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// Protocol Buffers - Google's data interchange format
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// Copyright 2012 Google Inc. All rights reserved.
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// http://code.google.com/p/protobuf/
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// This file is an internal atomic implementation, use atomicops.h instead.
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// LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears.
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#ifndef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_
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#define GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_
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// 0xffff0fc0 is the hard coded address of a function provided by
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// the kernel which implements an atomic compare-exchange. On older
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// ARM architecture revisions (pre-v6) this may be implemented using
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// a syscall. This address is stable, and in active use (hard coded)
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// by at least glibc-2.7 and the Android C library.
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typedef Atomic32 (*LinuxKernelCmpxchgFunc)(Atomic32 old_value,
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volatile Atomic32* ptr);
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LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak)) =
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(LinuxKernelCmpxchgFunc) 0xffff0fc0;
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typedef void (*LinuxKernelMemoryBarrierFunc)(void);
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LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
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(LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
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inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 prev_value = *ptr;
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if (!pLinuxKernelCmpxchg(old_value, new_value,
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const_cast<Atomic32*>(ptr))) {
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} while (prev_value == old_value);
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inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
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} while (pLinuxKernelCmpxchg(old_value, new_value,
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const_cast<Atomic32*>(ptr)));
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inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
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return Barrier_AtomicIncrement(ptr, increment);
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inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
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// Atomic exchange the old value with an incremented one.
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Atomic32 old_value = *ptr;
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Atomic32 new_value = old_value + increment;
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if (pLinuxKernelCmpxchg(old_value, new_value,
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const_cast<Atomic32*>(ptr)) == 0) {
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// The exchange took place as expected.
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// Otherwise, *ptr changed mid-loop and we need to retry.
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inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 new_value) {
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return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
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inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 new_value) {
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return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
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inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
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inline void MemoryBarrier() {
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pLinuxKernelMemoryBarrier();
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inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
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inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
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inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
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inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
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Atomic32 value = *ptr;
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inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
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} // namespace internal
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} // namespace protobuf
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} // namespace google
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#endif // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_