package-info.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.
 */

/**
 * Normalization of text before the tokenizer.
 * <p>
 *   CharFilters are chainable filters that normalize text before tokenization 
 *   and provide mappings between normalized text offsets and the corresponding 
 *   offset in the original text.
 * </p>
 * <H2>CharFilter offset mappings</H2>
 * <p>
 *   CharFilters modify an input stream via a series of substring
 *   replacements (including deletions and insertions) to produce an output
 *   stream. There are three possible replacement cases: the replacement
 *   string has the same length as the original substring; the replacement
 *   is shorter; and the replacement is longer. In the latter two cases
 *   (when the replacement has a different length than the original),
 *   one or more offset correction mappings are required.
 * </p>
 * <p>
 *   When the replacement is shorter than the original (e.g. when the
 *   replacement is the empty string), a single offset correction mapping
 *   should be added at the replacement's end offset in the output stream.
 *   The <code>cumulativeDiff</code> parameter to the
 *   <code>addOffCorrectMapping()</code> method will be the sum of all
 *   previous replacement offset adjustments, with the addition of the
 *   difference between the lengths of the original substring and the
 *   replacement string (a positive value).
 * </p>
 * <p>
 *   When the replacement is longer than the original (e.g. when the
 *   original is the empty string), you should add as many offset
 *   correction mappings as the difference between the lengths of the
 *   replacement string and the original substring, starting at the
 *   end offset the original substring would have had in the output stream.
 *   The <code>cumulativeDiff</code> parameter to the
 *   <code>addOffCorrectMapping()</code> method will be the sum of all
 *   previous replacement offset adjustments, with the addition of the
 *   difference between the lengths of the original substring and the
 *   replacement string so far (a negative value).
 * </p>
 */
package org.apache.lucene.analysis.charfilter;