fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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52 lines
1.8 KiB
52 lines
1.8 KiB
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include <atomic>
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#include <cstdint>
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namespace folly {
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/**
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* Sets a bit at the given index in the binary representation of the integer
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* to 1. Returns the previous value of the bit, so true if the bit was not
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* changed, false otherwise
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*
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* On some architectures, using this is more efficient than the corresponding
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* std::atomic::fetch_or() with a mask. For example to set the first (least
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* significant) bit of an integer, you could do atomic.fetch_or(0b1)
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*
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* The efficiency win is only visible in x86 (yet) and comes from the
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* implementation using the x86 bts instruction when possible.
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*
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* When something other than std::atomic is passed, the implementation assumed
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* incompatibility with this interface and calls Atomic::fetch_or()
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*/
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template <typename Atomic>
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bool atomic_fetch_set(
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Atomic& atomic,
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std::size_t bit,
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std::memory_order order = std::memory_order_seq_cst);
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/**
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* Resets a bit at the given index in the binary representation of the integer
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* to 0. Returns the previous value of the bit, so true if the bit was
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* changed, false otherwise
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*
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* This follows the same underlying principle and implementation as
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* fetch_set(). Using the optimized implementation when possible and falling
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* back to std::atomic::fetch_and() when in debug mode or in an architecture
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* where an optimization is not possible
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*/
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template <typename Atomic>
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bool atomic_fetch_reset(
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Atomic& atomic,
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std::size_t bit,
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std::memory_order order = std::memory_order_seq_cst);
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} // namespace folly
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#include <folly/synchronization/AtomicUtil-inl.h>
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