ai.vespa.airlift.zstd.UnsafeUtil Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of airlift-zstd Show documentation

Fork of https://github.com/airlift/aircompressor (zstd only). This module is temporary until we get an official release that includes the ZstdInputStream API (which is already implemented by two different people but neither PR shows any progress).

There is a newer version: 8.251.23

Show newest version

/*
 * 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 ai.vespa.airlift.zstd;

import ai.vespa.airlift.compress.IncompatibleJvmException;
import sun.misc.Unsafe;

import java.lang.reflect.Field;
import java.nio.Buffer;
import java.nio.ByteOrder;

import static java.lang.String.format;

final class UnsafeUtil
{
    public static final Unsafe UNSAFE;
    private static final long ADDRESS_OFFSET;

    private UnsafeUtil() {}

    static {
        ByteOrder order = ByteOrder.nativeOrder();
        if (!order.equals(ByteOrder.LITTLE_ENDIAN)) {
            throw new IncompatibleJvmException(format("Zstandard requires a little endian platform (found %s)", order));
        }

        try {
            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
            theUnsafe.setAccessible(true);
            UNSAFE = (Unsafe) theUnsafe.get(null);
        }
        catch (Exception e) {
            throw new IncompatibleJvmException("Zstandard requires access to sun.misc.Unsafe");
        }

        try {
            // fetch the address field for direct buffers
            ADDRESS_OFFSET = UNSAFE.objectFieldOffset(Buffer.class.getDeclaredField("address"));
        }
        catch (NoSuchFieldException e) {
            throw new IncompatibleJvmException("Zstandard requires access to java.nio.Buffer raw address field");
        }
    }

    public static long getAddress(Buffer buffer)
    {
        if (!buffer.isDirect()) {
            throw new IllegalArgumentException("buffer is not direct");
        }

        return UNSAFE.getLong(buffer, ADDRESS_OFFSET);
    }
}