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/* chert_positionlist.cc: A position list in a chert database.
*
* Copyright (C) 2004,2005,2006,2008,2010,2013 Olly Betts
*
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
* USA
*/
#include <config.h>
#include "chert_positionlist.h"
#include <xapian/types.h>
#include "bitstream.h"
#include "debuglog.h"
#include "pack.h"
#include <string>
#include <vector>
using namespace std;
void
ChertPositionListTable::set_positionlist(Xapian::docid did,
const string & tname,
Xapian::PositionIterator pos,
const Xapian::PositionIterator &pos_end,
bool check_for_update)
{
LOGCALL_VOID(DB, "ChertPositionListTable::set_positionlist", did | tname | pos | pos_end | check_for_update);
Assert(pos != pos_end);
// FIXME: avoid the need for this copy!
vector<Xapian::termpos> poscopy(pos, pos_end);
string key = make_key(did, tname);
string s;
pack_uint(s, poscopy.back());
if (poscopy.size() > 1) {
BitWriter wr(s);
wr.encode(poscopy[0], poscopy.back());
wr.encode(poscopy.size() - 2, poscopy.back() - poscopy[0]);
wr.encode_interpolative(poscopy, 0, poscopy.size() - 1);
swap(s, wr.freeze());
}
if (check_for_update) {
string old_tag;
if (get_exact_entry(key, old_tag) && s == old_tag)
return;
}
add(key, s);
}
Xapian::termcount
ChertPositionListTable::positionlist_count(Xapian::docid did,
const string & term) const
{
LOGCALL(DB, Xapian::termcount, "ChertPositionListTable::positionlist_count", did | term);
string data;
if (!get_exact_entry(make_key(did, term), data)) {
RETURN(0);
}
const char * pos = data.data();
const char * end = pos + data.size();
Xapian::termpos pos_last;
if (!unpack_uint(&pos, end, &pos_last)) {
throw Xapian::DatabaseCorruptError("Position list data corrupt");
}
if (pos == end) {
// Special case for single entry position list.
RETURN(1);
}
// Skip the header we just read.
BitReader rd(data, pos - data.data());
Xapian::termpos pos_first = rd.decode(pos_last);
Xapian::termpos pos_size = rd.decode(pos_last - pos_first) + 2;
RETURN(pos_size);
}
///////////////////////////////////////////////////////////////////////////
bool
ChertPositionList::read_data(const ChertTable * table, Xapian::docid did,
const string & tname)
{
LOGCALL(DB, bool, "ChertPositionList::read_data", table | did | tname);
have_started = false;
string data;
if (!table->get_exact_entry(ChertPositionListTable::make_key(did, tname), data)) {
// There's no positional information for this term.
size = 0;
last = 0;
current_pos = 1;
RETURN(false);
}
const char * pos = data.data();
const char * end = pos + data.size();
Xapian::termpos pos_last;
if (!unpack_uint(&pos, end, &pos_last)) {
throw Xapian::DatabaseCorruptError("Position list data corrupt");
}
if (pos == end) {
// Special case for single entry position list.
size = 1;
current_pos = last = pos_last;
RETURN(true);
}
// Skip the header we just read.
rd.init(data, pos - data.data());
Xapian::termpos pos_first = rd.decode(pos_last);
Xapian::termpos pos_size = rd.decode(pos_last - pos_first) + 2;
rd.decode_interpolative(0, pos_size - 1, pos_first, pos_last);
size = pos_size;
last = pos_last;
current_pos = pos_first;
RETURN(true);
}
Xapian::termcount
ChertPositionList::get_size() const
{
LOGCALL(DB, Xapian::termcount, "ChertPositionList::get_size", NO_ARGS);
RETURN(size);
}
Xapian::termpos
ChertPositionList::get_position() const
{
LOGCALL(DB, Xapian::termpos, "ChertPositionList::get_position", NO_ARGS);
Assert(have_started);
RETURN(current_pos);
}
void
ChertPositionList::next()
{
LOGCALL_VOID(DB, "ChertPositionList::next", NO_ARGS);
if (rare(!have_started)) {
have_started = true;
return;
}
if (current_pos == last) {
last = 0;
current_pos = 1;
return;
}
current_pos = rd.decode_interpolative_next();
}
void
ChertPositionList::skip_to(Xapian::termpos termpos)
{
LOGCALL_VOID(DB, "ChertPositionList::skip_to", termpos);
have_started = true;
if (termpos >= last) {
if (termpos == last) {
current_pos = last;
return;
}
last = 0;
current_pos = 1;
return;
}
while (current_pos < termpos) {
if (current_pos == last) {
last = 0;
current_pos = 1;
return;
}
current_pos = rd.decode_interpolative_next();
}
}
bool
ChertPositionList::at_end() const
{
LOGCALL(DB, bool, "ChertPositionList::at_end", NO_ARGS);
Assert(have_started);
RETURN(current_pos > last);
}
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