honey_cursor.h

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/* Copyright (C) 2017,2018,2024 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, see
 * <https://www.gnu.org/licenses/>.
 */
 
#ifndef XAPIAN_INCLUDED_HONEY_CURSOR_H
#define XAPIAN_INCLUDED_HONEY_CURSOR_H
 
#include "honey_table.h"
 
class HoneyCursor {
    bool do_find(std::string_view key, bool greater_than);
 
    bool do_next();
 
    bool next_from_index();
 
    BufferedFile store;
 
  public:
    std::string current_key, current_tag;
    mutable size_t val_size = 0;
    bool current_compressed = false;
    mutable CompressionStream comp_stream;
    bool is_at_end = false;
    mutable std::string last_key;
 
    // File offset to start of index.
    off_t root;
 
    // File offset to start of table (zero except for single-file DB).
    off_t offset;
 
    // Forward to next constructor form.
    explicit HoneyCursor(const HoneyTable* table)
        : store(table->store),
          comp_stream(Z_DEFAULT_STRATEGY),
          root(table->get_root()),
          offset(table->get_offset())
    {
        store.set_pos(offset); // FIXME root
    }
 
    HoneyCursor(const HoneyCursor& o)
        : store(o.store),
          current_key(o.current_key),
          current_tag(o.current_tag), // FIXME really copy?
          val_size(o.val_size),
          current_compressed(o.current_compressed),
          comp_stream(Z_DEFAULT_STRATEGY),
          is_at_end(o.is_at_end),
          last_key(o.last_key),
          root(o.root),
          offset(o.offset)
    {
        store.set_pos(o.store.get_pos());
    }
 
    void rewind() {
        store.set_pos(offset); // FIXME root
        current_key = last_key = std::string();
        is_at_end = false;
        val_size = 0;
    }
 
    void to_end() { is_at_end = true; }
 
    bool after_end() const { return is_at_end; }
 
    bool next() {
        if (store.was_forced_closed()) {
            HoneyTable::throw_database_closed();
        }
 
        return do_next();
    }
 
    bool read_tag(bool keep_compressed = false);
 
    bool find_exact(std::string_view key) {
        return do_find(key, false);
    }
 
    bool find_entry_ge(std::string_view key) {
        return do_find(key, true);
    }
 
    bool prev();
};
 
class MutableHoneyCursor : public HoneyCursor {
    HoneyTable* table;
 
  public:
    MutableHoneyCursor(HoneyTable* table_)
        : HoneyCursor(table_),
          table(table_)
    { }
 
    bool del() {
        Assert(!is_at_end);
        std::string key_to_del = current_key;
        bool res = next();
        table->del(key_to_del);
        return res;
    }
};
 
#endif // XAPIAN_INCLUDED_HONEY_CURSOR_H