honey_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 "honey_metadata.h"
 
#include "honey_cursor.h"
 
#include "backends/databaseinternal.h"
#include "debuglog.h"
#include "omassert.h"
#include "stringutils.h"
 
#include "xapian/error.h"
 
#include <string>
#include <string_view>
 
using namespace std;
using namespace std::string_literals;
using Xapian::Internal::intrusive_ptr;
 
HoneyMetadataTermList::HoneyMetadataTermList(
        const Xapian::Database::Internal* database_,
        HoneyCursor* cursor_,
        string_view prefix_)
    : database(database_), cursor(cursor_), prefix("\0\0"s.append(prefix_))
{
    LOGCALL_CTOR(DB, "HoneyMetadataTermList", database_ | cursor_ | prefix_);
    Assert(cursor);
    // Set the cursor to its end to signal we haven't started yet.
    cursor->to_end();
}
 
HoneyMetadataTermList::~HoneyMetadataTermList()
{
    LOGCALL_DTOR(DB, "HoneyMetadataTermList");
    delete cursor;
}
 
Xapian::termcount
HoneyMetadataTermList::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
HoneyMetadataTermList::get_termfreq() const
{
    throw Xapian::InvalidOperationError("HoneyMetadataTermList::get_termfreq() "
                                        "not meaningful");
}
 
TermList*
HoneyMetadataTermList::next()
{
    LOGCALL(DB, TermList*, "HoneyMetadataTermList::next", NO_ARGS);
    Assert(cursor != NULL);
 
    if (cursor->after_end()) {
        // This is the first action on a new HoneyMetadataTermList.
        if (cursor->find_entry_ge(prefix))
            RETURN(NULL);
    } else {
        cursor->next();
    }
 
    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);
}
 
TermList*
HoneyMetadataTermList::skip_to(string_view key)
{
    LOGCALL(DB, TermList*, "HoneyMetadataTermList::skip_to", key);
    Assert(cursor != NULL);
 
    // k is the table key (key is the user metadata key).
    string k(2, '\0');
    k += key;
    if (cursor->after_end() && prefix > k) {
        // This is the first action on a new HoneySynonymTermList and we were
        // asked to skip to a key before the prefix - this ought to leave us
        // on the first key with the specified prefix.
        k = prefix;
    }
 
    if (cursor->find_entry_ge(k)) {
        // Exact match.
        current_term = key;
    } else {
        // The exact key we asked for isn't there, so check if the next
        // key after it also has the right prefix.
        if (cursor->after_end() || !startswith(cursor->current_key, prefix)) {
            // We've reached the end of the prefixed keys.
            RETURN(this);
        }
        current_term.assign(cursor->current_key, 2);
    }
    RETURN(NULL);
}