/*
 * lock.c - data locking code for lib
 *
 * Copyright (C) Chris Ison  2001-2011
 * Copyright (C) Bret Curtis 2013-2016
 *
 * This file is part of WildMIDI.
 *
 * WildMIDI is free software: you can redistribute and/or modify the player
 * under the terms of the GNU General Public License and you can redistribute
 * and/or modify the library under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, either version 3 of
 * the licenses, or(at your option) any later version.
 *
 * WildMIDI 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 General Public License and
 * the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License and the
 * GNU Lesser General Public License along with WildMIDI.  If not,  see
 * <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#if !defined(WM_NO_LOCK)

#ifdef _WIN32
#include <windows.h>
#elif defined(__OS2__) || defined(__EMX__)
#define INCL_DOS
#include <os2.h>
#elif defined(WILDMIDI_AMIGA)
#include <proto/dos.h>
#else /* unixish ... */
#define _GNU_SOURCE
#include <unistd.h> /* usleep() */
#endif

#include "lock.h"

/*
 _WM_Lock(wmlock)

 wmlock = a pointer to a value

 returns nothing

 Attempts to set a lock on the MDI tree so that
 only 1 library command may access it at any time.
 If lock fails the process retries until successful.
 */
void _WM_Lock(int * wmlock) {
    LOCK_START:
    /* Check if lock is clear, if so set it */
    if (__builtin_expect(((*wmlock) == 0), 1)) {
        (*wmlock)++;
        /* Now that the lock is set, make sure we
         * don't have a race condition.  If so,
         * decrement the lock by one and retry.  */
        if (__builtin_expect(((*wmlock) == 1), 1)) {
            return; /* Lock cleanly set */
        }
        (*wmlock)--;
    }
#ifdef _WIN32
    Sleep(10);
#elif defined(__OS2__) || defined(__EMX__)
    DosSleep(10);
#elif defined(WILDMIDI_AMIGA)
    Delay(1);
#else
    usleep(500);
#endif
    goto LOCK_START;
}

/*
 _WM_Unlock(wmlock)

 wmlock = a pointer to a value

 returns nothing

 Removes a lock previously placed on the MDI tree.
 */
void _WM_Unlock(int *wmlock) {
    /* We don't want a -1 lock, so just to make sure */
    if ((*wmlock) != 0) {
        (*wmlock)--;
    }
}

#endif /* !WM_NO_LOCK */
