8010325: Remove hash32() method and hash32 int field from java.lang.String
Reviewed-by: alanb, mduigou
--- a/jdk/src/share/classes/java/lang/String.java Wed Jun 12 09:44:34 2013 +0100
+++ b/jdk/src/share/classes/java/lang/String.java Wed Jun 12 11:11:59 2013 -0700
@@ -3156,101 +3156,4 @@
* guaranteed to be from a pool of unique strings.
*/
public native String intern();
-
- /**
- * Seed value used for each alternative hash calculated.
- */
- private static final int HASHING_SEED;
-
- static {
- long nanos = System.nanoTime();
- long now = System.currentTimeMillis();
- int SEED_MATERIAL[] = {
- System.identityHashCode(String.class),
- System.identityHashCode(System.class),
- (int) (nanos >>> 32),
- (int) nanos,
- (int) (now >>> 32),
- (int) now,
- (int) (System.nanoTime() >>> 2)
- };
-
- // Use murmur3 to scramble the seeding material.
- // Inline implementation to avoid loading classes
- int h1 = 0;
-
- // body
- for(int k1 : SEED_MATERIAL) {
- k1 *= 0xcc9e2d51;
- k1 = (k1 << 15) | (k1 >>> 17);
- k1 *= 0x1b873593;
-
- h1 ^= k1;
- h1 = (h1 << 13) | (h1 >>> 19);
- h1 = h1 * 5 + 0xe6546b64;
- }
-
- // tail (always empty, as body is always 32-bit chunks)
-
- // finalization
-
- h1 ^= SEED_MATERIAL.length * 4;
-
- // finalization mix force all bits of a hash block to avalanche
- h1 ^= h1 >>> 16;
- h1 *= 0x85ebca6b;
- h1 ^= h1 >>> 13;
- h1 *= 0xc2b2ae35;
- h1 ^= h1 >>> 16;
-
- HASHING_SEED = h1;
- }
-
- /**
- * Cached value of the hashing algorithm result
- */
- private transient int hash32 = 0;
-
- /**
- * Return a 32-bit hash code value for this object.
- * <p>
- * The general contract of {@code hash32} is:
- * <ul>
- * <li>Whenever it is invoked on the same object more than once during
- * an execution of a Java application, the {@code hash32} method
- * must consistently return the same integer, provided no information
- * used in {@code equals} comparisons on the object is modified.
- * This integer need not remain consistent from one execution of an
- * application to another execution of the same application.
- * <li>If two objects are equal according to the {@code equals(Object)}
- * method, then calling the {@code hash32} method on each of
- * the two objects must produce the same integer result.
- * <li>It is <em>not</em> required that if two objects are unequal
- * according to the {@link java.lang.Object#equals(java.lang.Object)}
- * method, then calling the {@code hash32} method on each of the
- * two objects must produce distinct integer results. However, the
- * programmer should be aware that producing distinct integer results
- * for unequal objects may improve the performance of hash tables.
- * </ul>
- *
- * The hash value will never be zero.
- *
- * @return a hash code value for this object.
- * @see java.lang.Object#equals(java.lang.Object)
- */
- public int hash32() {
- int h = hash32;
- if (0 == h) {
- // harmless data race on hash32 here.
- h = sun.misc.Hashing.murmur3_32(HASHING_SEED, value, 0, value.length);
-
- // ensure result is not zero to avoid recalcing
- h = (0 != h) ? h : 1;
-
- hash32 = h;
- }
-
- return h;
- }
-
}
--- a/jdk/src/share/classes/java/util/HashMap.java Wed Jun 12 09:44:34 2013 +0100
+++ b/jdk/src/share/classes/java/util/HashMap.java Wed Jun 12 11:11:59 2013 -0700
@@ -28,6 +28,7 @@
import java.io.*;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
+import java.util.concurrent.ThreadLocalRandom;
import java.util.function.Consumer;
import java.util.function.BiFunction;
import java.util.function.Function;
@@ -912,7 +913,8 @@
*/
final int initHashSeed() {
if (sun.misc.VM.isBooted() && Holder.USE_HASHSEED) {
- return sun.misc.Hashing.randomHashSeed(this);
+ int seed = ThreadLocalRandom.current().nextInt();
+ return (seed != 0) ? seed : 1;
}
return 0;
}
@@ -2572,8 +2574,9 @@
// set other fields that need values
if (Holder.USE_HASHSEED) {
+ int seed = ThreadLocalRandom.current().nextInt();
Holder.UNSAFE.putIntVolatile(this, Holder.HASHSEED_OFFSET,
- sun.misc.Hashing.randomHashSeed(this));
+ (seed != 0) ? seed : 1);
}
table = EMPTY_TABLE;
--- a/jdk/src/share/classes/java/util/Hashtable.java Wed Jun 12 09:44:34 2013 +0100
+++ b/jdk/src/share/classes/java/util/Hashtable.java Wed Jun 12 11:11:59 2013 -0700
@@ -26,6 +26,7 @@
package java.util;
import java.io.*;
+import java.util.concurrent.ThreadLocalRandom;
import java.util.function.BiConsumer;
import java.util.function.Function;
import java.util.function.BiFunction;
@@ -219,7 +220,8 @@
*/
final int initHashSeed() {
if (sun.misc.VM.isBooted() && Holder.USE_HASHSEED) {
- return sun.misc.Hashing.randomHashSeed(this);
+ int seed = ThreadLocalRandom.current().nextInt();
+ return (seed != 0) ? seed : 1;
}
return 0;
}
@@ -1206,8 +1208,9 @@
// set hashMask
if (Holder.USE_HASHSEED) {
+ int seed = ThreadLocalRandom.current().nextInt();
Holder.UNSAFE.putIntVolatile(this, Holder.HASHSEED_OFFSET,
- sun.misc.Hashing.randomHashSeed(this));
+ (seed != 0) ? seed : 1);
}
// Read the original length of the array and number of elements
--- a/jdk/src/share/classes/java/util/WeakHashMap.java Wed Jun 12 09:44:34 2013 +0100
+++ b/jdk/src/share/classes/java/util/WeakHashMap.java Wed Jun 12 11:11:59 2013 -0700
@@ -27,6 +27,7 @@
import java.lang.ref.WeakReference;
import java.lang.ref.ReferenceQueue;
+import java.util.concurrent.ThreadLocalRandom;
import java.util.function.Consumer;
@@ -215,7 +216,8 @@
if (sun.misc.VM.isBooted() && Holder.USE_HASHSEED) {
// Do not set hashSeed more than once!
// assert hashSeed == 0;
- hashSeed = sun.misc.Hashing.randomHashSeed(this);
+ int seed = ThreadLocalRandom.current().nextInt();
+ hashSeed = (seed != 0) ? seed : 1;
}
}
--- a/jdk/src/share/classes/sun/misc/Hashing.java Wed Jun 12 09:44:34 2013 +0100
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,239 +0,0 @@
-/*
- * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation. Oracle designates this
- * particular file as subject to the "Classpath" exception as provided
- * by Oracle in the LICENSE file that accompanied this code.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-package sun.misc;
-
-import java.util.concurrent.ThreadLocalRandom;
-
-/**
- * Hashing utilities.
- *
- * Little endian implementations of Murmur3 hashing.
- */
-public class Hashing {
-
- /**
- * Static utility methods only.
- */
- private Hashing() {
- throw new Error("No instances");
- }
-
- public static int murmur3_32(byte[] data) {
- return murmur3_32(0, data, 0, data.length);
- }
-
- public static int murmur3_32(int seed, byte[] data) {
- return murmur3_32(seed, data, 0, data.length);
- }
-
- @SuppressWarnings("fallthrough")
- public static int murmur3_32(int seed, byte[] data, int offset, int len) {
- int h1 = seed;
- int count = len;
-
- // body
- while (count >= 4) {
- int k1 = (data[offset] & 0x0FF)
- | (data[offset + 1] & 0x0FF) << 8
- | (data[offset + 2] & 0x0FF) << 16
- | data[offset + 3] << 24;
-
- count -= 4;
- offset += 4;
-
- k1 *= 0xcc9e2d51;
- k1 = Integer.rotateLeft(k1, 15);
- k1 *= 0x1b873593;
-
- h1 ^= k1;
- h1 = Integer.rotateLeft(h1, 13);
- h1 = h1 * 5 + 0xe6546b64;
- }
-
- // tail
-
- if (count > 0) {
- int k1 = 0;
-
- switch (count) {
- case 3:
- k1 ^= (data[offset + 2] & 0xff) << 16;
- // fall through
- case 2:
- k1 ^= (data[offset + 1] & 0xff) << 8;
- // fall through
- case 1:
- k1 ^= (data[offset] & 0xff);
- // fall through
- default:
- k1 *= 0xcc9e2d51;
- k1 = Integer.rotateLeft(k1, 15);
- k1 *= 0x1b873593;
- h1 ^= k1;
- }
- }
-
- // finalization
-
- h1 ^= len;
-
- // finalization mix force all bits of a hash block to avalanche
- h1 ^= h1 >>> 16;
- h1 *= 0x85ebca6b;
- h1 ^= h1 >>> 13;
- h1 *= 0xc2b2ae35;
- h1 ^= h1 >>> 16;
-
- return h1;
- }
-
- public static int murmur3_32(char[] data) {
- return murmur3_32(0, data, 0, data.length);
- }
-
- public static int murmur3_32(int seed, char[] data) {
- return murmur3_32(seed, data, 0, data.length);
- }
-
- public static int murmur3_32(int seed, char[] data, int offset, int len) {
- int h1 = seed;
-
- int off = offset;
- int count = len;
-
- // body
- while (count >= 2) {
- int k1 = (data[off++] & 0xFFFF) | (data[off++] << 16);
-
- count -= 2;
-
- k1 *= 0xcc9e2d51;
- k1 = Integer.rotateLeft(k1, 15);
- k1 *= 0x1b873593;
-
- h1 ^= k1;
- h1 = Integer.rotateLeft(h1, 13);
- h1 = h1 * 5 + 0xe6546b64;
- }
-
- // tail
-
- if (count > 0) {
- int k1 = data[off];
-
- k1 *= 0xcc9e2d51;
- k1 = Integer.rotateLeft(k1, 15);
- k1 *= 0x1b873593;
- h1 ^= k1;
- }
-
- // finalization
-
- h1 ^= len * (Character.SIZE / Byte.SIZE);
-
- // finalization mix force all bits of a hash block to avalanche
- h1 ^= h1 >>> 16;
- h1 *= 0x85ebca6b;
- h1 ^= h1 >>> 13;
- h1 *= 0xc2b2ae35;
- h1 ^= h1 >>> 16;
-
- return h1;
- }
-
- public static int murmur3_32(int[] data) {
- return murmur3_32(0, data, 0, data.length);
- }
-
- public static int murmur3_32(int seed, int[] data) {
- return murmur3_32(seed, data, 0, data.length);
- }
-
- public static int murmur3_32(int seed, int[] data, int offset, int len) {
- int h1 = seed;
-
- int off = offset;
- int end = offset + len;
-
- // body
- while (off < end) {
- int k1 = data[off++];
-
- k1 *= 0xcc9e2d51;
- k1 = Integer.rotateLeft(k1, 15);
- k1 *= 0x1b873593;
-
- h1 ^= k1;
- h1 = Integer.rotateLeft(h1, 13);
- h1 = h1 * 5 + 0xe6546b64;
- }
-
- // tail (always empty, as body is always 32-bit chunks)
-
- // finalization
-
- h1 ^= len * (Integer.SIZE / Byte.SIZE);
-
- // finalization mix force all bits of a hash block to avalanche
- h1 ^= h1 >>> 16;
- h1 *= 0x85ebca6b;
- h1 ^= h1 >>> 13;
- h1 *= 0xc2b2ae35;
- h1 ^= h1 >>> 16;
-
- return h1;
- }
-
- /**
- * Return a non-zero 32-bit pseudo random value. The {@code instance} object
- * may be used as part of the value.
- *
- * @param instance an object to use if desired in choosing value.
- * @return a non-zero 32-bit pseudo random value.
- */
- public static int randomHashSeed(Object instance) {
- int seed;
- if (sun.misc.VM.isBooted()) {
- seed = ThreadLocalRandom.current().nextInt();
- } else {
- // lower quality "random" seed value--still better than zero and not
- // not practically reversible.
- int hashing_seed[] = {
- System.identityHashCode(Hashing.class),
- System.identityHashCode(instance),
- System.identityHashCode(Thread.currentThread()),
- (int) Thread.currentThread().getId(),
- (int) (System.currentTimeMillis() >>> 2), // resolution is poor
- (int) (System.nanoTime() >>> 5), // resolution is poor
- (int) (Runtime.getRuntime().freeMemory() >>> 4) // alloc min
- };
-
- seed = murmur3_32(hashing_seed);
- }
-
- // force to non-zero.
- return (0 != seed) ? seed : 1;
- }
-}
--- a/jdk/test/sun/misc/Hashing.java Wed Jun 12 09:44:34 2013 +0100
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,127 +0,0 @@
-/*
- * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-
-/*
- * @test @summary Ensure that Murmur3 hash performs according to specification.
- * @compile -XDignore.symbol.file Hashing.java
- */
-public class Hashing {
-
- static final byte ONE_BYTE[] = {
- (byte) 0x80};
- static final byte TWO_BYTE[] = {
- (byte) 0x80, (byte) 0x81};
- static final char ONE_CHAR[] = {
- (char) 0x8180};
- static final byte THREE_BYTE[] = {
- (byte) 0x80, (byte) 0x81, (byte) 0x82};
- static final byte FOUR_BYTE[] = {
- (byte) 0x80, (byte) 0x81, (byte) 0x82, (byte) 0x83};
- static final char TWO_CHAR[] = {
- (char) 0x8180, (char) 0x8382};
- static final int ONE_INT[] = {
- 0x83828180};
- static final byte SIX_BYTE[] = {
- (byte) 0x80, (byte) 0x81, (byte) 0x82,
- (byte) 0x83, (byte) 0x84, (byte) 0x85};
- static final char THREE_CHAR[] = {
- (char) 0x8180, (char) 0x8382, (char) 0x8584};
- static final byte EIGHT_BYTE[] = {
- (byte) 0x80, (byte) 0x81, (byte) 0x82,
- (byte) 0x83, (byte) 0x84, (byte) 0x85,
- (byte) 0x86, (byte) 0x87};
- static final char FOUR_CHAR[] = {
- (char) 0x8180, (char) 0x8382,
- (char) 0x8584, (char) 0x8786};
- static final int TWO_INT[] = {
- 0x83828180, 0x87868584};
- // per http://code.google.com/p/smhasher/source/browse/trunk/main.cpp, line:72
- static final int MURMUR3_32_X86_CHECK_VALUE = 0xB0F57EE3;
-
- public static void testMurmur3_32_ByteArray() {
- System.out.println("testMurmur3_32_ByteArray");
-
- byte[] vector = new byte[256];
- byte[] hashes = new byte[4 * 256];
-
- for (int i = 0; i < 256; i++) {
- vector[i] = (byte) i;
- }
-
- // Hash subranges {}, {0}, {0,1}, {0,1,2}, ..., {0,...,255}
- for (int i = 0; i < 256; i++) {
- int hash = sun.misc.Hashing.murmur3_32(256 - i, vector, 0, i);
-
- hashes[i * 4] = (byte) hash;
- hashes[i * 4 + 1] = (byte) (hash >>> 8);
- hashes[i * 4 + 2] = (byte) (hash >>> 16);
- hashes[i * 4 + 3] = (byte) (hash >>> 24);
- }
-
- // hash to get final result.
- int final_hash = sun.misc.Hashing.murmur3_32(0, hashes);
-
- if (MURMUR3_32_X86_CHECK_VALUE != final_hash) {
- throw new RuntimeException(
- String.format("Calculated hash result not as expected. Expected %08X got %08X",
- MURMUR3_32_X86_CHECK_VALUE,
- final_hash));
- }
- }
-
- public static void testEquivalentHashes() {
- int bytes, chars, ints;
-
- System.out.println("testEquivalentHashes");
-
- bytes = sun.misc.Hashing.murmur3_32(TWO_BYTE);
- chars = sun.misc.Hashing.murmur3_32(ONE_CHAR);
- if (bytes != chars) {
- throw new RuntimeException(String.format("Hashes did not match. b:%08x != c:%08x", bytes, chars));
- }
-
- bytes = sun.misc.Hashing.murmur3_32(FOUR_BYTE);
- chars = sun.misc.Hashing.murmur3_32(TWO_CHAR);
- ints = sun.misc.Hashing.murmur3_32(ONE_INT);
- if ((bytes != chars) || (bytes != ints)) {
- throw new RuntimeException(String.format("Hashes did not match. b:%08x != c:%08x != i:%08x", bytes, chars, ints));
- }
- bytes = sun.misc.Hashing.murmur3_32(SIX_BYTE);
- chars = sun.misc.Hashing.murmur3_32(THREE_CHAR);
- if (bytes != chars) {
- throw new RuntimeException(String.format("Hashes did not match. b:%08x != c:%08x", bytes, chars));
- }
-
- bytes = sun.misc.Hashing.murmur3_32(EIGHT_BYTE);
- chars = sun.misc.Hashing.murmur3_32(FOUR_CHAR);
- ints = sun.misc.Hashing.murmur3_32(TWO_INT);
- if ((bytes != chars) || (bytes != ints)) {
- throw new RuntimeException(String.format("Hashes did not match. b:%08x != c:%08x != i:%08x", bytes, chars, ints));
- }
- }
-
- public static void main(String[] args) {
- testMurmur3_32_ByteArray();
- testEquivalentHashes();
- }
-}