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1 | // |
2 | // detail/call_stack.hpp | |
3 | // ~~~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2016 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_CALL_STACK_HPP | |
12 | #define BOOST_ASIO_DETAIL_CALL_STACK_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/config.hpp> | |
19 | #include <boost/asio/detail/noncopyable.hpp> | |
20 | #include <boost/asio/detail/tss_ptr.hpp> | |
21 | ||
22 | #include <boost/asio/detail/push_options.hpp> | |
23 | ||
24 | namespace boost { | |
25 | namespace asio { | |
26 | namespace detail { | |
27 | ||
28 | // Helper class to determine whether or not the current thread is inside an | |
29 | // invocation of io_service::run() for a specified io_service object. | |
30 | template <typename Key, typename Value = unsigned char> | |
31 | class call_stack | |
32 | { | |
33 | public: | |
34 | // Context class automatically pushes the key/value pair on to the stack. | |
35 | class context | |
36 | : private noncopyable | |
37 | { | |
38 | public: | |
39 | // Push the key on to the stack. | |
40 | explicit context(Key* k) | |
41 | : key_(k), | |
42 | next_(call_stack<Key, Value>::top_) | |
43 | { | |
44 | value_ = reinterpret_cast<unsigned char*>(this); | |
45 | call_stack<Key, Value>::top_ = this; | |
46 | } | |
47 | ||
48 | // Push the key/value pair on to the stack. | |
49 | context(Key* k, Value& v) | |
50 | : key_(k), | |
51 | value_(&v), | |
52 | next_(call_stack<Key, Value>::top_) | |
53 | { | |
54 | call_stack<Key, Value>::top_ = this; | |
55 | } | |
56 | ||
57 | // Pop the key/value pair from the stack. | |
58 | ~context() | |
59 | { | |
60 | call_stack<Key, Value>::top_ = next_; | |
61 | } | |
62 | ||
63 | // Find the next context with the same key. | |
64 | Value* next_by_key() const | |
65 | { | |
66 | context* elem = next_; | |
67 | while (elem) | |
68 | { | |
69 | if (elem->key_ == key_) | |
70 | return elem->value_; | |
71 | elem = elem->next_; | |
72 | } | |
73 | return 0; | |
74 | } | |
75 | ||
76 | private: | |
77 | friend class call_stack<Key, Value>; | |
78 | ||
79 | // The key associated with the context. | |
80 | Key* key_; | |
81 | ||
82 | // The value associated with the context. | |
83 | Value* value_; | |
84 | ||
85 | // The next element in the stack. | |
86 | context* next_; | |
87 | }; | |
88 | ||
89 | friend class context; | |
90 | ||
91 | // Determine whether the specified owner is on the stack. Returns address of | |
92 | // key if present, 0 otherwise. | |
93 | static Value* contains(Key* k) | |
94 | { | |
95 | context* elem = top_; | |
96 | while (elem) | |
97 | { | |
98 | if (elem->key_ == k) | |
99 | return elem->value_; | |
100 | elem = elem->next_; | |
101 | } | |
102 | return 0; | |
103 | } | |
104 | ||
105 | // Obtain the value at the top of the stack. | |
106 | static Value* top() | |
107 | { | |
108 | context* elem = top_; | |
109 | return elem ? elem->value_ : 0; | |
110 | } | |
111 | ||
112 | private: | |
113 | // The top of the stack of calls for the current thread. | |
114 | static tss_ptr<context> top_; | |
115 | }; | |
116 | ||
117 | template <typename Key, typename Value> | |
118 | tss_ptr<typename call_stack<Key, Value>::context> | |
119 | call_stack<Key, Value>::top_; | |
120 | ||
121 | } // namespace detail | |
122 | } // namespace asio | |
123 | } // namespace boost | |
124 | ||
125 | #include <boost/asio/detail/pop_options.hpp> | |
126 | ||
127 | #endif // BOOST_ASIO_DETAIL_CALL_STACK_HPP |