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SDL_syssem.c
231 lines (197 loc) · 4.67 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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#include "SDL_thread.h"
#include "SDL_timer.h"
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <errno.h>
#include "SDL_error.h"
#include "SDL_thread.h"
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struct SDL_semaphore
{
int id;
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};
/* Not defined by many operating systems, use configure to detect */
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/*
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#if !defined(HAVE_SEMUN)
union semun {
int val;
struct semid_ds *buf;
ushort *array;
};
#endif
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*/
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static struct sembuf op_trywait[2] = {
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{0, -1, (IPC_NOWAIT | SEM_UNDO)} /* Decrement semaphore, no block */
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};
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static struct sembuf op_wait[2] = {
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{0, -1, SEM_UNDO} /* Decrement semaphore */
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};
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static struct sembuf op_post[1] = {
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{0, 1, (IPC_NOWAIT | SEM_UNDO)} /* Increment semaphore */
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};
/* Create a blockable semaphore */
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SDL_sem *
SDL_CreateSemaphore(Uint32 initial_value)
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{
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extern int _creating_thread_lock; /* SDL_threads.c */
SDL_sem *sem;
union semun init;
sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
if (sem == NULL) {
SDL_OutOfMemory();
return (NULL);
}
sem->id = semget(IPC_PRIVATE, 1, (0600 | IPC_CREAT));
if (sem->id < 0) {
SDL_SetError("Couldn't create semaphore");
SDL_free(sem);
return (NULL);
}
init.val = initial_value; /* Initialize semaphore */
semctl(sem->id, 0, SETVAL, init);
return (sem);
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}
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void
SDL_DestroySemaphore(SDL_sem * sem)
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{
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if (sem) {
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#ifdef __IRIX__
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semctl(sem->id, 0, IPC_RMID);
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#else
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union semun dummy;
dummy.val = 0;
semctl(sem->id, 0, IPC_RMID, dummy);
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#endif
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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;
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if (!sem) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
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retval = 0;
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tryagain:
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if (semop(sem->id, op_trywait, 1) < 0) {
if (errno == EINTR) {
goto tryagain;
}
retval = SDL_MUTEX_TIMEDOUT;
}
return retval;
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}
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int
SDL_SemWait(SDL_sem * sem)
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{
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int retval;
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if (!sem) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
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retval = 0;
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tryagain:
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if (semop(sem->id, op_wait, 1) < 0) {
if (errno == EINTR) {
goto tryagain;
}
SDL_SetError("Semaphore operation error");
retval = -1;
}
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;
}
/* Try the easy cases first */
if (timeout == 0) {
return SDL_SemTryWait(sem);
}
if (timeout == SDL_MUTEX_MAXWAIT) {
return SDL_SemWait(sem);
}
/* Ack! We have to busy wait... */
timeout += SDL_GetTicks();
do {
retval = SDL_SemTryWait(sem);
if (retval == 0) {
break;
}
SDL_Delay(1);
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} while (SDL_GetTicks() < timeout);
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return retval;
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}
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Uint32
SDL_SemValue(SDL_sem * sem)
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{
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int semval;
Uint32 value;
value = 0;
if (sem) {
tryagain:
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#ifdef __IRIX__
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semval = semctl(sem->id, 0, GETVAL);
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#else
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{
union semun arg;
arg.val = 0;
semval = semctl(sem->id, 0, GETVAL, arg);
}
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#endif
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if (semval < 0) {
if (errno == EINTR) {
goto tryagain;
}
} else {
value = (Uint32) semval;
}
}
return value;
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}
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int
SDL_SemPost(SDL_sem * sem)
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{
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int retval;
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if (!sem) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
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retval = 0;
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tryagain:
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if (semop(sem->id, op_post, 1) < 0) {
if (errno == EINTR) {
goto tryagain;
}
SDL_SetError("Semaphore operation error");
retval = -1;
}
return retval;
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}
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/* vi: set ts=4 sw=4 expandtab: */