1//
2// detail/op_queue.hpp
3// ~~~~~~~~~~~~~~~~~~~
4//
5// Copyright (c) 2003-2015 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
22namespace boost {
23namespace asio {
24namespace detail {
25
26template <typename Operation>
27class op_queue;
28
29class op_queue_access
30{
31public:
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
63template <typename Operation>
64class op_queue
65 : private noncopyable
66{
67public:
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
142private:
143 friend class op_queue_access;
144
145 // The front of the queue.
146 Operation* front_;
147
148 // The back of the queue.
149 Operation* back_;
150};
151
152} // namespace detail
153} // namespace asio
154} // namespace boost
155
156#include <boost/asio/detail/pop_options.hpp>
157
158#endif // BOOST_ASIO_DETAIL_OP_QUEUE_HPP
159