lucene/core/src/java/org/apache/lucene/util/automaton/Lev1ParametricDescription.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.util.automaton;

// The following code was generated with the moman/finenight pkg
// This package is available under the MIT License, see NOTICE.txt
// for more details.

import org.apache.lucene.util.automaton.LevenshteinAutomata.ParametricDescription;

/** Parametric description for generating a Levenshtein automaton of degree 1 */
class Lev1ParametricDescription extends ParametricDescription {

  @Override
  int transition(int absState, int position, int vector) {
    // null absState should never be passed in
    assert absState != -1;

    // decode absState -> state, offset
    int state = absState / (w + 1);
    int offset = absState % (w + 1);
    assert offset >= 0;

    if (position == w) {
      if (state < 2) {
        final int loc = vector * 2 + state;
        offset += unpack(offsetIncrs0, loc, 1);
        state = unpack(toStates0, loc, 2) - 1;
      }
    } else if (position == w - 1) {
      if (state < 3) {
        final int loc = vector * 3 + state;
        offset += unpack(offsetIncrs1, loc, 1);
        state = unpack(toStates1, loc, 2) - 1;
      }
    } else if (position == w - 2) {
      if (state < 5) {
        final int loc = vector * 5 + state;
        offset += unpack(offsetIncrs2, loc, 2);
        state = unpack(toStates2, loc, 3) - 1;
      }
    } else {
      if (state < 5) {
        final int loc = vector * 5 + state;
        offset += unpack(offsetIncrs3, loc, 2);
        state = unpack(toStates3, loc, 3) - 1;
      }
    }

    if (state == -1) {
      // null state
      return -1;
    } else {
      // translate back to abs
      return state * (w + 1) + offset;
    }
  }

  // 1 vectors; 2 states per vector; array length = 2
  private static final long[] toStates0 = new long[] /*2 bits per value */ {0x2L};
  private static final long[] offsetIncrs0 = new long[] /*1 bits per value */ {0x0L};

  // 2 vectors; 3 states per vector; array length = 6
  private static final long[] toStates1 = new long[] /*2 bits per value */ {0xa43L};
  private static final long[] offsetIncrs1 = new long[] /*1 bits per value */ {0x38L};

  // 4 vectors; 5 states per vector; array length = 20
  private static final long[] toStates2 = new long[] /*3 bits per value */ {0x4da292442420003L};
  private static final long[] offsetIncrs2 = new long[] /*2 bits per value */ {0x5555528000L};

  // 8 vectors; 5 states per vector; array length = 40
  private static final long[] toStates3 =
      new long[] /*3 bits per value */ {0x14d0812112018003L, 0xb1a29b46d48a49L};
  private static final long[] offsetIncrs3 =
      new long[] /*2 bits per value */ {0x555555e80a0f0000L, 0x5555L};

  // state map
  //   0 -> [(0, 0)]
  //   1 -> [(0, 1)]
  //   2 -> [(0, 1), (1, 1)]
  //   3 -> [(0, 1), (1, 1), (2, 1)]
  //   4 -> [(0, 1), (2, 1)]

  public Lev1ParametricDescription(int w) {
    super(w, 1, new int[] {0, 1, 0, -1, -1});
  }
}