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 1.3 2009/04/24 10:13:06 danielk1977 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))

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

/* Enable for debugging */
#ifndef NDEBUG
#include <stdio.h>
static int sqlite3async_trace = 0;
# define ASYNC_TRACE(X) if( sqlite3async_trace ) asyncTrace X
static void asyncTrace(const char *zFormat, ...){
  char *z;
  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);
}
#endif

/*
** THREAD SAFETY NOTES
**
** Basic rules:
**
**     * Both read and write access to the global write-op queue must be 

*/
static struct TestAsyncStaticData {
  AsyncWrite *pQueueFirst;     /* Next write operation to be processed */
  AsyncWrite *pQueueLast;      /* Last write operation on the list */
  AsyncLock *pLock;            /* Linked list of all AsyncLock structures */
  volatile int ioDelay;        /* Extra delay between write operations */
  volatile int eHalt;          /* One of the SQLITEASYNC_HALT_XXX values */
  volatile int bLockFiles;     /* Current value of "lockfiles" parameter */
  int ioError;                 /* True if an IO error has occurred */
  int nFile;                   /* Number of open files (from sqlite pov) */
} async = { 0,0,0,0,0,1,0,0 };

/* Possible values of AsyncWrite.op */
#define ASYNC_NOOP          0
#define ASYNC_WRITE         1
#define ASYNC_SYNC          2
#define ASYNC_TRUNCATE      3
#define ASYNC_CLOSE         4

** structures is allocated) and stored in the async.aLock hash table. The
** keys for async.aLock are the full pathnames of the opened files.
**
** AsyncLock.pList points to the head of a linked list of AsyncFileLock
** structures, one for each handle currently open on the file.
**
** If the opened file is not a main-database (the SQLITE_OPEN_MAIN_DB is
** not passed to the sqlite3OsOpen() call), or if async.bLockFiles is 
** false, variables AsyncLock.pFile and AsyncLock.eLock are never used. 
** Otherwise, pFile is a file handle opened on the file in question and 
** used to obtain the file-system locks required by database connections 
** within this process.
**
** See comments above the asyncLock() function for more details on 
** the implementation of database locking used by this backend.
*/
struct AsyncLock {
  char *zFile;
  int nFile;

  if( zName && rc==SQLITE_OK ){
    pLock = findLock(pData->zName, pData->nName);
    if( !pLock ){
      int nByte = pVfs->szOsFile + sizeof(AsyncLock) + pData->nName + 1; 
      pLock = (AsyncLock *)sqlite3_malloc(nByte);
      if( pLock ){
        memset(pLock, 0, nByte);

        if( async.bLockFiles && (flags&SQLITE_OPEN_MAIN_DB) ){
          pLock->pFile = (sqlite3_file *)&pLock[1];
          rc = pVfs->xOpen(pVfs, pData->zName, pLock->pFile, flags, 0);
          if( rc!=SQLITE_OK ){
            sqlite3_free(pLock);
            pLock = 0;
          }
        }

        if( pLock ){
          pLock->nFile = pData->nName;
          pLock->zFile = &((char *)(&pLock[1]))[pVfs->szOsFile];
          memcpy(pLock->zFile, pData->zName, pLock->nFile);
          pLock->pNext = async.pLock;
          async.pLock = pLock;
        }

  switch( op ){
    case SQLITEASYNC_HALT: {
      int eWhen = va_arg(ap, int);
      if( eWhen!=SQLITEASYNC_HALT_NEVER
       && eWhen!=SQLITEASYNC_HALT_NOW
       && eWhen!=SQLITEASYNC_HALT_IDLE
      ){
        return SQLITE_MISUSE;
      }
      async.eHalt = eWhen;
      async_mutex_enter(ASYNC_MUTEX_QUEUE);
      async_cond_signal(ASYNC_COND_QUEUE);
      async_mutex_leave(ASYNC_MUTEX_QUEUE);
      break;
    }

    case SQLITEASYNC_DELAY: {
      int iDelay = va_arg(ap, int);
      if( iDelay<0 ){
        return SQLITE_MISUSE;
      }
      async.ioDelay = iDelay;
      break;
    }

    case SQLITEASYNC_LOCKFILES: {
      int bLock = va_arg(ap, int);
      async_mutex_enter(ASYNC_MUTEX_QUEUE);
      if( async.nFile || async.pQueueFirst ){
        async_mutex_leave(ASYNC_MUTEX_QUEUE);
        return SQLITE_MISUSE;
      }
      async.bLockFiles = bLock;
      async_mutex_leave(ASYNC_MUTEX_QUEUE);
      break;
    }
      
    case SQLITEASYNC_GET_HALT: {
      int *peWhen = va_arg(ap, int *);
      *peWhen = async.eHalt;
      break;
    }
    case SQLITEASYNC_GET_DELAY: {
      int *piDelay = va_arg(ap, int *);
      *piDelay = async.ioDelay;
      break;
    }
    case SQLITEASYNC_GET_LOCKFILES: {
      int *piDelay = va_arg(ap, int *);
      *piDelay = async.bLockFiles;
      break;
    }

    default:
      return SQLITE_ERROR;
  }
  return SQLITE_OK;
}

#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO) */

/*
** 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 1.60 2009/04/24 10:13:06 danielk1977 Exp $
**
** This file contains a binding of the asynchronous IO extension interface
** (defined in ext/async/sqlite3async.h) to Tcl.
*/

#define TCL_THREADS 
#include <tcl.h>

  Tcl_ThreadId x;
  const int nStack = TCL_THREAD_STACK_DEFAULT;
  const int flags = TCL_THREAD_NOFLAGS;
  int rc;

  rc = Tcl_CreateThread(&x, tclWriterThread, threadData, nStack, flags);
  if( rc!=TCL_OK ){
    Tcl_AppendResult(interp, "Tcl_CreateThread() failed", 0);
    return TCL_ERROR;
  }





  while( isStarted==0 ) { /* Busy loop */ }
  return TCL_OK;
}

/*
** sqlite3async_wait
**
** Wait for the current writer thread to terminate.