honey_postlist.h

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/* Copyright (C) 2007,2009,2011,2013,2015,2016,2017,2018,2024 Olly Betts
 * Copyright (C) 2009 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/>.
 */
 
#ifndef XAPIAN_INCLUDED_HONEY_POSTLIST_H
#define XAPIAN_INCLUDED_HONEY_POSTLIST_H
 
#include "backends/leafpostlist.h"
#include "honey_positionlist.h"
#include "pack.h"
 
#include <string>
#include <string_view>
 
class HoneyCursor;
class HoneyDatabase;
 
namespace Honey {
 
inline std::string
make_postingchunk_key(std::string_view term)
{
    std::string key;
    pack_string_preserving_sort(key, term, true);
    return key;
}
 
inline std::string
make_postingchunk_key(std::string_view term, Xapian::docid did)
{
    std::string key;
    pack_string_preserving_sort(key, term);
    pack_uint_preserving_sort(key, did);
    return key;
}
 
inline Xapian::docid
docid_from_key(const std::string& term, const std::string& key)
{
    if (key.size() < term.size()) {
        // A key can't be shorter than the term it contains.
        return false;
    }
    const char* p = key.data();
    const char* end = p + key.size();
    // Most terms don't contain zero bytes, so we could optimise this.
    std::string term_in_key;
    // FIXME: the next key might not be for a postlist chunk...
    if (!unpack_string_preserving_sort(&p, end, term_in_key))
        throw Xapian::DatabaseCorruptError("bad postlist key");
    if (term_in_key != term)
        return false;
    Xapian::docid did;
    if (!unpack_uint_preserving_sort(&p, end, &did))
        throw Xapian::DatabaseCorruptError("bad postlist key");
    return did;
}
 
class PostingChunkReader {
    const char* p = nullptr;
    const char* end;
 
    Xapian::docid did;
 
    Xapian::termcount wdf;
 
    Xapian::docid last_did;
 
    Xapian::doccount termfreq;
 
    Xapian::termcount collfreq_info;
 
  public:
    PostingChunkReader() { }
 
    void init() {
        p = NULL;
        termfreq = 0;
    }
 
    void init(Xapian::doccount tf, Xapian::termcount cf_info) {
        p = NULL;
        termfreq = tf;
        collfreq_info = cf_info;
    }
 
    void assign(const char* p_, size_t len, Xapian::docid did);
 
    void assign(const char* p_, size_t len, Xapian::docid did_,
                Xapian::docid last_did_in_chunk,
                Xapian::termcount wdf_);
 
    bool at_end() const { return p == NULL; }
 
    Xapian::docid get_docid() const { return did; }
 
    Xapian::termcount get_wdf() const { return wdf; }
 
    bool next();
 
    bool skip_to(Xapian::docid target);
};
 
}
 
class HoneyPostList : public LeafPostList {
    HoneyPostList& operator=(const HoneyPostList&) = delete;
 
    HoneyPostList(const HoneyPostList&) = delete;
 
    HoneyCursor* cursor;
 
    Honey::PostingChunkReader reader;
 
    Xapian::docid last_did;
 
    const HoneyDatabase* db;
 
    Xapian::termcount wdf_max;
 
    bool started = false;
 
    bool update_reader();
 
  public:
    HoneyPostList(const HoneyDatabase* db_,
                  std::string_view term_,
                  HoneyCursor* cursor_);
 
    ~HoneyPostList();
 
    bool open_nearby_postlist(std::string_view term_,
                              bool need_read_pos,
                              LeafPostList*& pl) const;
 
    Xapian::docid get_docid() const;
 
    Xapian::termcount get_wdf() const;
 
    bool at_end() const;
 
    PositionList* open_position_list() const;
 
    PostList* next(double w_min);
 
    PostList* skip_to(Xapian::docid did, double w_min);
 
    Xapian::termcount get_wdf_upper_bound() const;
 
    void get_docid_range(Xapian::docid& first, Xapian::docid& last) const;
 
    std::string get_description() const;
};
 
class HoneyPosPostList : public HoneyPostList {
    HoneyRePositionList position_list;
 
  public:
    HoneyPosPostList(const HoneyDatabase* db_,
                     std::string_view term_,
                     HoneyCursor* cursor_);
 
    PositionList* read_position_list();
 
    std::string get_description() const;
};
 
#endif // XAPIAN_INCLUDED_HONEY_POSTLIST_H