SQLite

}
int sqlite3OsShmLock(sqlite3_file *id, int offset, int n, int flags){
  return id->pMethods->xShmLock(id, offset, n, flags);
}
void sqlite3OsShmBarrier(sqlite3_file *id){
  id->pMethods->xShmBarrier(id);
}
int sqlite3OsShmUnmap(sqlite3_file *id, int deleteFlag){
  return id->pMethods->xShmUnmap(id, deleteFlag);
}
int sqlite3OsShmMap(
  sqlite3_file *id,               /* Database file handle */
  int iPage,
  int pgsz,
  int bExtend,                    /* True to extend file if necessary */

int sqlite3OsFileControl(sqlite3_file*,int,void*);
#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
int sqlite3OsSectorSize(sqlite3_file *id);
int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
void sqlite3OsShmBarrier(sqlite3_file *id);
int sqlite3OsShmUnmap(sqlite3_file *id, int);

/* 
** Functions for accessing sqlite3_vfs methods 
*/
int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
int sqlite3OsDelete(sqlite3_vfs *, const char *, int);
int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut);

  unixEnterMutex();
  unixLeaveMutex();
}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**
** If there is no shared memory associated with the connection then this
** routine is a harmless no-op.
*/
static int unixShmUnmap(
  sqlite3_file *fd,               /* The underlying database file */
  int deleteFlag                  /* Delete shared-memory if true */
){
  unixShm *p;                     /* The connection to be closed */
  unixShmNode *pShmNode;          /* The underlying shared-memory file */

  return rc;
}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
*/
static int winShmUnmap(
  sqlite3_file *fd,          /* Database holding shared memory */
  int deleteFlag             /* Delete after closing if true */
){
  winFile *pDbFd;       /* Database holding shared-memory */
  winShm *p;            /* The connection to be closed */
  winShmNode *pShmNode; /* The underlying shared-memory file */
  winShm **pp;          /* For looping over sibling connections */

  return rc;
}

#else
# define winShmMap     0
# define winShmLock    0
# define winShmBarrier 0
# define winShmUnmap   0
#endif /* #ifndef SQLITE_OMIT_WAL */

/*
** Here ends the implementation of all sqlite3_file methods.
**
********************** End sqlite3_file Methods *******************************
******************************************************************************/

  winCheckReservedLock,           /* xCheckReservedLock */
  winFileControl,                 /* xFileControl */
  winSectorSize,                  /* xSectorSize */
  winDeviceCharacteristics,       /* xDeviceCharacteristics */
  winShmMap,                      /* xShmMap */
  winShmLock,                     /* xShmLock */
  winShmBarrier,                  /* xShmBarrier */
  winShmUnmap                     /* xShmUnmap */
};

/****************************************************************************
**************************** sqlite3_vfs methods ****************************
**
** This division contains the implementation of methods on the
** sqlite3_vfs object.

*/
static int cfShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
  return sqlite3OsShmLock(((CrashFile*)pFile)->pRealFile, ofst, n, flags);
}
static void cfShmBarrier(sqlite3_file *pFile){
  sqlite3OsShmBarrier(((CrashFile*)pFile)->pRealFile);
}
static int cfShmUnmap(sqlite3_file *pFile, int delFlag){
  return sqlite3OsShmUnmap(((CrashFile*)pFile)->pRealFile, delFlag);
}
static int cfShmMap(
  sqlite3_file *pFile,            /* Handle open on database file */
  int iRegion,                    /* Region to retrieve */
  int sz,                         /* Size of regions */
  int w,                          /* True to extend file if necessary */
  void volatile **pp              /* OUT: Mapped memory */

  cfCheckReservedLock,          /* xCheckReservedLock */
  cfFileControl,                /* xFileControl */
  cfSectorSize,                 /* xSectorSize */
  cfDeviceCharacteristics,      /* xDeviceCharacteristics */
  cfShmMap,                     /* xShmMap */
  cfShmLock,                    /* xShmLock */
  cfShmBarrier,                 /* xShmBarrier */
  cfShmUnmap                    /* xShmUnmap */
};

/*
** Application data for the crash VFS
*/
struct crashAppData {
  sqlite3_vfs *pOrig;                   /* Wrapped vfs structure */

static int devsymCheckReservedLock(sqlite3_file*, int *);
static int devsymFileControl(sqlite3_file*, int op, void *pArg);
static int devsymSectorSize(sqlite3_file*);
static int devsymDeviceCharacteristics(sqlite3_file*);
static int devsymShmLock(sqlite3_file*,int,int,int);
static int devsymShmMap(sqlite3_file*,int,int,int, void volatile **);
static void devsymShmBarrier(sqlite3_file*);
static int devsymShmUnmap(sqlite3_file*,int);

/*
** Method declarations for devsym_vfs.
*/
static int devsymOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int devsymDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int devsymAccess(sqlite3_vfs*, const char *zName, int flags, int *);

  devsymCheckReservedLock,          /* xCheckReservedLock */
  devsymFileControl,                /* xFileControl */
  devsymSectorSize,                 /* xSectorSize */
  devsymDeviceCharacteristics,      /* xDeviceCharacteristics */
  devsymShmMap,                     /* xShmMap */
  devsymShmLock,                    /* xShmLock */
  devsymShmBarrier,                 /* xShmBarrier */
  devsymShmUnmap                    /* xShmUnmap */
};

struct DevsymGlobal {
  sqlite3_vfs *pVfs;
  int iDeviceChar;
  int iSectorSize;
};

  devsym_file *p = (devsym_file *)pFile;
  return sqlite3OsShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
}
static void devsymShmBarrier(sqlite3_file *pFile){
  devsym_file *p = (devsym_file *)pFile;
  sqlite3OsShmBarrier(p->pReal);
}
static int devsymShmUnmap(sqlite3_file *pFile, int delFlag){
  devsym_file *p = (devsym_file *)pFile;
  return sqlite3OsShmUnmap(p->pReal, delFlag);
}



/*
** Open an devsym file handle.
*/

  fsCheckReservedLock,          /* xCheckReservedLock */
  fsFileControl,                /* xFileControl */
  fsSectorSize,                 /* xSectorSize */
  fsDeviceCharacteristics,      /* xDeviceCharacteristics */
  0,                            /* xShmMap */
  0,                            /* xShmLock */
  0,                            /* xShmBarrier */
  0                             /* xShmUnmap */
};


static sqlite3_io_methods tmp_io_methods = {
  1,                            /* iVersion */
  tmpClose,                     /* xClose */
  tmpRead,                      /* xRead */
  tmpWrite,                     /* xWrite */
  tmpTruncate,                  /* xTruncate */
  tmpSync,                      /* xSync */
  tmpFileSize,                  /* xFileSize */
  tmpLock,                      /* xLock */
  tmpUnlock,                    /* xUnlock */
  tmpCheckReservedLock,         /* xCheckReservedLock */
  tmpFileControl,               /* xFileControl */
  tmpSectorSize,                /* xSectorSize */
  tmpDeviceCharacteristics,     /* xDeviceCharacteristics */
  0,                            /* xShmMap */
  0,                            /* xShmLock */
  0,                            /* xShmBarrier */
  0                             /* xShmUnmap */
};

/* Useful macros used in several places */
#define MIN(x,y) ((x)<(y)?(x):(y))
#define MAX(x,y) ((x)>(y)?(x):(y))

  return rc;
}

/*
** Close an open wal-index.
*/
static void walIndexClose(Wal *pWal, int isDelete){
  sqlite3OsShmUnmap(pWal->pDbFd, isDelete);
}

/* 
** Open a connection to the WAL file zWalName. The database file must 
** already be opened on connection pDbFd. The buffer that zWalName points
** to must remain valid for the lifetime of the returned Wal* handle.
**