src/mutex.h

   1 /*
   2 ** 2007 August 28
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 **
  13 ** This file contains the common header for all mutex implementations.
  14 ** The sqliteInt.h header #includes this file so that it is available
  15 ** to all source files.  We break it out in an effort to keep the code
  16 ** better organized.
  17 **
  18 ** NOTE:  source files should *not* #include this header file directly.
  19 ** Source files should #include the sqliteInt.h file and let that file
  20 ** include this one indirectly.
  21 */
  22
  23
  24 /*
  25 ** Figure out what version of the code to use.  The choices are
  26 **
  27 **   SQLITE_MUTEX_OMIT         No mutex logic.  Not even stubs.  The
  28 **                             mutexes implementation cannot be overridden
  29 **                             at start-time.
  30 **
  31 **   SQLITE_MUTEX_NOOP         For single-threaded applications.  No
  32 **                             mutual exclusion is provided.  But this
  33 **                             implementation can be overridden at
  34 **                             start-time.
  35 **
  36 **   SQLITE_MUTEX_PTHREADS     For multi-threaded applications on Unix.
  37 **
  38 **   SQLITE_MUTEX_W32          For multi-threaded applications on Win32.
  39 */
  40 #if !SQLITE_THREADSAFE
  41 # define SQLITE_MUTEX_OMIT
  42 #endif
  43 #if SQLITE_THREADSAFE && !defined(SQLITE_MUTEX_NOOP)
  44 #  if SQLITE_OS_UNIX
  45 #    define SQLITE_MUTEX_PTHREADS
  46 #  elif SQLITE_OS_WIN
  47 #    define SQLITE_MUTEX_W32
  48 #  else
  49 #    define SQLITE_MUTEX_NOOP
  50 #  endif
  51 #endif
  52
  53 #ifdef SQLITE_MUTEX_OMIT
  54 /*
  55 ** If this is a no-op implementation, implement everything as macros.
  56 */
  57 #define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
  58 #define sqlite3_mutex_free(X)
  59 #define sqlite3_mutex_enter(X)
  60 #define sqlite3_mutex_try(X)      SQLITE_OK
  61 #define sqlite3_mutex_leave(X)
  62 #define sqlite3_mutex_held(X)     ((void)(X),1)
  63 #define sqlite3_mutex_notheld(X)  ((void)(X),1)
  64 #define sqlite3MutexAlloc(X)      ((sqlite3_mutex*)8)
  65 #define sqlite3MutexInit()        SQLITE_OK
  66 #define sqlite3MutexEnd()
  67 #define MUTEX_LOGIC(X)
  68 #else
  69 #define MUTEX_LOGIC(X)            X
  70 #endif /* defined(SQLITE_MUTEX_OMIT) */