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/*
 * 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.Beta;
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 */ @Beta @GwtCompatible 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 (char 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]; }





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