SQLite

/*
** 2005 December 14
**
** 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.
**
*************************************************************************
**
** $Id: sqlite3async.c,v 1.6 2009/04/30 17:45:34 shane Exp $
**
** This file contains the implementation of an asynchronous IO backend 
** for SQLite.
*/

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO)

#include "sqlite3async.h"
#include "sqlite3.h"
#include <stdarg.h>
#include <string.h>
#include <assert.h>

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

#ifndef SQLITE_AMALGAMATION
/* Macro to mark parameters as unused and silence compiler warnings. */
#define UNUSED_PARAMETER(x) (void)(x)
#endif

/* Forward references */
typedef struct AsyncWrite AsyncWrite;
typedef struct AsyncFile AsyncFile;
typedef struct AsyncFileData AsyncFileData;
typedef struct AsyncFileLock AsyncFileLock;
typedef struct AsyncLock AsyncLock;

/* Values for use as the 'eCond' argument of the above functions. */
#define ASYNC_COND_QUEUE    0

/*************************************************************************
** Start of OS specific code.
*/
#if SQLITE_OS_WIN || defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)

#include <windows.h>

/* The following block contains the win32 specific code. */

#define mutex_held(X) (GetCurrentThreadId()==primitives.aHolder[X])

static struct AsyncPrimitives {
  int isInit;

  async_mutex_enter(eMutex);
}
static void async_cond_signal(int eCond){
  assert( mutex_held(ASYNC_MUTEX_QUEUE) );
  SetEvent(primitives.aCond[eCond]);
}
static void async_sched_yield(void){

  Sleep(0);
}
#else

/* The following block contains the pthreads specific code. */
#include <pthread.h>
#include <sched.h>

      )){
        sqlite3_int64 iBeginOut = (pWrite->iOffset-iOffset);
        sqlite3_int64 iBeginIn = -iBeginOut;
        int nCopy;

        if( iBeginIn<0 ) iBeginIn = 0;
        if( iBeginOut<0 ) iBeginOut = 0;
        nCopy = (int)MIN(pWrite->nByte-iBeginIn, iAmt-iBeginOut);

        if( nCopy>0 ){
          memcpy(&((char *)zOut)[iBeginOut], &pWrite->zBuf[iBeginIn], nCopy);
          ASYNC_TRACE(("OVERREAD %d bytes at %d\n", nCopy, iBeginOut+iOffset));
        }
      }
    }

  AsyncFileData *p = ((AsyncFile *)pFile)->pData;
  int rc = SQLITE_OK;
  sqlite3_int64 s = 0;
  sqlite3_file *pBase;

  async_mutex_enter(ASYNC_MUTEX_QUEUE);

  /* Read the filesystem size from the base file. If pMethods is NULL, this
  ** means the file hasn't been opened yet. In this case all relevant data 
  ** must be in the write-op queue anyway, so we can omit reading from the
  ** file-system.
  */
  pBase = p->pBaseRead;
  if( pBase->pMethods ){
    rc = pBase->pMethods->xFileSize(pBase, &s);