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      1 #ifndef _DETHREADSAFERINGBUFFER_HPP
      2 #define _DETHREADSAFERINGBUFFER_HPP
      3 /*-------------------------------------------------------------------------
      4  * drawElements C++ Base Library
      5  * -----------------------------
      6  *
      7  * Copyright 2014 The Android Open Source Project
      8  *
      9  * Licensed under the Apache License, Version 2.0 (the "License");
     10  * you may not use this file except in compliance with the License.
     11  * You may obtain a copy of the License at
     12  *
     13  *      http://www.apache.org/licenses/LICENSE-2.0
     14  *
     15  * Unless required by applicable law or agreed to in writing, software
     16  * distributed under the License is distributed on an "AS IS" BASIS,
     17  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     18  * See the License for the specific language governing permissions and
     19  * limitations under the License.
     20  *
     21  *//*!
     22  * \file
     23  * \brief Thread-safe ring buffer template.
     24  *//*--------------------------------------------------------------------*/
     25 
     26 #include "deDefs.hpp"
     27 #include "deMutex.hpp"
     28 #include "deSemaphore.hpp"
     29 
     30 #include <vector>
     31 
     32 namespace de
     33 {
     34 
     35 void ThreadSafeRingBuffer_selfTest (void);
     36 
     37 /** Thread-safe ring buffer template. */
     38 template <typename T>
     39 class ThreadSafeRingBuffer
     40 {
     41 public:
     42 					ThreadSafeRingBuffer	(size_t size);
     43 					~ThreadSafeRingBuffer	(void) {}
     44 
     45 	void			pushFront				(const T& elem);
     46 	bool			tryPushFront			(const T& elem);
     47 	T				popBack					(void);
     48 	bool			tryPopBack				(T& dst);
     49 
     50 protected:
     51 	void			pushFrontInternal		(const T& elem);
     52 	T				popBackInternal			(void);
     53 
     54 	const size_t	m_size;
     55 	std::vector<T>	m_elements;
     56 
     57 	size_t			m_front;
     58 	size_t			m_back;
     59 
     60 	Mutex			m_writeMutex;
     61 	Mutex			m_readMutex;
     62 
     63 	Semaphore		m_fill;
     64 	Semaphore		m_empty;
     65 };
     66 
     67 // ThreadSafeRingBuffer implementation.
     68 
     69 template <typename T>
     70 ThreadSafeRingBuffer<T>::ThreadSafeRingBuffer (size_t size)
     71 	: m_size		(size+1)
     72 	, m_elements	(m_size)
     73 	, m_front		(0)
     74 	, m_back		(0)
     75 	, m_fill		(0)
     76 	, m_empty		((int)size)
     77 {
     78 	// Semaphores currently only support INT_MAX
     79 	DE_ASSERT(size > 0 && size < 0x7fffffff);
     80 }
     81 
     82 template <typename T>
     83 inline void ThreadSafeRingBuffer<T>::pushFrontInternal (const T& elem)
     84 {
     85 	m_elements[m_front] = elem;
     86 	m_front = (m_front + 1) % m_size;
     87 }
     88 
     89 template <typename T>
     90 inline T ThreadSafeRingBuffer<T>::popBackInternal ()
     91 {
     92 	const size_t ndx = m_back;
     93 	m_back = (m_back + 1) % m_size;
     94 	return m_elements[ndx];
     95 }
     96 
     97 template <typename T>
     98 void ThreadSafeRingBuffer<T>::pushFront (const T& elem)
     99 {
    100 	m_writeMutex.lock();
    101 	m_empty.decrement();
    102 	pushFrontInternal(elem);
    103 	m_fill.increment();
    104 	m_writeMutex.unlock();
    105 }
    106 
    107 template <typename T>
    108 bool ThreadSafeRingBuffer<T>::tryPushFront (const T& elem)
    109 {
    110 	if (!m_writeMutex.tryLock())
    111 		return false;
    112 
    113 	const bool success = m_empty.tryDecrement();
    114 
    115 	if (success)
    116 	{
    117 		pushFrontInternal(elem);
    118 		m_fill.increment();
    119 	}
    120 
    121 	m_writeMutex.unlock();
    122 	return success;
    123 }
    124 
    125 template <typename T>
    126 T ThreadSafeRingBuffer<T>::popBack ()
    127 {
    128 	m_readMutex.lock();
    129 	m_fill.decrement();
    130 	T elem = popBackInternal();
    131 	m_empty.increment();
    132 	m_readMutex.unlock();
    133 	return elem;
    134 }
    135 
    136 template <typename T>
    137 bool ThreadSafeRingBuffer<T>::tryPopBack (T& dst)
    138 {
    139 	if (!m_readMutex.tryLock())
    140 		return false;
    141 
    142 	bool success = m_fill.tryDecrement();
    143 
    144 	if (success)
    145 	{
    146 		dst = popBackInternal();
    147 		m_empty.increment();
    148 	}
    149 
    150 	m_readMutex.unlock();
    151 
    152 	return success;
    153 }
    154 
    155 } // de
    156 
    157 #endif // _DETHREADSAFERINGBUFFER_HPP
    158