null char.
+  */
+  DWORD error = GetLastError();
+  WCHAR *zTempWide = 0;
+  DWORD dwLen;
+  char *zOut = 0;
+
+  SXUNUSED(pVfs);
+  dwLen = FormatMessageW(
+          FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+          0,
+          error,
+          0,
+          (LPWSTR) &zTempWide,
+          0,
+          0
+          );
+    if( dwLen > 0 ){
+      /* allocate a buffer and convert to UTF8 */
+      zOut = unicodeToUtf8(zTempWide);
+      /* free the system buffer allocated by FormatMessage */
+      LocalFree(zTempWide);
+    }
+        if( 0 == dwLen ){
+                Systrcpy(zBuf,(sxu32)nBuf,"OS Error",sizeof("OS Error")-1);
+        }else{
+                /* copy a maximum of nBuf chars to output buffer */
+                Systrcpy(zBuf,(sxu32)nBuf,zOut,0 /* Compute input length automatically */);
+                /* free the UTF8 buffer */
+                HeapFree(GetProcessHeap(),0,zOut);
+        }
+  return 0;
+}
+/*
+** Open a file.
+*/
+static int winOpen(
+  unqlite_vfs *pVfs,        /* Not used */
+  const char *zName,        /* Name of the file (UTF-8) */
+  unqlite_file *id,         /* Write the UnQLite file handle here */
+  unsigned int flags                /* Open mode flags */
+){
+  HANDLE h;
+  DWORD dwDesiredAccess;
+  DWORD dwShareMode;
+  DWORD dwCreationDisposition;
+  DWORD dwFlagsAndAttributes = 0;
+  winFile *pFile = (winFile*)id;
+  void *zConverted;              /* Filename in OS encoding */
+  const char *zUtf8Name = zName; /* Filename in UTF-8 encoding */
+  int isExclusive  = (flags & UNQLITE_OPEN_EXCLUSIVE);
+  int isDelete     = (flags & UNQLITE_OPEN_TEMP_DB);
+  int isCreate     = (flags & UNQLITE_OPEN_CREATE);
+  int isReadWrite  = (flags & UNQLITE_OPEN_READWRITE);
+
+  pFile->h = INVALID_HANDLE_VALUE;
+  /* Convert the filename to the system encoding. */
+  zConverted = convertUtf8Filename(zUtf8Name);
+  if( zConverted==0 ){
+    return UNQLITE_NOMEM;
+  }
+  if( isReadWrite ){
+    dwDesiredAccess = GENERIC_READ | GENERIC_WRITE;
+  }else{
+    dwDesiredAccess = GENERIC_READ;
+  }
+  /* UNQLITE_OPEN_EXCLUSIVE is used to make sure that a new file is 
+  ** created.
+  */
+  if( isExclusive ){
+    /* Creates a new file, only if it does not already exist. */
+    /* If the file exists, it fails. */
+    dwCreationDisposition = CREATE_NEW;
+  }else if( isCreate ){
+    /* Open existing file, or create if it doesn't exist */
+    dwCreationDisposition = OPEN_ALWAYS;
+  }else{
+    /* Opens a file, only if it exists. */
+    dwCreationDisposition = OPEN_EXISTING;
+  }
+
+  dwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
+
+  if( isDelete ){
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_TEMPORARY
+                               | FILE_ATTRIBUTE_HIDDEN
+                               | FILE_FLAG_DELETE_ON_CLOSE;
+  }else{
+    dwFlagsAndAttributes = FILE_ATTRIBUTE_NORMAL;
+  }
+  h = CreateFileW((WCHAR*)zConverted,
+       dwDesiredAccess,
+       dwShareMode,
+       NULL,
+       dwCreationDisposition,
+       dwFlagsAndAttributes,
+       NULL
+    );
+  if( h==INVALID_HANDLE_VALUE ){
+    pFile->lastErrno = GetLastError();
+    HeapFree(GetProcessHeap(),0,zConverted);
+        return UNQLITE_IOERR;
+  }
+  SyZero(pFile,sizeof(*pFile));
+  pFile->pMethod = &winIoMethod;
+  pFile->h = h;
+  pFile->lastErrno = NO_ERROR;
+  pFile->pVfs = pVfs;
+  pFile->sectorSize = getSectorSize(pVfs, zUtf8Name);
+  HeapFree(GetProcessHeap(),0,zConverted);
+  return UNQLITE_OK;
+}
+/*
+ * Export the Windows Vfs.
+ */
+UNQLITE_PRIVATE const unqlite_vfs * unqliteExportBuiltinVfs(void)
+{
+        static const unqlite_vfs sWinvfs = {
+                "Windows",           /* Vfs name */
+                1,                   /* Vfs structure version */
+                sizeof(winFile),     /* szOsFile */
+                MAX_PATH,            /* mxPathName */
+                winOpen,             /* xOpen */
+                winDelete,           /* xDelete */
+                winAccess,           /* xAccess */
+                winFullPathname,     /* xFullPathname */
+                0,                   /* xTmp */
+                winSleep,            /* xSleep */
+                winCurrentTime,      /* xCurrentTime */
+                winGetLastError,     /* xGetLastError */
+        };
+        return &sWinvfs;
+}
+#endif /* __WINNT__ */