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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.
// This file is an internal atomic implementation, use atomicops.h instead.
//
// LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears.
#ifndef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_
#define GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_
namespace google {
namespace protobuf {
namespace internal {
// 0xffff0fc0 is the hard coded address of a function provided by
// the kernel which implements an atomic compare-exchange. On older
// ARM architecture revisions (pre-v6) this may be implemented using
// a syscall. This address is stable, and in active use (hard coded)
// by at least glibc-2.7 and the Android C library.
typedef Atomic32 (*LinuxKernelCmpxchgFunc)(Atomic32 old_value,
Atomic32 new_value,
volatile Atomic32* ptr);
LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak)) =
(LinuxKernelCmpxchgFunc) 0xffff0fc0;
typedef void (*LinuxKernelMemoryBarrierFunc)(void);
LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
(LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
Atomic32 prev_value = *ptr;
do {
if (!pLinuxKernelCmpxchg(old_value, new_value,
const_cast<Atomic32*>(ptr))) {
return old_value;
}
prev_value = *ptr;
} while (prev_value == old_value);
return prev_value;
}
inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
Atomic32 new_value) {
Atomic32 old_value;
do {
old_value = *ptr;
} while (pLinuxKernelCmpxchg(old_value, new_value,
const_cast<Atomic32*>(ptr)));
return old_value;
}
inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
Atomic32 increment) {
return Barrier_AtomicIncrement(ptr, increment);
}
inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
Atomic32 increment) {
for (;;) {
// Atomic exchange the old value with an incremented one.
Atomic32 old_value = *ptr;
Atomic32 new_value = old_value + increment;
if (pLinuxKernelCmpxchg(old_value, new_value,
const_cast<Atomic32*>(ptr)) == 0) {
// The exchange took place as expected.
return new_value;
}
// Otherwise, *ptr changed mid-loop and we need to retry.
}
}
inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
}
inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
}
inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
*ptr = value;
}
inline void MemoryBarrier() {
pLinuxKernelMemoryBarrier();
}
inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
*ptr = value;
MemoryBarrier();
}
inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
MemoryBarrier();
*ptr = value;
}
inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
return *ptr;
}
inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
Atomic32 value = *ptr;
MemoryBarrier();
return value;
}
inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
MemoryBarrier();
return *ptr;
}
} // namespace internal
} // namespace protobuf
} // namespace google
#endif // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_ARM_GCC_H_
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