001/*
002 * Copyright (C) 2006 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.escape;
016
017import static com.google.common.base.Preconditions.checkNotNull;
018
019import com.google.common.annotations.Beta;
020import com.google.common.annotations.GwtCompatible;
021import com.google.errorprone.annotations.CanIgnoreReturnValue;
022import java.util.HashMap;
023import java.util.Map;
024
025/**
026 * Simple helper class to build a "sparse" array of objects based on the indexes that were added to
027 * it. The array will be from 0 to the maximum index given. All non-set indexes will contain null
028 * (so it's not really a sparse array, just a pseudo sparse array). The builder can also return a
029 * CharEscaper based on the generated array.
030 *
031 * @author Sven Mawson
032 * @since 15.0
033 */
034@Beta
035@GwtCompatible
036public final class CharEscaperBuilder {
037  /**
038   * Simple decorator that turns an array of replacement char[]s into a CharEscaper, this results in
039   * a very fast escape method.
040   */
041  private static class CharArrayDecorator extends CharEscaper {
042    private final char[][] replacements;
043    private final int replaceLength;
044
045    CharArrayDecorator(char[][] replacements) {
046      this.replacements = replacements;
047      this.replaceLength = replacements.length;
048    }
049
050    /*
051     * Overriding escape method to be slightly faster for this decorator. We test the replacements
052     * array directly, saving a method call.
053     */
054    @Override
055    public String escape(String s) {
056      int slen = s.length();
057      for (int index = 0; index < slen; index++) {
058        char c = s.charAt(index);
059        if (c < replacements.length && replacements[c] != null) {
060          return escapeSlow(s, index);
061        }
062      }
063      return s;
064    }
065
066    @Override
067    protected char[] escape(char c) {
068      return c < replaceLength ? replacements[c] : null;
069    }
070  }
071
072  // Replacement mappings.
073  private final Map<Character, String> map;
074
075  // The highest index we've seen so far.
076  private int max = -1;
077
078  /**
079   * Construct a new sparse array builder.
080   */
081  public CharEscaperBuilder() {
082    this.map = new HashMap<Character, String>();
083  }
084
085  /**
086   * Add a new mapping from an index to an object to the escaping.
087   */
088  @CanIgnoreReturnValue
089  public CharEscaperBuilder addEscape(char c, String r) {
090    map.put(c, checkNotNull(r));
091    if (c > max) {
092      max = c;
093    }
094    return this;
095  }
096
097  /**
098   * Add multiple mappings at once for a particular index.
099   */
100  @CanIgnoreReturnValue
101  public CharEscaperBuilder addEscapes(char[] cs, String r) {
102    checkNotNull(r);
103    for (char c : cs) {
104      addEscape(c, r);
105    }
106    return this;
107  }
108
109  /**
110   * Convert this builder into an array of char[]s where the maximum index is the value of the
111   * highest character that has been seen. The array will be sparse in the sense that any unseen
112   * index will default to null.
113   *
114   * @return a "sparse" array that holds the replacement mappings.
115   */
116  public char[][] toArray() {
117    char[][] result = new char[max + 1][];
118    for (Map.Entry<Character, String> entry : map.entrySet()) {
119      result[entry.getKey()] = entry.getValue().toCharArray();
120    }
121    return result;
122  }
123
124  /**
125   * Convert this builder into a char escaper which is just a decorator around the underlying array
126   * of replacement char[]s.
127   *
128   * @return an escaper that escapes based on the underlying array.
129   */
130  public Escaper toEscaper() {
131    return new CharArrayDecorator(toArray());
132  }
133}