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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 namespace de
     31 {
     32 
     33 void ThreadSafeRingBuffer_selfTest (void);
     34 
     35 /** Thread-safe ring buffer template. */
     36 template <typename T>
     37 class ThreadSafeRingBuffer
     38 {
     39 public:
     40 				ThreadSafeRingBuffer	(int size);
     41 				~ThreadSafeRingBuffer	(void) {}
     42 
     43 	void		pushFront				(const T& elem);
     44 	bool		tryPushFront			(const T& elem);
     45 	T			popBack					(void);
     46 	bool		tryPopBack				(T& dst);
     47 
     48 protected:
     49 	void		pushFrontInternal		(const T& elem);
     50 	T			popBackInternal			(void);
     51 
     52 	int			m_front;
     53 	int			m_back;
     54 	T*			m_buffer;
     55 	int			m_size;
     56 
     57 	Mutex		m_writeMutex;
     58 	Mutex		m_readMutex;
     59 
     60 	Semaphore	m_fill;
     61 	Semaphore	m_empty;
     62 };
     63 
     64 // ThreadSafeRingBuffer implementation.
     65 
     66 template <typename T>
     67 ThreadSafeRingBuffer<T>::ThreadSafeRingBuffer (int size)
     68 	: m_front		(0)
     69 	, m_back		(0)
     70 	, m_size		(size+1)
     71 	, m_fill		(0)
     72 	, m_empty		(size)
     73 {
     74 	DE_ASSERT(size > 0);
     75 	m_buffer = new T[m_size];
     76 }
     77 
     78 template <typename T>
     79 inline void ThreadSafeRingBuffer<T>::pushFrontInternal (const T& elem)
     80 {
     81 	m_buffer[m_front] = elem;
     82 	m_front = (m_front + 1) % m_size;
     83 }
     84 
     85 template <typename T>
     86 inline T ThreadSafeRingBuffer<T>::popBackInternal ()
     87 {
     88 	int ndx = m_back;
     89 	m_back = (m_back + 1) % m_size;
     90 	return m_buffer[ndx];
     91 }
     92 
     93 template <typename T>
     94 void ThreadSafeRingBuffer<T>::pushFront (const T& elem)
     95 {
     96 	m_writeMutex.lock();
     97 	m_empty.decrement();
     98 	pushFrontInternal(elem);
     99 	m_fill.increment();
    100 	m_writeMutex.unlock();
    101 }
    102 
    103 template <typename T>
    104 bool ThreadSafeRingBuffer<T>::tryPushFront (const T& elem)
    105 {
    106 	if (!m_writeMutex.tryLock())
    107 		return false;
    108 	bool success = m_empty.tryDecrement();
    109 	if (success)
    110 	{
    111 		pushFrontInternal(elem);
    112 		m_fill.increment();
    113 	}
    114 	m_writeMutex.unlock();
    115 	return success;
    116 }
    117 
    118 template <typename T>
    119 T ThreadSafeRingBuffer<T>::popBack ()
    120 {
    121 	m_readMutex.lock();
    122 	m_fill.decrement();
    123 	T elem = popBackInternal();
    124 	m_empty.increment();
    125 	m_readMutex.unlock();
    126 	return elem;
    127 }
    128 
    129 template <typename T>
    130 bool ThreadSafeRingBuffer<T>::tryPopBack (T& dst)
    131 {
    132 	if (!m_readMutex.tryLock())
    133 		return false;
    134 
    135 	bool success = m_fill.tryDecrement();
    136 
    137 	if (success)
    138 	{
    139 		dst = popBackInternal();
    140 		m_empty.increment();
    141 	}
    142 
    143 	m_readMutex.unlock();
    144 
    145 	return success;
    146 }
    147 
    148 } // de
    149 
    150 #endif // _DETHREADSAFERINGBUFFER_HPP
    151