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