Imported gcc-4.4.3

[msp430-gcc.git] / libstdc++-v3 / include / parallel / queue.h

diff --git a/libstdc++-v3/include/parallel/queue.h b/libstdc++-v3/include/parallel/queue.h
new file mode 100644 (file)
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+++ b/libstdc++-v3/include/parallel/queue.h
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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 */