scheduler_utility.h

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/*
    Copyright (c) 2005-2020 Intel Corporation

    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.
*/

#ifndef _TBB_scheduler_utility_H
#define _TBB_scheduler_utility_H

#include "scheduler.h"

namespace tbb {
namespace internal {

//------------------------------------------------------------------------
// auto_empty_task
//------------------------------------------------------------------------

class auto_empty_task {
    task* my_task;
    generic_scheduler* my_scheduler;
public:
    auto_empty_task ( __TBB_CONTEXT_ARG(generic_scheduler *s, task_group_context* context) )
        : my_task( new(&s->allocate_task(sizeof(empty_task), __TBB_CONTEXT_ARG(NULL, context))) empty_task )
        , my_scheduler(s)
    {}
    // empty_task has trivial destructor, so there's no need to call it.
    ~auto_empty_task () { my_scheduler->free_task<small_local_task>(*my_task); }

    operator task& () { return *my_task; }
    task* operator & () { return my_task; }
    task_prefix& prefix () { return my_task->prefix(); }
}; // class auto_empty_task

//------------------------------------------------------------------------
// fast_reverse_vector
//------------------------------------------------------------------------


template<typename T, size_t max_segments = 16>
class fast_reverse_vector
{
public:
    fast_reverse_vector ( T* initial_segment, size_t segment_size )
        : m_cur_segment(initial_segment)
        , m_cur_segment_size(segment_size)
        , m_pos(segment_size)
        , m_num_segments(0)
        , m_size(0)
    {
        __TBB_ASSERT ( initial_segment && segment_size, "Nonempty initial segment must be supplied");
    }

    ~fast_reverse_vector ()
    {
        for ( size_t i = 1; i < m_num_segments; ++i )
            NFS_Free( m_segments[i] );
    }

    size_t size () const { return m_size + m_cur_segment_size - m_pos; }

    void push_back ( const T& val )
    {
        if ( !m_pos ) {
            if ( !m_num_segments ) m_segments[m_num_segments++] = m_cur_segment;
            m_size += m_cur_segment_size;
            m_cur_segment_size *= 2;
            m_pos = m_cur_segment_size;
            m_segments[m_num_segments++] = m_cur_segment = (T*)NFS_Allocate( m_cur_segment_size, sizeof(T), NULL );
            __TBB_ASSERT ( m_num_segments < max_segments, "Maximal capacity exceeded" );
        }
        m_cur_segment[--m_pos] = val;
    }


    void copy_memory ( T* dst ) const
    {
        size_t sz = m_cur_segment_size - m_pos;
        memcpy( dst, m_cur_segment + m_pos, sz * sizeof(T) );
        dst += sz;
        sz = m_cur_segment_size / 2;
        for ( long i = (long)m_num_segments - 2; i >= 0; --i ) {
            memcpy( dst, m_segments[i], sz * sizeof(T) );
            dst += sz;
            sz /= 2;
        }
    }

protected:
    T       *m_cur_segment;

    size_t  m_cur_segment_size;

    size_t  m_pos;

    T       *m_segments[max_segments];

    size_t  m_num_segments;

    size_t  m_size;

}; // class fast_reverse_vector

} // namespace internal
} // namespace tbb

#endif /* _TBB_scheduler_utility_H */