Imported Upstream version 1.49.0upstream/1.49.0

1 files changed, 152 insertions, 0 deletions

diff --git a/boost/pending/fenced_priority_queue.hpp b/boost/pending/fenced_priority_queue.hpp
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+//  (C) Copyright Jeremiah Willcock 2004 
+//  Distributed under the Boost Software License, Version 1.0. (See
+//  accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_FENCED_PRIORITY_QUEUE_HPP
+#define BOOST_FENCED_PRIORITY_QUEUE_HPP
+
+#include <vector>
+#include <queue>
+#include <functional>
+#include <boost/pending/queue.hpp>
+
+// Fenced priority queue
+// Jeremiah Willcock
+
+// This class implements a fenced priority queue.  This is similar to
+// a normal priority queue (sorts its members, and only returns the
+// first), except that members cannot be sorted around a "fence" that
+// can be placed into the buffer.  This fence is inserted using the
+// fence() member function or (possibly) implicitly by the top() and
+// pop() methods, and is removed automatically when the elements
+// around it are popped.
+
+// The implementation is as follows:  Q is an unsorted queue that
+// contains the already-sorted list data, and PQ is a priority queue
+// that contains new elements (since the last fence) that have yet to
+// be sorted.  New elements are inserted into PQ, and a fence moves
+// all elements in PQ into the back of Q in sorted order.  Elements
+// are then popped from the front of Q, and if that is empty the front
+// of PQ.
+
+namespace boost {
+
+  template<class T, class Compare = std::less<T>, bool implicit_fence = true,
+           class Buffer = boost::queue<T> >
+  class fenced_priority_queue {
+  public:
+    typedef T value_type;
+    typedef typename Buffer::size_type size_type;
+
+    fenced_priority_queue(const Compare _comp = Compare() ) 
+      : PQ(_comp) {} 
+    
+    void push(const T& data);
+    void pop(void);
+    T& top(void);
+    const T& top(void) const;
+    size_type size(void) const;
+    bool empty(void) const;
+    void fence(void);
+    
+  private:
+    void fence(void) const;
+
+    //let them mutable to allow const version of top and the same 
+    //semantics with non-constant version. Rich Lee
+    mutable std::priority_queue<T, std::vector<T>, Compare> PQ;
+    mutable Buffer Q;
+  };
+  
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline void 
+  fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  push(const T &t) {
+    // Push a new element after the last fence.  This puts it into the
+    // priority queue to be sorted with all other elements in its
+    // partition.
+    PQ.push(t);
+  }
+
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline void fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  pop(void) {
+    // Pop one element from the front of the queue.  Removes from the
+    // already-sorted part of the queue if it is non-empty, otherwise
+    // removes from the new-element priority queue.  Runs an implicit
+    // "fence" operation if the implicit_fence template argument is
+    // true.
+    if (implicit_fence) fence();
+    if ( !Q.empty() )
+      Q.pop();
+    else
+      PQ.pop();
+  }
+
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline T& fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  top(void) {
+    // Get the top element from the queue.  This element comes from Q if
+    // possible, otherwise from PQ.  Causes an implicit "fence"
+    // operation if the implicit_fence template argument is true.
+    if (implicit_fence) fence();
+    if ( !Q.empty() )
+      return Q.top();
+    else
+      //std::priority_queue only have const version of top. Rich Lee
+      return const_cast<T&>(PQ.top());
+  }
+
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline const T&
+  fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  top(void) const {
+    if (implicit_fence) fence();
+    if ( !Q.empty() )
+      return Q.top();
+    else
+      return PQ.top();
+  }
+
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline typename fenced_priority_queue<T, Compare, implicit_fence, Buffer>::size_type 
+  fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  size(void) const {
+    // Returns the size of the queue (both parts together).
+    return Q.size() + PQ.size();
+  }
+
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline bool 
+  fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  empty(void) const {
+    // Returns if the queue is empty, i.e. both parts are empty.
+    return Q.empty() && PQ.empty();
+  }
+  
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline void 
+  fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  fence(void) {
+    // Perform a fence operation.  Remove elements from PQ in sorted
+    // order and insert them in the back of Q.
+    while ( !PQ.empty() ) {
+      Q.push(PQ.top());
+      PQ.pop();
+    }
+  }
+  template<class T, class Compare, bool implicit_fence, class Buffer>
+  inline void 
+  fenced_priority_queue<T, Compare, implicit_fence, Buffer>::
+  fence(void) const {
+    // Perform a fence operation.  Remove elements from PQ in sorted
+    // order and insert them in the back of Q.
+    while ( !PQ.empty() ) {
+      Q.push(PQ.top());
+      PQ.pop();
+    }
+  }
+
+}  
+#endif /* BOOST_FENCED_PRIORITY_QUEUE_HPP */