com.hazelcast.nio.UnsafeHelper Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2016, Hazelcast, Inc. All Rights Reserved.
*
* 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.hazelcast.nio;
import com.hazelcast.logging.Logger;
import sun.misc.Unsafe;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedAction;
/**
* Unsafe accessor.
*
* Warning: Although both array base-offsets and array index-scales are constant over time currently,
* a later JVM implementation can change this behaviour to allow varying index-scales and base-offsets
* over time or per array instances (e.g. compressed primitive arrays or backwards growing arrays...)
*
* See Gil Tene's comment related to Unsafe usage;
* https://groups.google.com/d/msg/mechanical-sympathy/X-GtLuG0ETo/LMV1d_2IybQJ
*/
public final class UnsafeHelper {
public static final Unsafe UNSAFE;
public static final boolean UNSAFE_AVAILABLE;
public static final long BYTE_ARRAY_BASE_OFFSET;
public static final long BOOLEAN_ARRAY_BASE_OFFSET;
public static final long SHORT_ARRAY_BASE_OFFSET;
public static final long CHAR_ARRAY_BASE_OFFSET;
public static final long INT_ARRAY_BASE_OFFSET;
public static final long FLOAT_ARRAY_BASE_OFFSET;
public static final long LONG_ARRAY_BASE_OFFSET;
public static final long DOUBLE_ARRAY_BASE_OFFSET;
public static final int BOOLEAN_ARRAY_INDEX_SCALE;
public static final int BYTE_ARRAY_INDEX_SCALE;
public static final int SHORT_ARRAY_INDEX_SCALE;
public static final int CHAR_ARRAY_INDEX_SCALE;
public static final int INT_ARRAY_INDEX_SCALE;
public static final int FLOAT_ARRAY_INDEX_SCALE;
public static final int LONG_ARRAY_INDEX_SCALE;
public static final int DOUBLE_ARRAY_INDEX_SCALE;
public static final int MEM_COPY_THRESHOLD = 1024 * 1024;
private static final String UNSAFE_MODE_PROPERTY_NAME = "hazelcast.unsafe.mode";
private static final String UNSAFE_EXPLICITLY_DISABLED = "disabled";
private static final String UNSAFE_EXPLICITLY_ENABLED = "enforced";
private static final String UNSAFE_WARNING_WHEN_NOT_FOUND = "sun.misc.Unsafe isn't available, some features might "
+ "be not available";
private static final String UNSAFE_WARNING_WHEN_EXPLICTLY_DISABLED = "sun.misc.Unsafe has been disabled "
+ "via System Property " + UNSAFE_MODE_PROPERTY_NAME + ", some features might be not available.";
private static final String UNSAFE_WARNING_WHEN_UNALIGNED_ACCESS_NOT_ALLOWED = "sun.misc.Unsafe has been disabled "
+ "because your platform does not support unaligned access to memory, some features might be not available.";
private static final String UNSAFE_WARNING_WHEN_ENFORCED_ON_PLATFORM_WHERE_NOT_SUPPORTED = "You platform does not "
+ "seem to support unaligned access to memory. Unsafe usage has been enforced via System Property "
+ UNSAFE_MODE_PROPERTY_NAME + " This is not a supported configuration and it can crash JVM or corrupt your data!";
static {
Unsafe unsafe;
try {
unsafe = findUnsafeIfAllowed();
} catch (RuntimeException e) {
unsafe = null;
}
UNSAFE = unsafe;
BYTE_ARRAY_BASE_OFFSET = arrayBaseOffset(byte[].class, unsafe);
BOOLEAN_ARRAY_BASE_OFFSET = arrayBaseOffset(boolean[].class, unsafe);
SHORT_ARRAY_BASE_OFFSET = arrayBaseOffset(short[].class, unsafe);
CHAR_ARRAY_BASE_OFFSET = arrayBaseOffset(char[].class, unsafe);
INT_ARRAY_BASE_OFFSET = arrayBaseOffset(int[].class, unsafe);
FLOAT_ARRAY_BASE_OFFSET = arrayBaseOffset(float[].class, unsafe);
LONG_ARRAY_BASE_OFFSET = arrayBaseOffset(long[].class, unsafe);
DOUBLE_ARRAY_BASE_OFFSET = arrayBaseOffset(double[].class, unsafe);
BYTE_ARRAY_INDEX_SCALE = arrayIndexScale(byte[].class, unsafe);
BOOLEAN_ARRAY_INDEX_SCALE = arrayIndexScale(boolean[].class, unsafe);
SHORT_ARRAY_INDEX_SCALE = arrayIndexScale(short[].class, unsafe);
CHAR_ARRAY_INDEX_SCALE = arrayIndexScale(char[].class, unsafe);
INT_ARRAY_INDEX_SCALE = arrayIndexScale(int[].class, unsafe);
FLOAT_ARRAY_INDEX_SCALE = arrayIndexScale(float[].class, unsafe);
LONG_ARRAY_INDEX_SCALE = arrayIndexScale(long[].class, unsafe);
DOUBLE_ARRAY_INDEX_SCALE = arrayIndexScale(double[].class, unsafe);
boolean unsafeAvailable = false;
try {
// test if unsafe has required methods...
if (unsafe != null) {
byte[] buffer = new byte[8];
unsafe.putChar(buffer, BYTE_ARRAY_BASE_OFFSET, '0');
unsafe.putBoolean(buffer, BYTE_ARRAY_BASE_OFFSET, false);
unsafe.putShort(buffer, BYTE_ARRAY_BASE_OFFSET, (short) 1);
unsafe.putInt(buffer, BYTE_ARRAY_BASE_OFFSET, 2);
unsafe.putFloat(buffer, BYTE_ARRAY_BASE_OFFSET, 3f);
unsafe.putLong(buffer, BYTE_ARRAY_BASE_OFFSET, 4L);
unsafe.putDouble(buffer, BYTE_ARRAY_BASE_OFFSET, 5d);
unsafe.copyMemory(new byte[8], BYTE_ARRAY_BASE_OFFSET, buffer, BYTE_ARRAY_BASE_OFFSET, buffer.length);
unsafeAvailable = true;
}
} catch (Throwable e) {
Logger.getLogger(UnsafeHelper.class).warning(UNSAFE_WARNING_WHEN_NOT_FOUND);
}
UNSAFE_AVAILABLE = unsafeAvailable;
}
private UnsafeHelper() {
}
private static long arrayBaseOffset(Class type, Unsafe unsafe) {
return unsafe == null ? -1 : unsafe.arrayBaseOffset(type);
}
private static int arrayIndexScale(Class type, Unsafe unsafe) {
return unsafe == null ? -1 : unsafe.arrayIndexScale(type);
}
static Unsafe findUnsafeIfAllowed() {
if (isUnsafeExplicitlyDisabled()) {
Logger.getLogger(UnsafeHelper.class).warning(UNSAFE_WARNING_WHEN_EXPLICTLY_DISABLED);
return null;
}
if (!isUnalignedAccessAllowed()) {
if (isUnsafeExplicitlyEnforced()) {
Logger.getLogger(UnsafeHelper.class).warning(UNSAFE_WARNING_WHEN_ENFORCED_ON_PLATFORM_WHERE_NOT_SUPPORTED);
} else {
Logger.getLogger(UnsafeHelper.class).warning(UNSAFE_WARNING_WHEN_UNALIGNED_ACCESS_NOT_ALLOWED);
return null;
}
}
Unsafe unsafe = findUnsafe();
if (unsafe == null) {
Logger.getLogger(UnsafeHelper.class).warning(UNSAFE_WARNING_WHEN_NOT_FOUND);
}
return unsafe;
}
private static boolean isUnsafeExplicitlyDisabled() {
String mode = System.getProperty(UNSAFE_MODE_PROPERTY_NAME);
return UNSAFE_EXPLICITLY_DISABLED.equals(mode);
}
private static boolean isUnsafeExplicitlyEnforced() {
String mode = System.getProperty(UNSAFE_MODE_PROPERTY_NAME);
return UNSAFE_EXPLICITLY_ENABLED.equals(mode);
}
private static boolean isUnalignedAccessAllowed() {
// we can't use Unsafe to access memory on platforms where unaligned access is not allowed
// see https://github.com/hazelcast/hazelcast/issues/5518 for details.
String arch = System.getProperty("os.arch");
// list of architectures copied from OpenJDK - java.nio.Bits::unaligned
return arch.equals("i386") || arch.equals("x86") || arch.equals("amd64") || arch.equals("x86_64");
}
private static Unsafe findUnsafe() {
try {
return Unsafe.getUnsafe();
} catch (SecurityException se) {
return AccessController.doPrivileged(new PrivilegedAction() {
@Override
public Unsafe run() {
try {
Class type = Unsafe.class;
try {
Field field = type.getDeclaredField("theUnsafe");
field.setAccessible(true);
return type.cast(field.get(type));
} catch (Exception e) {
for (Field field : type.getDeclaredFields()) {
if (type.isAssignableFrom(field.getType())) {
field.setAccessible(true);
return type.cast(field.get(type));
}
}
}
} catch (Exception e) {
throw new RuntimeException("Unsafe unavailable", e);
}
throw new RuntimeException("Unsafe unavailable");
}
});
}
}
}
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