base/libs/qdecoder/qShm.c

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/*
 * Copyright 2008 The qDecoder Project. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE QDECODER PROJECT ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE QDECODER PROJECT BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef DISABLE_IPC

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <sys/shm.h>
#include "qDecoder.h"

int qShmInit(const char *keyfile, int keyid, size_t size, bool ifexistdestroy) {
    key_t semkey;
    int shmid;

    /* generate unique key using ftok() */
    if(keyfile != NULL) {
        semkey = ftok(keyfile, keyid);
        if (semkey == -1) return -1;
    } else {
        semkey = IPC_PRIVATE;
    }

    /* create shared memory */
    if ((shmid = shmget(semkey, size, IPC_CREAT | IPC_EXCL | 0666)) == -1) {
        if(ifexistdestroy == false) return -1;

        /* destroy & re-create */
        if((shmid = qShmGetId(keyfile, keyid)) >= 0) qShmFree(shmid);
        if ((shmid = shmget(semkey, size, IPC_CREAT | IPC_EXCL | 0666)) == -1) return -1;
    }

    return shmid;
}

int qShmGetId(const char *keyfile, int keyid) {
    int shmid;

    /* generate unique key using ftok() */
    key_t semkey = ftok(keyfile, keyid);
    if (semkey == -1) return -1;

    /* get current shared memory id */
    if ((shmid = shmget(semkey, 0, 0)) == -1) return -1;

    return shmid;
}

void *qShmGet(int shmid) {
    void *pShm;

    if (shmid < 0) return NULL;
    pShm = shmat(shmid, 0, 0);
    if(pShm == (void *)-1) return NULL;
    return pShm;
}

bool qShmFree(int shmid) {
    if (shmid < 0) return false;
    if (shmctl(shmid, IPC_RMID, 0) != 0) return false;
    return true;
}

#endif /* DISABLE_IPC */

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