/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2009 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"

/* Semaphore functions using the OS/2 API */

#define INCL_DOS
#define INCL_DOSERRORS
#define INCL_DOSSEMAPHORES
#include <os2.h>

#include "SDL_thread.h"
#include "SDL_timer.h"


struct SDL_semaphore
{
    HMTX id;
    HEV changed;
    Uint32 value;
};


/* Create a semaphore */
DECLSPEC SDL_sem *SDLCALL
SDL_CreateSemaphore(Uint32 initial_value)
{
    SDL_sem *sem;
    ULONG ulrc;

    /* Allocate sem memory */
    sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
    if (sem) {
        /* Create the mutex semaphore */
        ulrc = DosCreateMutexSem(NULL, &(sem->id), 0, TRUE);
        if (ulrc) {
            SDL_SetError("Couldn't create semaphore");
            SDL_free(sem);
            sem = NULL;
        } else {
            DosCreateEventSem(NULL, &(sem->changed), 0, FALSE);
            sem->value = initial_value;
            DosReleaseMutexSem(sem->id);
        }
    } else {
        SDL_OutOfMemory();
    }
    return (sem);
}

/* Free the semaphore */
DECLSPEC void SDLCALL
SDL_DestroySemaphore(SDL_sem * sem)
{
    if (sem) {
        if (sem->id) {
            DosCloseEventSem(sem->changed);
            DosCloseMutexSem(sem->id);
            sem->id = 0;
        }
        SDL_free(sem);
    }
}

DECLSPEC int SDLCALL
SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
{
    ULONG ulrc;

    if (!sem) {
        SDL_SetError("Passed a NULL sem");
        return -1;
    }

    if (timeout == SDL_MUTEX_MAXWAIT) {
        while (1) {
            ulrc = DosRequestMutexSem(sem->id, SEM_INDEFINITE_WAIT);
            if (ulrc) {
                /* if error waiting mutex */
                SDL_SetError("DosRequestMutexSem() failed");
                return -1;
            } else if (sem->value) {
                sem->value--;
                DosReleaseMutexSem(sem->id);
                return 0;
            } else {
                ULONG ulPostCount;
                DosResetEventSem(sem->changed, &ulPostCount);
                DosReleaseMutexSem(sem->id);
                /* continue waiting until somebody posts the semaphore */
                DosWaitEventSem(sem->changed, SEM_INDEFINITE_WAIT);
            }
        }
    } else if (timeout == 0) {
        ulrc = DosRequestMutexSem(sem->id, SEM_INDEFINITE_WAIT);
        if (ulrc == NO_ERROR) {
            if (sem->value) {
                sem->value--;
                DosReleaseMutexSem(sem->id);
                return 0;
            } else {
                DosReleaseMutexSem(sem->id);
                return SDL_MUTEX_TIMEDOUT;
            }
        } else {
            SDL_SetError("DosRequestMutexSem() failed");
            return -1;
        }
    } else {
        ulrc = DosRequestMutexSem(sem->id, SEM_INDEFINITE_WAIT);
        if (ulrc) {
            /* if error waiting mutex */
            SDL_SetError("DosRequestMutexSem() failed");
            return -1;
        } else if (sem->value) {
            sem->value--;
            DosReleaseMutexSem(sem->id);
            return 0;
        } else {
            ULONG ulPostCount;
            DosResetEventSem(sem->changed, &ulPostCount);
            DosReleaseMutexSem(sem->id);
            /* continue waiting until somebody posts the semaphore */
            ulrc = DosWaitEventSem(sem->changed, timeout);
            if (ulrc == NO_ERROR)
                return 0;
            else
                return SDL_MUTEX_TIMEDOUT;
        }
    }
    /* never reached */
    return -1;
}

DECLSPEC int SDLCALL
SDL_SemTryWait(SDL_sem * sem)
{
    return SDL_SemWaitTimeout(sem, 0);
}

DECLSPEC int SDLCALL
SDL_SemWait(SDL_sem * sem)
{
    return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
}

/* Returns the current count of the semaphore */
DECLSPEC Uint32 SDLCALL
SDL_SemValue(SDL_sem * sem)
{
    if (!sem) {
        SDL_SetError("Passed a NULL sem");
        return 0;
    }
    return sem->value;
}

DECLSPEC int SDLCALL
SDL_SemPost(SDL_sem * sem)
{
    if (!sem) {
        SDL_SetError("Passed a NULL sem");
        return -1;
    }
    if (DosRequestMutexSem(sem->id, SEM_INDEFINITE_WAIT)) {
        SDL_SetError("DosRequestMutexSem() failed");
        return -1;
    }
    sem->value++;
    DosPostEventSem(sem->changed);
    DosReleaseMutexSem(sem->id);
    return 0;
}

/* vi: set ts=4 sw=4 expandtab: */
