+++ /dev/null
-Boost Software License - Version 1.0 - August 17th, 2003
-
-Permission is hereby granted, free of charge, to any person or organization
-obtaining a copy of the software and accompanying documentation covered by
-this license (the "Software") to use, reproduce, display, distribute,
-execute, and transmit the Software, and to prepare derivative works of the
-Software, and to permit third-parties to whom the Software is furnished to
-do so, all subject to the following:
-
-The copyright notices in the Software and this entire statement, including
-the above license grant, this restriction and the following disclaimer,
-must be included in all copies of the Software, in whole or in part, and
-all derivative works of the Software, unless such copies or derivative
-works are solely in the form of machine-executable object code generated by
-a source language processor.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
-SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
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-DEALINGS IN THE SOFTWARE.
+++ /dev/null
-//
-// coroutine.hpp
-// ~~~~~~~~~~~~~
-//
-// Copyright (c) 2003-2018 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_COROUTINE_HPP
-#define BOOST_ASIO_COROUTINE_HPP
-
-namespace boost {
-namespace asio {
-namespace detail {
-
-class coroutine_ref;
-
-} // namespace detail
-
-/// Provides support for implementing stackless coroutines.
-/**
- * The @c coroutine class may be used to implement stackless coroutines. The
- * class itself is used to store the current state of the coroutine.
- *
- * Coroutines are copy-constructible and assignable, and the space overhead is
- * a single int. They can be used as a base class:
- *
- * @code class session : coroutine
- * {
- * ...
- * }; @endcode
- *
- * or as a data member:
- *
- * @code class session
- * {
- * ...
- * coroutine coro_;
- * }; @endcode
- *
- * or even bound in as a function argument using lambdas or @c bind(). The
- * important thing is that as the application maintains a copy of the object
- * for as long as the coroutine must be kept alive.
- *
- * @par Pseudo-keywords
- *
- * A coroutine is used in conjunction with certain "pseudo-keywords", which
- * are implemented as macros. These macros are defined by a header file:
- *
- * @code #include <boost/asio/yield.hpp>@endcode
- *
- * and may conversely be undefined as follows:
- *
- * @code #include <boost/asio/unyield.hpp>@endcode
- *
- * <b>reenter</b>
- *
- * The @c reenter macro is used to define the body of a coroutine. It takes a
- * single argument: a pointer or reference to a coroutine object. For example,
- * if the base class is a coroutine object you may write:
- *
- * @code reenter (this)
- * {
- * ... coroutine body ...
- * } @endcode
- *
- * and if a data member or other variable you can write:
- *
- * @code reenter (coro_)
- * {
- * ... coroutine body ...
- * } @endcode
- *
- * When @c reenter is executed at runtime, control jumps to the location of the
- * last @c yield or @c fork.
- *
- * The coroutine body may also be a single statement, such as:
- *
- * @code reenter (this) for (;;)
- * {
- * ...
- * } @endcode
- *
- * @b Limitation: The @c reenter macro is implemented using a switch. This
- * means that you must take care when using local variables within the
- * coroutine body. The local variable is not allowed in a position where
- * reentering the coroutine could bypass the variable definition.
- *
- * <b>yield <em>statement</em></b>
- *
- * This form of the @c yield keyword is often used with asynchronous operations:
- *
- * @code yield socket_->async_read_some(buffer(*buffer_), *this); @endcode
- *
- * This divides into four logical steps:
- *
- * @li @c yield saves the current state of the coroutine.
- * @li The statement initiates the asynchronous operation.
- * @li The resume point is defined immediately following the statement.
- * @li Control is transferred to the end of the coroutine body.
- *
- * When the asynchronous operation completes, the function object is invoked
- * and @c reenter causes control to transfer to the resume point. It is
- * important to remember to carry the coroutine state forward with the
- * asynchronous operation. In the above snippet, the current class is a
- * function object object with a coroutine object as base class or data member.
- *
- * The statement may also be a compound statement, and this permits us to
- * define local variables with limited scope:
- *
- * @code yield
- * {
- * mutable_buffers_1 b = buffer(*buffer_);
- * socket_->async_read_some(b, *this);
- * } @endcode
- *
- * <b>yield return <em>expression</em> ;</b>
- *
- * This form of @c yield is often used in generators or coroutine-based parsers.
- * For example, the function object:
- *
- * @code struct interleave : coroutine
- * {
- * istream& is1;
- * istream& is2;
- * char operator()(char c)
- * {
- * reenter (this) for (;;)
- * {
- * yield return is1.get();
- * yield return is2.get();
- * }
- * }
- * }; @endcode
- *
- * defines a trivial coroutine that interleaves the characters from two input
- * streams.
- *
- * This type of @c yield divides into three logical steps:
- *
- * @li @c yield saves the current state of the coroutine.
- * @li The resume point is defined immediately following the semicolon.
- * @li The value of the expression is returned from the function.
- *
- * <b>yield ;</b>
- *
- * This form of @c yield is equivalent to the following steps:
- *
- * @li @c yield saves the current state of the coroutine.
- * @li The resume point is defined immediately following the semicolon.
- * @li Control is transferred to the end of the coroutine body.
- *
- * This form might be applied when coroutines are used for cooperative
- * threading and scheduling is explicitly managed. For example:
- *
- * @code struct task : coroutine
- * {
- * ...
- * void operator()()
- * {
- * reenter (this)
- * {
- * while (... not finished ...)
- * {
- * ... do something ...
- * yield;
- * ... do some more ...
- * yield;
- * }
- * }
- * }
- * ...
- * };
- * ...
- * task t1, t2;
- * for (;;)
- * {
- * t1();
- * t2();
- * } @endcode
- *
- * <b>yield break ;</b>
- *
- * The final form of @c yield is used to explicitly terminate the coroutine.
- * This form is comprised of two steps:
- *
- * @li @c yield sets the coroutine state to indicate termination.
- * @li Control is transferred to the end of the coroutine body.
- *
- * Once terminated, calls to is_complete() return true and the coroutine cannot
- * be reentered.
- *
- * Note that a coroutine may also be implicitly terminated if the coroutine
- * body is exited without a yield, e.g. by return, throw or by running to the
- * end of the body.
- *
- * <b>fork <em>statement</em></b>
- *
- * The @c fork pseudo-keyword is used when "forking" a coroutine, i.e. splitting
- * it into two (or more) copies. One use of @c fork is in a server, where a new
- * coroutine is created to handle each client connection:
- *
- * @code reenter (this)
- * {
- * do
- * {
- * socket_.reset(new tcp::socket(io_context_));
- * yield acceptor->async_accept(*socket_, *this);
- * fork server(*this)();
- * } while (is_parent());
- * ... client-specific handling follows ...
- * } @endcode
- *
- * The logical steps involved in a @c fork are:
- *
- * @li @c fork saves the current state of the coroutine.
- * @li The statement creates a copy of the coroutine and either executes it
- * immediately or schedules it for later execution.
- * @li The resume point is defined immediately following the semicolon.
- * @li For the "parent", control immediately continues from the next line.
- *
- * The functions is_parent() and is_child() can be used to differentiate
- * between parent and child. You would use these functions to alter subsequent
- * control flow.
- *
- * Note that @c fork doesn't do the actual forking by itself. It is the
- * application's responsibility to create a clone of the coroutine and call it.
- * The clone can be called immediately, as above, or scheduled for delayed
- * execution using something like io_context::post().
- *
- * @par Alternate macro names
- *
- * If preferred, an application can use macro names that follow a more typical
- * naming convention, rather than the pseudo-keywords. These are:
- *
- * @li @c BOOST_ASIO_CORO_REENTER instead of @c reenter
- * @li @c BOOST_ASIO_CORO_YIELD instead of @c yield
- * @li @c BOOST_ASIO_CORO_FORK instead of @c fork
- */
-class coroutine
-{
-public:
- /// Constructs a coroutine in its initial state.
- coroutine() : value_(0) {}
-
- /// Returns true if the coroutine is the child of a fork.
- bool is_child() const { return value_ < 0; }
-
- /// Returns true if the coroutine is the parent of a fork.
- bool is_parent() const { return !is_child(); }
-
- /// Returns true if the coroutine has reached its terminal state.
- bool is_complete() const { return value_ == -1; }
-
-private:
- friend class detail::coroutine_ref;
- int value_;
-};
-
-
-namespace detail {
-
-class coroutine_ref
-{
-public:
- coroutine_ref(coroutine& c) : value_(c.value_), modified_(false) {}
- coroutine_ref(coroutine* c) : value_(c->value_), modified_(false) {}
- ~coroutine_ref() { if (!modified_) value_ = -1; }
- operator int() const { return value_; }
- int& operator=(int v) { modified_ = true; return value_ = v; }
-private:
- void operator=(const coroutine_ref&);
- int& value_;
- bool modified_;
-};
-
-} // namespace detail
-} // namespace asio
-} // namespace boost
-
-#define BOOST_ASIO_CORO_REENTER(c) \
- switch (::boost::asio::detail::coroutine_ref _coro_value = c) \
- case -1: if (_coro_value) \
- { \
- goto terminate_coroutine; \
- terminate_coroutine: \
- _coro_value = -1; \
- goto bail_out_of_coroutine; \
- bail_out_of_coroutine: \
- break; \
- } \
- else /* fall-through */ case 0:
-
-#define BOOST_ASIO_CORO_YIELD_IMPL(n) \
- for (_coro_value = (n);;) \
- if (_coro_value == 0) \
- { \
- case (n): ; \
- break; \
- } \
- else \
- switch (_coro_value ? 0 : 1) \
- for (;;) \
- /* fall-through */ case -1: if (_coro_value) \
- goto terminate_coroutine; \
- else for (;;) \
- /* fall-through */ case 1: if (_coro_value) \
- goto bail_out_of_coroutine; \
- else /* fall-through */ case 0:
-
-#define BOOST_ASIO_CORO_FORK_IMPL(n) \
- for (_coro_value = -(n);; _coro_value = (n)) \
- if (_coro_value == (n)) \
- { \
- case -(n): ; \
- break; \
- } \
- else
-
-#if defined(_MSC_VER)
-# define BOOST_ASIO_CORO_YIELD BOOST_ASIO_CORO_YIELD_IMPL(__COUNTER__ + 1)
-# define BOOST_ASIO_CORO_FORK BOOST_ASIO_CORO_FORK_IMPL(__COUNTER__ + 1)
-#else // defined(_MSC_VER)
-# define BOOST_ASIO_CORO_YIELD BOOST_ASIO_CORO_YIELD_IMPL(__LINE__)
-# define BOOST_ASIO_CORO_FORK BOOST_ASIO_CORO_FORK_IMPL(__LINE__)
-#endif // defined(_MSC_VER)
-
-#endif // BOOST_ASIO_COROUTINE_HPP
projects / thirdparty / kea.git / commitdiff
