content: /*
   *
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.bookkeeper.util;
  
  import com.google.common.annotations.VisibleForTesting;
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.ChannelHandler.Sharable;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOutboundHandlerAdapter;
  import io.netty.channel.ChannelPromise;
  import io.netty.util.AbstractReferenceCounted;
  import io.netty.util.Recycler;
  import io.netty.util.Recycler.Handle;
  import io.netty.util.ReferenceCountUtil;
  import io.netty.util.ReferenceCounted;
  import java.util.ArrayList;
  
  /**
   * ByteBufList is a holder of a sequence of {@link ByteBuf} objects.
   *
   * <p>This class doesn't trying to mimic the {@link ByteBuf}, but rather exposes itself just like a regular object which
   * will need to be encoded on the channel. There are 2 utility encoders:
   * <ul>
   * <li>{@link #ENCODER}: regular encode that will write all the buffers in the {@link ByteBufList} on the channel</li>
   * </ul>
   *
   * <p>Example:
   *
   * <pre>
   * bootstrap.handler(new ChannelInitializer&lt;SocketChannel&gt;() {
   *     public void initChannel(SocketChannel ch) throws Exception {
   *         ChannelPipeline pipeline = ch.pipeline();
   *         pipeline.addLast("bytebufList", ByteBufList.ENCODER);
   *         pipeline.addLast("mainhandler", MyHandler.class);
   *     }
   * });
   * </pre>
   *
   * <p>ByteBufList is pooling the instances and uses ref-counting to release them.
   */
  public class ByteBufList extends AbstractReferenceCounted {
      private final ArrayList<ByteBuf> buffers;
      private final Handle<ByteBufList> recyclerHandle;
  
      private static final int INITIAL_LIST_SIZE = 4;
  
      private static final Recycler<ByteBufList> RECYCLER = new Recycler<ByteBufList>() {
          @Override
          protected ByteBufList newObject(Recycler.Handle<ByteBufList> handle) {
              return new ByteBufList(handle);
          }
      };
  
      private ByteBufList(Handle<ByteBufList> recyclerHandle) {
          this.recyclerHandle = recyclerHandle;
          this.buffers = new ArrayList<>(INITIAL_LIST_SIZE);
      }
  
      /**
       * Get a new {@link ByteBufList} from the pool and assign 2 buffers to it.
       *
       * <p>The buffers b1 and b2 lifecycles are now managed by the ByteBufList: when the {@link ByteBufList} is
       * deallocated, b1 and b2 will be released as well.
       *
       * @param b1
       *            first buffer
       * @param b2
       *            second buffer
       * @return a {@link ByteBufList} instance from the pool
       */
      public static ByteBufList get(ByteBuf b1, ByteBuf b2) {
          ByteBufList buf = get();
          buf.add(b1);
          buf.add(b2);
          return buf;
      }
  
      /**
       * Get a new {@link ByteBufList} from the pool and assign 1 buffer to it.
       *
       * <p>The buffer b1 lifecycle is now managed by the ByteBufList: when the {@link ByteBufList} is
       * deallocated, b1 will be released as well.
       *
       * @param b1
       *            first buffer
       * @return a {@link ByteBufList} instance from the pool
       */
      public static ByteBufList get(ByteBuf b1) {
          ByteBufList buf = get();
          buf.add(b1);
          return buf;
      }
  
      /**
       * Get a new {@link ByteBufList} instance from the pool that is the clone of an already existing instance.
       */
      public static ByteBufList clone(ByteBufList other) {
          ByteBufList buf = get();
          for (int i = 0; i < other.buffers.size(); i++) {
              // Create a duplicate of the buffer so that there is no interference from other threads
              buf.add(other.buffers.get(i).retainedDuplicate());
          }
          return buf;
      }
  
      public static ByteBufList get() {
          ByteBufList buf = RECYCLER.get();
          buf.setRefCnt(1);
          return buf;
      }
  
      /**
       * Append a {@link ByteBuf} at the end of this {@link ByteBufList}.
       */
      public void add(ByteBuf buf) {
          buffers.add(buf);
      }
  
      /**
       * Prepend a {@link ByteBuf} at the beginning of this {@link ByteBufList}.
       */
      public void prepend(ByteBuf buf) {
          buffers.add(0, buf);
      }
  
      /**
       * @return the total amount of readable bytes across all the {@link ByteBuf} included in the list
       */
      public int readableBytes() {
          int readableBytes = 0;
          for (int i = 0; i < buffers.size(); i++) {
              readableBytes += buffers.get(i).readableBytes();
          }
          return readableBytes;
      }
  
      /**
       * Get access to a particular buffer in the list.
       *
       * @param index
       *            the index of the buffer
       * @return the buffer
       */
      public ByteBuf getBuffer(int index) {
          return buffers.get(index);
      }
  
      /**
       * @return the number of buffers included in the {@link ByteBufList}
       */
      public int size() {
          return buffers.size();
      }
  
      /**
       * Write bytes from the current {@link ByteBufList} into a byte array.
       *
       * <p>This won't modify the reader index of the internal buffers.
       *
       * @param dst
       *            the destination byte array
       * @return the number of copied bytes
       */
      public int getBytes(byte[] dst) {
          int copied = 0;
          for (int idx = 0; idx < buffers.size() && copied < dst.length; idx++) {
              ByteBuf b = buffers.get(idx);
              int len = Math.min(b.readableBytes(), dst.length - copied);
              b.getBytes(b.readerIndex(), dst, copied, len);
  
              copied += len;
          }
  
          return copied;
      }
  
      /**
       * Creates a copy of the readable content of the internal buffers and returns the copy.
       * @return an array containing all the internal buffers content
       */
      public byte[] toArray() {
          byte[] a = new byte[readableBytes()];
          getBytes(a);
          return a;
      }
  
      /**
       * Returns {@code true} if this buffer has a single backing byte array.
       * If this method returns true, you can safely call {@link #array()} and
       * {@link #arrayOffset()}.
       * @return true, if this {@link ByteBufList} is backed by a single array
       */
      public boolean hasArray() {
          return buffers.size() == 1 && buffers.get(0).hasArray();
      }
  
      /**
       * Returns a reference to the array backing this {@link ByteBufList}.
       * This method must only be called if {@link #hasArray()} returns {@code true}.
       * @return the array backing this {@link ByteBufList}
       */
      public byte[] array() {
          return buffers.get(0).array();
      }
  
      /**
       * Returns the offset of the first byte within the backing byte array of
       * this buffer.
       * This method must only be called if {@link #hasArray()} returns {@code true}.
       * @return the offset of the first byte within the backing byte array.
       */
      public int arrayOffset() {
          return buffers.get(0).arrayOffset();
      }
  
      /**
       * @return a single buffer with the content of both individual buffers
       */
      @VisibleForTesting
      public static ByteBuf coalesce(ByteBufList list) {
          ByteBuf res = Unpooled.buffer(list.readableBytes());
          for (int i = 0; i < list.buffers.size(); i++) {
              ByteBuf b = list.buffers.get(i);
              res.writeBytes(b, b.readerIndex(), b.readableBytes());
          }
  
          return res;
      }
  
      @Override
      public ByteBufList retain() {
          super.retain();
          return this;
      }
  
      @Override
      protected void deallocate() {
          for (int i = 0; i < buffers.size(); i++) {
              buffers.get(i).release();
          }
  
          buffers.clear();
          recyclerHandle.recycle(this);
      }
  
      @Override
      public ReferenceCounted touch(Object hint) {
          for (int i = 0; i < buffers.size(); i++) {
              buffers.get(i).touch(hint);
          }
          return this;
      }
  
      /**
       * Encoder for the {@link ByteBufList} that doesn't prepend any size header.
       */
      public static final Encoder ENCODER = new Encoder();
  
      /**
       * {@link ByteBufList} encoder.
       */
      @Sharable
      public static class Encoder extends ChannelOutboundHandlerAdapter {
  
          @Override
          public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
              if (msg instanceof ByteBufList) {
                  ByteBufList b = (ByteBufList) msg;
  
                  ChannelPromise compositePromise = ctx.newPromise();
                  compositePromise.addListener(future -> {
                      // release the ByteBufList after the write operation is completed
                      ReferenceCountUtil.safeRelease(b);
                      // complete the promise passed as an argument unless it's a void promise
                      if (promise != null && !promise.isVoid()) {
                          if (future.isSuccess()) {
                              promise.setSuccess();
                          } else {
                              promise.setFailure(future.cause());
                          }
                      }
                  });
  
                  // Write each buffer individually on the socket. The retain() here is needed to preserve the fact
                  // that ByteBuf are automatically released after a write. If the ByteBufPair ref count is increased
                  // and it gets written multiple times, the individual buffers refcount should be reflected as well.
                  int buffersCount = b.buffers.size();
                  for (int i = 0; i < buffersCount; i++) {
                      ByteBuf bx = b.buffers.get(i);
                      // Last buffer will carry on the final promise to notify when everything was written on the
                      // socket
                      ctx.write(bx.retainedDuplicate(), i == (buffersCount - 1) ? compositePromise : ctx.voidPromise());
                  }
              } else {
                  ctx.write(msg, promise);
              }
          }
      }
  
  }
  