once.h

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/*
* Copyright (c) 2011-2012 MLBA-Team. All rights reserved.
*
* @MLBA_OPEN_LICENSE_HEADER_START@
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* @MLBA_OPEN_LICENSE_HEADER_END@
*/


#ifndef XDISPATCH_ONCE_H_
#define XDISPATCH_ONCE_H_

#ifndef __XDISPATCH_INDIRECT__
#error "Please #include <xdispatch/dispatch.h> instead of this file directly."
#endif

#include <iostream>

__XDISPATCH_BEGIN_NAMESPACE

class operation;

class XDISPATCH_EXPORT once {

    public:
        once();
        once( dispatch_once_t* );

        dispatch_once_t* native_once() const;

        void operator()(operation&);
#ifdef XDISPATCH_HAS_BLOCKS

        inline void operator()(dispatch_block_t b) {
            once_block op(b);
            operator()( op );
        }
#endif

    private:
        dispatch_once_t _once_obj;
        dispatch_once_t* _once;

#ifdef XDISPATCH_HAS_BLOCKS
        // we define our own block class
        // as the block_operation does a
        // copy of the stored block, something
        // we do not need in here
        class once_block : public operation {
            public:
                once_block(dispatch_block_t b)
                    : operation(), block( b ) {}

                void operator()() {
                    XDISPATCH_BLOCK_EXEC(block)();
                }

            private:
                dispatch_block_t block;
        };
#endif

        friend XDISPATCH_EXPORT std::ostream& operator<<(std::ostream&, const once& );
};

XDISPATCH_EXPORT std::ostream& operator<<(std::ostream&, const once* );
XDISPATCH_EXPORT std::ostream& operator<<(std::ostream&, const once& );

__XDISPATCH_END_NAMESPACE

#endif /* XDISPATCH_ONCE_H_ */