Package org.apache.bookkeeper.util

Class ByteBufVisitor

java.lang.Object

org.apache.bookkeeper.util.ByteBufVisitor

public class ByteBufVisitor
extends Object

This class visits the possible wrapped child buffers of a Netty ByteBuf for a given offset and length.

The Netty ByteBuf API does not provide a method to visit the wrapped child buffers. The ByteBuf.unwrap() method is not suitable for this purpose as it loses the ByteBuf.readerIndex() state, resulting in incorrect offset and length information.

Despite Netty not having a public API for visiting the sub buffers, it is possible to achieve this using the ByteBuf.getBytes(int, ByteBuf, int, int) method. This class uses this method to visit the wrapped child buffers by providing a suitable ByteBuf implementation. This implementation supports the role of the destination buffer for the getBytes call. It requires implementing the ByteBuf.setBytes(int, ByteBuf, int, int) and ByteBuf.setBytes(int, byte[], int, int) methods and other methods required by getBytes such as ByteBuf.hasArray(), ByteBuf.hasMemoryAddress(), ByteBuf.nioBufferCount() and ByteBuf.capacity(). All other methods in the internal ByteBuf implementation are not supported and will throw an exception. This is to ensure correctness and to fail fast if some ByteBuf implementation is not following the expected and supported interface contract.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	ByteBufVisitor.ByteBufVisitorCallback<T>	The callback interface for visiting buffers.
(package private) static class	ByteBufVisitor.GetBytesCallbackByteBuf<T>	A ByteBuf implementation that can be used as the destination buffer for a ByteBuf.getBytes(int, ByteBuf) for visiting the wrapped child buffers.

Method Summary

Modifier and Type	Method	Description
static <T> void	visitBuffers(io.netty.buffer.ByteBuf buffer, int offset, int length, ByteBufVisitor.ByteBufVisitorCallback<T> callback, T context)	This method traverses the potential nested composite buffers of the provided buffer, given a specific offset and length.
static <T> void	visitBuffers(io.netty.buffer.ByteBuf buffer, int offset, int length, ByteBufVisitor.ByteBufVisitorCallback<T> callback, T context, int maxDepth)	See @visitBuffers(ByteBuf, int, int, ByteBufVisitorCallback, Object).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

visitBuffers

public static <T> void visitBuffers(io.netty.buffer.ByteBuf buffer,
 int offset,
 int length,
 ByteBufVisitor.ByteBufVisitorCallback<T> callback,
 T context)

This method traverses the potential nested composite buffers of the provided buffer, given a specific offset and length. The traversal continues until it encounters a buffer that is backed by an array or a memory address, which allows for the inspection of individual buffer segments without the need for data duplication. If no such wrapped buffer is found, the callback function is invoked with the original buffer, offset, and length as parameters.

Parameters:

buffer - the buffer to visit

offset - the offset for the buffer

length - the length for the buffer

callback - the callback to call for each visited buffer

context - the context to pass to the callback

visitBuffers

public static <T> void visitBuffers(io.netty.buffer.ByteBuf buffer,
 int offset,
 int length,
 ByteBufVisitor.ByteBufVisitorCallback<T> callback,
 T context,
 int maxDepth)

See @visitBuffers(ByteBuf, int, int, ByteBufVisitorCallback, Object). This method allows to specify the maximum depth of recursion for visiting wrapped buffers.