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-// -*- C++ -*-
-
-// Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
-//
-// This file is part of the GNU ISO C++ Library. This library 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, or (at your option) any later
-// version.
-
-// This library 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.
-
-// Under Section 7 of GPL version 3, you are granted additional
-// permissions described in the GCC Runtime Library Exception, version
-// 3.1, as published by the Free Software Foundation.
-
-// You should have received a copy of the GNU General Public License and
-// a copy of the GCC Runtime Library Exception along with this program;
-// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
-// <http://www.gnu.org/licenses/>.
-
-/** @file parallel/queue.h
- * @brief Lock-free double-ended queue.
- * This file is a GNU parallel extension to the Standard C++ Library.
- */
-
-// Written by Johannes Singler.
-
-#ifndef _GLIBCXX_PARALLEL_QUEUE_H
-#define _GLIBCXX_PARALLEL_QUEUE_H 1
-
-#include <parallel/types.h>
-#include <parallel/base.h>
-#include <parallel/compatibility.h>
-
-/** @brief Decide whether to declare certain variable volatile in this file. */
-#define _GLIBCXX_VOLATILE volatile
-
-namespace __gnu_parallel
-{
- /**@brief Double-ended queue of bounded size, allowing lock-free
- * atomic access. push_front() and pop_front() must not be called
- * concurrently to each other, while pop_back() can be called
- * concurrently at all times.
- * @c empty(), @c size(), and @c top() are intentionally not provided.
- * Calling them would not make sense in a concurrent setting.
- * @param T Contained element type. */
- template<typename T>
- class RestrictedBoundedConcurrentQueue
- {
- private:
- /** @brief Array of elements, seen as cyclic buffer. */
- T* base;
-
- /** @brief Maximal number of elements contained at the same time. */
- sequence_index_t max_size;
-
- /** @brief Cyclic begin and end pointers contained in one
- atomically changeable value. */
- _GLIBCXX_VOLATILE lcas_t borders;
-
- public:
- /** @brief Constructor. Not to be called concurrent, of course.
- * @param max_size Maximal number of elements to be contained. */
- RestrictedBoundedConcurrentQueue(sequence_index_t max_size)
- {
- this->max_size = max_size;
- base = new T[max_size];
- borders = encode2(0, 0);
-#pragma omp flush
- }
-
- /** @brief Destructor. Not to be called concurrent, of course. */
- ~RestrictedBoundedConcurrentQueue()
- { delete[] base; }
-
- /** @brief Pushes one element into the queue at the front end.
- * Must not be called concurrently with pop_front(). */
- void
- push_front(const T& t)
- {
- lcas_t former_borders = borders;
- int former_front, former_back;
- decode2(former_borders, former_front, former_back);
- *(base + former_front % max_size) = t;
-#if _GLIBCXX_ASSERTIONS
- // Otherwise: front - back > max_size eventually.
- _GLIBCXX_PARALLEL_ASSERT(((former_front + 1) - former_back)
- <= max_size);
-#endif
- fetch_and_add(&borders, encode2(1, 0));
- }
-
- /** @brief Pops one element from the queue at the front end.
- * Must not be called concurrently with pop_front(). */
- bool
- pop_front(T& t)
- {
- int former_front, former_back;
-#pragma omp flush
- decode2(borders, former_front, former_back);
- while (former_front > former_back)
- {
- // Chance.
- lcas_t former_borders = encode2(former_front, former_back);
- lcas_t new_borders = encode2(former_front - 1, former_back);
- if (compare_and_swap(&borders, former_borders, new_borders))
- {
- t = *(base + (former_front - 1) % max_size);
- return true;
- }
-#pragma omp flush
- decode2(borders, former_front, former_back);
- }
- return false;
- }
-
- /** @brief Pops one element from the queue at the front end.
- * Must not be called concurrently with pop_front(). */
- bool
- pop_back(T& t) //queue behavior
- {
- int former_front, former_back;
-#pragma omp flush
- decode2(borders, former_front, former_back);
- while (former_front > former_back)
- {
- // Chance.
- lcas_t former_borders = encode2(former_front, former_back);
- lcas_t new_borders = encode2(former_front, former_back + 1);
- if (compare_and_swap(&borders, former_borders, new_borders))
- {
- t = *(base + former_back % max_size);
- return true;
- }
-#pragma omp flush
- decode2(borders, former_front, former_back);
- }
- return false;
- }
- };
-} //namespace __gnu_parallel
-
-#undef _GLIBCXX_VOLATILE
-
-#endif /* _GLIBCXX_PARALLEL_QUEUE_H */