intel-linux-sgx/SampleCode/LocalAttestation/AppResponder/Queue.h

/*
 * Copyright (C) 2011-2021 Intel Corporation. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * 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.
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 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 COPYRIGHT
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 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef _QUEUE_H
#define _QUEUE_H

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <queue>
#include <pthread.h>

template <typename T>
class Queue  {
    public:
        Queue();
        ~Queue();

        void push(T*);
        T* blockingPop();
        void close();

    private:
        std::queue<T*>  m_queue;
        pthread_cond_t            m_queueCond;
        pthread_mutex_t           m_queueMutex;
        volatile  uint8_t         m_events;
    private:
        Queue& operator=(const Queue&);
        Queue(const Queue&);
};

#define QUEUE_EVENT_CLOSE    1

template<typename T>
Queue<T>::Queue() :
    m_queue()
{
    int rc;

    rc = pthread_mutex_init(&m_queueMutex, NULL);
    if (rc != 0)
    {
	printf("failed to call pthread_mutex_init");
        exit(-1); 
    }

    rc = pthread_cond_init(&m_queueCond, NULL);
    if (rc != 0)
    {
	printf("failed to call pthread_cond_init.\n");
        exit(-1);
    }
    m_events = 0;
}

template<typename T>
Queue<T>::~Queue()
{
    int rc;

    rc = pthread_mutex_destroy(&m_queueMutex);
    if (rc != 0)
        printf("Failed to destroy mutex");

    rc = pthread_cond_destroy(&m_queueCond);
    if (rc != 0)
        printf("Failed to destory a condition variable");
}

template<typename T>
void Queue<T>::push(T* value)
{
    int rc;

    rc = pthread_mutex_lock(&m_queueMutex);
    if (rc != 0)
    {
        printf("Failed to acquire mutex");
        exit(-1);
    }
    m_queue.push(value);

    rc = pthread_cond_signal(&m_queueCond);
    if (rc != 0)
    {
        printf("Failed to signal condition");
        exit(-1);
    }

    rc = pthread_mutex_unlock(&m_queueMutex);
    if (rc != 0)
    {
        printf("Failed to unlock mutex");
        exit(-1);
    }
}

template<typename T> 
T* Queue<T>::blockingPop()
{
    
    T* value = NULL;

	int rc;
    rc = pthread_mutex_lock(&m_queueMutex);
    if (rc != 0)
    {
        printf("Failed to acquire mutex");
        exit(-1);
    }

    while(1) {
        if (m_events & QUEUE_EVENT_CLOSE) {			
            //epmty the queue
            while (!m_queue.empty())
            {
                value = m_queue.front();
                m_queue.pop();
                free(value);
            }
            value = NULL;			
            break;
        }
        if (!m_queue.empty()) {
            // queue is not empty
            value = m_queue.front();
            m_queue.pop();
            break;
        }
        else {
            rc = pthread_cond_wait(&m_queueCond, &m_queueMutex);

            if (rc != 0)
            {
                printf("Failed wait on a condition");
                exit(-1);
            }
        }
    }

    rc = pthread_mutex_unlock(&m_queueMutex);
    if (rc != 0)
    {
        printf("Failed to unlock mutex");
        exit(-1);
    }

    return value;
}

template<typename T>
void Queue<T>::close()
{
    int rc;
    rc = pthread_mutex_lock(&m_queueMutex);
    if (rc != 0)
    {
        printf("Failed to acquire mutex");
        exit(-1);
    }

    m_events |= QUEUE_EVENT_CLOSE;

    rc = pthread_cond_signal(&m_queueCond);
    if (rc != 0)
    {
        printf("Failed to signal a condition");
        exit(-1);
    }

    rc = pthread_mutex_unlock(&m_queueMutex);
    if (rc != 0)
    {
        printf("Failed to unlock mutex");
        exit(-1);
    }
}

#endif