126 lines
2.8 KiB
C++
126 lines
2.8 KiB
C++
//
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// detail/call_stack.hpp
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// ~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef ASIO_DETAIL_CALL_STACK_HPP
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#define ASIO_DETAIL_CALL_STACK_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include "asio/detail/noncopyable.hpp"
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#include "asio/detail/tss_ptr.hpp"
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#include "asio/detail/push_options.hpp"
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namespace asio {
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namespace detail {
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// Helper class to determine whether or not the current thread is inside an
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// invocation of io_context::run() for a specified io_context object.
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template <typename Key, typename Value = unsigned char>
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class call_stack
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{
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public:
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// Context class automatically pushes the key/value pair on to the stack.
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class context
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: private noncopyable
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{
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public:
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// Push the key on to the stack.
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explicit context(Key* k)
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: key_(k),
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next_(call_stack<Key, Value>::top_)
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{
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value_ = reinterpret_cast<unsigned char*>(this);
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call_stack<Key, Value>::top_ = this;
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}
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// Push the key/value pair on to the stack.
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context(Key* k, Value& v)
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: key_(k),
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value_(&v),
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next_(call_stack<Key, Value>::top_)
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{
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call_stack<Key, Value>::top_ = this;
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}
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// Pop the key/value pair from the stack.
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~context()
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{
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call_stack<Key, Value>::top_ = next_;
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}
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// Find the next context with the same key.
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Value* next_by_key() const
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{
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context* elem = next_;
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while (elem)
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{
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if (elem->key_ == key_)
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return elem->value_;
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elem = elem->next_;
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}
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return 0;
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}
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private:
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friend class call_stack<Key, Value>;
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// The key associated with the context.
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Key* key_;
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// The value associated with the context.
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Value* value_;
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// The next element in the stack.
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context* next_;
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};
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friend class context;
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// Determine whether the specified owner is on the stack. Returns address of
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// key if present, 0 otherwise.
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static Value* contains(Key* k)
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{
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context* elem = top_;
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while (elem)
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{
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if (elem->key_ == k)
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return elem->value_;
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elem = elem->next_;
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}
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return 0;
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}
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// Obtain the value at the top of the stack.
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static Value* top()
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{
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context* elem = top_;
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return elem ? elem->value_ : 0;
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}
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private:
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// The top of the stack of calls for the current thread.
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static tss_ptr<context> top_;
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};
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template <typename Key, typename Value>
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tss_ptr<typename call_stack<Key, Value>::context>
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call_stack<Key, Value>::top_;
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} // namespace detail
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#endif // ASIO_DETAIL_CALL_STACK_HPP
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