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+// Protocol Buffers - Google's data interchange format
+// Copyright 2012 Google Inc. All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// The routines exported by this module are subtle. If you use them, even if
+// you get the code right, it will depend on careful reasoning about atomicity
+// and memory ordering; it will be less readable, and harder to maintain. If
+// you plan to use these routines, you should have a good reason, such as solid
+// evidence that performance would otherwise suffer, or there being no
+// alternative. You should assume only properties explicitly guaranteed by the
+// specifications in this file. You are almost certainly _not_ writing code
+// just for the x86; if you assume x86 semantics, x86 hardware bugs and
+// implementations on other archtectures will cause your code to break. If you
+// do not know what you are doing, avoid these routines, and use a Mutex.
+//
+// It is incorrect to make direct assignments to/from an atomic variable.
+// You should use one of the Load or Store routines. The NoBarrier
+// versions are provided when no barriers are needed:
+// NoBarrier_Store()
+// NoBarrier_Load()
+// Although there are currently no compiler enforcement, you are encouraged
+// to use these.
+
+// This header and the implementations for each platform (located in
+// atomicops_internals_*) must be kept in sync with the upstream code (V8).
+
+#ifndef GOOGLE_PROTOBUF_ATOMICOPS_H_
+#define GOOGLE_PROTOBUF_ATOMICOPS_H_
+
+// Don't include this file for people not concerned about thread safety.
+#ifndef GOOGLE_PROTOBUF_NO_THREAD_SAFETY
+
+#include <google/protobuf/stubs/platform_macros.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+typedef int32 Atomic32;
+#ifdef GOOGLE_PROTOBUF_ARCH_64_BIT
+// We need to be able to go between Atomic64 and AtomicWord implicitly. This
+// means Atomic64 and AtomicWord should be the same type on 64-bit.
+#if defined(__ILP32__) || defined(GOOGLE_PROTOBUF_OS_NACL)
+// NaCl's intptr_t is not actually 64-bits on 64-bit!
+// http://code.google.com/p/nativeclient/issues/detail?id=1162
+typedef int64 Atomic64;
+#else
+typedef intptr_t Atomic64;
+#endif
+#endif
+
+// Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or
+// Atomic64 routines below, depending on your architecture.
+typedef intptr_t AtomicWord;
+
+// Atomically execute:
+// result = *ptr;
+// if (*ptr == old_value)
+// *ptr = new_value;
+// return result;
+//
+// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value".
+// Always return the old value of "*ptr"
+//
+// This routine implies no memory barriers.
+Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
+ Atomic32 old_value,
+ Atomic32 new_value);
+
+// Atomically store new_value into *ptr, returning the previous value held in
+// *ptr. This routine implies no memory barriers.
+Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value);
+
+// Atomically increment *ptr by "increment". Returns the new value of
+// *ptr with the increment applied. This routine implies no memory barriers.
+Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment);
+
+Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
+ Atomic32 increment);
+
+// These following lower-level operations are typically useful only to people
+// implementing higher-level synchronization operations like spinlocks,
+// mutexes, and condition-variables. They combine CompareAndSwap(), a load, or
+// a store with appropriate memory-ordering instructions. "Acquire" operations
+// ensure that no later memory access can be reordered ahead of the operation.
+// "Release" operations ensure that no previous memory access can be reordered
+// after the operation. "Barrier" operations have both "Acquire" and "Release"
+// semantics. A MemoryBarrier() has "Barrier" semantics, but does no memory
+// access.
+Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
+ Atomic32 old_value,
+ Atomic32 new_value);
+Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
+ Atomic32 old_value,
+ Atomic32 new_value);
+
+#if defined(__MINGW32__) && defined(MemoryBarrier)
+#undef MemoryBarrier
+#endif
+void MemoryBarrier();
+void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value);
+void Acquire_Store(volatile Atomic32* ptr, Atomic32 value);
+void Release_Store(volatile Atomic32* ptr, Atomic32 value);
+
+Atomic32 NoBarrier_Load(volatile const Atomic32* ptr);
+Atomic32 Acquire_Load(volatile const Atomic32* ptr);
+Atomic32 Release_Load(volatile const Atomic32* ptr);
+
+// 64-bit atomic operations (only available on 64-bit processors).
+#ifdef GOOGLE_PROTOBUF_ARCH_64_BIT
+Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
+ Atomic64 old_value,
+ Atomic64 new_value);
+Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value);
+Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
+Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
+
+Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
+ Atomic64 old_value,
+ Atomic64 new_value);
+Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
+ Atomic64 old_value,
+ Atomic64 new_value);
+void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value);
+void Acquire_Store(volatile Atomic64* ptr, Atomic64 value);
+void Release_Store(volatile Atomic64* ptr, Atomic64 value);
+Atomic64 NoBarrier_Load(volatile const Atomic64* ptr);
+Atomic64 Acquire_Load(volatile const Atomic64* ptr);
+Atomic64 Release_Load(volatile const Atomic64* ptr);
+#endif // GOOGLE_PROTOBUF_ARCH_64_BIT
+
+} // namespace internal
+} // namespace protobuf
+} // namespace google
+
+// Include our platform specific implementation.
+#define GOOGLE_PROTOBUF_ATOMICOPS_ERROR \
+#error "Atomic operations are not supported on your platform"
+
+// ThreadSanitizer, http://clang.llvm.org/docs/ThreadSanitizer.html.
+#if defined(THREAD_SANITIZER)
+#include <google/protobuf/stubs/atomicops_internals_tsan.h>
+// MSVC.
+#elif defined(_MSC_VER)
+#if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64)
+#include <google/protobuf/stubs/atomicops_internals_x86_msvc.h>
+#else
+GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+#endif
+
+// Apple.
+#elif defined(GOOGLE_PROTOBUF_OS_APPLE)
+#include <google/protobuf/stubs/atomicops_internals_macosx.h>
+
+// GCC.
+#elif defined(__GNUC__)
+#if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64)
+#include <google/protobuf/stubs/atomicops_internals_x86_gcc.h>
+#elif defined(GOOGLE_PROTOBUF_ARCH_ARM) && defined(__linux__)
+#include <google/protobuf/stubs/atomicops_internals_arm_gcc.h>
+#elif defined(GOOGLE_PROTOBUF_ARCH_AARCH64)
+#include <google/protobuf/stubs/atomicops_internals_arm64_gcc.h>
+#elif defined(GOOGLE_PROTOBUF_ARCH_ARM_QNX)
+#include <google/protobuf/stubs/atomicops_internals_arm_qnx.h>
+#elif defined(GOOGLE_PROTOBUF_ARCH_MIPS) || defined(GOOGLE_PROTOBUF_ARCH_MIPS64)
+#include <google/protobuf/stubs/atomicops_internals_mips_gcc.h>
+#elif defined(__native_client__)
+#include <google/protobuf/stubs/atomicops_internals_pnacl.h>
+#elif (((__GNUC__ == 4) && (__GNUC_MINOR__ >= 7)) || (__GNUC__ > 4))
+#include <google/protobuf/stubs/atomicops_internals_generic_gcc.h>
+#else
+GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+#endif
+
+// Unknown.
+#else
+GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+#endif
+
+// On some platforms we need additional declarations to make AtomicWord
+// compatible with our other Atomic* types.
+#if defined(GOOGLE_PROTOBUF_OS_APPLE)
+#include <google/protobuf/stubs/atomicops_internals_atomicword_compat.h>
+#endif
+
+#undef GOOGLE_PROTOBUF_ATOMICOPS_ERROR
+
+#endif // GOOGLE_PROTOBUF_NO_THREAD_SAFETY
+
+#endif // GOOGLE_PROTOBUF_ATOMICOPS_H_