com.facebook.presto.jdbc.internal.io.airlift.slice.JvmUtils Maven / Gradle / Ivy
/*
* 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.facebook.presto.jdbc.internal.io.airlift.slice;
import sun.misc.Unsafe;
import java.lang.reflect.Field;
import java.nio.Buffer;
import static com.facebook.presto.jdbc.internal.io.airlift.slice.Preconditions.checkArgument;
import static sun.misc.Unsafe.ARRAY_BOOLEAN_INDEX_SCALE;
import static sun.misc.Unsafe.ARRAY_BYTE_INDEX_SCALE;
import static sun.misc.Unsafe.ARRAY_DOUBLE_INDEX_SCALE;
import static sun.misc.Unsafe.ARRAY_FLOAT_INDEX_SCALE;
import static sun.misc.Unsafe.ARRAY_INT_INDEX_SCALE;
import static sun.misc.Unsafe.ARRAY_LONG_INDEX_SCALE;
import static sun.misc.Unsafe.ARRAY_SHORT_INDEX_SCALE;
final class JvmUtils
{
static final Unsafe unsafe;
private static final long ADDRESS_OFFSET;
static {
try {
// fetch theUnsafe object
Field field = Unsafe.class.getDeclaredField("theUnsafe");
field.setAccessible(true);
unsafe = (Unsafe) field.get(null);
if (unsafe == null) {
throw new RuntimeException("Unsafe access not available");
}
// verify the stride of arrays matches the width of primitives
assertArrayIndexScale("Boolean", ARRAY_BOOLEAN_INDEX_SCALE, 1);
assertArrayIndexScale("Byte", ARRAY_BYTE_INDEX_SCALE, 1);
assertArrayIndexScale("Short", ARRAY_SHORT_INDEX_SCALE, 2);
assertArrayIndexScale("Int", ARRAY_INT_INDEX_SCALE, 4);
assertArrayIndexScale("Long", ARRAY_LONG_INDEX_SCALE, 8);
assertArrayIndexScale("Float", ARRAY_FLOAT_INDEX_SCALE, 4);
assertArrayIndexScale("Double", ARRAY_DOUBLE_INDEX_SCALE, 8);
// fetch the address field for direct buffers
ADDRESS_OFFSET = unsafe.objectFieldOffset(Buffer.class.getDeclaredField("address"));
}
catch (ReflectiveOperationException e) {
throw new RuntimeException(e);
}
}
private static void assertArrayIndexScale(final String name, int actualIndexScale, int expectedIndexScale)
{
if (actualIndexScale != expectedIndexScale) {
throw new IllegalStateException(name + " array index scale must be " + expectedIndexScale + ", but is " + actualIndexScale);
}
}
static long bufferAddress(Buffer buffer)
{
checkArgument(buffer.isDirect(), "buffer is not direct");
return unsafe.getLong(buffer, ADDRESS_OFFSET);
}
private JvmUtils() {}
}
© 2015 - 2024 Weber Informatics LLC | Privacy Policy