// // detail/call_stack.hpp // ~~~~~~~~~~~~~~~~~~~~~ // // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com) // // 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 ASIO_DETAIL_CALL_STACK_HPP #define ASIO_DETAIL_CALL_STACK_HPP #if defined(_MSC_VER) && (_MSC_VER >= 1200) # pragma once #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) #include "asio/detail/config.hpp" #include "asio/detail/noncopyable.hpp" #include "asio/detail/tss_ptr.hpp" #include "asio/detail/push_options.hpp" namespace asio { namespace detail { // Helper class to determine whether or not the current thread is inside an // invocation of io_context::run() for a specified io_context object. template class call_stack { public: // Context class automatically pushes the key/value pair on to the stack. class context : private noncopyable { public: // Push the key on to the stack. explicit context(Key* k) : key_(k), next_(call_stack::top_) { value_ = reinterpret_cast(this); call_stack::top_ = this; } // Push the key/value pair on to the stack. context(Key* k, Value& v) : key_(k), value_(&v), next_(call_stack::top_) { call_stack::top_ = this; } // Pop the key/value pair from the stack. ~context() { call_stack::top_ = next_; } // Find the next context with the same key. Value* next_by_key() const { context* elem = next_; while (elem) { if (elem->key_ == key_) return elem->value_; elem = elem->next_; } return 0; } private: friend class call_stack; // The key associated with the context. Key* key_; // The value associated with the context. Value* value_; // The next element in the stack. context* next_; }; friend class context; // Determine whether the specified owner is on the stack. Returns address of // key if present, 0 otherwise. static Value* contains(Key* k) { context* elem = top_; while (elem) { if (elem->key_ == k) return elem->value_; elem = elem->next_; } return 0; } // Obtain the value at the top of the stack. static Value* top() { context* elem = top_; return elem ? elem->value_ : 0; } private: // The top of the stack of calls for the current thread. static tss_ptr top_; }; template tss_ptr::context> call_stack::top_; } // namespace detail } // namespace asio #include "asio/detail/pop_options.hpp" #endif // ASIO_DETAIL_CALL_STACK_HPP