SDL_syssem.c
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/*
SDL - Simple DirectMedia Layer
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Copyright (C) 1997-2012 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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/* Semaphore functions using the Win32 API */
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#define WIN32_LEAN_AND_MEAN
#include <windows.h>
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#include "SDL_thread.h"
#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
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#include "win_ce_semaphore.h"
#endif
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struct SDL_semaphore {
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#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
SYNCHHANDLE id;
#else
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HANDLE id;
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volatile LONG count;
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};
/* Create a semaphore */
SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
{
SDL_sem *sem;
/* Allocate sem memory */
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sem = (SDL_sem *)SDL_malloc(sizeof(*sem));
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if ( sem ) {
/* Create the semaphore, with max value 32K */
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#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
sem->id = CreateSemaphoreCE(NULL, initial_value, 32*1024, NULL);
#else
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sem->id = CreateSemaphore(NULL, initial_value, 32*1024, NULL);
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sem->count = (LONG) initial_value;
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if ( ! sem->id ) {
SDL_SetError("Couldn't create semaphore");
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SDL_free(sem);
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sem = NULL;
}
} else {
SDL_OutOfMemory();
}
return(sem);
}
/* Free the semaphore */
void SDL_DestroySemaphore(SDL_sem *sem)
{
if ( sem ) {
if ( sem->id ) {
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#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
CloseSynchHandle(sem->id);
#else
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CloseHandle(sem->id);
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sem->id = 0;
}
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SDL_free(sem);
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}
}
int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
{
int retval;
DWORD dwMilliseconds;
if ( ! sem ) {
SDL_SetError("Passed a NULL sem");
return -1;
}
if ( timeout == SDL_MUTEX_MAXWAIT ) {
dwMilliseconds = INFINITE;
} else {
dwMilliseconds = (DWORD)timeout;
}
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#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
switch (WaitForSemaphoreCE(sem->id, dwMilliseconds)) {
#else
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switch (WaitForSingleObject(sem->id, dwMilliseconds)) {
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case WAIT_OBJECT_0:
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InterlockedDecrement(&sem->count);
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retval = 0;
break;
case WAIT_TIMEOUT:
retval = SDL_MUTEX_TIMEDOUT;
break;
default:
SDL_SetError("WaitForSingleObject() failed");
retval = -1;
break;
}
return retval;
}
int SDL_SemTryWait(SDL_sem *sem)
{
return SDL_SemWaitTimeout(sem, 0);
}
int SDL_SemWait(SDL_sem *sem)
{
return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
}
/* Returns the current count of the semaphore */
Uint32 SDL_SemValue(SDL_sem *sem)
{
if ( ! sem ) {
SDL_SetError("Passed a NULL sem");
return 0;
}
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return (Uint32) sem->count;
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}
int SDL_SemPost(SDL_sem *sem)
{
if ( ! sem ) {
SDL_SetError("Passed a NULL sem");
return -1;
}
/* Increase the counter in the first place, because
* after a successful release the semaphore may
* immediately get destroyed by another thread which
* is waiting for this semaphore.
*/
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InterlockedIncrement(&sem->count);
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#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
if ( ReleaseSemaphoreCE(sem->id, 1, NULL) == FALSE ) {
#else
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if ( ReleaseSemaphore(sem->id, 1, NULL) == FALSE ) {
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InterlockedDecrement(&sem->count); /* restore */
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SDL_SetError("ReleaseSemaphore() failed");
return -1;
}
return 0;
}