// Copyright 2003 Google Inc.

// All Rights Reserved.

//

// For atomic operations on statistics counters, see atomic_stats_counter.h.

// For atomic operations on sequence numbers, see atomic_sequence_num.h.

// For atomic operations on reference counts, see atomic_refcount.h.

// Some fast atomic operations -- typically with machine-dependent

// implementations.  This file may need editing as Google code is

// ported to different architectures.

// 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 architectures will cause your code to break.  If you

// do not know what you are doing, avoid these routines, and use a Mutex.

//

// 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(),

// addition, exchange, a load, or a store with appropriate memory-ordering

// instructions.  "Acquire" operations ensure that no later memory access by

// the same thread can be reordered ahead of the operation.  "Release"

// operations ensure that no previous memory access by the same thread can be

// reordered after the operation.  "Barrier" operations have both "Acquire" and

// "Release" semantics.  A MemoryBarrier() has "Barrier" semantics, but does no

// memory access.  "NoBarrier" operations have no barrier:  the CPU is

// permitted to reorder them freely (as seen by other threads), even in ways

// the appear to violate functional dependence, just as it can for any normal

// variable access.

//

// 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.  Moreover, if you choose to use base::subtle::Atomic64 type,

// you MUST use one of the Load or Store routines to get correct behavior

// on 32-bit platforms.

//

// The intent is eventually to put all of these routines in namespace

// base::subtle

#pragma once

#include <stdint.h>

// ------------------------------------------------------------------------

// Include the platform specific implementations of the types

// and operations listed below.  Implementations are to provide Atomic32

// and Atomic64 operations. If there is a mismatch between intptr_t and

// the Atomic32 or Atomic64 types for a platform, the platform-specific header

// should define the macro, AtomicWordCastType in a clause similar to the

// following:

// #if ...pointers are 64 bits...

// # define AtomicWordCastType base::subtle::Atomic64

// #else

// # define AtomicWordCastType Atomic32

// #endif

// ------------------------------------------------------------------------

#define GUTILS_GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)

#define GUTILS_CLANG_VERSION \

    (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__)

// ThreadSanitizer provides own implementation of atomicops.

#if defined(THREAD_SANITIZER)

#include "gutil/atomicops-internals-tsan.h" // IWYU pragma: export

#elif defined(__GNUC__) && (defined(__i386) || defined(__x86_64__))

#include "gutil/atomicops-internals-x86.h" // IWYU pragma: export

#elif defined(__GNUC__) && GUTILS_GCC_VERSION >= 40700

#include "gutil/atomicops-internals-gcc.h" // IWYU pragma: export

#elif defined(__clang__) && GUTILS_CLANG_VERSION >= 30400

#include "gutil/atomicops-internals-gcc.h" // IWYU pragma: export

#else

#error You need to implement atomic operations for this architecture

#endif

// Signed type that can hold a pointer and supports the atomic ops below, as

// well as atomic loads and stores.  Instances must be naturally-aligned.

typedef intptr_t AtomicWord;

#ifdef AtomicWordCastType

// ------------------------------------------------------------------------

// This section is needed only when explicit type casting is required to

// cast AtomicWord to one of the basic atomic types (Atomic64 or Atomic32).

// It also serves to document the AtomicWord interface.

// ------------------------------------------------------------------------

namespace base {

namespace subtle {

// 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.

inline AtomicWord NoBarrier_CompareAndSwap(volatile AtomicWord* ptr, AtomicWord old_value,

                                           AtomicWord new_value) {

    return NoBarrier_CompareAndSwap(reinterpret_cast<volatile AtomicWordCastType*>(ptr), old_value,

                                    new_value);

}

// Atomically store new_value into *ptr, returning the previous value held in

// *ptr.  This routine implies no memory barriers.

inline AtomicWord NoBarrier_AtomicExchange(volatile AtomicWord* ptr, AtomicWord new_value) {

    return NoBarrier_AtomicExchange(reinterpret_cast<volatile AtomicWordCastType*>(ptr), new_value);

}

inline AtomicWord Acquire_AtomicExchange(volatile AtomicWord* ptr, AtomicWord new_value) {

    return Acquire_AtomicExchange(reinterpret_cast<volatile AtomicWordCastType*>(ptr), new_value);

}

inline AtomicWord Release_AtomicExchange(volatile AtomicWord* ptr, AtomicWord new_value) {

    return Release_AtomicExchange(reinterpret_cast<volatile AtomicWordCastType*>(ptr), new_value);

}

// Atomically increment *ptr by "increment".  Returns the new value of

// *ptr with the increment applied.  This routine implies no memory

// barriers.

inline AtomicWord NoBarrier_AtomicIncrement(volatile AtomicWord* ptr, AtomicWord increment) {

    return NoBarrier_AtomicIncrement(reinterpret_cast<volatile AtomicWordCastType*>(ptr),

                                     increment);

}

inline AtomicWord Barrier_AtomicIncrement(volatile AtomicWord* ptr, AtomicWord increment) {

    return Barrier_AtomicIncrement(reinterpret_cast<volatile AtomicWordCastType*>(ptr), increment);

}

inline AtomicWord Acquire_CompareAndSwap(volatile AtomicWord* ptr, AtomicWord old_value,

                                         AtomicWord new_value) {

    return base::subtle::Acquire_CompareAndSwap(reinterpret_cast<volatile AtomicWordCastType*>(ptr),

                                                old_value, new_value);

}

inline AtomicWord Release_CompareAndSwap(volatile AtomicWord* ptr, AtomicWord old_value,

                                         AtomicWord new_value) {

    return base::subtle::Release_CompareAndSwap(reinterpret_cast<volatile AtomicWordCastType*>(ptr),

                                                old_value, new_value);

}

inline void NoBarrier_Store(volatile AtomicWord* ptr, AtomicWord value) {

    NoBarrier_Store(reinterpret_cast<volatile AtomicWordCastType*>(ptr), value);

}

inline void Acquire_Store(volatile AtomicWord* ptr, AtomicWord value) {

    return base::subtle::Acquire_Store(reinterpret_cast<volatile AtomicWordCastType*>(ptr), value);

}

inline void Release_Store(volatile AtomicWord* ptr, AtomicWord value) {

    return base::subtle::Release_Store(reinterpret_cast<volatile AtomicWordCastType*>(ptr), value);

}

inline AtomicWord NoBarrier_Load(volatile const AtomicWord* ptr) {

    return NoBarrier_Load(reinterpret_cast<volatile const AtomicWordCastType*>(ptr));

}

inline AtomicWord Acquire_Load(volatile const AtomicWord* ptr) {

    return base::subtle::Acquire_Load(reinterpret_cast<volatile const AtomicWordCastType*>(ptr));

}

inline AtomicWord Release_Load(volatile const AtomicWord* ptr) {

    return base::subtle::Release_Load(reinterpret_cast<volatile const AtomicWordCastType*>(ptr));

}

} // namespace subtle

} // namespace base

#endif // AtomicWordCastType

// ------------------------------------------------------------------------

// Commented out type definitions and method declarations for documentation

// of the interface provided by this module.

// ------------------------------------------------------------------------

// ------------------------------------------------------------------------

// The following are to be deprecated when all uses have been changed to

// use the base::subtle namespace.

// ------------------------------------------------------------------------

#ifdef AtomicWordCastType

// AtomicWord versions to be deprecated

inline AtomicWord Acquire_CompareAndSwap(volatile AtomicWord* ptr, AtomicWord old_value,

                                         AtomicWord new_value) {

    return base::subtle::Acquire_CompareAndSwap(ptr, old_value, new_value);

}

inline AtomicWord Release_CompareAndSwap(volatile AtomicWord* ptr, AtomicWord old_value,

                                         AtomicWord new_value) {

    return base::subtle::Release_CompareAndSwap(ptr, old_value, new_value);

}

inline void Acquire_Store(volatile AtomicWord* ptr, AtomicWord value) {

    return base::subtle::Acquire_Store(ptr, value);

}

inline void Release_Store(volatile AtomicWord* ptr, AtomicWord value) {

    return base::subtle::Release_Store(ptr, value);

}

inline AtomicWord Acquire_Load(volatile const AtomicWord* ptr) {

    return base::subtle::Acquire_Load(ptr);

}

inline AtomicWord Release_Load(volatile const AtomicWord* ptr) {

    return base::subtle::Release_Load(ptr);

}

#endif // AtomicWordCastType

// 32-bit Acquire/Release operations to be deprecated.

inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, Atomic32 old_value,

                                       Atomic32 new_value) {

    return base::subtle::Acquire_CompareAndSwap(ptr, old_value, new_value);

}

inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, Atomic32 old_value,

                                       Atomic32 new_value) {

    return base::subtle::Release_CompareAndSwap(ptr, old_value, new_value);

}

inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {

    base::subtle::Acquire_Store(ptr, value);

}

inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {

    return base::subtle::Release_Store(ptr, value);

}

inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {

    return base::subtle::Acquire_Load(ptr);

}

inline Atomic32 Release_Load(volatile const Atomic32* ptr) {

    return base::subtle::Release_Load(ptr);

}

// 64-bit Acquire/Release operations to be deprecated.

inline base::subtle::Atomic64 Acquire_CompareAndSwap(volatile base::subtle::Atomic64* ptr,

                                                     base::subtle::Atomic64 old_value,

                                                     base::subtle::Atomic64 new_value) {

    return base::subtle::Acquire_CompareAndSwap(ptr, old_value, new_value);

}

inline base::subtle::Atomic64 Release_CompareAndSwap(volatile base::subtle::Atomic64* ptr,

                                                     base::subtle::Atomic64 old_value,

                                                     base::subtle::Atomic64 new_value) {

    return base::subtle::Release_CompareAndSwap(ptr, old_value, new_value);

}

inline void Acquire_Store(volatile base::subtle::Atomic64* ptr, base::subtle::Atomic64 value) {

    base::subtle::Acquire_Store(ptr, value);

}

inline void Release_Store(volatile base::subtle::Atomic64* ptr, base::subtle::Atomic64 value) {

    return base::subtle::Release_Store(ptr, value);

}

inline base::subtle::Atomic64 Acquire_Load(volatile const base::subtle::Atomic64* ptr) {

    return base::subtle::Acquire_Load(ptr);

}

inline base::subtle::Atomic64 Release_Load(volatile const base::subtle::Atomic64* ptr) {

    return base::subtle::Release_Load(ptr);

}