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
037@ElementTypesAreNonnullByDefault
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[] @Nullable [] replacements;
045    private final int replaceLength;
046
047    CharArrayDecorator(char[] @Nullable [] 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
057    public String escape(String s) {
058      int slen = s.length();
059      for (int index = 0; index < slen; index++) {
060        char c = s.charAt(index);
061        if (c < replacements.length && replacements[c] != null) {
062          return escapeSlow(s, index);
063        }
064      }
065      return s;
066    }
067
068    @Override
069    @CheckForNull
070    protected char[] escape(char c) {
071      return c < replaceLength ? replacements[c] : null;
072    }
073  }
074
075  // Replacement mappings.
076  private final Map<Character, String> map;
077
078  // The highest index we've seen so far.
079  private int max = -1;
080
081  /** Construct a new sparse array builder. */
082  public CharEscaperBuilder() {
083    this.map = new HashMap<>();
084  }
085
086  /** Add a new mapping from an index to an object to the escaping. */
087  @CanIgnoreReturnValue
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  /** Add multiple mappings at once for a particular index. */
097  @CanIgnoreReturnValue
098  public CharEscaperBuilder addEscapes(char[] cs, String r) {
099    checkNotNull(r);
100    for (char c : cs) {
101      addEscape(c, r);
102    }
103    return this;
104  }
105
106  /**
107   * Convert this builder into an array of char[]s where the maximum index is the value of the
108   * highest character that has been seen. The array will be sparse in the sense that any unseen
109   * index will default to null.
110   *
111   * @return a "sparse" array that holds the replacement mappings.
112   */
113  public char[] @Nullable [] toArray() {
114    char[][] result = new char[max + 1][];
115    for (Entry<Character, String> entry : map.entrySet()) {
116      result[entry.getKey()] = entry.getValue().toCharArray();
117    }
118    return result;
119  }
120
121  /**
122   * Convert this builder into a char escaper which is just a decorator around the underlying array
123   * of replacement char[]s.
124   *
125   * @return an escaper that escapes based on the underlying array.
126   */
127  public Escaper toEscaper() {
128    return new CharArrayDecorator(toArray());
129  }
130}