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311 lines
10 KiB
C++
311 lines
10 KiB
C++
//----------------------------------------------------------------------------
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// This is free and unencumbered software released into the public domain.
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//
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// Anyone is free to copy, modify, publish, use, compile, sell, or distribute
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// this software, either in source code form or as a compiled binary, for any
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// purpose, commercial or non-commercial, and by any means.
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//
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// In jurisdictions that recognize copyright laws, the author or authors of
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// this software dedicate any and all copyright interest in the software to the
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// public domain. We make this dedication for the benefit of the public at
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// large and to the detriment of our heirs and successors. We intend this
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// dedication to be an overt act of relinquishment in perpetuity of all present
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// and future rights to this software under copyright law.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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//
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// For more information, please refer to <http://unlicense.org/>
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//-----------------------------------------------------------------------------
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// SRT Project information:
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// This file was adopted from a Public Domain project from
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// https://github.com/mbitsnbites/atomic
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// Only namespaces were changed to adopt it for SRT project.
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#ifndef SRT_SYNC_ATOMIC_H_
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#define SRT_SYNC_ATOMIC_H_
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// Macro for disallowing copying of an object.
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#if __cplusplus >= 201103L
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#define ATOMIC_DISALLOW_COPY(T) \
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T(const T&) = delete; \
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T& operator=(const T&) = delete;
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#else
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#define ATOMIC_DISALLOW_COPY(T) \
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T(const T&); \
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T& operator=(const T&);
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#endif
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// A portable static assert.
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#if __cplusplus >= 201103L
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#define ATOMIC_STATIC_ASSERT(condition, message) \
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static_assert((condition), message)
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#else
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// Based on: http://stackoverflow.com/a/809465/5778708
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#define ATOMIC_STATIC_ASSERT(condition, message) \
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_impl_STATIC_ASSERT_LINE(condition, __LINE__)
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#define _impl_PASTE(a, b) a##b
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#ifdef __GNUC__
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#define _impl_UNUSED __attribute__((__unused__))
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#else
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#define _impl_UNUSED
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#endif
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#define _impl_STATIC_ASSERT_LINE(condition, line) \
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typedef char _impl_PASTE( \
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STATIC_ASSERT_failed_, \
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line)[(2 * static_cast<int>(!!(condition))) - 1] _impl_UNUSED
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#endif
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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// NOTE: Defined at the top level.
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#elif __cplusplus >= 201103L
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// NOTE: Prefer to use the c++11 std::atomic.
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#define ATOMIC_USE_CPP11_ATOMIC
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#elif (defined(__clang__) && defined(__clang_major__) && (__clang_major__ > 5)) \
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|| defined(__xlc__)
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// NOTE: Clang <6 does not support GCC __atomic_* intrinsics. I am unsure
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// about Clang6. Since Clang sets __GNUC__ and __GNUC_MINOR__ of this era
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// to <4.5, older Clang will catch the setting below to use the
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// POSIX Mutex Implementation.
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#define ATOMIC_USE_GCC_INTRINSICS
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#elif defined(__GNUC__) \
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&& ( (__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 7)) )
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// NOTE: The __atomic_* family of intrisics were introduced in GCC-4.7.0.
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// NOTE: This follows #if defined(__clang__), because most if, not all,
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// versions of Clang define __GNUC__ and __GNUC_MINOR__ but often define
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// them to 4.4 or an even earlier version. Most of the newish versions
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// of Clang also support GCC Atomic Intrisics even if they set GCC version
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// macros to <4.7.
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#define ATOMIC_USE_GCC_INTRINSICS
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#elif defined(__GNUC__) && !defined(ATOMIC_USE_SRT_SYNC_MUTEX)
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// NOTE: GCC compiler built-ins for atomic operations are pure
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// compiler extensions prior to GCC-4.7 and were grouped into the
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// the __sync_* family of functions. GCC-4.7, both the c++11 and C11
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// standards had been finalized, and GCC updated their built-ins to
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// better reflect the new memory model and the new functions grouped
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// into the __atomic_* family. Also the memory models were defined
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// differently, than in pre 4.7.
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// TODO: PORT to the pre GCC-4.7 __sync_* intrinsics. In the meantime use
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// the POSIX Mutex Implementation.
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#define ATOMIC_USE_SRT_SYNC_MUTEX 1
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#elif defined(_MSC_VER)
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#define ATOMIC_USE_MSVC_INTRINSICS
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#include "atomic_msvc.h"
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#else
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#error Unsupported compiler / system.
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#endif
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// Include any necessary headers for the selected Atomic Implementation.
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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#include "sync.h"
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#endif
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#if defined(ATOMIC_USE_CPP11_ATOMIC)
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#include <atomic>
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#endif
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namespace srt {
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namespace sync {
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template <typename T>
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class atomic {
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public:
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ATOMIC_STATIC_ASSERT(sizeof(T) == 1 || sizeof(T) == 2 || sizeof(T) == 4 ||
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sizeof(T) == 8,
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"Only types of size 1, 2, 4 or 8 are supported");
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atomic()
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: value_(static_cast<T>(0))
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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, mutex_()
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#endif
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{
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// No-Op
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}
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explicit atomic(const T value)
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: value_(value)
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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, mutex_()
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#endif
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{
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// No-Op
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}
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~atomic()
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{
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// No-Op
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}
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/// @brief Performs an atomic increment operation (value + 1).
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/// @returns The new value of the atomic object.
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T operator++() {
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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ScopedLock lg_(mutex_);
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const T t = ++value_;
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return t;
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#elif defined(ATOMIC_USE_GCC_INTRINSICS)
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return __atomic_add_fetch(&value_, 1, __ATOMIC_SEQ_CST);
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#elif defined(ATOMIC_USE_MSVC_INTRINSICS)
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return msvc::interlocked<T>::increment(&value_);
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#elif defined(ATOMIC_USE_CPP11_ATOMIC)
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return ++value_;
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#else
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#error "Implement Me."
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#endif
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}
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/// @brief Performs an atomic decrement operation (value - 1).
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/// @returns The new value of the atomic object.
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T operator--() {
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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ScopedLock lg_(mutex_);
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const T t = --value_;
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return t;
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#elif defined(ATOMIC_USE_GCC_INTRINSICS)
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return __atomic_sub_fetch(&value_, 1, __ATOMIC_SEQ_CST);
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#elif defined(ATOMIC_USE_MSVC_INTRINSICS)
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return msvc::interlocked<T>::decrement(&value_);
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#elif defined(ATOMIC_USE_CPP11_ATOMIC)
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return --value_;
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#else
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#error "Implement Me."
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#endif
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}
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/// @brief Performs an atomic compare-and-swap (CAS) operation.
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///
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/// The value of the atomic object is only updated to the new value if the
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/// old value of the atomic object matches @c expected_val.
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///
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/// @param expected_val The expected value of the atomic object.
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/// @param new_val The new value to write to the atomic object.
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/// @returns True if new_value was written to the atomic object.
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bool compare_exchange(const T expected_val, const T new_val) {
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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ScopedLock lg_(mutex_);
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bool result = false;
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if (expected_val == value_)
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{
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value_ = new_val;
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result = true;
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}
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return result;
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#elif defined(ATOMIC_USE_GCC_INTRINSICS)
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T e = expected_val;
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return __atomic_compare_exchange_n(
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&value_, &e, new_val, true, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
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#elif defined(ATOMIC_USE_MSVC_INTRINSICS)
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const T old_val =
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msvc::interlocked<T>::compare_exchange(&value_, new_val, expected_val);
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return (old_val == expected_val);
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#elif defined(ATOMIC_USE_CPP11_ATOMIC)
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T e = expected_val;
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return value_.compare_exchange_weak(e, new_val);
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#else
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#error "Implement Me."
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#endif
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}
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/// @brief Performs an atomic set operation.
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///
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/// The value of the atomic object is unconditionally updated to the new
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/// value.
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///
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/// @param new_val The new value to write to the atomic object.
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void store(const T new_val) {
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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ScopedLock lg_(mutex_);
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value_ = new_val;
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#elif defined(ATOMIC_USE_GCC_INTRINSICS)
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__atomic_store_n(&value_, new_val, __ATOMIC_SEQ_CST);
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#elif defined(ATOMIC_USE_MSVC_INTRINSICS)
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(void)msvc::interlocked<T>::exchange(&value_, new_val);
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#elif defined(ATOMIC_USE_CPP11_ATOMIC)
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value_.store(new_val);
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#else
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#error "Implement Me."
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#endif
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}
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/// @returns the current value of the atomic object.
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/// @note Be careful about how this is used, since any operations on the
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/// returned value are inherently non-atomic.
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T load() const {
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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ScopedLock lg_(mutex_);
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const T t = value_;
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return t;
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#elif defined(ATOMIC_USE_GCC_INTRINSICS)
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return __atomic_load_n(&value_, __ATOMIC_SEQ_CST);
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#elif defined(ATOMIC_USE_MSVC_INTRINSICS)
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// TODO(m): Is there a better solution for MSVC?
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return value_;
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#elif defined(ATOMIC_USE_CPP11_ATOMIC)
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return value_;
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#else
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#error "Implement Me."
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#endif
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}
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/// @brief Performs an atomic exchange operation.
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///
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/// The value of the atomic object is unconditionally updated to the new
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/// value, and the old value is returned.
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///
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/// @param new_val The new value to write to the atomic object.
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/// @returns the old value.
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T exchange(const T new_val) {
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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ScopedLock lg_(mutex_);
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const T t = value_;
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value_ = new_val;
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return t;
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#elif defined(ATOMIC_USE_GCC_INTRINSICS)
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return __atomic_exchange_n(&value_, new_val, __ATOMIC_SEQ_CST);
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#elif defined(ATOMIC_USE_MSVC_INTRINSICS)
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return msvc::interlocked<T>::exchange(&value_, new_val);
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#elif defined(ATOMIC_USE_CPP11_ATOMIC)
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return value_.exchange(new_val);
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#else
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#error "Implement Me."
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#endif
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}
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T operator=(const T new_value) {
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store(new_value);
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return new_value;
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}
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operator T() const {
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return load();
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}
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private:
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#if defined(ATOMIC_USE_SRT_SYNC_MUTEX) && (ATOMIC_USE_SRT_SYNC_MUTEX == 1)
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T value_;
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mutable Mutex mutex_;
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#elif defined(ATOMIC_USE_GCC_INTRINSICS)
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volatile T value_;
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#elif defined(ATOMIC_USE_MSVC_INTRINSICS)
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volatile T value_;
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#elif defined(ATOMIC_USE_CPP11_ATOMIC)
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std::atomic<T> value_;
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#else
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#error "Implement Me. (value_ type)"
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#endif
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ATOMIC_DISALLOW_COPY(atomic)
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};
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} // namespace sync
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} // namespace srt
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// Undef temporary defines.
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#undef ATOMIC_USE_GCC_INTRINSICS
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#undef ATOMIC_USE_MSVC_INTRINSICS
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#undef ATOMIC_USE_CPP11_ATOMIC
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#endif // ATOMIC_ATOMIC_H_
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