libcore/include/sirikata/core/util/Liveness.hpp

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/*  Sirikata
 *  Liveness.hpp
 *
 *  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
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _SIRIKATA_CORE_UTIL_LIVENESS_TOKEN_HPP_
#define _SIRIKATA_CORE_UTIL_LIVENESS_TOKEN_HPP_

namespace Sirikata {

class SIRIKATA_EXPORT Liveness {
    typedef std::tr1::shared_ptr<int> StrongInternalToken;
    typedef std::tr1::weak_ptr<int> InternalToken;

  public:
    struct SIRIKATA_EXPORT Token {
        InternalToken mData;

        Token(InternalToken t);
        operator bool() const { return mData.lock(); }
    };

    struct SIRIKATA_EXPORT Lock {
        StrongInternalToken mData;

        Lock(InternalToken t);
        Lock(const Token& t);
        operator bool() const { return mData; }
    };

    Liveness();
    ~Liveness();

    Token livenessToken() const { return Token(mLivenessStrongToken); }

    void letDie();

  protected:
    bool livenessAlive() const { return mLivenessStrongToken; }

  private:
    StrongInternalToken mLivenessStrongToken;
};

}

#endif //_SIRIKATA_CORE_UTIL_LIVENESS_TOKEN_HPP_