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/*
** SWISH++
** index_segment.h
**
** 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.
*/
#ifndef index_segment_H
#define index_segment_H
// standard
#include <cstddef> /* for ptrdiff_t */
#include <iterator>
#include <sys/types.h> /* for off_t */
// local
#include "mmap_file.h"
//*****************************************************************************
//
// SYNOPSIS
//
class index_segment
//
// DESCRIPTION
//
// An instance of this class is used to access either the word, stop-word,
// file, or meta-name index portions of a generated index.
//
// By implementing fully-blown random access iterators for it, the STL
// algorithms work, in particular binary_search() and equal_range() that
// are used to do look ups.
//
//*****************************************************************************
{
public:
////////// typedefs ///////////////////////////////////////////////////////
typedef unsigned long size_type;
typedef ptrdiff_t difference_type;
typedef char const* value_type;
typedef char const** const_pointer;
typedef char const* const_reference;
enum segment_id {
isi_word = 0,
isi_stop_word = 1,
isi_dir = 2,
isi_file = 3,
isi_meta_name = 4
};
////////// constructors ///////////////////////////////////////////////////
index_segment() { }
index_segment( PJL::mmap_file const &file, segment_id id ) {
set_index_file( file, id );
}
////////// member functions ///////////////////////////////////////////////
void set_index_file( PJL::mmap_file const&, segment_id );
size_type size() const { return num_entries_; }
const_reference operator[]( size_type i ) const {
return begin_ + offset_[ i ];
}
////////// iterators //////////////////////////////////////////////////////
class const_iterator;
friend class const_iterator;
class const_iterator :
public std::iterator< std::random_access_iterator_tag, value_type > {
private:
index_segment const *index_;
size_type i_;
const_iterator( index_segment const *index, size_type i ) :
index_( index ), i_( i ) { }
friend class index_segment;
public:
const_iterator() { }
const_reference operator*() const { return (*index_)[ i_ ]; }
const_iterator& operator++() {
return ++i_, *this;
}
const_iterator& operator--() {
return --i_, *this;
}
const_iterator operator++(int) {
return const_iterator( index_, i_++ );
}
const_iterator operator--(int) {
return const_iterator( index_, i_-- );
}
const_iterator& operator+=( int n ) {
return i_ += n, *this;
}
const_iterator& operator-=( int n ) {
return i_ -= n, *this;
}
friend bool
operator==( const_iterator const &i, const_iterator const &j ) {
return i.i_ == j.i_;
}
friend bool
operator!=( const_iterator const &i, const_iterator const &j ) {
return !( i == j );
}
friend const_iterator
operator+( const_iterator const &i, int n ) {
return const_iterator( i.index_, i.i_ + n );
}
friend const_iterator
operator-( const_iterator const &i, int n ) {
return const_iterator( i.index_, i.i_ - n );
}
friend difference_type
operator-( const_iterator const &i, const_iterator const &j ) {
return i.i_ - j.i_;
}
// default copy constructor is OK
// default assignment operator is OK
};
const_iterator begin() const {
return const_iterator( this, 0 );
}
const_iterator end() const {
return const_iterator( this, num_entries_ );
}
private:
PJL::mmap_file::const_iterator begin_;
size_type num_entries_;
off_t const *offset_;
};
#endif /* index_segment_H */
/* vim:set et sw=4 ts=4: */
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