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/*********************************************************************************/
/*!
@file Queue.h
@brief xxxx.
@author L. J. Barman
Copyright (c) 2008-2013, L. J. Barman, all rights reserved
This file is part of the PianoBooster application
PianoBooster is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
PianoBooster 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with PianoBooster. If not, see <http://www.gnu.org/licenses/>.
*/
/*********************************************************************************/
#ifndef __QUEUE_H__
#define __QUEUE_H__
#include <assert.h>
// A Queue or circular buffer also also call a FIFO a First In First Out buffer
// different threads could be running each end of the queue
//
template <class TYPE>
class CQueue
{
public:
explicit CQueue(int size)
{
m_size = size;
m_buffer = new TYPE[size];
clear();
}
~CQueue()
{
delete [] m_buffer;
}
void clear()
{
m_count = m_head = m_tail=0;
}
// pushes the item into the queue and returns a pointer to the item in the buffer
TYPE* push(TYPE c)
{
if (!space())
{
assert(false);
return 0;
}
TYPE* itemPtr = &m_buffer[m_head];
m_buffer[m_head] = c;
m_head++;
if (m_head >= m_size)
m_head = 0;
// This must be last if a different thread is using pop()
m_count++;
return itemPtr;
}
TYPE pop()
{
TYPE c;
if (!length())
{
assert(false);
return m_buffer[m_tail];
}
c = m_buffer[m_tail++];
if (m_tail >= m_size)
m_tail = 0;
// This must be last if a different thread is using push()
m_count--;
return c;
}
// returns a pointer to the item starting at the end of the queue
TYPE * indexPtr(int index)
{
int offset;
if (index >= length())
{
assert(false);
return &m_buffer[m_head];
}
offset = m_tail + index;
if (offset >= m_size)
offset -= m_size;
return &m_buffer[offset];
}
TYPE index(int index){ return *indexPtr(index);}
int length() {return m_count;}
int space() {return m_size - m_count;}
private:
TYPE * m_buffer;
int m_size;
int m_head;
int m_tail;
// this should be atomic operation when two different threads are at each end of the queue
volatile int m_count;
};
#endif //__QUEUE_H__
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