merge_sorted_runs.h

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// -*- mode: c++; tab-width: 4; indent-tabs-mode: t; c-file-style: "stroustrup"; -*-
// vi:set ts=4 sts=4 sw=4 noet :
// Copyright 2008, The TPIE development team
// 
// This file is part of TPIE.
// 
// TPIE is free software: you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License as published by the
// Free Software Foundation, either version 3 of the License, or (at your
// option) any later version.
// 
// TPIE 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 Lesser General Public
// License for more details.
// 
// You should have received a copy of the GNU Lesser General Public License
// along with TPIE.  If not, see <http://www.gnu.org/licenses/>

#ifndef _MERGE_SORTED_RUNS_H
#define _MERGE_SORTED_RUNS_H


// Get definitions for working with Unix and Windows
#include <tpie/portability.h>

// Includes needed from TPIE
#include <tpie/mergeheap.h>     //For templated heaps

#include <tpie/progress_indicator_base.h>


namespace tpie {

    namespace ami {

        typedef TPIE_OS_SIZE_T arity_t;
    
        template <class T, class M>
        void merge_sorted_runs(typename tpie::array<tpie::auto_ptr<file_stream<T> > >::iterator start,
                               typename tpie::array<tpie::auto_ptr<file_stream<T> > >::iterator end,
                               file_stream<T> *outStream,  M* MergeHeap,
                               TPIE_OS_OFFSET cutoff=-1, 
                               progress_indicator_base* indicator = NULL) {
        
            size_t i;
            size_t arity = end-start;

            //Pointers to current leading elements of streams
            tpie::array<const T *> in_objects(arity);
            tpie::array<TPIE_OS_OFFSET> nread(arity);
            
            // **************************************************************
            // * Read first element from stream. Do not rewind! We may read *
            // * more elements from the same stream later.                  *
            // **************************************************************

            for (i = 0; i < arity; i++) {
                file_stream<T> * stream = (start+i)->get();
                if (stream->can_read()) {
                    in_objects[i] = &stream->read();
                    MergeHeap->insert( in_objects[i], i );
                } else 
                    in_objects[i] = NULL;
                nread[i] = 1;
                if (indicator) indicator->step();
            }

            // *********************************************************
            // * Build a heap from the smallest items of each stream   *
            // *********************************************************
        
            MergeHeap->initialize ( );

            // *********************************************************
            // * Perform the merge until the inputs are exhausted.     *
            // *********************************************************
            while (MergeHeap->sizeofheap() > 0) {
                i = MergeHeap->get_min_run_id ();
                outStream->write(*in_objects[i]);

                bool eof = false;
        
                //Check if we read as many elements as we are allowed to
                if ( (cutoff != -1) && (nread[i]>=cutoff))
                    eof = true;
                else {
                    file_stream<T> * stream = (start+i)->get();
                    if (stream->can_read()) in_objects[i] = &stream->read();
                    else eof = true;
            
                    if (indicator) indicator->step();
                } 
        
                if (eof)
                    MergeHeap->delete_min_and_insert(NULL);
                else { 
                    nread[i]++;
                    MergeHeap->delete_min_and_insert (in_objects[i]);
                }
            }  //  while
        }
    
    
        template <class T, class CMPR>
        void merge_sorted(typename tpie::array<std::auto_ptr<file_stream<T> > >::iterator start,
                         typename tpie::array<std::auto_ptr<file_stream<T> > >::iterator end,
                         file_stream<T> *outStream, CMPR *cmp) {
        
            // make a merge heap which uses the user's comparison object
            // and initialize it
            merge_heap_obj<T,CMPR> mrgheap (cmp);
            mrgheap.allocate(end-start);
        
            //Rewind all the input streams
            for (typename tpie::array<std::auto_ptr<file_stream<T> > >::iterator i=start; 
                 i != end; ++i)
                i->seek(0); 
        
            merge_sorted_runs(start, end, outStream, mrgheap);
        }

    
        template <class T, class CMPR>
        void ptr_merge_sorted(typename tpie::array<tpie::auto_ptr<file_stream<T> > >::iterator start,
                             typename tpie::array<tpie::auto_ptr<file_stream<T> > >::iterator end,
                             file_stream<T> *outStream, 
                             CMPR *cmp) {

            // make a merge heap of pointers which uses the user's comparison
            // object and initialize it
            merge_heap_ptr_obj<T,CMPR> mrgheap (cmp);
            mrgheap.allocate(end-start);
        
            // Rewind all the input streams
            for (typename tpie::array<std::auto_ptr<file_stream<T> > >::iteratorarity_t i=start; 
                 i != end; ++i)
                i->seek(0); 
        
            merge_sorted_runs(start, end, outStream, mrgheap);
        }
    }  //  ami namespace
    
}  //  tpie namespace

#endif //_MERGE_SORTED_RUNS_H