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https://github.com/matrix-construct/construct
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39 lines
1.4 KiB
C++
39 lines
1.4 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_CTX_CRITICAL_INDICATOR_H
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namespace ircd::ctx {
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inline namespace this_ctx
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{
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struct critical_indicator; // Indicates if yielding happened for a section
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}}
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/// An instance of critical_indicator reports if context switching happened.
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///
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/// A critical_indicator remains true after construction until a context switch
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/// has occurred. It then becomes false. This is not an assertion and is
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/// available in optimized builds for real use. For example, a context may
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/// want to recompute some value after a context switch and opportunistically
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/// skip this effort when this indicator shows no switch occurred.
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///
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class ircd::ctx::this_ctx::critical_indicator
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{
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uint64_t state;
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public:
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uint64_t count() const { return epoch(cur()) - state; }
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operator bool() const { return epoch(cur()) == state; }
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critical_indicator()
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:state(epoch(cur()))
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{}
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};
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