/* Simple DirectMedia Layer Copyright (C) 1997-2012 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. */ #ifdef SAVE_RCSID static char rcsid = "@(#) $Id: SDL_syssem.c,v 1.2 2001/04/26 16:50:18 hercules Exp $"; #endif /* An implementation of semaphores using mutexes and condition variables */ #include <stdlib.h> #include "SDL_error.h" #include "SDL_timer.h" #include "SDL_thread.h" #include "SDL_systhread_c.h" #ifdef DISABLE_THREADS SDL_sem * SDL_CreateSemaphore(Uint32 initial_value) { SDL_SetError("SDL not configured with thread support"); return (SDL_sem *) 0; } void SDL_DestroySemaphore(SDL_sem * sem) { return; } int SDL_SemTryWait(SDL_sem * sem) { SDL_SetError("SDL not configured with thread support"); return -1; } int SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout) { SDL_SetError("SDL not configured with thread support"); return -1; } int SDL_SemWait(SDL_sem * sem) { SDL_SetError("SDL not configured with thread support"); return -1; } Uint32 SDL_SemValue(SDL_sem * sem) { return 0; } int SDL_SemPost(SDL_sem * sem) { SDL_SetError("SDL not configured with thread support"); return -1; } #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 *) malloc(sizeof(*sem)); if (!sem) { SDL_OutOfMemory(); return (0); } 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 (0); } 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); SDL_mutexP(sem->count_lock); SDL_mutexV(sem->count_lock); SDL_DestroyMutex(sem->count_lock); free(sem); } } int SDL_SemTryWait(SDL_sem * sem) { int retval; if (!sem) { SDL_SetError("Passed a NULL semaphore"); return -1; } 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) { SDL_SetError("Passed a NULL semaphore"); return -1; } /* 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; --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) { SDL_SetError("Passed a NULL semaphore"); return -1; } 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 /* DISABLE_THREADS */ /* vi: set ts=4 sw=4 expandtab: */