com.google.common.escape.ArrayBasedEscaperMap Maven / Gradle / Ivy
/*
* Copyright (C) 2009 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.common.escape;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import java.util.Collections;
import java.util.Map;
/**
* An implementation-specific parameter class suitable for initializing {@link
* ArrayBasedCharEscaper} or {@link ArrayBasedUnicodeEscaper} instances. This class should be used
* when more than one escaper is created using the same character replacement mapping to allow the
* underlying (implementation specific) data structures to be shared.
*
* The size of the data structure used by ArrayBasedCharEscaper and ArrayBasedUnicodeEscaper is
* proportional to the highest valued character that has a replacement. For example a replacement
* map containing the single character '{@literal \}u1000' will require approximately 16K of memory.
* As such sharing this data structure between escaper instances is the primary goal of this class.
*
* @author David Beaumont
* @since 15.0
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class ArrayBasedEscaperMap {
/**
* Returns a new ArrayBasedEscaperMap for creating ArrayBasedCharEscaper or
* ArrayBasedUnicodeEscaper instances.
*
* @param replacements a map of characters to their escaped representations
*/
public static ArrayBasedEscaperMap create(Map replacements) {
return new ArrayBasedEscaperMap(createReplacementArray(replacements));
}
// The underlying replacement array we can share between multiple escaper
// instances.
private final char[][] replacementArray;
private ArrayBasedEscaperMap(char[][] replacementArray) {
this.replacementArray = replacementArray;
}
// Returns the non-null array of replacements for fast lookup.
char[][] getReplacementArray() {
return replacementArray;
}
// Creates a replacement array from the given map. The returned array is a
// linear lookup table of replacement character sequences indexed by the
// original character value.
@VisibleForTesting
static char[][] createReplacementArray(Map map) {
checkNotNull(map); // GWT specific check (do not optimize)
if (map.isEmpty()) {
return EMPTY_REPLACEMENT_ARRAY;
}
char max = Collections.max(map.keySet());
char[][] replacements = new char[max + 1][];
for (Character c : map.keySet()) {
replacements[c] = map.get(c).toCharArray();
}
return replacements;
}
// Immutable empty array for when there are no replacements.
private static final char[][] EMPTY_REPLACEMENT_ARRAY = new char[0][0];
}