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/*
Copyright (C) 2003-2006 Tommi Junttila
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License version 2
as published by the Free Software Foundation.
This program 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 this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/* FSF address fixed in the above notice on 1 Oct 2009 by Tamas Nepusz */
#ifndef BLISS_KQUEUE_HH
#define BLISS_KQUEUE_HH
#include "bliss_defs.hh"
#include <cstdlib> // malloc
namespace igraph {
/*
* A queue with fixed capacity
*/
template <class Type>
class KQueue
{
public:
KQueue();
~KQueue();
void init(const unsigned int k);
bool is_empty() const;
unsigned int size() const;
unsigned int capacity() const;
void clear();
Type front() const;
Type pop_front();
void push_front(Type e);
Type pop_back();
void push_back(Type e);
private:
Type *entries, *end;
Type *head, *tail;
};
template <class Type>
KQueue<Type>::KQueue()
{
entries = 0;
end = 0;
head = 0;
tail = 0;
}
template <class Type>
KQueue<Type>::~KQueue()
{
if(entries)
free(entries);
}
template <class Type>
void KQueue<Type>::init(const unsigned int k)
{
assert(k > 0);
if(entries)
free(entries);
entries = (Type*)malloc((k + 1) * sizeof(Type));
end = entries + k + 1;
head = entries;
tail = head;
}
template <class Type>
void KQueue<Type>::clear()
{
head = entries;
tail = head;
}
template <class Type>
bool KQueue<Type>::is_empty() const
{
return(head == tail);
}
template <class Type>
unsigned int KQueue<Type>::size() const
{
if(tail >= head)
return(tail - head);
return((end - head) + (tail - entries));
}
template <class Type>
Type KQueue<Type>::front() const
{
DEBUG_ASSERT(head != tail);
return *head;
}
template <class Type>
Type KQueue<Type>::pop_front()
{
DEBUG_ASSERT(head != tail);
Type *old_head = head;
head++;
if(head == end)
head = entries;
return *old_head;
}
template <class Type>
void KQueue<Type>::push_front(Type e)
{
if(head == entries)
head = end - 1;
else
head--;
DEBUG_ASSERT(head != tail);
*head = e;
}
template <class Type>
void KQueue<Type>::push_back(Type e)
{
*tail = e;
tail++;
if(tail == end)
tail = entries;
DEBUG_ASSERT(head != tail);
}
}
#endif
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