sdl

SDL_syssem.c (4670B)

---

 /*
   Simple DirectMedia Layer
   Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
   arising from the use of this software.
 
   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:
 
   1. The origin of this software must not be misrepresented; you must not
      claim that you wrote the original software. If you use this software
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.
   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
 #include "../../SDL_internal.h"
 
 /* An implementation of semaphores using mutexes and condition variables */
 
 #include "SDL_timer.h"
 #include "SDL_thread.h"
 #include "SDL_systhread_c.h"
 
 
 #if SDL_THREADS_DISABLED
 
 SDL_sem *
 SDL_CreateSemaphore(Uint32 initial_value)
 {
     SDL_SetError("SDL not built with thread support");
     return (SDL_sem *) 0;
 }
 
 void
 SDL_DestroySemaphore(SDL_sem * sem)
 {
 }
 
 int
 SDL_SemTryWait(SDL_sem * sem)
 {
     return SDL_SetError("SDL not built with thread support");
 }
 
 int
 SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
 {
     return SDL_SetError("SDL not built with thread support");
 }
 
 int
 SDL_SemWait(SDL_sem * sem)
 {
     return SDL_SetError("SDL not built with thread support");
 }
 
 Uint32
 SDL_SemValue(SDL_sem * sem)
 {
     return 0;
 }
 
 int
 SDL_SemPost(SDL_sem * sem)
 {
     return SDL_SetError("SDL not built with thread support");
 }
 
 #else
 
 struct SDL_semaphore
 {
     Uint32 count;
     Uint32 waiters_count;
     SDL_mutex *count_lock;
     SDL_cond *count_nonzero;
 };
 
 SDL_sem *
 SDL_CreateSemaphore(Uint32 initial_value)
 {
     SDL_sem *sem;
 
     sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
     if (!sem) {
         SDL_OutOfMemory();
         return NULL;
     }
     sem->count = initial_value;
     sem->waiters_count = 0;
 
     sem->count_lock = SDL_CreateMutex();
     sem->count_nonzero = SDL_CreateCond();
     if (!sem->count_lock || !sem->count_nonzero) {
         SDL_DestroySemaphore(sem);
         return NULL;
     }
 
     return sem;
 }
 
 /* WARNING:
    You cannot call this function when another thread is using the semaphore.
 */
 void
 SDL_DestroySemaphore(SDL_sem * sem)
 {
     if (sem) {
         sem->count = 0xFFFFFFFF;
         while (sem->waiters_count > 0) {
             SDL_CondSignal(sem->count_nonzero);
             SDL_Delay(10);
         }
         SDL_DestroyCond(sem->count_nonzero);
         if (sem->count_lock) {
             SDL_LockMutex(sem->count_lock);
             SDL_UnlockMutex(sem->count_lock);
             SDL_DestroyMutex(sem->count_lock);
         }
         SDL_free(sem);
     }
 }
 
 int
 SDL_SemTryWait(SDL_sem * sem)
 {
     int retval;
 
     if (!sem) {
         return SDL_SetError("Passed a NULL semaphore");
     }
 
     retval = SDL_MUTEX_TIMEDOUT;
     SDL_LockMutex(sem->count_lock);
     if (sem->count > 0) {
         --sem->count;
         retval = 0;
     }
     SDL_UnlockMutex(sem->count_lock);
 
     return retval;
 }
 
 int
 SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
 {
     int retval;
 
     if (!sem) {
         return SDL_SetError("Passed a NULL semaphore");
     }
 
     /* A timeout of 0 is an easy case */
     if (timeout == 0) {
         return SDL_SemTryWait(sem);
     }
 
     SDL_LockMutex(sem->count_lock);
     ++sem->waiters_count;
     retval = 0;
     while ((sem->count == 0) && (retval != SDL_MUTEX_TIMEDOUT)) {
         retval = SDL_CondWaitTimeout(sem->count_nonzero,
                                      sem->count_lock, timeout);
     }
     --sem->waiters_count;
     if (retval == 0) {
         --sem->count;
     }
     SDL_UnlockMutex(sem->count_lock);
 
     return retval;
 }
 
 int
 SDL_SemWait(SDL_sem * sem)
 {
     return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
 }
 
 Uint32
 SDL_SemValue(SDL_sem * sem)
 {
     Uint32 value;
 
     value = 0;
     if (sem) {
         SDL_LockMutex(sem->count_lock);
         value = sem->count;
         SDL_UnlockMutex(sem->count_lock);
     }
     return value;
 }
 
 int
 SDL_SemPost(SDL_sem * sem)
 {
     if (!sem) {
         return SDL_SetError("Passed a NULL semaphore");
     }
 
     SDL_LockMutex(sem->count_lock);
     if (sem->waiters_count > 0) {
         SDL_CondSignal(sem->count_nonzero);
     }
     ++sem->count;
     SDL_UnlockMutex(sem->count_lock);
 
     return 0;
 }
 
 #endif /* SDL_THREADS_DISABLED */
 /* vi: set ts=4 sw=4 expandtab: */