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//
// detail/call_stack.hpp
// ~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2015 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 BOOST_ASIO_DETAIL_CALL_STACK_HPP
#define BOOST_ASIO_DETAIL_CALL_STACK_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/config.hpp>
#include <boost/asio/detail/noncopyable.hpp>
#include <boost/asio/detail/tss_ptr.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
namespace detail {
// Helper class to determine whether or not the current thread is inside an
// invocation of io_service::run() for a specified io_service object.
template <typename Key, typename Value = unsigned char>
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<Key, Value>::top_)
{
value_ = reinterpret_cast<unsigned char*>(this);
call_stack<Key, Value>::top_ = this;
}
// Push the key/value pair on to the stack.
context(Key* k, Value& v)
: key_(k),
value_(&v),
next_(call_stack<Key, Value>::top_)
{
call_stack<Key, Value>::top_ = this;
}
// Pop the key/value pair from the stack.
~context()
{
call_stack<Key, Value>::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<Key, Value>;
// 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<context> top_;
};
template <typename Key, typename Value>
tss_ptr<typename call_stack<Key, Value>::context>
call_stack<Key, Value>::top_;
} // namespace detail
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_DETAIL_CALL_STACK_HPP
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