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    Copyright 2005-2018 Intel Corporation.  All Rights Reserved.

    The source code contained or described herein and all documents related
    to the source code ("Material") are owned by Intel Corporation or its
    suppliers or licensors.  Title to the Material remains with Intel
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    by worldwide copyright laws and treaty provisions.  No part of the
    Material may be used, copied, reproduced, modified, published, uploaded,
    posted, transmitted, distributed, or disclosed in any way without
    Intel's prior express written permission.

    No license under any patent, copyright, trade secret or other
    intellectual property right is granted to or conferred upon you by
    disclosure or delivery of the Materials, either expressly, by
    implication, inducement, estoppel or otherwise.  Any license under such
    intellectual property rights must be express and approved by Intel in
    writing.
*/

#ifndef __TBB_parallel_while
#define __TBB_parallel_while

#include "task.h"
#include <new>

namespace tbb {

template<typename Body>
class parallel_while;

//! @cond INTERNAL
namespace internal {

    template<typename Stream, typename Body> class while_task;

    //! For internal use only.
    /** Executes one iteration of a while.
        @ingroup algorithms */
    template<typename Body>
    class while_iteration_task: public task {
        const Body& my_body;
        typename Body::argument_type my_value;
        task* execute() __TBB_override {
            my_body(my_value);
            return NULL;
        }
        while_iteration_task( const typename Body::argument_type& value, const Body& body ) :
            my_body(body), my_value(value)
        {}
        template<typename Body_> friend class while_group_task;
        friend class tbb::parallel_while<Body>;
    };

    //! For internal use only
    /** Unpacks a block of iterations.
        @ingroup algorithms */
    template<typename Body>
    class while_group_task: public task {
        static const size_t max_arg_size = 4;
        const Body& my_body;
        size_t size;
        typename Body::argument_type my_arg[max_arg_size];
        while_group_task( const Body& body ) : my_body(body), size(0) {}
        task* execute() __TBB_override {
            typedef while_iteration_task<Body> iteration_type;
            __TBB_ASSERT( size>0, NULL );
            task_list list;
            task* t;
            size_t k=0;
            for(;;) {
                t = new( allocate_child() ) iteration_type(my_arg[k],my_body);
                if( ++k==size ) break;
                list.push_back(*t);
            }
            set_ref_count(int(k+1));
            spawn(list);
            spawn_and_wait_for_all(*t);
            return NULL;
        }
        template<typename Stream, typename Body_> friend class while_task;
    };

    //! For internal use only.
    /** Gets block of iterations from a stream and packages them into a while_group_task.
        @ingroup algorithms */
    template<typename Stream, typename Body>
    class while_task: public task {
        Stream& my_stream;
        const Body& my_body;
        empty_task& my_barrier;
        task* execute() __TBB_override {
            typedef while_group_task<Body> block_type;
            block_type& t = *new( allocate_additional_child_of(my_barrier) ) block_type(my_body);
            size_t k=0;
            while( my_stream.pop_if_present(t.my_arg[k]) ) {
                if( ++k==block_type::max_arg_size ) {
                    // There might be more iterations.
                    recycle_to_reexecute();
                    break;
                }
            }
            if( k==0 ) {
                destroy(t);
                return NULL;
            } else {
                t.size = k;
                return &t;
            }
        }
        while_task( Stream& stream, const Body& body, empty_task& barrier ) :
            my_stream(stream),
            my_body(body),
            my_barrier(barrier)
        {}
        friend class tbb::parallel_while<Body>;
    };

} // namespace internal
//! @endcond

//! Parallel iteration over a stream, with optional addition of more work.
/** The Body b has the requirement: \n
        "b(v)"                      \n
        "b.argument_type"           \n
    where v is an argument_type
    @ingroup algorithms */
template<typename Body>
class parallel_while: internal::no_copy {
public:
    //! Construct empty non-running parallel while.
    parallel_while() : my_body(NULL), my_barrier(NULL) {}

    //! Destructor cleans up data members before returning.
    ~parallel_while() {
        if( my_barrier ) {
            my_barrier->destroy(*my_barrier);
            my_barrier = NULL;
        }
    }

    //! Type of items
    typedef typename Body::argument_type value_type;

    //! Apply body.apply to each item in the stream.
    /** A Stream s has the requirements \n
         "S::value_type"                \n
         "s.pop_if_present(value) is convertible to bool */
    template<typename Stream>
    void run( Stream& stream, const Body& body );

    //! Add a work item while running.
    /** Should be executed only by body.apply or a thread spawned therefrom. */
    void add( const value_type& item );

private:
    const Body* my_body;
    empty_task* my_barrier;
};

template<typename Body>
template<typename Stream>
void parallel_while<Body>::run( Stream& stream, const Body& body ) {
    using namespace internal;
    empty_task& barrier = *new( task::allocate_root() ) empty_task();
    my_body = &body;
    my_barrier = &barrier;
    my_barrier->set_ref_count(2);
    while_task<Stream,Body>& w = *new( my_barrier->allocate_child() ) while_task<Stream,Body>( stream, body, barrier );
    my_barrier->spawn_and_wait_for_all(w);
    my_barrier->destroy(*my_barrier);
    my_barrier = NULL;
    my_body = NULL;
}

template<typename Body>
void parallel_while<Body>::add( const value_type& item ) {
    __TBB_ASSERT(my_barrier,"attempt to add to parallel_while that is not running");
    typedef internal::while_iteration_task<Body> iteration_type;
    iteration_type& i = *new( task::allocate_additional_child_of(*my_barrier) ) iteration_type(item,*my_body);
    task::self().spawn( i );
}

} // namespace

#endif /* __TBB_parallel_while */
