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 1.5 2009/04/29 18:12:00 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 "sqliteInt.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))

  va_list ap;
  va_start(ap, zFormat);
  z = sqlite3_vmprintf(zFormat, ap);
  va_end(ap);
  fprintf(stderr, "[%d] %s", 0 /* (int)pthread_self() */, z);
  sqlite3_free(z);
}
#else
# define ASYNC_TRACE(X)
#endif

/*
** THREAD SAFETY NOTES
**
** Basic rules:
**

}
static void async_cond_signal(int eCond){
  assert( mutex_held(ASYNC_MUTEX_QUEUE) );
  SetEvent(primitives.aCond[eCond]);
}
static void async_sched_yield(void){
  /* Todo: Find out if win32 offers anything like sched_yield() */
  Sleep(0);
}
#else

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

  }

  if( pBase->pMethods ){
    rc = pBase->pMethods->xFileSize(pBase, &filesize);
    if( rc!=SQLITE_OK ){
      goto asyncread_out;
    }
    nRead = (int)MIN(filesize - iOffset, iAmt);
    if( nRead>0 ){
      rc = pBase->pMethods->xRead(pBase, zOut, nRead, iOffset);
      ASYNC_TRACE(("READ %s %d bytes at %d\n", p->zName, nRead, iOffset));
    }
  }

  if( rc==SQLITE_OK ){
    AsyncWrite *pWrite;
    char *zName = p->zName;

    for(pWrite=async.pQueueFirst; pWrite; pWrite = pWrite->pNext){
      if( pWrite->op==ASYNC_WRITE && (
        (pWrite->pFileData==p) ||
        (zName && pWrite->pFileData->zName==zName)
      )){
        sqlite3_int64 iBeginOut = (pWrite->iOffset-iOffset);
        sqlite3_int64 iBeginIn = -iBeginOut;
        int nCopy;

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

        if( nCopy>0 ){

  AsyncFileLock *pIter;
  AsyncFileData *p = ((AsyncFile *)pFile)->pData;

  async_mutex_enter(ASYNC_MUTEX_LOCK);
  for(pIter=p->pLock->pList; pIter; pIter=pIter->pNext){
    if( pIter->eLock>=SQLITE_LOCK_RESERVED ){
      ret = 1;
      break;
    }
  }
  async_mutex_leave(ASYNC_MUTEX_LOCK);

  ASYNC_TRACE(("CHECK-LOCK %d (%s)\n", ret, p->zName));
  *pResOut = ret;
  return SQLITE_OK;

    }
  }
  return SQLITE_ERROR;
}

/* 
** Return the device characteristics and sector-size of the device. It
** is tricky to implement these correctly, as this backend might 
** not have an open file handle at this point.
*/
static int asyncSectorSize(sqlite3_file *pFile){
  UNUSED_PARAMETER(pFile);
  return 512;
}
static int asyncDeviceCharacteristics(sqlite3_file *pFile){
  UNUSED_PARAMETER(pFile);
  return 0;
}

static int unlinkAsyncFile(AsyncFileData *pData){
  AsyncFileLock **ppIter;
  int rc = SQLITE_OK;

  AsyncFileData *pData;
  AsyncLock *pLock = 0;
  char *z;
  int isAsyncOpen = doAsynchronousOpen(flags);

  /* If zName is NULL, then the upper layer is requesting an anonymous file */
  if( zName ){
    nName = (int)strlen(zName)+1;
  }

  nByte = (
    sizeof(AsyncFileData) +        /* AsyncFileData structure */
    2 * pVfs->szOsFile +           /* AsyncFileData.pBaseRead and pBaseWrite */
    nName                          /* AsyncFileData.zName */
  ); 

}

/*
** Implementation of sqlite3OsDelete. Add an entry to the end of the 
** write-op queue to perform the delete.
*/
static int asyncDelete(sqlite3_vfs *pAsyncVfs, const char *z, int syncDir){
  UNUSED_PARAMETER(pAsyncVfs);
  return addNewAsyncWrite(0, ASYNC_DELETE, syncDir, (int)strlen(z)+1, z);
}

/*
** Implementation of sqlite3OsAccess. This method holds the mutex from
** start to finish.
*/
static int asyncAccess(