**
**    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.
**
*************************************************************************
**
** @(#) $Id: journal.c,v 1.3 2007/08/24 08:15:54 danielk1977 Exp $
*/

#ifdef SQLITE_ENABLE_ATOMIC_WRITE

/*
** This file implements a special kind of sqlite3_file object used
** by SQLite to create journal files if the atomic-write optimization
................................................................................
  jrnlWrite,     /* xWrite */
  jrnlTruncate,  /* xTruncate */
  jrnlSync,      /* xSync */
  jrnlFileSize,  /* xFileSize */
  0,             /* xLock */
  0,             /* xUnlock */
  0,             /* xCheckReservedLock */
  0,             /* xBreakLock */
  0,             /* xLockState */
  0,             /* xSectorSize */
  0              /* xDeviceCharacteristics */
};

/* 
** Open a journal file.
*/
................................................................................
** Return the number of bytes required to store a JournalFile that uses vfs
** pVfs to create the underlying on-disk files.
*/
int sqlite3JournalSize(sqlite3_vfs *pVfs){
  return (pVfs->szOsFile+sizeof(JournalFile));
}
#endif

**
**    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.
**
*************************************************************************
**
** @(#) $Id: journal.c,v 1.4 2007/08/31 18:34:59 drh Exp $
*/

#ifdef SQLITE_ENABLE_ATOMIC_WRITE

/*
** This file implements a special kind of sqlite3_file object used
** by SQLite to create journal files if the atomic-write optimization
................................................................................
  jrnlWrite,     /* xWrite */
  jrnlTruncate,  /* xTruncate */
  jrnlSync,      /* xSync */
  jrnlFileSize,  /* xFileSize */
  0,             /* xLock */
  0,             /* xUnlock */
  0,             /* xCheckReservedLock */
  0,             /* xFileControl */

  0,             /* xSectorSize */
  0              /* xDeviceCharacteristics */
};

/* 
** Open a journal file.
*/
................................................................................
** Return the number of bytes required to store a JournalFile that uses vfs
** pVfs to create the underlying on-disk files.
*/
int sqlite3JournalSize(sqlite3_vfs *pVfs){
  return (pVfs->szOsFile+sizeof(JournalFile));
}
#endif

  int sqlite3OsSectorSize(sqlite3_file *id){
    int (*xSectorSize)(sqlite3_file*) = id->pMethods->xSectorSize;
    return (xSectorSize ? xSectorSize(id) : SQLITE_DEFAULT_SECTOR_SIZE);
  }
  int sqlite3OsDeviceCharacteristics(sqlite3_file *id){
    return id->pMethods->xDeviceCharacteristics(id);
  }
#endif

#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
  /* These methods are currently only used for testing and debugging. */
  int sqlite3OsFileHandle(sqlite3_file *id){
    /* return id->pMethods->xFileHandle(id); */
    return 0;
  }
  int sqlite3OsLockState(sqlite3_file *id){
    return id->pMethods->xLockState(id);
  }
#endif

/*
** The next group of routines are convenience wrappers around the
** VFS methods.
*/
int sqlite3OsOpen(

  int sqlite3OsSectorSize(sqlite3_file *id){
    int (*xSectorSize)(sqlite3_file*) = id->pMethods->xSectorSize;
    return (xSectorSize ? xSectorSize(id) : SQLITE_DEFAULT_SECTOR_SIZE);
  }
  int sqlite3OsDeviceCharacteristics(sqlite3_file *id){
    return id->pMethods->xDeviceCharacteristics(id);
  }











#endif

/*
** The next group of routines are convenience wrappers around the
** VFS methods.
*/
int sqlite3OsOpen(

int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
int sqlite3OsTruncate(sqlite3_file*, i64 size);
int sqlite3OsSync(sqlite3_file*, int);
int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
int sqlite3OsLock(sqlite3_file*, int);
int sqlite3OsUnlock(sqlite3_file*, int);
int sqlite3OsCheckReservedLock(sqlite3_file *id);
int sqlite3OsLockState(sqlite3_file *id);
int sqlite3OsFileControl(sqlite3_file*,int,void*);
int sqlite3OsSectorSize(sqlite3_file *id);
int sqlite3OsDeviceCharacteristics(sqlite3_file *id);

/* 
** Functions for accessing sqlite3_vfs methods 
*/
................................................................................
/*
** Convenience functions for opening and closing files using 
** sqlite3_malloc() to obtain space for the file-handle structure.
*/
int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);
int sqlite3OsCloseFree(sqlite3_file *);

#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
  int sqlite3OsFileHandle(sqlite3_file *id);
  int sqlite3OsLockState(sqlite3_file *id);
#endif

/*
** Each OS-specific backend defines an instance of the following
** structure for returning a pointer to its sqlite3_vfs.  If OS_OTHER
** is defined (meaning that the application-defined OS interface layer
** is used) then there is no default VFS.   The application must
** register one or more VFS structures using sqlite3_vfs_register()
** before attempting to use SQLite.

int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
int sqlite3OsTruncate(sqlite3_file*, i64 size);
int sqlite3OsSync(sqlite3_file*, int);
int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
int sqlite3OsLock(sqlite3_file*, int);
int sqlite3OsUnlock(sqlite3_file*, int);
int sqlite3OsCheckReservedLock(sqlite3_file *id);

int sqlite3OsFileControl(sqlite3_file*,int,void*);
int sqlite3OsSectorSize(sqlite3_file *id);
int sqlite3OsDeviceCharacteristics(sqlite3_file *id);

/* 
** Functions for accessing sqlite3_vfs methods 
*/
................................................................................
/*
** Convenience functions for opening and closing files using 
** sqlite3_malloc() to obtain space for the file-handle structure.
*/
int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);
int sqlite3OsCloseFree(sqlite3_file *);






/*
** Each OS-specific backend defines an instance of the following
** structure for returning a pointer to its sqlite3_vfs.  If OS_OTHER
** is defined (meaning that the application-defined OS interface layer
** is used) then there is no default VFS.   The application must
** register one or more VFS structures using sqlite3_vfs_register()
** before attempting to use SQLite.

  return SQLITE_OK;
}

#endif /* SQLITE_ENABLE_LOCKING_STYLE */


/*
** No xFileControl opcodes are implemented by this VFS.
*/
static int unixFileControl(sqlite3_file *id, int op, void *pArg){






  return SQLITE_ERROR;
}

/*
** Return an integer that indices the type of lock currently held
** by this handle.  (Used for testing and analysis only.)
*/
static int unixLockState(sqlite3_file *id){
  return ((unixFile*)id)->locktype;
}

/*
** 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.
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  unixLock,
  unixUnlock,
  unixCheckReservedLock,
  unixLockState,
  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

#ifdef SQLITE_ENABLE_LOCKING_STYLE
/*
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  afpUnixLock,
  afpUnixUnlock,
  afpUnixCheckReservedLock,
  unixLockState,
  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  flockUnixLock,
  flockUnixUnlock,
  flockUnixCheckReservedLock,
  unixLockState,
  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  dotlockUnixLock,
  dotlockUnixUnlock,
  dotlockUnixCheckReservedLock,
  unixLockState,
  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  nolockUnixLock,
  nolockUnixUnlock,
  nolockUnixCheckReservedLock,
  unixLockState,
  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

#endif /* SQLITE_ENABLE_LOCKING_STYLE */

  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.
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  unixLock,
  unixUnlock,
  unixCheckReservedLock,

  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

#ifdef SQLITE_ENABLE_LOCKING_STYLE
/*
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  afpUnixLock,
  afpUnixUnlock,
  afpUnixCheckReservedLock,

  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  flockUnixLock,
  flockUnixUnlock,
  flockUnixCheckReservedLock,

  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  dotlockUnixLock,
  dotlockUnixUnlock,
  dotlockUnixCheckReservedLock,

  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

/*
** This vector defines all the methods that can operate on an sqlite3_file
................................................................................
  unixWrite,
  unixTruncate,
  unixSync,
  unixFileSize,
  nolockUnixLock,
  nolockUnixUnlock,
  nolockUnixCheckReservedLock,

  unixFileControl,
  unixSectorSize,
  unixDeviceCharacteristics
};

#endif /* SQLITE_ENABLE_LOCKING_STYLE */

    UnlockFile(pFile->h, PENDING_BYTE, 0, 1, 0);
  }
  pFile->locktype = locktype;
  return rc;
}

/*
** No xFileControl operations are currently implemented.
*/
static int winFileControl(sqlite3_file *id){






  return SQLITE_ERROR;
}

/*
** Return an integer that indices the type of lock currently held
** by this handle.  (Used for testing and analysis only.)
*/
static int winLockState(sqlite3_file *id){
  winFile *pFile = (winFile*)id;
  return pFile->locktype;
}

/*
** 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.
................................................................................
  winWrite,
  winTruncate,
  winSync,
  winFileSize,
  winLock,
  winUnlock,
  winCheckReservedLock,
  winLockState,
  winFileControl,
  winSectorSize,
  winDeviceCharacteristics
};

/***************************************************************************
** Here ends the I/O methods that form the sqlite3_io_methods object.

    UnlockFile(pFile->h, PENDING_BYTE, 0, 1, 0);
  }
  pFile->locktype = locktype;
  return rc;
}

/*
** Control and query of the open file handle.
*/
static int winFileControl(sqlite3_file *id, int op, void *pArg){
  switch( op ){
    case SQLITE_FCNTL_LOCKSTATE: {
      *(int*)pArg = ((winFile*)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.
................................................................................
  winWrite,
  winTruncate,
  winSync,
  winFileSize,
  winLock,
  winUnlock,
  winCheckReservedLock,

  winFileControl,
  winSectorSize,
  winDeviceCharacteristics
};

/***************************************************************************
** Here ends the I/O methods that form the sqlite3_io_methods object.

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.382 2007/08/31 16:11:36 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*
................................................................................
  assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
  if( eMode>=0 && !pPager->tempFile ){
    pPager->exclusiveMode = eMode;
  }
  return (int)pPager->exclusiveMode;
}

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
/*
** Return the current state of the file lock for the given pager.
** The return value is one of NO_LOCK, SHARED_LOCK, RESERVED_LOCK,
** PENDING_LOCK, or EXCLUSIVE_LOCK.
*/
int sqlite3PagerLockstate(Pager *pPager){
  return sqlite3OsLockState(pPager->fd);
}
#endif

#ifdef SQLITE_DEBUG
/*
** Print a listing of all referenced pages and their ref count.
*/
void sqlite3PagerRefdump(Pager *pPager){
  PgHdr *pPg;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.383 2007/08/31 18:34:59 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*
................................................................................
  assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
  if( eMode>=0 && !pPager->tempFile ){
    pPager->exclusiveMode = eMode;
  }
  return (int)pPager->exclusiveMode;
}












#ifdef SQLITE_DEBUG
/*
** Print a listing of all referenced pages and their ref count.
*/
void sqlite3PagerRefdump(Pager *pPager){
  PgHdr *pPg;
  for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.65 2007/08/31 16:11:36 drh Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** The type used to represent a page number.  The first page in a file
................................................................................
#endif

#if !defined(NDEBUG) || defined(SQLITE_TEST)
  Pgno sqlite3PagerPagenumber(DbPage*);
  int sqlite3PagerIswriteable(DbPage*);
#endif

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
  int sqlite3PagerLockstate(Pager*);
#endif

#ifdef SQLITE_TEST
  int *sqlite3PagerStats(Pager*);
  void sqlite3PagerRefdump(Pager*);
  int pager3_refinfo_enable;
#endif

#ifdef SQLITE_TEST

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem.  The page cache subsystem reads and writes a file a page
** at a time and provides a journal for rollback.
**
** @(#) $Id: pager.h,v 1.66 2007/08/31 18:34:59 drh Exp $
*/

#ifndef _PAGER_H_
#define _PAGER_H_

/*
** The type used to represent a page number.  The first page in a file
................................................................................
#endif

#if !defined(NDEBUG) || defined(SQLITE_TEST)
  Pgno sqlite3PagerPagenumber(DbPage*);
  int sqlite3PagerIswriteable(DbPage*);
#endif





#ifdef SQLITE_TEST
  int *sqlite3PagerStats(Pager*);
  void sqlite3PagerRefdump(Pager*);
  int pager3_refinfo_enable;
#endif

#ifdef SQLITE_TEST

**    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 used to implement the PRAGMA command.
**
** $Id: pragma.c,v 1.148 2007/08/30 10:07:39 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/* Ignore this whole file if pragmas are disabled
*/
#if !defined(SQLITE_OMIT_PRAGMA) && !defined(SQLITE_OMIT_PARSER)
................................................................................
    Vdbe *v = sqlite3GetVdbe(pParse);
    sqlite3VdbeSetNumCols(v, 2);
    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "database", P3_STATIC);
    sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "status", P3_STATIC);
    for(i=0; i<db->nDb; i++){
      Btree *pBt;
      Pager *pPager;


      if( db->aDb[i].zName==0 ) continue;
      sqlite3VdbeOp3(v, OP_String8, 0, 0, db->aDb[i].zName, P3_STATIC);
      pBt = db->aDb[i].pBt;
      if( pBt==0 || (pPager = sqlite3BtreePager(pBt))==0 ){
        sqlite3VdbeOp3(v, OP_String8, 0, 0, "closed", P3_STATIC);
      }else{
        int j = sqlite3PagerLockstate(pPager);
        sqlite3VdbeOp3(v, OP_String8, 0, 0, 
            (j>=0 && j<=4) ? azLockName[j] : "unknown", P3_STATIC);
      }

      sqlite3VdbeAddOp(v, OP_Callback, 2, 0);
    }
  }else
#endif

#ifdef SQLITE_SSE
  /*

**    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 used to implement the PRAGMA command.
**
** $Id: pragma.c,v 1.149 2007/08/31 18:34:59 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/* Ignore this whole file if pragmas are disabled
*/
#if !defined(SQLITE_OMIT_PRAGMA) && !defined(SQLITE_OMIT_PARSER)
................................................................................
    Vdbe *v = sqlite3GetVdbe(pParse);
    sqlite3VdbeSetNumCols(v, 2);
    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "database", P3_STATIC);
    sqlite3VdbeSetColName(v, 1, COLNAME_NAME, "status", P3_STATIC);
    for(i=0; i<db->nDb; i++){
      Btree *pBt;
      Pager *pPager;
      const char *zState = "unknown";
      int j;
      if( db->aDb[i].zName==0 ) continue;
      sqlite3VdbeOp3(v, OP_String8, 0, 0, db->aDb[i].zName, P3_STATIC);
      pBt = db->aDb[i].pBt;
      if( pBt==0 || (pPager = sqlite3BtreePager(pBt))==0 ){
        zState = "closed";
      }else if( sqlite3_file_control(db, db->aDb[i].zName, 
                                     SQLITE_FCNTL_LOCKSTATE, &j)==SQLITE_OK ){
         zState = azLockName[j];

      }
      sqlite3VdbeOp3(v, OP_String8, 0, 0, zState, P3_STATIC);
      sqlite3VdbeAddOp(v, OP_Callback, 2, 0);
    }
  }else
#endif

#ifdef SQLITE_SSE
  /*

** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.252 2007/08/31 16:11:36 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
** [sqlite3_file_control()] interface.  The second argument (the
** "op" argument) is intended to be an integer opcode.  The third
** argument is a generic pointer which is intended to be a pointer
** to a structure that may contain arguments or space in which to
** write return values.  Potential uses for xFileControl() might be
** functions to enable blocking locks with timeouts, to change the
** locking strategy (for example to use dot-file locks), to inquire
** about the status of a lock, or to break stale locks.  No standard
** xFileControl opcodes are currently defined, but this may change in 
** future releases.  Applications that define a custom xFileControl
** method should use opcodes greater than 100 to avoid conflicts
** with future official opcodes which will be less than that value.
**
** The xSectorSize() method returns the sector size of the
** device that underlies the file.  The sector size is the
** minimum write that can be performed without disturbing
** other bytes in the file.  The xDeviceCharacteristics()
** method returns a bit vector describing behaviors of the
** underlying device:
................................................................................
  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite_int64 iOfst);
  int (*xTruncate)(sqlite3_file*, sqlite_int64 size);
  int (*xSync)(sqlite3_file*, int flags);
  int (*xFileSize)(sqlite3_file*, sqlite_int64 *pSize);
  int (*xLock)(sqlite3_file*, int);
  int (*xUnlock)(sqlite3_file*, int);
  int (*xCheckReservedLock)(sqlite3_file*);
  int (*xLockState)(sqlite3_file *);
  int (*xFileControl)(sqlite3_file*, int op, void *pArg);
  int (*xSectorSize)(sqlite3_file*);
  int (*xDeviceCharacteristics)(sqlite3_file*);
  /* Additional methods may be added in future releases */
};


















/*
** CAPI3REF: Mutex Handle
**
** The mutex module within SQLite defines [sqlite3_mutex] to be an
** abstract type for a mutex object.  The SQLite core never looks
** at the internal representation of an [sqlite3_mutex].  It only
** deals with pointers to the [sqlite3_mutex] object.

** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.253 2007/08/31 18:34:59 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
** [sqlite3_file_control()] interface.  The second argument (the
** "op" argument) is intended to be an integer opcode.  The third
** argument is a generic pointer which is intended to be a pointer
** to a structure that may contain arguments or space in which to
** write return values.  Potential uses for xFileControl() might be
** functions to enable blocking locks with timeouts, to change the
** locking strategy (for example to use dot-file locks), to inquire
** about the status of a lock, or to break stale locks.  The SQLite
** core reserves opcodes less than 100 for its own use.  Applications
** that define a custom xFileControl method should use opcodes 
** greater than 100 to avoid conflicts.

**
** The xSectorSize() method returns the sector size of the
** device that underlies the file.  The sector size is the
** minimum write that can be performed without disturbing
** other bytes in the file.  The xDeviceCharacteristics()
** method returns a bit vector describing behaviors of the
** underlying device:
................................................................................
  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite_int64 iOfst);
  int (*xTruncate)(sqlite3_file*, sqlite_int64 size);
  int (*xSync)(sqlite3_file*, int flags);
  int (*xFileSize)(sqlite3_file*, sqlite_int64 *pSize);
  int (*xLock)(sqlite3_file*, int);
  int (*xUnlock)(sqlite3_file*, int);
  int (*xCheckReservedLock)(sqlite3_file*);

  int (*xFileControl)(sqlite3_file*, int op, void *pArg);
  int (*xSectorSize)(sqlite3_file*);
  int (*xDeviceCharacteristics)(sqlite3_file*);
  /* Additional methods may be added in future releases */
};

/*
** CAPI3REF: Standard File Control Opcodes
**
** These integer constants are opcodes for the xFileControl method
** of the [sqlite3_io_methods] object and to the [sqlite3_file_control()]
** interface.
**
** The [SQLITE_FCNTL_LOCKSTATE] opcode is used for debugging.  This
** opcode cases the xFileControl method to write the current state of
** the lock (one of [SQLITE_LOCK_NONE], [SQLITE_LOCK_SHARED],
** [SQLITE_LOCK_RESERVED], [SQLITE_LOCK_PENDING], or [SQLITE_LOCK_EXCLUSIVE])
** into an integer that the pArg argument points to.  This capability
** is used during testing and only needs to be supported when SQLITE_TEST
** is defined.
*/
#define SQLITE_FCNTL_LOCKSTATE        1

/*
** CAPI3REF: Mutex Handle
**
** The mutex module within SQLite defines [sqlite3_mutex] to be an
** abstract type for a mutex object.  The SQLite core never looks
** at the internal representation of an [sqlite3_mutex].  It only
** deals with pointers to the [sqlite3_mutex] object.

}
static int cfUnlock(sqlite3_file *pFile, int eLock){
  return sqlite3OsUnlock(((CrashFile *)pFile)->pRealFile, eLock);
}
static int cfCheckReservedLock(sqlite3_file *pFile){
  return sqlite3OsCheckReservedLock(((CrashFile *)pFile)->pRealFile);
}
static int cfLockState(sqlite3_file *pFile){
  return sqlite3OsLockState(((CrashFile *)pFile)->pRealFile);
}
static int cfFileControl(sqlite3_file *pFile, int op, void *pArg){
  return sqlite3OsFileControl(((CrashFile *)pFile)->pRealFile, op, pArg);
}

/*
** The xSectorSize() and xDeviceCharacteristics() functions return
** the global values configured by the [sqlite_crashparams] tcl
................................................................................
  cfWrite,                      /* xWrite */
  cfTruncate,                   /* xTruncate */
  cfSync,                       /* xSync */
  cfFileSize,                   /* xFileSize */
  cfLock,                       /* xLock */
  cfUnlock,                     /* xUnlock */
  cfCheckReservedLock,          /* xCheckReservedLock */
  cfLockState,                  /* xLockState */
  cfFileControl,                /* xFileControl */
  cfSectorSize,                 /* xSectorSize */
  cfDeviceCharacteristics       /* xDeviceCharacteristics */
};

/*
** Application data for the crash VFS

}
static int cfUnlock(sqlite3_file *pFile, int eLock){
  return sqlite3OsUnlock(((CrashFile *)pFile)->pRealFile, eLock);
}
static int cfCheckReservedLock(sqlite3_file *pFile){
  return sqlite3OsCheckReservedLock(((CrashFile *)pFile)->pRealFile);
}



static int cfFileControl(sqlite3_file *pFile, int op, void *pArg){
  return sqlite3OsFileControl(((CrashFile *)pFile)->pRealFile, op, pArg);
}

/*
** The xSectorSize() and xDeviceCharacteristics() functions return
** the global values configured by the [sqlite_crashparams] tcl
................................................................................
  cfWrite,                      /* xWrite */
  cfTruncate,                   /* xTruncate */
  cfSync,                       /* xSync */
  cfFileSize,                   /* xFileSize */
  cfLock,                       /* xLock */
  cfUnlock,                     /* xUnlock */
  cfCheckReservedLock,          /* xCheckReservedLock */

  cfFileControl,                /* xFileControl */
  cfSectorSize,                 /* xSectorSize */
  cfDeviceCharacteristics       /* xDeviceCharacteristics */
};

/*
** Application data for the crash VFS

  ASYNC_TRACE(("CHECK-LOCK %d (%s)\n", rc, p->zName));
  return rc>SHARED_LOCK;
}

/* 
** This is a no-op, as the asynchronous backend does not support locking.
*/
static int asyncBreakLock(sqlite3_file *id){
  return SQLITE_OK;
}

/* 
** This is broken. But sqlite3OsLockState() is only used for testing anyway.
*/
static int asyncLockState(sqlite3_file *id){
  return SQLITE_OK;
}

/* 
** Return the device characteristics and sector-size of the device. It
** is not tricky to implement these correctly, as this backend might 
** not have an open file handle at this point.
*/
................................................................................
    asyncWrite,                      /* xWrite */
    asyncTruncate,                   /* xTruncate */
    asyncSync,                       /* xSync */
    asyncFileSize,                   /* xFileSize */
    asyncLock,                       /* xLock */
    asyncUnlock,                     /* xUnlock */
    asyncCheckReservedLock,          /* xCheckReservedLock */
    asyncBreakLock,                  /* xBreakLock */
    asyncLockState,                  /* xLockState */
    asyncSectorSize,                 /* xSectorSize */
    asyncDeviceCharacteristics       /* xDeviceCharacteristics */
  };

  sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData;
  AsyncFile *p = (AsyncFile *)pFile;
  int nName = strlen(zName);;

  ASYNC_TRACE(("CHECK-LOCK %d (%s)\n", rc, p->zName));
  return rc>SHARED_LOCK;
}

/* 
** This is a no-op, as the asynchronous backend does not support locking.
*/
static int asyncFileControl(sqlite3_file *id, int op, void *pArg){
  return SQLITE_ERROR;







}

/* 
** Return the device characteristics and sector-size of the device. It
** is not tricky to implement these correctly, as this backend might 
** not have an open file handle at this point.
*/
................................................................................
    asyncWrite,                      /* xWrite */
    asyncTruncate,                   /* xTruncate */
    asyncSync,                       /* xSync */
    asyncFileSize,                   /* xFileSize */
    asyncLock,                       /* xLock */
    asyncUnlock,                     /* xUnlock */
    asyncCheckReservedLock,          /* xCheckReservedLock */
    asyncFileControl,                /* xFileControl */

    asyncSectorSize,                 /* xSectorSize */
    asyncDeviceCharacteristics       /* xDeviceCharacteristics */
  };

  sqlite3_vfs *pVfs = (sqlite3_vfs *)pAsyncVfs->pAppData;
  AsyncFile *p = (AsyncFile *)pFile;
  int nName = strlen(zName);;