glass_metadata.cc

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/* Copyright (C) 2004,2005,2006,2007,2008,2009,2010,2011,2017,2024 Olly Betts
 * Copyright (C) 2008 Lemur Consulting Ltd
 *
 * 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, see
 * <https://www.gnu.org/licenses/>.
 */
 
#include <config.h>
 
#include "glass_metadata.h"
 
#include "glass_cursor.h"
 
#include "backends/databaseinternal.h"
#include "debuglog.h"
#include "omassert.h"
#include "stringutils.h"
 
#include "xapian/error.h"
 
#include <string_view>
 
using namespace std;
using namespace std::string_literals;
using Xapian::Internal::intrusive_ptr;
 
GlassMetadataTermList::GlassMetadataTermList(
        intrusive_ptr<const Xapian::Database::Internal> database_,
        GlassCursor * cursor_,
        string_view prefix_)
        : database(database_),
          cursor(cursor_),
          prefix("\x00\xc0"s.append(prefix_))
{
    LOGCALL_CTOR(DB, "GlassMetadataTermList", database_ | cursor_ | prefix_);
    Assert(cursor);
    // Seek to the first key before the first metadata key.
    cursor->find_entry_lt(prefix);
}
 
GlassMetadataTermList::~GlassMetadataTermList()
{
    LOGCALL_DTOR(DB, "GlassMetadataTermList");
    delete cursor;
}
 
Xapian::termcount
GlassMetadataTermList::get_approx_size() const
{
    // Very approximate!  This is only used to build a balanced or tree, so
    // at least we'll get an even tree by returning a constant answer.
    return 1;
}
 
Xapian::doccount
GlassMetadataTermList::get_termfreq() const
{
    throw Xapian::InvalidOperationError("GlassMetadataTermList::get_termfreq() not meaningful");
}
 
TermList *
GlassMetadataTermList::next()
{
    LOGCALL(DB, TermList *, "GlassMetadataTermList::next", NO_ARGS);
    Assert(!cursor->after_end());
 
    if (!cursor->next() || !startswith(cursor->current_key, prefix)) {
        // We've reached the end of the prefixed terms.
        RETURN(this);
    }
    current_term.assign(cursor->current_key, 2);
    RETURN(NULL);
}
 
TermList*
GlassMetadataTermList::skip_to(string_view key)
{
    LOGCALL(DB, TermList *, "GlassMetadataTermList::skip_to", key);
    Assert(!cursor->after_end());
 
    if (cursor->find_entry_ge(string("\x00\xc0", 2).append(key))) {
        // Exact match.
        current_term = key;
    } else {
        // The exact term we asked for isn't there, so check if the next
        // term after it also has the right prefix.
        if (cursor->after_end() || !startswith(cursor->current_key, prefix)) {
            // We've reached the end of the prefixed terms.
            RETURN(this);
        }
        current_term.assign(cursor->current_key, 2);
    }
    RETURN(NULL);
}