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//
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// detail/call_stack.hpp
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// ~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2015 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 BOOST_ASIO_DETAIL_CALL_STACK_HPP
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#define BOOST_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 <boost/asio/detail/config.hpp>
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#include <boost/asio/detail/noncopyable.hpp>
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#include <boost/asio/detail/tss_ptr.hpp>
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#include <boost/asio/detail/push_options.hpp>
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namespace boost {
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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_service::run() for a specified io_service 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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} // namespace boost
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#include <boost/asio/detail/pop_options.hpp>
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#endif // BOOST_ASIO_DETAIL_CALL_STACK_HPP