gl/windows-mutex.c

   1 /* Plain mutexes (native Windows implementation).
   2    Copyright (C) 2005-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2005.
  18    Based on GCC's gthr-win32.h.  */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include "windows-mutex.h"
  24
  25 #include <errno.h>
  26
  27 void
  28 glwthread_mutex_init (glwthread_mutex_t *mutex)
  29 {
  30   InitializeCriticalSection (&mutex->lock);
  31   mutex->guard.done = 1;
  32 }
  33
  34 int
  35 glwthread_mutex_lock (glwthread_mutex_t *mutex)
  36 {
  37   if (!mutex->guard.done)
  38     {
  39       if (InterlockedIncrement (&mutex->guard.started) == 0)
  40         /* This thread is the first one to need this mutex.  Initialize it.  */
  41         glwthread_mutex_init (mutex);
  42       else
  43         {
  44           /* Don't let mutex->guard.started grow and wrap around.  */
  45           InterlockedDecrement (&mutex->guard.started);
  46           /* Yield the CPU while waiting for another thread to finish
  47              initializing this mutex.  */
  48           while (!mutex->guard.done)
  49             Sleep (0);
  50         }
  51     }
  52   EnterCriticalSection (&mutex->lock);
  53   return 0;
  54 }
  55
  56 int
  57 glwthread_mutex_trylock (glwthread_mutex_t *mutex)
  58 {
  59   if (!mutex->guard.done)
  60     {
  61       if (InterlockedIncrement (&mutex->guard.started) == 0)
  62         /* This thread is the first one to need this mutex.  Initialize it.  */
  63         glwthread_mutex_init (mutex);
  64       else
  65         {
  66           /* Don't let mutex->guard.started grow and wrap around.  */
  67           InterlockedDecrement (&mutex->guard.started);
  68           /* Let another thread finish initializing this mutex, and let it also
  69              lock this mutex.  */
  70           return EBUSY;
  71         }
  72     }
  73   if (!TryEnterCriticalSection (&mutex->lock))
  74     return EBUSY;
  75   return 0;
  76 }
  77
  78 int
  79 glwthread_mutex_unlock (glwthread_mutex_t *mutex)
  80 {
  81   if (!mutex->guard.done)
  82     return EINVAL;
  83   LeaveCriticalSection (&mutex->lock);
  84   return 0;
  85 }
  86
  87 int
  88 glwthread_mutex_destroy (glwthread_mutex_t *mutex)
  89 {
  90   if (!mutex->guard.done)
  91     return EINVAL;
  92   DeleteCriticalSection (&mutex->lock);
  93   mutex->guard.done = 0;
  94   return 0;
  95 }