/*
* Copyright (c) 2008-2017, 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.internal.memory.impl;
import com.hazelcast.logging.ILogger;
import com.hazelcast.logging.Logger;
import com.hazelcast.nio.Bits;
import sun.misc.Unsafe;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedAction;
import static com.hazelcast.util.ExceptionUtil.rethrow;
import static com.hazelcast.util.QuickMath.normalize;
/**
* Utility class for {@link sun.misc.Unsafe}.
*/
public final class UnsafeUtil {
/**
* If this constant is {@code true}, then {@link #UNSAFE} refers to a usable {@link sun.misc.Unsafe} instance.
*/
public static final boolean UNSAFE_AVAILABLE;
/**
* The {@link sun.misc.Unsafe} instance which is available and ready to use.
*/
public static final Unsafe UNSAFE;
private static final ILogger LOGGER = Logger.getLogger(UnsafeUtil.class);
static {
Unsafe unsafe;
try {
unsafe = findUnsafe();
if (unsafe != null) {
// test if unsafe has required methods...
checkUnsafeInstance(unsafe);
}
} catch (Throwable t) {
unsafe = null;
logFailureToFindUnsafeDueTo(t);
}
UNSAFE = unsafe;
UNSAFE_AVAILABLE = UNSAFE != null;
}
private UnsafeUtil() {
}
private static Unsafe findUnsafe() {
try {
return Unsafe.getUnsafe();
} catch (SecurityException se) {
return AccessController.doPrivileged(new PrivilegedAction<Unsafe>() {
@Override
public Unsafe run() {
try {
Class<Unsafe> 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 (Throwable t) {
throw rethrow(t);
}
throw new RuntimeException("Unsafe unavailable");
}
});
}
}
@SuppressWarnings("checkstyle:magicnumber")
private static void checkUnsafeInstance(Unsafe unsafe) {
long arrayBaseOffset = unsafe.arrayBaseOffset(byte[].class);
byte[] buffer = new byte[(int) arrayBaseOffset + (2 * Bits.LONG_SIZE_IN_BYTES)];
unsafe.putByte(buffer, arrayBaseOffset, (byte) 0x00);
unsafe.putBoolean(buffer, arrayBaseOffset, false);
unsafe.putChar(buffer, normalize(arrayBaseOffset, Bits.CHAR_SIZE_IN_BYTES), '0');
unsafe.putShort(buffer, normalize(arrayBaseOffset, Bits.SHORT_SIZE_IN_BYTES), (short) 1);
unsafe.putInt(buffer, normalize(arrayBaseOffset, Bits.INT_SIZE_IN_BYTES), 2);
unsafe.putFloat(buffer, normalize(arrayBaseOffset, Bits.FLOAT_SIZE_IN_BYTES), 3f);
unsafe.putLong(buffer, normalize(arrayBaseOffset, Bits.LONG_SIZE_IN_BYTES), 4L);
unsafe.putDouble(buffer, normalize(arrayBaseOffset, Bits.DOUBLE_SIZE_IN_BYTES), 5d);
unsafe.copyMemory(new byte[buffer.length], arrayBaseOffset, buffer, arrayBaseOffset, buffer.length);
}
private static void logFailureToFindUnsafeDueTo(final Throwable reason) {
if (LOGGER.isFinestEnabled()) {
LOGGER.finest("Unable to get an instance of Unsafe. Unsafe-based operations will be unavailable", reason);
} else {
LOGGER.warning("Unable to get an instance of Unsafe. Unsafe-based operations will be unavailable");
}
}
}