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 org.checkerframework.checker.nullness.qual.Nullable;
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@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[] @Nullable [] replacements;
043    private final int replaceLength;
044
045    CharArrayDecorator(char[] @Nullable [] 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 @Nullable [] 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  /** Construct a new sparse array builder. */
079  public CharEscaperBuilder() {
080    this.map = new HashMap<>();
081  }
082
083  /** Add a new mapping from an index to an object to the escaping. */
084  @CanIgnoreReturnValue
085  public CharEscaperBuilder addEscape(char c, String r) {
086    map.put(c, checkNotNull(r));
087    if (c > max) {
088      max = c;
089    }
090    return this;
091  }
092
093  /** Add multiple mappings at once for a particular index. */
094  @CanIgnoreReturnValue
095  public CharEscaperBuilder addEscapes(char[] cs, String r) {
096    checkNotNull(r);
097    for (char c : cs) {
098      addEscape(c, r);
099    }
100    return this;
101  }
102
103  /**
104   * Convert this builder into an array of char[]s where the maximum index is the value of the
105   * highest character that has been seen. The array will be sparse in the sense that any unseen
106   * index will default to null.
107   *
108   * @return a "sparse" array that holds the replacement mappings.
109   */
110  public char[] @Nullable [] toArray() {
111    char[][] result = new char[max + 1][];
112    for (Entry<Character, String> entry : map.entrySet()) {
113      result[entry.getKey()] = entry.getValue().toCharArray();
114    }
115    return result;
116  }
117
118  /**
119   * Convert this builder into a char escaper which is just a decorator around the underlying array
120   * of replacement char[]s.
121   *
122   * @return an escaper that escapes based on the underlying array.
123   */
124  public Escaper toEscaper() {
125    return new CharArrayDecorator(toArray());
126  }
127}