src/thread/windows/SDL_syssem.c
author Sam Lantinga <slouken@libsdl.org>
Fri, 15 Feb 2013 08:47:44 -0800
changeset 6885 700f1b25f77f
parent 6430 48d519500f7e
child 7037 3fedf1f25b94
permissions -rw-r--r--
Happy New Year!
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/*
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  Simple DirectMedia Layer
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  Copyright (C) 1997-2013 Sam Lantinga <slouken@libsdl.org>
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  This software is provided 'as-is', without any express or implied
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  warranty.  In no event will the authors be held liable for any damages
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  arising from the use of this software.
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  Permission is granted to anyone to use this software for any purpose,
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  including commercial applications, and to alter it and redistribute it
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  freely, subject to the following restrictions:
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  1. The origin of this software must not be misrepresented; you must not
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     claim that you wrote the original software. If you use this software
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     in a product, an acknowledgment in the product documentation would be
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     appreciated but is not required.
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  2. Altered source versions must be plainly marked as such, and must not be
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     misrepresented as being the original software.
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  3. This notice may not be removed or altered from any source distribution.
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*/
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#include "SDL_config.h"
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#if SDL_THREAD_WINDOWS
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/* Semaphore functions using the Win32 API */
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#include "../../core/windows/SDL_windows.h"
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#include "SDL_thread.h"
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struct SDL_semaphore
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{
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    HANDLE id;
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    LONG count;
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};
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/* Create a semaphore */
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SDL_sem *
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SDL_CreateSemaphore(Uint32 initial_value)
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{
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    SDL_sem *sem;
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    /* Allocate sem memory */
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    sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
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    if (sem) {
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        /* Create the semaphore, with max value 32K */
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        sem->id = CreateSemaphore(NULL, initial_value, 32 * 1024, NULL);
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        sem->count = initial_value;
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        if (!sem->id) {
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            SDL_SetError("Couldn't create semaphore");
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            SDL_free(sem);
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            sem = NULL;
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        }
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    } else {
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        SDL_OutOfMemory();
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    }
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    return (sem);
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}
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/* Free the semaphore */
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void
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SDL_DestroySemaphore(SDL_sem * sem)
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{
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    if (sem) {
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        if (sem->id) {
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            CloseHandle(sem->id);
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            sem->id = 0;
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        }
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        SDL_free(sem);
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    }
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}
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int
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SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
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{
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    int retval;
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    DWORD dwMilliseconds;
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    if (!sem) {
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        SDL_SetError("Passed a NULL sem");
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        return -1;
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    }
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    if (timeout == SDL_MUTEX_MAXWAIT) {
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        dwMilliseconds = INFINITE;
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    } else {
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        dwMilliseconds = (DWORD) timeout;
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    }
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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;
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        break;
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    case WAIT_TIMEOUT:
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        retval = SDL_MUTEX_TIMEDOUT;
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        break;
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    default:
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        SDL_SetError("WaitForSingleObject() failed");
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        retval = -1;
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        break;
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    }
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    return retval;
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}
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int
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SDL_SemTryWait(SDL_sem * sem)
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{
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    return SDL_SemWaitTimeout(sem, 0);
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}
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int
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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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/* Returns the current count of the semaphore */
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Uint32
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SDL_SemValue(SDL_sem * sem)
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{
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    if (!sem) {
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        SDL_SetError("Passed a NULL sem");
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        return 0;
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    }
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    return (Uint32)sem->count;
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}
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int
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SDL_SemPost(SDL_sem * sem)
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{
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    if (!sem) {
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        SDL_SetError("Passed a NULL sem");
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        return -1;
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    }
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    /* Increase the counter in the first place, because
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     * after a successful release the semaphore may
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     * immediately get destroyed by another thread which
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     * is waiting for this semaphore.
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     */
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    InterlockedIncrement(&sem->count);
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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");
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        return -1;
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    }
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    return 0;
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}
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#endif /* SDL_THREAD_WINDOWS */
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/* vi: set ts=4 sw=4 expandtab: */