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/*
* 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
*/
#ifndef AVFILTER_DNN_SAFE_QUEUE_H
#define AVFILTER_DNN_SAFE_QUEUE_H
/**
* Double-ended queue with mutex locks ensuring
* data consistency while multithreading.
*/
typedef struct SafeQueue SafeQueue;
/**
* @brief Create and initialize a SafeQueue instance.
*
* @return Pointer to the SafeQueue
* @retval NULL if initialization fails
*/
SafeQueue *ff_safe_queue_create(void);
/**
* @brief Destroy the SafeQueue instance.
* It also frees all elements of the queue,
* destroys the mutex and condition variable.
*/
void ff_safe_queue_destroy(SafeQueue *sq);
/**
* @brief Return the length of the SafeQueue
*/
size_t ff_safe_queue_size(SafeQueue *sq);
/**
* @brief Add data to the head of queue in the
* SafeQueue after locking mutex. After adding
* the data, it signals the condition variable
* and unlocks the mutex. It increases the length
* of queue in the SafeQueue by one.
*
* @param sq pointer to the SafeQueue
* @param v data to be added
* @return The length of the queue
* @retval 0 if the queue is not initialized
* @retval -1 if new entry cannot be created
*/
int ff_safe_queue_push_front(SafeQueue *sq, void *v);
/**
* @brief Add data to the tail of queue in the
* SafeQueue after locking mutex. After adding
* the data, it signals the condition variable
* and unlocks the mutex. It increases the length
* of queue in the SafeQueue by one.
*
* @param sq pointer to the SafeQueue
* @param v data to be added
* @return The length of the queue
* @retval 0 if the queue is not initialized
* @retval -1 if new entry cannot be created
*/
int ff_safe_queue_push_back(SafeQueue *sq, void *v);
/**
* @brief Remove and free first element from
* the queue in SafeQueue. Before removing, it
* waits for the condition variable to signal and
* acquires the mutex. Finally, it signals the
* condition and unlocks the mutex.
* It shrinks the length of queue in the SafeQueue
* by one.
*
* @param sq pointer to the SafeQueue.
* @return The value of first element as void.
* If a null pointer or empty queue is passed,
* it returns NULL
*/
void *ff_safe_queue_pop_front(SafeQueue *sq);
#endif
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