seahag/mq.c

/*                 _,.---._    .-._        .--.-. ,--.--------.         
 *   _,..---._   ,-.' , -  `. /==/ \  .-._/==/  //==/,  -   , -\
 * /==/,   -  \ /==/_,  ,  - \|==|, \/ /, |==\ -\\==\.-.  - ,-./        
 * |==|   _   _\==|   .=.     |==|-  \|  | \==\- \`--`\==\- \
 * |==|  .=.   |==|_ : ;=:  - |==| ,  | -|  `--`-'     \==\_ \
 * |==|,|   | -|==| , '='     |==| -   _ |             |==|- |          
 * |==|  '='   /\==\ -    ,_ /|==|  /\ , |             |==|, |          
 * |==|-,   _`/  '.='. -   .' /==/, | |- |             /==/ -/          
 * `-.`.____.'     `--`--''   `--`./  `--`             `--`--`          
 *                    _ __    ,---.      .-._         .=-.-.  _,.----.   
 *                 .-`.' ,`..--.'  \    /==/ \  .-._ /==/_ /.' .' -   \
 *                /==/, -   \==\-/\ \   |==|, \/ /, /==|, |/==/  ,  ,-'  
 *               |==| _ .=. /==/-|_\ |  |==|-  \|  ||==|  ||==|-   |  .  
 *               |==| , '=',\==\,   - \ |==| ,  | -||==|- ||==|_   `-' \
 *               |==|-  '..'/==/ -   ,| |==| -   _ ||==| ,||==|   _  , | 
 *               |==|,  |  /==/-  /\ - \|==|  /\ , ||==|- |\==\.       / 
 *               /==/ - |  \==\ _.\=\.-'/==/, | |- |/==/. / `-.`.___.-'  
 *               `--`---'   `--`        `--`./  `--``--`-`
 *
 *	@(#)Copyright (c) 2023, Nathan D. Fisher.
 *
 *      This is free software.  It comes with NO WARRANTY.
 *      Permission to use, modify and distribute this source code
 *      is granted subject to the following conditions.
 *      1/ that the above copyright notice and this notice
 *      are preserved in all copies and that due credit be given
 *      to the author.
 *      2/ that any changes to this code are clearly commented
 *      as such so that the author does not get blamed for bugs
 *      other than his own.
*/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>    // free, malloc

#include "haggis.h"
#include "mq.h"

haggis_msg* haggis_msg_init(haggis_message_type tag, haggis_message_body body) {
    haggis_msg *msg = calloc(1, sizeof(haggis_msg));
    if (msg == NULL)
        return NULL;
    msg->next = msg->prev = NULL;
    msg->tag = tag;
    msg->body = body;
    return msg;
}

void haggis_msg_deinit(haggis_msg *msg) {
    switch (msg->tag) {
    case NodeCreated:
    case NodeExtracted:
        free(msg->body.f_name);
        break;
    case EndOfArchive:
    case ArchiveError:
        break;
    }
    free(msg);
}

int haggis_mq_init(haggis_mq *mq) {
    int ret;

    mq->head = NULL;
    mq->tail = NULL;
    ret = pthread_mutex_init(&mq->mutex, NULL);
    if (ret != 0)
        return ret;
    return pthread_cond_init(&mq->cond, NULL);
}

int haggis_mq_push(haggis_mq *queue, haggis_msg *msg) {
    pthread_mutex_lock(&queue->mutex);
    if (queue->tail == NULL) {
        queue->tail = queue->head = msg;
    } else {
        msg->next = queue->tail;
        queue->tail->prev = msg;
        queue->tail = msg;
    }
    queue->count++;
    pthread_mutex_unlock(&queue->mutex);
    return 0;
}

haggis_msg* haggis_mq_pop(haggis_mq *queue) {
    haggis_msg *msg;

    while (queue->count == 0)
        pthread_cond_wait(&queue->cond, &queue->mutex);
    pthread_mutex_lock(&queue->mutex);
    queue->count--;
    msg = queue->head;
    if (msg->tag == EndOfArchive)
        return msg;
    if (queue->tail == queue->head) {
        queue->tail = queue->head = NULL;
    } else {
        queue->head = queue->head->prev;
    }
    pthread_mutex_unlock(&queue->mutex);
    msg->prev = msg->next = NULL;
    return msg;
}