predictive-cursor.hpp

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/* -*- c-basic-offset: 2 -*- */
/* Copyright(C) 2011 Brazil

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License version 2.1 as published by the Free Software Foundation.

  This library 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#ifndef GRN_DAT_PREDICTIVE_CURSOR_HPP_
#define GRN_DAT_PREDICTIVE_CURSOR_HPP_

#include "cursor.hpp"
#include "vector.hpp"

namespace grn {
namespace dat {

class Trie;

class GRN_DAT_API PredictiveCursor : public Cursor {
 public:
  PredictiveCursor();
  ~PredictiveCursor();

  void open(const Trie &trie,
            const String &str,
            UInt32 offset = 0,
            UInt32 limit = MAX_UINT32,
            UInt32 flags = 0);

  void close();

  const Key &next();

  UInt32 offset() const {
    return offset_;
  }
  UInt32 limit() const {
    return limit_;
  }
  UInt32 flags() const {
    return flags_;
  }

 private:
  const Trie *trie_;
  UInt32 offset_;
  UInt32 limit_;
  UInt32 flags_;

  Vector<UInt32> buf_;
  UInt32 cur_;
  UInt32 end_;
  UInt32 min_length_;

  PredictiveCursor(const Trie &trie,
                   UInt32 offset, UInt32 limit, UInt32 flags);

  UInt32 fix_flags(UInt32 flags) const;
  void init(const String &str);
  void swap(PredictiveCursor *cursor);

  const Key &ascending_next();
  const Key &descending_next();

  static const UInt32 IS_ROOT_FLAG    = 0x80000000U;
  static const UInt32 POST_ORDER_FLAG = 0x80000000U;

  // Disallows copy and assignment.
  PredictiveCursor(const PredictiveCursor &);
  PredictiveCursor &operator=(const PredictiveCursor &);
};

}  // namespace dat
}  // namespace grn

#endif  // GRN_DAT_PREDICTIVE_CURSOR_HPP_