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;
024import java.util.Map.Entry;
025
026/**
027 * Simple helper class to build a "sparse" array of objects based on the indexes that were added to
028 * it. The array will be from 0 to the maximum index given. All non-set indexes will contain null
029 * (so it's not really a sparse array, just a pseudo sparse array). The builder can also return a
030 * CharEscaper based on the generated array.
031 *
032 * @author Sven Mawson
033 * @since 15.0
034 */
035@Beta
036@GwtCompatible
037public final class CharEscaperBuilder {
038  /**
039   * Simple decorator that turns an array of replacement char[]s into a CharEscaper, this results in
040   * a very fast escape method.
041   */
042  private static class CharArrayDecorator extends CharEscaper {
043    private final char[][] replacements;
044    private final int replaceLength;
045
046    CharArrayDecorator(char[][] replacements) {
047      this.replacements = replacements;
048      this.replaceLength = replacements.length;
049    }
050
051    /*
052     * Overriding escape method to be slightly faster for this decorator. We test the replacements
053     * array directly, saving a method call.
054     */
055    @Override
056    public String escape(String s) {
057      int slen = s.length();
058      for (int index = 0; index < slen; index++) {
059        char c = s.charAt(index);
060        if (c < replacements.length && replacements[c] != null) {
061          return escapeSlow(s, index);
062        }
063      }
064      return s;
065    }
066
067    @Override
068    protected char[] escape(char c) {
069      return c < replaceLength ? replacements[c] : null;
070    }
071  }
072
073  // Replacement mappings.
074  private final Map<Character, String> map;
075
076  // The highest index we've seen so far.
077  private int max = -1;
078
079  /** Construct a new sparse array builder. */
080  public CharEscaperBuilder() {
081    this.map = new HashMap<>();
082  }
083
084  /** Add a new mapping from an index to an object to the escaping. */
085  @CanIgnoreReturnValue
086  public CharEscaperBuilder addEscape(char c, String r) {
087    map.put(c, checkNotNull(r));
088    if (c > max) {
089      max = c;
090    }
091    return this;
092  }
093
094  /** Add multiple mappings at once for a particular index. */
095  @CanIgnoreReturnValue
096  public CharEscaperBuilder addEscapes(char[] cs, String r) {
097    checkNotNull(r);
098    for (char c : cs) {
099      addEscape(c, r);
100    }
101    return this;
102  }
103
104  /**
105   * Convert this builder into an array of char[]s where the maximum index is the value of the
106   * highest character that has been seen. The array will be sparse in the sense that any unseen
107   * index will default to null.
108   *
109   * @return a "sparse" array that holds the replacement mappings.
110   */
111  public char[][] toArray() {
112    char[][] result = new char[max + 1][];
113    for (Entry<Character, String> entry : map.entrySet()) {
114      result[entry.getKey()] = entry.getValue().toCharArray();
115    }
116    return result;
117  }
118
119  /**
120   * Convert this builder into a char escaper which is just a decorator around the underlying array
121   * of replacement char[]s.
122   *
123   * @return an escaper that escapes based on the underlying array.
124   */
125  public Escaper toEscaper() {
126    return new CharArrayDecorator(toArray());
127  }
128}