ceph/src/boost/boost/asio/detail/op_queue.hpp

   1 //
   2 // detail/op_queue.hpp
   3 // ~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
   6 //
   7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   9 //
  10
  11 #ifndef BOOST_ASIO_DETAIL_OP_QUEUE_HPP
  12 #define BOOST_ASIO_DETAIL_OP_QUEUE_HPP
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  15 # pragma once
  16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  17
  18 #include <boost/asio/detail/noncopyable.hpp>
  19
  20 #include <boost/asio/detail/push_options.hpp>
  21
  22 namespace boost {
  23 namespace asio {
  24 namespace detail {
  25
  26 template <typename Operation>
  27 class op_queue;
  28
  29 class op_queue_access
  30 {
  31 public:
  32   template <typename Operation>
  33   static Operation* next(Operation* o)
  34   {
  35     return static_cast<Operation*>(o->next_);
  36   }
  37
  38   template <typename Operation1, typename Operation2>
  39   static void next(Operation1*& o1, Operation2* o2)
  40   {
  41     o1->next_ = o2;
  42   }
  43
  44   template <typename Operation>
  45   static void destroy(Operation* o)
  46   {
  47     o->destroy();
  48   }
  49
  50   template <typename Operation>
  51   static Operation*& front(op_queue<Operation>& q)
  52   {
  53     return q.front_;
  54   }
  55
  56   template <typename Operation>
  57   static Operation*& back(op_queue<Operation>& q)
  58   {
  59     return q.back_;
  60   }
  61 };
  62
  63 template <typename Operation>
  64 class op_queue
  65   : private noncopyable
  66 {
  67 public:
  68   // Constructor.
  69   op_queue()
  70     : front_(0),
  71       back_(0)
  72   {
  73   }
  74
  75   // Destructor destroys all operations.
  76   ~op_queue()
  77   {
  78     while (Operation* op = front_)
  79     {
  80       pop();
  81       op_queue_access::destroy(op);
  82     }
  83   }
  84
  85   // Get the operation at the front of the queue.
  86   Operation* front()
  87   {
  88     return front_;
  89   }
  90
  91   // Pop an operation from the front of the queue.
  92   void pop()
  93   {
  94     if (front_)
  95     {
  96       Operation* tmp = front_;
  97       front_ = op_queue_access::next(front_);
  98       if (front_ == 0)
  99         back_ = 0;
 100       op_queue_access::next(tmp, static_cast<Operation*>(0));
 101     }
 102   }
 103
 104   // Push an operation on to the back of the queue.
 105   void push(Operation* h)
 106   {
 107     op_queue_access::next(h, static_cast<Operation*>(0));
 108     if (back_)
 109     {
 110       op_queue_access::next(back_, h);
 111       back_ = h;
 112     }
 113     else
 114     {
 115       front_ = back_ = h;
 116     }
 117   }
 118
 119   // Push all operations from another queue on to the back of the queue. The
 120   // source queue may contain operations of a derived type.
 121   template <typename OtherOperation>
 122   void push(op_queue<OtherOperation>& q)
 123   {
 124     if (Operation* other_front = op_queue_access::front(q))
 125     {
 126       if (back_)
 127         op_queue_access::next(back_, other_front);
 128       else
 129         front_ = other_front;
 130       back_ = op_queue_access::back(q);
 131       op_queue_access::front(q) = 0;
 132       op_queue_access::back(q) = 0;
 133     }
 134   }
 135
 136   // Whether the queue is empty.
 137   bool empty() const
 138   {
 139     return front_ == 0;
 140   }
 141
 142   // Test whether an operation is already enqueued.
 143   bool is_enqueued(Operation* o) const
 144   {
 145     return op_queue_access::next(o) != 0 || back_ == o;
 146   }
 147
 148 private:
 149   friend class op_queue_access;
 150
 151   // The front of the queue.
 152   Operation* front_;
 153
 154   // The back of the queue.
 155   Operation* back_;
 156 };
 157
 158 } // namespace detail
 159 } // namespace asio
 160 } // namespace boost
 161
 162 #include <boost/asio/detail/pop_options.hpp>
 163
 164 #endif // BOOST_ASIO_DETAIL_OP_QUEUE_HPP