001/* 002 * Copyright (C) 2009 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.common.annotations.VisibleForTesting; 021import java.util.Collections; 022import java.util.Map; 023 024/** 025 * An implementation-specific parameter class suitable for initializing {@link 026 * ArrayBasedCharEscaper} or {@link ArrayBasedUnicodeEscaper} instances. This class should be used 027 * when more than one escaper is created using the same character replacement mapping to allow the 028 * underlying (implementation specific) data structures to be shared. 029 * 030 * <p>The size of the data structure used by ArrayBasedCharEscaper and ArrayBasedUnicodeEscaper is 031 * proportional to the highest valued character that has a replacement. For example a replacement 032 * map containing the single character '{@literal \}u1000' will require approximately 16K of memory. 033 * As such sharing this data structure between escaper instances is the primary goal of this class. 034 * 035 * @author David Beaumont 036 * @since 15.0 037 */ 038@GwtCompatible 039@ElementTypesAreNonnullByDefault 040public final class ArrayBasedEscaperMap { 041 /** 042 * Returns a new ArrayBasedEscaperMap for creating ArrayBasedCharEscaper or 043 * ArrayBasedUnicodeEscaper instances. 044 * 045 * @param replacements a map of characters to their escaped representations 046 */ 047 public static ArrayBasedEscaperMap create(Map<Character, String> replacements) { 048 return new ArrayBasedEscaperMap(createReplacementArray(replacements)); 049 } 050 051 // The underlying replacement array we can share between multiple escaper 052 // instances. 053 private final char[][] replacementArray; 054 055 private ArrayBasedEscaperMap(char[][] replacementArray) { 056 this.replacementArray = replacementArray; 057 } 058 059 // Returns the non-null array of replacements for fast lookup. 060 char[][] getReplacementArray() { 061 return replacementArray; 062 } 063 064 // Creates a replacement array from the given map. The returned array is a 065 // linear lookup table of replacement character sequences indexed by the 066 // original character value. 067 @VisibleForTesting 068 static char[][] createReplacementArray(Map<Character, String> map) { 069 checkNotNull(map); // GWT specific check (do not optimize) 070 if (map.isEmpty()) { 071 return EMPTY_REPLACEMENT_ARRAY; 072 } 073 char max = Collections.max(map.keySet()); 074 char[][] replacements = new char[max + 1][]; 075 for (Character c : map.keySet()) { 076 replacements[c] = map.get(c).toCharArray(); 077 } 078 return replacements; 079 } 080 081 // Immutable empty array for when there are no replacements. 082 private static final char[][] EMPTY_REPLACEMENT_ARRAY = new char[0][0]; 083}