Update #0 - First Release

sources/main/java/com/google/common/escape/ArrayBasedEscaperMap.java

@@ -0,0 +1,91 @@
+/*
+ * 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 java.util.Collections;
+import java.util.Map;
+
+import com.google.common.annotations.Beta;
+import com.google.common.annotations.GwtCompatible;
+import com.google.common.annotations.VisibleForTesting;
+
+/**
+ * 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.
+ *
+ * <p>
+ * 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<Character, String> 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<Character, String> 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];
+}