SDL_syssem.c
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/*
SDL - Simple DirectMedia Layer
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Copyright (C) 1997-2006 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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/* An implementation of semaphores using mutexes and condition variables */
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#include "SDL_thread.h"
#include "SDL_systhread_c.h"
struct SDL_semaphore
{
struct SignalSemaphore Sem;
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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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#define D(x)
SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
{
SDL_sem *sem;
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sem = (SDL_sem *)SDL_malloc(sizeof(*sem));
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if ( ! sem ) {
SDL_OutOfMemory();
return(0);
}
D(bug("Creating semaphore %lx...\n",sem));
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SDL_memset(sem,0,sizeof(*sem));
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InitSemaphore(&sem->Sem);
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return(sem);
}
void SDL_DestroySemaphore(SDL_sem *sem)
{
D(bug("Destroying semaphore %lx...\n",sem));
if ( sem ) {
// Condizioni per liberare i task in attesa?
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SDL_free(sem);
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}
}
int SDL_SemTryWait(SDL_sem *sem)
{
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
D(bug("TryWait semaphore...%lx\n",sem));
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ObtainSemaphore(&sem->Sem);
// ReleaseSemaphore(&sem->Sem);
return 1;
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}
int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
{
int retval;
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if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
D(bug("WaitTimeout (%ld) semaphore...%lx\n",timeout,sem));
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/* 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);
*/
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if(!(retval=AttemptSemaphore(&sem->Sem)))
{
SDL_Delay(timeout);
retval=AttemptSemaphore(&sem->Sem);
}
if(retval==TRUE)
{
// ReleaseSemaphore(&sem->Sem);
retval=1;
}
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return retval;
}
int SDL_SemWait(SDL_sem *sem)
{
ObtainSemaphore(&sem->Sem);
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return 0;
// return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
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}
Uint32 SDL_SemValue(SDL_sem *sem)
{
Uint32 value;
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value = 0;
if ( sem ) {
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#ifdef STORMC4_WOS
value = sem->Sem.ssppc_SS.ss_NestCount;
#else
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value = sem->Sem.ss_NestCount;
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#endif
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// SDL_UnlockMutex(sem->count_lock);
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}
return value;
}
int SDL_SemPost(SDL_sem *sem)
{
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
D(bug("SemPost semaphore...%lx\n",sem));
ReleaseSemaphore(&sem->Sem);
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#if 0
SDL_LockMutex(sem->count_lock);
if ( sem->waiters_count > 0 ) {
SDL_CondSignal(sem->count_nonzero);
}
++sem->count;
SDL_UnlockMutex(sem->count_lock);
#endif
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return 0;
}