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