/*
    Copyright 2005-2012 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks.

    Threading Building Blocks is free software; you can redistribute it
    and/or modify it under the terms of the GNU General Public License
    version 2 as published by the Free Software Foundation.

    Threading Building Blocks is distributed in the hope that it will be
    useful, but WITHOUT ANY WARRANTY; without even the implied warranty
    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Threading Building Blocks; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    As a special exception, you may use this file as part of a free software
    library without restriction.  Specifically, if other files instantiate
    templates or use macros or inline functions from this file, or you compile
    this file and link it with other files to produce an executable, this
    file does not by itself cause the resulting executable to be covered by
    the GNU General Public License.  This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

#ifndef _TBB_scheduler_utility_H
#define _TBB_scheduler_utility_H

#include "scheduler.h"

namespace tbb {
namespace internal {

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

//! Smart holder for the empty task class with automatic destruction
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
//------------------------------------------------------------------------

//! Vector that grows without reallocations, and stores items in the reverse order.
/** Requires to initialize its first segment with a preallocated memory chunk
    (usually it is static array or an array allocated on the stack).
    The second template parameter specifies maximal number of segments. Each next 
    segment is twice as large as the previous one. **/
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), 1, NULL );
            __TBB_ASSERT ( m_num_segments < max_segments, "Maximal capacity exceeded" );
        }
        m_cur_segment[--m_pos] = val;
    }

    //! Copies the contents of the vector into the dst array. 
    /** Can only be used when T is a POD type, as copying does not invoke copy constructors. **/
    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:
    //! The current (not completely filled) segment
    T       *m_cur_segment;

    //! Capacity of m_cur_segment
    size_t  m_cur_segment_size;

    //! Insertion position in m_cur_segment
    size_t  m_pos;

    //! Array of segments (has fixed size specified by the second template parameter)
    T       *m_segments[max_segments];
    
    //! Number of segments (the size of m_segments)
    size_t  m_num_segments;

    //! Number of items in the segments in m_segments
    size_t  m_size;

}; // class fast_reverse_vector

} // namespace internal
} // namespace tbb

#endif /* _TBB_scheduler_utility_H */
