1 // 2 // detail/call_stack.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_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. context(Key * k)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. context(Key * k,Value & v)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. ~context()58 ~context() 59 { 60 call_stack<Key, Value>::top_ = next_; 61 } 62 63 // Find the next context with the same key. next_by_key() const64 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. contains(Key * k)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. top()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 128