File: index_segment.c

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/*
**      SWISH++
**      index_segment.c
**
**      Copyright (C) 1998  Paul J. Lucas
**
**      This program is free software; you can redistribute it and/or modify
**      it under the terms of the GNU General Public License as published by
**      the Free Software Foundation; either version 2 of the License, or
**      (at your option) any later version.
**
**      This program 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 this program; if not, write to the Free Software
**      Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

// local
#include "index_segment.h"

using namespace PJL;

//*****************************************************************************
//
// SYNOPSIS
//
        void index_segment::set_index_file(
            mmap_file const &file, segment_id id
        )
//
// DESCRIPTION
//
//      Set the index file to use by setting data members to the proper
//      positions within the index file.
//
// CAVEAT
//
//      Ideally, this function would be part of the constructor, but the name
//      of the index file can be passed in via the command line and that isn't
//      parsed until after the instance is constructed.
//
// SEE ALSO
//
//      index.c     write_full_index() -- format of index file
//
//*****************************************************************************
{
    register mmap_file::const_iterator c = begin_ = file.begin();
    register size_type const *p = reinterpret_cast<size_type const*>( c );
    num_entries_ = p[ 0 ];
    for ( int i = id; i > 0; --i ) {
        c += sizeof( num_entries_ ) + num_entries_ * sizeof( off_t );
        p = reinterpret_cast<size_type const*>( c );
        num_entries_ = p[ 0 ];
    }
    offset_ = reinterpret_cast<off_t const*>( &p[ 1 ] );
}
/* vim:set et sw=4 ts=4: */