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Overview
Comment:Restore the sqlite3_mutex_try() optimization on winNT systems. (CVS 4402)
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SHA1: 3aace2fa91e96038f7a32366828ac7520470fa67
User & Date: drh 2007-09-05 14:30:42.000
Context
2007-09-05
14:32
Test that the asynchronous backend works with components like "." or ".." in the path to the database file. (CVS 4403) (check-in: 0a87a85422 user: danielk1977 tags: trunk)
14:30
Restore the sqlite3_mutex_try() optimization on winNT systems. (CVS 4402) (check-in: 3aace2fa91 user: drh tags: trunk)
13:56
Remove the unixFile.isOpen variable (no longer in use). (CVS 4401) (check-in: 1786e9c881 user: danielk1977 tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/mutex_w32.c. 
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/*
** 2007 August 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.
**
*************************************************************************
** This file contains the C functions that implement mutexes for win32
**
** $Id: mutex_w32.c,v 1.3 2007/09/04 22:31:37 drh Exp $
*/
#include "sqliteInt.h"

/*
** The code in this file is only used if we are compiling multithreaded
** on a win32 system.
*/
#ifdef SQLITE_MUTEX_W32

/*
** Each recursive mutex is an instance of the following structure.
*/
struct sqlite3_mutex {
  CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
  int id;                    /* Mutex type */
  int nRef;                  /* Number of enterances */
  DWORD owner;               /* Thread holding this mutex */
};




























/*
** The sqlite3_mutex_alloc() routine allocates a new
** mutex and returns a pointer to it.  If it returns NULL
** that means that a mutex could not be allocated.  SQLite
** will unwind its stack and return an error.  The argument
** to sqlite3_mutex_alloc() is one of these integer constants:














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/*
** 2007 August 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.
**
*************************************************************************
** This file contains the C functions that implement mutexes for win32
**
** $Id: mutex_w32.c,v 1.4 2007/09/05 14:30:42 drh Exp $
*/
#include "sqliteInt.h"

/*
** The code in this file is only used if we are compiling multithreaded
** on a win32 system.
*/
#ifdef SQLITE_MUTEX_W32

/*
** Each recursive mutex is an instance of the following structure.
*/
struct sqlite3_mutex {
  CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
  int id;                    /* Mutex type */
  int nRef;                  /* Number of enterances */
  DWORD owner;               /* Thread holding this mutex */
};

/*
** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
** or WinCE.  Return false (zero) for Win95, Win98, or WinME.
**
** Here is an interesting observation:  Win95, Win98, and WinME lack
** the LockFileEx() API.  But we can still statically link against that
** API as long as we don't call it win running Win95/98/ME.  A call to
** this routine is used to determine if the host is Win95/98/ME or
** WinNT/2K/XP so that we will know whether or not we can safely call
** the LockFileEx() API.
*/
#if OS_WINCE
# define mutexIsNT()  (1)
#else
  static int mutexIsNT(void){
    static int osType = 0;
    if( osType==0 ){
      OSVERSIONINFO sInfo;
      sInfo.dwOSVersionInfoSize = sizeof(sInfo);
      GetVersionEx(&sInfo);
      osType = sInfo.dwPlatformId==VER_PLATFORM_WIN32_NT ? 2 : 1;
    }
    return osType==2;
  }
#endif /* OS_WINCE */


/*
** The sqlite3_mutex_alloc() routine allocates a new
** mutex and returns a pointer to it.  If it returns NULL
** that means that a mutex could not be allocated.  SQLite
** will unwind its stack and return an error.  The argument
** to sqlite3_mutex_alloc() is one of these integer constants:
︙︙
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  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
  EnterCriticalSection(&p->mutex);
  p->owner = GetCurrentThreadId(); 
  p->nRef++;
}
int sqlite3_mutex_try(sqlite3_mutex *p){
  /* The TryEnterCriticalSection() interface is not available on all
  ** windows systems.  Since sqlite3_mutex_try() is only used as an
  ** optimization, we can skip it on windows. */
  return SQLITE_BUSY;

#if 0  /* Not Available */
  int rc;
  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
  if( TryEnterCriticalSection(&p->mutex) ){
    p->owner = GetCurrentThreadId();
    p->nRef++;
    rc = SQLITE_OK;
  }else{
    rc = SQLITE_BUSY;
  }
  return rc;
#endif
}

/*
** The sqlite3_mutex_leave() routine exits a mutex that was
** previously entered by the same thread.  The behavior
** is undefined if the mutex is not currently entered or
** is not currently allocated.  SQLite will never do either.








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  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
  EnterCriticalSection(&p->mutex);
  p->owner = GetCurrentThreadId(); 
  p->nRef++;
}
int sqlite3_mutex_try(sqlite3_mutex *p){






  int rc;
  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
  if( mutexIsNT() && TryEnterCriticalSection(&p->mutex) ){
    p->owner = GetCurrentThreadId();
    p->nRef++;
    rc = SQLITE_OK;
  }else{
    rc = SQLITE_BUSY;
  }
  return rc;

}

/*
** The sqlite3_mutex_leave() routine exits a mutex that was
** previously entered by the same thread.  The behavior
** is undefined if the mutex is not currently entered or
** is not currently allocated.  SQLite will never do either.
︙︙