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- [/
- Copyright Oliver Kowalke 2014.
- 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
- ]
- [section:overview Overview]
- __boost_context__ is a foundational library that provides a sort of cooperative
- multitasking on a single thread. By providing an abstraction of the current
- execution state in the current thread, including the stack (with local
- variables) and stack pointer, all registers and CPU flags, and the instruction
- pointer, a execution context represents a specific point in the application's
- execution path. This is useful for building higher-level abstractions, like
- __coroutines__, __coop_threads__ or an equivalent to
- [@http://msdn.microsoft.com/en-us/library/9k7k7cf0%28v=vs.80%29.aspx C# keyword __yield__]
- in C++.
- __cc__/__con__ provides the means to suspend the current execution path and to
- transfer execution control, thereby permitting another context to run on the
- current thread. This state full transfer mechanism enables a context to suspend
- execution from within nested functions and, later, to resume from where it was
- suspended. While the execution path represented by a __con__ only runs on a
- single thread, it can be migrated to another thread at any given time.
- A [@http://en.wikipedia.org/wiki/Context_switch context switch] between threads
- requires system calls (involving the OS kernel), which can cost more than
- thousand CPU cycles on x86 CPUs. By contrast, transferring control vias
- __cc__/__con__ requires only few CPU cycles because it does not involve system
- calls as it is done within a single thread.
- All functions and classes are contained in the namespace __context_ns__.
- [note This library requires C++11!]
- [important Windows using fcontext_t: turn off global program optimization (/GL) and change /EHsc (compiler
- assumes that functions declared as extern "C" never throw a C++ exception) to /EHs (tells
- compiler assumes that functions declared as extern "C" may throw an exception).]
- [endsect]
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