109 lines
1.9 KiB
C++
109 lines
1.9 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) 2008-2012 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__FIFO_H_
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#define _INCLUDE__UTIL__FIFO_H_
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namespace Genode {
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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 Fifo
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{
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private:
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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 Element
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{
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protected:
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friend class Fifo;
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QT *_next;
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bool _is_enqueued;
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public:
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Element(): _next(0), _is_enqueued(false) { }
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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 _is_enqueued; }
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};
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public:
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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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Fifo(): _head(0), _tail(0) { }
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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->Fifo::Element::_next = 0;
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e->Fifo::Element::_is_enqueued = true;
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if (empty()) {
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_tail = _head = e;
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return;
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}
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_tail->Fifo::Element::_next = e;
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_tail = e;
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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->Fifo::Element::_next;
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/* mark fifo queue element as free */
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if (result) {
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result->Fifo::Element::_next = 0;
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result->Fifo::Element::_is_enqueued = false;
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}
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return result;
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}
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};
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}
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#endif /* _INCLUDE__UTIL__FIFO_H_ */
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