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/*
* Copyright 2014-2023 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.FragmentHandler;
import io.aeron.logbuffer.Header;
import org.agrona.BitUtil;
import org.agrona.DirectBuffer;
import static io.aeron.logbuffer.FrameDescriptor.*;
import static io.aeron.protocol.DataHeaderFlyweight.HEADER_LENGTH;
/**
* A {@link FragmentHandler} 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}.
*
* Unfragmented messages are delegated without copy. Fragmented messages are copied to a temporary
* buffer for reassembly before delegation.
*
* The {@link Header} passed to the delegate on assembling a message will be that of the last fragment.
*/
public class ImageFragmentAssembler implements FragmentHandler
{
private final FragmentHandler delegate;
private final BufferBuilder builder;
/**
* Construct an adapter to reassemble message fragments and delegate on only whole messages.
*
* @param delegate onto which whole messages are forwarded.
*/
public ImageFragmentAssembler(final FragmentHandler delegate)
{
this(delegate, 0, false);
}
/**
* Construct an adapter to reassemble message fragments and delegate on only whole messages.
*
* @param delegate onto which whole messages are forwarded.
* @param initialBufferLength to be used for the session.
*/
public ImageFragmentAssembler(final FragmentHandler delegate, final int initialBufferLength)
{
this.delegate = delegate;
this.builder = new BufferBuilder(initialBufferLength, false);
}
/**
* Construct an adapter to reassemble message fragments and delegate on only 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 ImageFragmentAssembler(
final FragmentHandler 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 FragmentHandler delegate()
{
return delegate;
}
/**
* Get the {@link BufferBuilder} for resetting this assembler.
*
* @return the {@link BufferBuilder} for resetting this assembler.
*/
public BufferBuilder bufferBuilder()
{
return builder;
}
/**
* The implementation of {@link FragmentHandler} 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.
*/
public void onFragment(final DirectBuffer buffer, final int offset, final int length, final Header header)
{
final byte flags = header.flags();
if ((flags & UNFRAGMENTED) == UNFRAGMENTED)
{
delegate.onFragment(buffer, offset, length, header);
}
else
{
handleFragment(buffer, offset, length, header, flags);
}
}
private void handleFragment(
final DirectBuffer buffer, final int offset, final int length, final Header header, final byte flags)
{
if ((flags & BEGIN_FRAG_FLAG) == BEGIN_FRAG_FLAG)
{
builder.reset()
.append(buffer, offset, length)
.nextTermOffset(BitUtil.align(offset + length + HEADER_LENGTH, FRAME_ALIGNMENT));
}
else if (offset == builder.nextTermOffset())
{
builder.append(buffer, offset, length);
if ((flags & END_FRAG_FLAG) == END_FRAG_FLAG)
{
delegate.onFragment(builder.buffer(), 0, builder.limit(), header);
builder.reset();
}
else
{
builder.nextTermOffset(BitUtil.align(offset + length + HEADER_LENGTH, FRAME_ALIGNMENT));
}
}
else
{
builder.reset();
}
}
}