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/** @file chert_valuelist.cc
* @brief Chert class for value streams.
*/
/* Copyright (C) 2007,2008 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_valuelist.h"
#include "chert_cursor.h"
#include "chert_database.h"
#include "omassert.h"
#include "str.h"
using namespace std;
bool
ChertValueList::update_reader()
{
Xapian::docid first_did = docid_from_key(slot, cursor->current_key);
if (!first_did) return false;
cursor->read_tag();
const string & tag = cursor->current_tag;
reader.assign(tag.data(), tag.size(), first_did);
return true;
}
ChertValueList::~ChertValueList()
{
delete cursor;
}
Xapian::docid
ChertValueList::get_docid() const
{
Assert(!at_end());
return reader.get_docid();
}
Xapian::valueno
ChertValueList::get_valueno() const
{
return slot;
}
std::string
ChertValueList::get_value() const
{
Assert(!at_end());
return reader.get_value();
}
bool
ChertValueList::at_end() const
{
return cursor == NULL;
}
void
ChertValueList::next()
{
if (!cursor) {
cursor = db->get_postlist_cursor();
if (!cursor) return;
cursor->find_entry_ge(make_valuechunk_key(slot, 1));
} else if (!reader.at_end()) {
reader.next();
if (!reader.at_end()) return;
cursor->next();
}
if (!cursor->after_end()) {
if (update_reader()) {
if (!reader.at_end()) return;
}
}
// We've reached the end.
delete cursor;
cursor = NULL;
}
void
ChertValueList::skip_to(Xapian::docid did)
{
if (!cursor) {
cursor = db->get_postlist_cursor();
if (!cursor) return;
} else if (!reader.at_end()) {
reader.skip_to(did);
if (!reader.at_end()) return;
}
if (!cursor->find_entry(make_valuechunk_key(slot, did))) {
if (update_reader()) {
reader.skip_to(did);
if (!reader.at_end()) return;
}
// The requested docid is between two chunks.
cursor->next();
}
// Either an exact match, or in a gap before the start of a chunk.
if (!cursor->after_end()) {
if (update_reader()) {
if (!reader.at_end()) return;
}
}
// We've reached the end.
delete cursor;
cursor = NULL;
}
bool
ChertValueList::check(Xapian::docid did)
{
if (!cursor) {
cursor = db->get_postlist_cursor();
if (!cursor) return true;
} else if (!reader.at_end()) {
// Check for the requested docid in the current block.
reader.skip_to(did);
if (!reader.at_end()) return true;
}
// Try moving to the appropriate chunk.
if (!cursor->find_entry(make_valuechunk_key(slot, did))) {
// We're in a chunk which might contain the docid.
if (update_reader()) {
reader.skip_to(did);
if (!reader.at_end()) return true;
}
return false;
}
// We had an exact match for a chunk starting with specified docid.
Assert(!cursor->after_end());
if (!update_reader()) {
// We found the exact key we built, so it must match the slot.
// Therefore update_reader() "can't possibly fail".
Assert(false);
}
return true;
}
string
ChertValueList::get_description() const
{
string desc("ChertValueList(slot=");
desc += str(slot);
desc += ')';
return desc;
}
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