43 lines
2.0 KiB
Plaintext
43 lines
2.0 KiB
Plaintext
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Copyright Oliver Kowalke 2009.
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt
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]
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[section:overview Overview]
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__boost_context__ is a foundational library that provides a sort of cooperative
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multitasking on a single thread. By providing an abstraction of the current
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execution state in the current thread, including the stack (with local
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variables) and stack pointer, all registers and CPU flags, and the instruction
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pointer, a __fcontext__ instance represents a specific point in the application's
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execution path. This is useful for building higher-level abstractions, like
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__coroutines__, __coop_threads__ or an equivalent to
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[@http://msdn.microsoft.com/en-us/library/9k7k7cf0%28v=vs.80%29.aspx C# keyword __yield__]
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in C++.
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A __fcontext__ provides the means to suspend the current execution path and to
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transfer execution control, thereby permitting another __fcontext__ to run on the
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current thread. This state full transfer mechanism enables a __fcontext__ to
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suspend execution from within nested functions and, later, to resume from where
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it was suspended. While the execution path represented by a __fcontext__ only
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runs on a single thread, it can be migrated to another thread at any given time.
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A context switch between threads requires system calls (involving the OS
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kernel), which can cost more than thousand CPU cycles on x86 CPUs. By contrast,
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transferring control among them requires only fewer than hundred CPU cycles because
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it does not involve system calls as it is done within a single thread.
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In order to use the classes and functions described here, you can either include
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the specific headers specified by the descriptions of each class or function, or
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include the master library header:
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#include <boost/context/all.hpp>
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which includes all the other headers in turn.
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All functions and classes are contained in the namespace __context_ns__.
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[endsect]
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