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.GwtCompatible;
020import com.google.errorprone.annotations.CanIgnoreReturnValue;
021import java.util.HashMap;
022import java.util.Map;
023import java.util.Map.Entry;
024import javax.annotation.CheckForNull;
025import org.checkerframework.checker.nullness.qual.Nullable;
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@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[] @Nullable [] replacements;
044    private final int replaceLength;
045
046    CharArrayDecorator(char[] @Nullable [] 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    @CheckForNull
069    protected char[] escape(char c) {
070      return c < replaceLength ? replacements[c] : null;
071    }
072  }
073
074  // Replacement mappings.
075  private final Map<Character, String> map;
076
077  // The highest index we've seen so far.
078  private int max = -1;
079
080  /** Construct a new sparse array builder. */
081  public CharEscaperBuilder() {
082    this.map = new HashMap<>();
083  }
084
085  /** Add a new mapping from an index to an object to the escaping. */
086  @CanIgnoreReturnValue
087  public CharEscaperBuilder addEscape(char c, String r) {
088    map.put(c, checkNotNull(r));
089    if (c > max) {
090      max = c;
091    }
092    return this;
093  }
094
095  /** Add multiple mappings at once for a particular index. */
096  @CanIgnoreReturnValue
097  public CharEscaperBuilder addEscapes(char[] cs, String r) {
098    checkNotNull(r);
099    for (char c : cs) {
100      addEscape(c, r);
101    }
102    return this;
103  }
104
105  /**
106   * Convert this builder into an array of char[]s where the maximum index is the value of the
107   * highest character that has been seen. The array will be sparse in the sense that any unseen
108   * index will default to null.
109   *
110   * @return a "sparse" array that holds the replacement mappings.
111   */
112  public char[] @Nullable [] toArray() {
113    char[][] result = new char[max + 1][];
114    for (Entry<Character, String> entry : map.entrySet()) {
115      result[entry.getKey()] = entry.getValue().toCharArray();
116    }
117    return result;
118  }
119
120  /**
121   * Convert this builder into a char escaper which is just a decorator around the underlying array
122   * of replacement char[]s.
123   *
124   * @return an escaper that escapes based on the underlying array.
125   */
126  public Escaper toEscaper() {
127    return new CharArrayDecorator(toArray());
128  }
129}