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SDL_syssem.c
226 lines (188 loc) · 4.58 KB
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/*
SDL - Simple DirectMedia Layer
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Copyright (C) 1997-2010 Sam Lantinga
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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Sam Lantinga
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slouken@libsdl.org
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*/
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#include "SDL_config.h"
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/* An implementation of semaphores using mutexes and condition variables */
#include "SDL_timer.h"
#include "SDL_thread.h"
#include "SDL_systhread_c.h"
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#if SDL_THREADS_DISABLED
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SDL_sem *
SDL_CreateSemaphore(Uint32 initial_value)
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{
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SDL_SetError("SDL not configured with thread support");
return (SDL_sem *) 0;
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}
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void
SDL_DestroySemaphore(SDL_sem * sem)
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{
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return;
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}
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int
SDL_SemTryWait(SDL_sem * sem)
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{
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SDL_SetError("SDL not configured with thread support");
return -1;
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}
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int
SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
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{
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SDL_SetError("SDL not configured with thread support");
return -1;
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}
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int
SDL_SemWait(SDL_sem * sem)
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{
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SDL_SetError("SDL not configured with thread support");
return -1;
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}
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Uint32
SDL_SemValue(SDL_sem * sem)
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{
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return 0;
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}
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int
SDL_SemPost(SDL_sem * sem)
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{
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SDL_SetError("SDL not configured with thread support");
return -1;
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}
#else
struct SDL_semaphore
{
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Uint32 count;
Uint32 waiters_count;
SDL_mutex *count_lock;
SDL_cond *count_nonzero;
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};
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SDL_sem *
SDL_CreateSemaphore(Uint32 initial_value)
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{
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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;
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}
/* WARNING:
You cannot call this function when another thread is using the semaphore.
*/
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void
SDL_DestroySemaphore(SDL_sem * sem)
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{
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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_mutexP(sem->count_lock);
SDL_mutexV(sem->count_lock);
SDL_DestroyMutex(sem->count_lock);
}
SDL_free(sem);
}
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}
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int
SDL_SemTryWait(SDL_sem * sem)
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{
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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;
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}
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int
SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
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{
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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;
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if (retval == 0) {
--sem->count;
}
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SDL_UnlockMutex(sem->count_lock);
return retval;
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}
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int
SDL_SemWait(SDL_sem * sem)
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{
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return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
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}
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Uint32
SDL_SemValue(SDL_sem * sem)
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{
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Uint32 value;
value = 0;
if (sem) {
SDL_LockMutex(sem->count_lock);
value = sem->count;
SDL_UnlockMutex(sem->count_lock);
}
return value;
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}
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int
SDL_SemPost(SDL_sem * sem)
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{
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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;
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}
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#endif /* SDL_THREADS_DISABLED */
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/* vi: set ts=4 sw=4 expandtab: */