The Tor Browser: ipc/chromium/src/base/atomic_ref

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     1 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.

     2 // Use of this source code is governed by a BSD-style license that can be

     3 // found in the LICENSE file.

     5 // This is a low level implementation of atomic semantics for reference

     6 // counting.  Please use base/ref_counted.h directly instead.

     8 #ifndef BASE_ATOMIC_REF_COUNT_H_

     9 #define BASE_ATOMIC_REF_COUNT_H_

    11 #include "base/atomicops.h"

    13 namespace base {

    15 typedef subtle::Atomic32 AtomicRefCount;

    17 // Increment a reference count by "increment", which must exceed 0.

    18 inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr,

    19                                AtomicRefCount increment) {

    20   subtle::NoBarrier_AtomicIncrement(ptr, increment);

    21 }

    23 // Decrement a reference count by "decrement", which must exceed 0,

    24 // and return whether the result is non-zero.

    25 // Insert barriers to ensure that state written before the reference count

    26 // became zero will be visible to a thread that has just made the count zero.

    27 inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr,

    28                                AtomicRefCount decrement) {

    29   return subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0;

    30 }

    32 // Increment a reference count by 1.

    33 inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) {

    34   base::AtomicRefCountIncN(ptr, 1);

    35 }

    37 // Decrement a reference count by 1 and return whether the result is non-zero.

    38 // Insert barriers to ensure that state written before the reference count

    39 // became zero will be visible to a thread that has just made the count zero.

    40 inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) {

    41   return base::AtomicRefCountDecN(ptr, 1);

    42 }

    44 // Return whether the reference count is one.  If the reference count is used

    45 // in the conventional way, a refrerence count of 1 implies that the current

    46 // thread owns the reference and no other thread shares it.  This call performs

    47 // the test for a reference count of one, and performs the memory barrier

    48 // needed for the owning thread to act on the object, knowing that it has

    49 // exclusive access to the object.

    50 inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) {

    51   return subtle::Acquire_Load(ptr) == 1;

    52 }

    54 // Return whether the reference count is zero.  With conventional object

    55 // referencing counting, the object will be destroyed, so the reference count

    56 // should never be zero.  Hence this is generally used for a debug check.

    57 inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) {

    58   return subtle::Acquire_Load(ptr) == 0;

    59 }

    61 }  // namespace base

    63 #endif  // BASE_ATOMIC_REF_COUNT_H_

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