Repository: netty/netty
File: buffer/src/main/java/io/netty/buffer/UnpooledUnsafeDirectByteBuf.java (Java)

Code before:
 * with the License. You may obtain a copy of the License at:
 *
 *   https://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 io.netty.buffer;

import io.netty.util.internal.CleanableDirectBuffer;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.UnstableApi;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;

/**
 * A NIO {@link ByteBuffer} based buffer. It is recommended to use
 * {@link UnpooledByteBufAllocator#directBuffer(int, int)}, {@link Unpooled#directBuffer(int)} and
 * {@link Unpooled#wrappedBuffer(ByteBuffer)} instead of calling the constructor explicitly.}
 */
public class UnpooledUnsafeDirectByteBuf extends UnpooledDirectByteBuf {

    private static final boolean USE_VAR_HANDLE =
            !PlatformDependent.isUnaligned() &&
            !PlatformDependent.isUnalignedAvailable() &&
            PlatformDependent.hasVarHandle();

    long memoryAddress;

    /**
     * Creates a new direct buffer.
     *
     * @param initialCapacity the initial capacity of the underlying direct buffer
     * @param maxCapacity     the maximum capacity of the underlying direct buffer
     */
    public UnpooledUnsafeDirectByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
        super(alloc, initialCapacity, maxCapacity);
    }

    /**
     * Creates a new direct buffer by wrapping the specified initial buffer.
     *
     * @param maxCapacity the maximum capacity of the underlying direct buffer
     */
    protected UnpooledUnsafeDirectByteBuf(ByteBufAllocator alloc, ByteBuffer initialBuffer, int maxCapacity) {

Review comment (suggestion):
Let me try to understand what is going on here, please confirm:
1. Netty detect presence of Unsafe - which will make it to allocate Unsafe-handled buffers
2. BUT...unalignment is not detected properly, so it can use VarHandle for multi-bytes accesses

This looks a bit odd, but kind-of make sense. 
And for SWAR, instead, I see that this benefit the non-Unsafe case too, or I'm misreading it?
Please confirm 🙏 
And thanks for this!

Code after:
 * with the License. You may obtain a copy of the License at:
 *
 *   https://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 io.netty.buffer;

import io.netty.util.internal.CleanableDirectBuffer;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.UnstableApi;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;

/**
 * A NIO {@link ByteBuffer} based buffer. It is recommended to use
 * {@link UnpooledByteBufAllocator#directBuffer(int, int)}, {@link Unpooled#directBuffer(int)} and
 * {@link Unpooled#wrappedBuffer(ByteBuffer)} instead of calling the constructor explicitly.}
 */
public class UnpooledUnsafeDirectByteBuf extends UnpooledDirectByteBuf {

    private static final boolean USE_VAR_HANDLE = PlatformDependent.useVarHandleForMultiByteAccess();

    long memoryAddress;

    /**
     * Creates a new direct buffer.
     *
     * @param initialCapacity the initial capacity of the underlying direct buffer
     * @param maxCapacity     the maximum capacity of the underlying direct buffer
     */
    public UnpooledUnsafeDirectByteBuf(ByteBufAllocator alloc, int initialCapacity, int maxCapacity) {
        super(alloc, initialCapacity, maxCapacity);
    }

    /**
     * Creates a new direct buffer by wrapping the specified initial buffer.
     *
     * @param maxCapacity the maximum capacity of the underlying direct buffer
     */
    protected UnpooledUnsafeDirectByteBuf(ByteBufAllocator alloc, ByteBuffer initialBuffer, int maxCapacity) {
        // We never try to free the buffer if it was provided by the end-user as we don't know if this is a duplicate or
        // a slice. This is done to prevent an IllegalArgumentException when using Java9 as Unsafe.invokeCleaner(...)
        // will check if the given buffer is either a duplicate or slice and in this case throw an