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- /*
- * Copyright 2017-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #pragma once
- #include <atomic>
- #include <cstdint>
- namespace folly {
- /**
- * Sets a bit at the given index in the binary representation of the integer
- * to 1. Returns the previous value of the bit, so true if the bit was not
- * changed, false otherwise
- *
- * On some architectures, using this is more efficient than the corresponding
- * std::atomic::fetch_or() with a mask. For example to set the first (least
- * significant) bit of an integer, you could do atomic.fetch_or(0b1)
- *
- * The efficiency win is only visible in x86 (yet) and comes from the
- * implementation using the x86 bts instruction when possible.
- *
- * When something other than std::atomic is passed, the implementation assumed
- * incompatibility with this interface and calls Atomic::fetch_or()
- */
- template <typename Atomic>
- bool atomic_fetch_set(
- Atomic& atomic,
- std::size_t bit,
- std::memory_order order = std::memory_order_seq_cst);
- /**
- * Resets a bit at the given index in the binary representation of the integer
- * to 0. Returns the previous value of the bit, so true if the bit was
- * changed, false otherwise
- *
- * This follows the same underlying principle and implementation as
- * fetch_set(). Using the optimized implementation when possible and falling
- * back to std::atomic::fetch_and() when in debug mode or in an architecture
- * where an optimization is not possible
- */
- template <typename Atomic>
- bool atomic_fetch_reset(
- Atomic& atomic,
- std::size_t bit,
- std::memory_order order = std::memory_order_seq_cst);
- } // namespace folly
- #include <folly/synchronization/AtomicUtil-inl.h>
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