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/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2012 Sam Lantinga
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
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
Lesser General Public License for more details.
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
Sam Lantinga
slouken@libsdl.org
*/
#include "SDL_config.h"
#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"
struct SDL_semaphore {
int id;
};
/* Not defined by many operating systems, use configure to detect */
/*
#if !defined(HAVE_SEMUN)
union semun {
int val;
struct semid_ds *buf;
ushort *array;
};
#endif
*/
static struct sembuf op_trywait[2] = {
{ 0, -1, (IPC_NOWAIT|SEM_UNDO) } /* Decrement semaphore, no block */
};
static struct sembuf op_wait[2] = {
{ 0, -1, SEM_UNDO } /* Decrement semaphore */
};
static struct sembuf op_post[1] = {
{ 0, 1, (IPC_NOWAIT|SEM_UNDO) } /* Increment semaphore */
};
/* Create a blockable semaphore */
SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
{
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);
}
void SDL_DestroySemaphore(SDL_sem *sem)
{
if ( sem ) {
#ifdef __IRIX__
semctl(sem->id, 0, IPC_RMID);
#else
union semun dummy;
dummy.val = 0;
semctl(sem->id, 0, IPC_RMID, dummy);
#endif
SDL_free(sem);
}
}
int SDL_SemTryWait(SDL_sem *sem)
{
int retval;
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
retval = 0;
tryagain:
if ( semop(sem->id, op_trywait, 1) < 0 ) {
if ( errno == EINTR ) {
goto tryagain;
}
retval = SDL_MUTEX_TIMEDOUT;
}
return retval;
}
int SDL_SemWait(SDL_sem *sem)
{
int retval;
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
retval = 0;
tryagain:
if ( semop(sem->id, op_wait, 1) < 0 ) {
if ( errno == EINTR ) {
goto tryagain;
}
SDL_SetError("Semaphore operation error");
retval = -1;
}
return retval;
}
int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
{
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);
} while ( SDL_GetTicks() < timeout );
return retval;
}
Uint32 SDL_SemValue(SDL_sem *sem)
{
int semval;
Uint32 value;
value = 0;
if ( sem ) {
tryagain:
#ifdef __IRIX__
semval = semctl(sem->id, 0, GETVAL);
#else
{
union semun arg;
arg.val = 0;
semval = semctl(sem->id, 0, GETVAL, arg);
}
#endif
if ( semval < 0 ) {
if ( errno == EINTR ) {
goto tryagain;
}
} else {
value = (Uint32)semval;
}
}
return value;
}
int SDL_SemPost(SDL_sem *sem)
{
int retval;
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
retval = 0;
tryagain:
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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