backends/quartz/quartz_positionlist.cc

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/* quartz_positionlist.cc
 *
 * ----START-LICENCE----
 * Copyright 1999,2000,2001 BrightStation PLC
 * Copyright 2002 Ananova Ltd
 * Copyright 2002,2003,2004 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 * -----END-LICENCE-----
 */

#include <config.h>
#include "omdebug.h"
#include "quartz_positionlist.h"
#include "quartz_utils.h"
#include "utils.h"

using std::string;

static inline void
make_key(Xapian::docid did, const string & tname, string & key)
{
    key = pack_uint(did) + tname;
}

void
QuartzPositionList::read_data(const Btree * table,
                              Xapian::docid did,
                              const string & tname)
{
    DEBUGCALL(DB, void, "QuartzPositionList::read_data",
              table << ", " << did << ", " << tname);

    string key;
    string tag;
    make_key(did, tname, key);
    if (!table->get_exact_entry(key, tag)) {
        // This isn't an error, since position list not be present simply
        // implies that there is no positional information available.
        data = "";
        pos = data.data();
        end = pos;
        is_at_end = false;
        have_started = false;
        current_pos = 0;
        number_of_entries = 0;
        return;
    }

    // FIXME: Unwanted copy
    data = tag;

    pos = data.data();
    end = pos + data.size();
    is_at_end = false;
    have_started = false;
    current_pos = 0;

    bool success = unpack_uint(&pos, end, &number_of_entries);
    if (! success) {
        if (pos == 0) {
            // data ran out
            throw Xapian::DatabaseCorruptError("Data ran out when reading position list length.");
        } else {
            // overflow
            throw Xapian::RangeError("Position list length too large.");
        }
    }
}

void
QuartzPositionList::next_internal()
{
    DEBUGCALL(DB, void, "QuartzPositionList::next_internal", "");
    if (pos == end) {
        is_at_end = true;
        return;
    }

    Xapian::termpos pos_increment;
    bool success = unpack_uint(&pos, end, &pos_increment);
    if (! success) {
        if (pos == 0) {
            // data ran out
            throw Xapian::DatabaseCorruptError("Data ran out when reading position list entry.");
        } else {
            // overflow
            throw Xapian::RangeError("Position list length too large.");
        }
    }
    Assert(pos != 0);
    current_pos += pos_increment + 1;
}

void
QuartzPositionList::next()
{
    DEBUGCALL(DB, void, "QuartzPositionList::next", "");
    Assert(!is_at_end);
    next_internal();
    have_started = true;
    DEBUGLINE(DB, string("QuartzPositionList - moved to ") <<
              (is_at_end ? string("end.") : std::string("position = ") +
               om_tostring(current_pos) + "."));
}

void
QuartzPositionList::skip_to(Xapian::termpos termpos)
{
    DEBUGCALL(DB, void, "QuartzPositionList::skip_to", termpos);
    if (!have_started) {
        next_internal();
        have_started = true;
    }
    while (!is_at_end && current_pos < termpos) next_internal();
    DEBUGLINE(DB, string("QuartzPositionList - skipped to ") <<
              (is_at_end ? string("end.") : std::string("position = ") +
               om_tostring(current_pos) + "."));
}

// Methods modifying position lists

void
QuartzPositionListTable::set_positionlist(Xapian::docid did,
                        const string & tname,
                        Xapian::PositionIterator pos,
                        const Xapian::PositionIterator &pos_end)
{
    DEBUGCALL(DB, void, "QuartzPositionList::set_positionlist", did << ", " << tname << ", " << pos << ", " << pos_end);
    string key;

    make_key(did, tname, key);
    string tag;

    Xapian::termpos prevpos = 0;
    unsigned int size = 0;
    for ( ; pos != pos_end; ++pos) {
        tag += pack_uint(*pos - prevpos - 1);
        prevpos = *pos;
        size++;
    }
    tag = pack_uint(size) + tag;
    add(key, tag);
}

void
QuartzPositionListTable::delete_positionlist(Xapian::docid did,
                        const string & tname)
{
    DEBUGCALL(DB, void, "QuartzPositionList::delete_positionlist", did << ", " << tname);
    string key;
    make_key(did, tname, key);
    del(key);
}

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