text: // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
  /* Copyright (c) 2010, 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 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 part spinlock.cc and once.cc
   * It may not be used directly by code outside of //base.
   */
  
  #pragma once
  
  #include "gutil/atomicops.h"
  #include "gutil/basictypes.h"
  
  namespace base {
  namespace internal {
  
  // SpinLockWait() waits until it can perform one of several transitions from
  // "from" to "to".  It returns when it performs a transition where done==true.
  struct SpinLockWaitTransition {
      int32 from;
      int32 to;
      bool done;
  };
  
  // Wait until *w can transition from trans[i].from to trans[i].to for some i
  // satisfying 0<=i<n && trans[i].done, atomically make the transition,
  // then return the old value of *w.   Make any other atomic tranistions
  // where !trans[i].done, but continue waiting.
  int32 SpinLockWait(volatile Atomic32* w, int n, const SpinLockWaitTransition trans[]);
  void SpinLockWake(volatile Atomic32* w, bool all);
  void SpinLockDelay(volatile Atomic32* w, int32 value, int loop);
  
  } // namespace internal
  } // namespace base
  