Update #0 - First Release

sources/main/java/com/google/common/collect/Hashing.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2008 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.collect;
+
+import javax.annotation.Nullable;
+
+import com.google.common.annotations.GwtCompatible;
+import com.google.common.primitives.Ints;
+
+/**
+ * Static methods for implementing hash-based collections.
+ *
+ * @author Kevin Bourrillion
+ * @author Jesse Wilson
+ * @author Austin Appleby
+ */
+@GwtCompatible
+final class Hashing {
+	private Hashing() {
+	}
+
+	private static final int C1 = 0xcc9e2d51;
+	private static final int C2 = 0x1b873593;
+
+	/*
+	 * This method was rewritten in Java from an intermediate step of the Murmur
+	 * hash function in
+	 * http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp, which
+	 * contained the following header:
+	 *
+	 * MurmurHash3 was written by Austin Appleby, and is placed in the public
+	 * domain. The author hereby disclaims copyright to this source code.
+	 */
+	static int smear(int hashCode) {
+		return C2 * Integer.rotateLeft(hashCode * C1, 15);
+	}
+
+	static int smearedHash(@Nullable Object o) {
+		return smear((o == null) ? 0 : o.hashCode());
+	}
+
+	private static int MAX_TABLE_SIZE = Ints.MAX_POWER_OF_TWO;
+
+	static int closedTableSize(int expectedEntries, double loadFactor) {
+		// Get the recommended table size.
+		// Round down to the nearest power of 2.
+		expectedEntries = Math.max(expectedEntries, 2);
+		int tableSize = Integer.highestOneBit(expectedEntries);
+		// Check to make sure that we will not exceed the maximum load factor.
+		if (expectedEntries > (int) (loadFactor * tableSize)) {
+			tableSize <<= 1;
+			return (tableSize > 0) ? tableSize : MAX_TABLE_SIZE;
+		}
+		return tableSize;
+	}
+
+	static boolean needsResizing(int size, int tableSize, double loadFactor) {
+		return size > loadFactor * tableSize && tableSize < MAX_TABLE_SIZE;
+	}
+}