text: // Copyright (c) 2014 Marshall A. Greenblatt. Portions copyright (c) 2011
  // Google Inc. All rights reserved.
  //
  // 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 name Chromium Embedded
  // Framework 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 is a low level implementation of atomic semantics for reference
  // counting.  Please use cef_ref_counted.h directly instead.
  //
  // The Chromium implementation includes annotations to avoid some false
  // positives when using data race detection tools. Annotations are not
  // currently supported by the CEF implementation.
  
  #ifndef CEF_INCLUDE_BASE_CEF_ATOMIC_REF_COUNT_H_
  #define CEF_INCLUDE_BASE_CEF_ATOMIC_REF_COUNT_H_
  #pragma once
  
  #if defined(BASE_ATOMIC_REF_COUNT_H_)
  // Do nothing if the Chromium header has already been included.
  // This can happen in cases where Chromium code is used directly by the
  // client application. When using Chromium code directly always include
  // the Chromium header first to avoid type conflicts.
  #elif defined(BUILDING_CEF_SHARED)
  // When building CEF include the Chromium header directly.
  #include "base/atomic_ref_count.h"
  #else  // !BUILDING_CEF_SHARED
  // The following is substantially similar to the Chromium implementation.
  // If the Chromium implementation diverges the below implementation should be
  // updated to match.
  
  #include "include/base/cef_atomicops.h"
  
  // Annotations are not currently supported.
  #define ANNOTATE_HAPPENS_BEFORE(obj) /* empty */
  #define ANNOTATE_HAPPENS_AFTER(obj) /* empty */
  
  namespace base {
  
  typedef subtle::Atomic32 AtomicRefCount;
  
  // Increment a reference count by "increment", which must exceed 0.
  inline void AtomicRefCountIncN(volatile AtomicRefCount *ptr,
                                 AtomicRefCount increment) {
    subtle::NoBarrier_AtomicIncrement(ptr, increment);
  }
  
  // Decrement a reference count by "decrement", which must exceed 0,
  // and return whether the result is non-zero.
  // Insert barriers to ensure that state written before the reference count
  // became zero will be visible to a thread that has just made the count zero.
  inline bool AtomicRefCountDecN(volatile AtomicRefCount *ptr,
                                 AtomicRefCount decrement) {
    ANNOTATE_HAPPENS_BEFORE(ptr);
    bool res = (subtle::Barrier_AtomicIncrement(ptr, -decrement) != 0);
    if (!res) {
      ANNOTATE_HAPPENS_AFTER(ptr);
    }
    return res;
  }
  
  // Increment a reference count by 1.
  inline void AtomicRefCountInc(volatile AtomicRefCount *ptr) {
    base::AtomicRefCountIncN(ptr, 1);
  }
  
  // Decrement a reference count by 1 and return whether the result is non-zero.
  // Insert barriers to ensure that state written before the reference count
  // became zero will be visible to a thread that has just made the count zero.
  inline bool AtomicRefCountDec(volatile AtomicRefCount *ptr) {
    return base::AtomicRefCountDecN(ptr, 1);
  }
  
  // Return whether the reference count is one.  If the reference count is used
  // in the conventional way, a refrerence count of 1 implies that the current
  // thread owns the reference and no other thread shares it.  This call performs
  // the test for a reference count of one, and performs the memory barrier
  // needed for the owning thread to act on the object, knowing that it has
  // exclusive access to the object.
  inline bool AtomicRefCountIsOne(volatile AtomicRefCount *ptr) {
    bool res = (subtle::Acquire_Load(ptr) == 1);
    if (res) {
      ANNOTATE_HAPPENS_AFTER(ptr);
    }
    return res;
  }
  
  // Return whether the reference count is zero.  With conventional object
  // referencing counting, the object will be destroyed, so the reference count
  // should never be zero.  Hence this is generally used for a debug check.
  inline bool AtomicRefCountIsZero(volatile AtomicRefCount *ptr) {
    bool res = (subtle::Acquire_Load(ptr) == 0);
    if (res) {
      ANNOTATE_HAPPENS_AFTER(ptr);
    }
    return res;
  }
  
  }  // namespace base
  
  #endif  // !BUILDING_CEF_SHARED
  
  #endif  // CEF_INCLUDE_BASE_CEF_ATOMIC_REF_COUNT_H_
  