buf_istream.h

/***************************************************************************
 * include/stxxl/bits/mng/buf_istream.h
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2002-2004 Roman Dementiev <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#ifndef STXXL_BUF_ISTREAM_HEADER
#define STXXL_BUF_ISTREAM_HEADER

#include <stxxl/bits/mng/config.h>
#include <stxxl/bits/mng/block_prefetcher.h>
#include <stxxl/bits/algo/async_schedule.h>


__STXXL_BEGIN_NAMESPACE



// a paranoid check
#define BUF_ISTREAM_CHECK_END


template <typename BlkTp_, typename BIDIteratorTp_>
class buf_istream
{
 typedef BlkTp_ block_type;
 typedef BIDIteratorTp_ bid_iterator_type;

 buf_istream() { }

protected:
 typedef block_prefetcher<block_type, bid_iterator_type> prefetcher_type;
 prefetcher_type * prefetcher;
 bid_iterator_type begin_bid, end_bid;
 int_type current_elem;
 block_type * current_blk;
 int_type * prefetch_seq;
#ifdef BUF_ISTREAM_CHECK_END
 bool not_finished;
#endif

public:
 typedef typename block_type::reference reference;
 typedef buf_istream<block_type, bid_iterator_type> _Self;

 buf_istream(bid_iterator_type _begin, bid_iterator_type _end, int_type nbuffers) :
 current_elem(0)
#ifdef BUF_ISTREAM_CHECK_END
 , not_finished(true)
#endif
 {
 //int_type i;
 const unsigned_type ndisks = config::get_instance()->disks_number();
 const int_type seq_length = _end - _begin;
 prefetch_seq = new int_type[seq_length];

 // obvious schedule
 //for(int_type i = 0; i< seq_length; ++i)
 // prefetch_seq[i] = i;

 // optimal schedule
 nbuffers = STXXL_MAX(2 * ndisks, unsigned_type(nbuffers - 1));
 compute_prefetch_schedule(_begin, _end, prefetch_seq,
 nbuffers, ndisks);


 prefetcher = new prefetcher_type(_begin, _end, prefetch_seq, nbuffers);

 current_blk = prefetcher->pull_block();
 }

 _Self & operator >> (reference record)
 {
#ifdef BUF_ISTREAM_CHECK_END
 assert(not_finished);
#endif

 record = current_blk->elem[current_elem++];

 if (current_elem >= block_type::size)
 {
 current_elem = 0;
#ifdef BUF_ISTREAM_CHECK_END
 not_finished = prefetcher->block_consumed(current_blk);
#else
 prefetcher->block_consumed(current_blk);
#endif
 }

 return (*this);
 }

 reference current() /* const */
 {
 return current_blk->elem[current_elem];
 }

 reference operator * () /* const */
 {
 return current_blk->elem[current_elem];
 }

 _Self & operator ++ ()
 {
#ifdef BUF_ISTREAM_CHECK_END
 assert(not_finished);
#endif

 current_elem++;

 if (current_elem >= block_type::size)
 {
 current_elem = 0;
#ifdef BUF_ISTREAM_CHECK_END
 not_finished = prefetcher->block_consumed(current_blk);
#else
 prefetcher->block_consumed(current_blk);
#endif
 }
 return *this;
 }

 virtual ~buf_istream()
 {
 delete prefetcher;
 delete[] prefetch_seq;
 }
};


__STXXL_END_NAMESPACE

#endif // !STXXL_BUF_ISTREAM_HEADER