text: /*  Sirikata
   *  Liveness.cpp
   *
   *  Copyright (c) 2011, Stanford University
   *  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 Sirikata 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.
   */
  
  #include <sirikata/core/util/Liveness.hpp>
  
  namespace Sirikata {
  
  Liveness::Token::Token(InternalToken t)
   : mData(t)
  {}
  
  Liveness::Lock::Lock(InternalToken t)
   : mData(t.lock())
  {}
  
  Liveness::Lock::Lock(const Token& t)
   : mData(t.mData.lock())
  {}
  
  Liveness::Liveness()
   : mLivenessStrongToken(new int)
  {}
  
  Liveness::~Liveness() {
      assert(!mLivenessStrongToken && "You need to call letDie in the subclass of Liveness");
  }
  
  void Liveness::letDie() {
      // The basic strategy is to save a weak pointer to the token, clear the
      // strong pointer, and then block until we can't lock the weak pointer
      // anymore, i.e. when all strong pointers have disappeared, meaning no other
      // thread could see the object as alive anymore.
      assert(mLivenessStrongToken);
  
      InternalToken weak_self = mLivenessStrongToken;
      mLivenessStrongToken.reset();
      // busy wait
      while(weak_self.lock()) {}
  }
  
  }
  