146 lines
2.3 KiB
C++
146 lines
2.3 KiB
C++
/*
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* \brief Queue with first-in first-out semantics
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* \author Norman Feske
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* \date 2008-08-15
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*/
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/*
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* Copyright (C) 2008-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__UTIL__QUEUE_H_
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#define _INCLUDE__UTIL__QUEUE_H_
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namespace Kernel {
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/*
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* \param QT queue element type
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*/
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template <typename QT>
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class Queue
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{
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protected:
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QT *_head; /* oldest element */
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QT *_tail; /* newest element */
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public:
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class Item
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{
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protected:
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friend class Queue;
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QT *_next;
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public:
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Item() : _next(0) {}
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~Item() { }
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// /**
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// * Return true is fifo element is enqueued in a fifo
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// */
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// bool is_enqueued() { return _next != 0; }
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};
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public:
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QT* head(){ return _head; }
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/**
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* Return true if queue is empty
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*/
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bool empty() { return _tail == 0; }
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/**
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* Constructor
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*
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* Start with an empty list.
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*/
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Queue(): _head(0), _tail(0) { }
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/**
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* Destructor
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*/
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virtual ~Queue() { }
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/**
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* Attach element at the end of the queue
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*/
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void enqueue(QT *e)
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{
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e->_next = 0;
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if (empty())
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_tail = _head = e;
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else {
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_tail->_next = e;
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_tail = e;
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}
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_enqueue__verbose__success();
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}
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/**
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* Obtain head element of the queue and remove element from queue
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*
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* \return head element or 0 if queue is empty
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*/
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QT *dequeue()
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{
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QT *result = _head;
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/* check if queue has only one last element */
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if (_head == _tail)
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_head = _tail = 0;
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else
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_head = _head->_next;
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/* mark fifo queue element as free */
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if (result)
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result->_next = 0;
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return result;
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}
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/**
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* Remove element from queue if it is enqueued
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*/
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void remove(QT *e)
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{
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QT* current=_head;
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QT* predecessor=0;
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if (current!=e){
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while (1){
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predecessor=current;
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current=current->_next;
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if (current==e || !current)
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break;
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}
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} else {
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dequeue();
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return;
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}
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if (!current) return;
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if (current==_tail) _tail=predecessor;
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predecessor->_next=e->_next;
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e->_next=0;
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}
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protected:
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virtual void _enqueue__verbose__success(){}
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};
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}
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#endif /* _INCLUDE__UTIL__QUEUE_H_ */
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