content: /*
   * Copyright 2014-2025 Real Logic Limited.
   *
   * 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
   *
   * 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.aeron;
  
  import io.aeron.logbuffer.ControlledFragmentHandler;
  import io.aeron.logbuffer.Header;
  import org.agrona.DirectBuffer;
  
  import static io.aeron.logbuffer.FrameDescriptor.*;
  
  /**
   * A {@link ControlledFragmentHandler} that sits in a chain-of-responsibility pattern that reassembles fragmented
   * messages so that the next handler in the chain only sees whole messages. This is for a single session on an
   * {@link Image} and not for multiple session {@link Image}s in a {@link Subscription}.
   * <p>
   * Unfragmented messages are delegated without copy. Fragmented messages are copied to a temporary
   * buffer for reassembly before delegation.
   * <p>
   * The {@link Header} passed to the delegate on assembling a message will be that of the last fragment.
   *
   * @see Image#controlledPoll(ControlledFragmentHandler, int)
   * @see Image#controlledPeek(long, ControlledFragmentHandler, long)
   */
  public class ImageControlledFragmentAssembler implements ControlledFragmentHandler
  {
      private final ControlledFragmentHandler delegate;
      private final BufferBuilder builder;
  
      /**
       * Construct an adapter to reassemble message fragments and delegate on whole messages.
       *
       * @param delegate onto which whole messages are forwarded.
       */
      public ImageControlledFragmentAssembler(final ControlledFragmentHandler delegate)
      {
          this(delegate, 0, false);
      }
  
      /**
       * Construct an adapter to reassemble message fragments and delegate on whole messages.
       *
       * @param delegate            onto which whole messages are forwarded.
       * @param initialBufferLength to be used for the session.
       */
      public ImageControlledFragmentAssembler(final ControlledFragmentHandler delegate, final int initialBufferLength)
      {
          this(delegate, initialBufferLength, false);
      }
  
      /**
       * Construct an adapter to reassemble message fragments and delegate on whole messages.
       *
       * @param delegate            onto which whole messages are forwarded.
       * @param initialBufferLength to be used for the session.
       * @param isDirectByteBuffer  is the underlying buffer to be a direct {@link java.nio.ByteBuffer}?
       */
      public ImageControlledFragmentAssembler(
          final ControlledFragmentHandler delegate, final int initialBufferLength, final boolean isDirectByteBuffer)
      {
          this.delegate = delegate;
          this.builder = new BufferBuilder(initialBufferLength, isDirectByteBuffer);
      }
  
      /**
       * Get the delegate unto which assembled messages are delegated.
       *
       * @return the delegate unto which assembled messages are delegated.
       */
      public ControlledFragmentHandler delegate()
      {
          return delegate;
      }
  
      /**
       * Get the {@link BufferBuilder} for resetting this assembler.
       *
       * @return the {@link BufferBuilder} for resetting this assembler.
       */
      BufferBuilder bufferBuilder()
      {
          return builder;
      }
  
      /**
       * The implementation of {@link ControlledFragmentHandler} that reassembles and forwards whole messages.
       *
       * @param buffer containing the data.
       * @param offset at which the data begins.
       * @param length of the data in bytes.
       * @param header representing the metadata for the data.
       * @return {@link io.aeron.logbuffer.ControlledFragmentHandler.Action} to be taken after processing fragment.
       */
      public Action onFragment(final DirectBuffer buffer, final int offset, final int length, final Header header)
      {
          Action action = Action.CONTINUE;
          final byte flags = header.flags();
  
          if ((flags & UNFRAGMENTED) == UNFRAGMENTED)
          {
              action = delegate.onFragment(buffer, offset, length, header);
          }
          else if ((flags & BEGIN_FRAG_FLAG) == BEGIN_FRAG_FLAG)
          {
              builder.reset()
                  .captureHeader(header)
                  .append(buffer, offset, length)
                  .nextTermOffset(header.nextTermOffset());
          }
          else if (header.termOffset() == builder.nextTermOffset())
          {
              final int limit = builder.limit();
  
              builder.append(buffer, offset, length);
  
              if ((flags & END_FRAG_FLAG) == END_FRAG_FLAG)
              {
                  action = delegate.onFragment(
                      builder.buffer(), 0, builder.limit(), builder.completeHeader(header));
  
                  if (Action.ABORT == action)
                  {
                      builder.limit(limit);
                  }
                  else
                  {
                      builder.reset();
                  }
              }
              else
              {
                  builder.nextTermOffset(header.nextTermOffset());
              }
          }
          else
          {
              builder.reset();
          }
  
          return action;
      }
  }
  