SQLite

**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains OS interface code that is common to all
** architectures.
**
** $Id: os.c,v 1.126 2009/03/25 14:24:42 drh Exp $
*/
#define _SQLITE_OS_C_ 1
#include "sqliteInt.h"
#undef _SQLITE_OS_C_

/*
** The default SQLite sqlite3_vfs implementations do not allocate

int sqlite3OsOpen(
  sqlite3_vfs *pVfs, 
  const char *zPath, 
  sqlite3_file *pFile, 
  int flags, 
  int *pFlagsOut
){
  int rc;
  DO_OS_MALLOC_TEST;
  rc = pVfs->xOpen(pVfs, zPath, pFile, flags, pFlagsOut);
  assert( rc==SQLITE_OK || pFile->pMethods==0 );
  return rc;
}
int sqlite3OsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
  return pVfs->xDelete(pVfs, zPath, dirSync);
}
int sqlite3OsAccess(
  sqlite3_vfs *pVfs, 
  const char *zPath, 

/*
** 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: test_async.c,v 1.51 2009/03/25 14:24:42 drh Exp $
**
** This file contains an example implementation of an asynchronous IO 
** backend for SQLite.
**
** WHAT IS ASYNCHRONOUS I/O?
**
** With asynchronous I/O, write requests are handled by a separate thread

struct AsyncFileData {
  char *zName;               /* Underlying OS filename - used for debugging */
  int nName;                 /* Number of characters in zName */
  sqlite3_file *pBaseRead;   /* Read handle to the underlying Os file */
  sqlite3_file *pBaseWrite;  /* Write handle to the underlying Os file */
  AsyncFileLock lock;        /* Lock state for this handle */
  AsyncLock *pLock;          /* AsyncLock object for this file system entry */
  AsyncWrite closeOp;        /* Preallocated close operation */
};

/*
** The following async_XXX functions are debugging wrappers around the
** corresponding pthread_XXX functions:
**
**     pthread_mutex_lock();

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

  /* Unlock the file, if it is locked */
  pthread_mutex_lock(&async.lockMutex);
  p->lock.eLock = 0;
  pthread_mutex_unlock(&async.lockMutex);

  addAsyncWrite(&p->closeOp);
  return SQLITE_OK;
}

/*
** Implementation of sqlite3OsWrite() for asynchronous files. Instead of 
** writing to the underlying file, this function adds an entry to the end of
** the global AsyncWrite list. Either SQLITE_OK or SQLITE_NOMEM may be

  }
  memset(z, 0, nByte);
  pData = (AsyncFileData*)z;
  z += sizeof(pData[0]);
  pData->pBaseRead = (sqlite3_file*)z;
  z += pVfs->szOsFile;
  pData->pBaseWrite = (sqlite3_file*)z;
  pData->closeOp.pFileData = pData;
  pData->closeOp.op = ASYNC_CLOSE;

  if( zName ){
    z += pVfs->szOsFile;
    pData->zName = z;
    pData->nName = nName;
    memcpy(pData->zName, zName, nName);
  }

      if( pOutFlags ) *pOutFlags = flags;
    }else{
      pthread_mutex_lock(&async.lockMutex);
      unlinkAsyncFile(pData);
      pthread_mutex_unlock(&async.lockMutex);
      sqlite3_free(pData);
    }
  }
  if( rc!=SQLITE_OK ){
    p->pMethod = 0;
  }
  return rc;
}

/*
** Implementation of sqlite3OsDelete. Add an entry to the end of the 
** write-op queue to perform the delete.