/* * Copyright (c) 2020 * * This file is part of FFmpeg. * * FFmpeg 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. * * FFmpeg 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 FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include <stdio.h>#include "queue.h"#include "libavutil/mem.h" typedef struct QueueEntry QueueEntry; struct QueueEntry {    void *value;    QueueEntry *prev;    QueueEntry *next;}; struct Queue {    QueueEntry *head;    QueueEntry *tail;    size_t length;}; static inline QueueEntry *create_entry(void *val){    QueueEntry *entry = av_malloc(sizeof(*entry));    if (entry)        entry->value = val;    return entry;} Queue* ff_queue_create(void){    Queue *q = av_malloc(sizeof(*q));    if (!q)        return NULL;     q->head = create_entry(q);    q->tail = create_entry(q);     if (!q->head || !q->tail) {        av_freep(&q->head);        av_freep(&q->tail);        av_freep(&q);        return NULL;    }     q->head->next = q->tail;    q->tail->prev = q->head;    q->head->prev = NULL;    q->tail->next = NULL;    q->length = 0;     return q;} void ff_queue_destroy(Queue *q){    QueueEntry *entry;    if (!q)        return;     entry = q->head;    while (entry != NULL) {        QueueEntry *temp = entry;        entry = entry->next;        av_freep(&temp);    }     av_freep(&q);} size_t ff_queue_size(Queue *q){     return q ? q->length : 0;} void *ff_queue_peek_front(Queue *q){    if (!q || q->length == 0)        return NULL;     return q->head->next->value;} void *ff_queue_peek_back(Queue *q){    if (!q || q->length == 0)        return NULL;     return q->tail->prev->value;} int ff_queue_push_front(Queue *q, void *v){    QueueEntry *new_entry;    QueueEntry *original_next;    if (!q)        return 0;     new_entry = create_entry(v);    if (!new_entry)        return -1;    original_next = q->head->next;     q->head->next = new_entry;    original_next->prev = new_entry;    new_entry->prev = q->head;    new_entry->next = original_next;    q->length++;     return q->length;} int ff_queue_push_back(Queue *q, void *v){    QueueEntry *new_entry;    QueueEntry *original_prev;    if (!q)        return 0;     new_entry = create_entry(v);    if (!new_entry)        return -1;    original_prev = q->tail->prev;     q->tail->prev = new_entry;    original_prev->next = new_entry;    new_entry->next = q->tail;    new_entry->prev = original_prev;    q->length++;     return q->length;} void *ff_queue_pop_front(Queue *q){    QueueEntry *front;    QueueEntry *new_head_next;    void *ret;     if (!q || q->length == 0)        return NULL;     front = q->head->next;    new_head_next = front->next;    ret = front->value;     q->head->next = new_head_next;    new_head_next->prev = q->head;     av_freep(&front);    q->length--;    return ret;} void *ff_queue_pop_back(Queue *q){    QueueEntry *back;    QueueEntry *new_tail_prev;    void *ret;     if (!q || q->length == 0)        return NULL;     back = q->tail->prev;    new_tail_prev = back->prev;    ret = back->value;     q->tail->prev = new_tail_prev;    new_tail_prev->next = q->tail;     av_freep(&back);    q->length--;    return ret;}