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/*
* Copyright 2012 The Netty Project
*
* The Netty Project 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:
*
* 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.
*/
/**
* Abstraction of a byte buffer - the fundamental data structure
* to represent a low-level binary and text message.
*
* Netty uses its own buffer API instead of NIO {@link java.nio.ByteBuffer} to
* represent a sequence of bytes. This approach has significant advantage over
* using {@link java.nio.ByteBuffer}. Netty's new buffer type,
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf}, has been designed from ground
* up to address the problems of {@link java.nio.ByteBuffer} and to meet the
* daily needs of network application developers. To list a few cool features:
*
*
You can define your buffer type if necessary.
*
Transparent zero copy is achieved by built-in composite buffer type.
*
A dynamic buffer type is provided out-of-the-box, whose capacity is
* expanded on demand, just like {@link java.lang.StringBuffer}.
*
There's no need to call the {@code flip()} method anymore.
*
It is often faster than {@link java.nio.ByteBuffer}.
*
*
*
Extensibility
*
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} has rich set of operations
* optimized for rapid protocol implementation. For example,
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} provides various operations
* for accessing unsigned values and strings and searching for certain byte
* sequence in a buffer. You can also extend or wrap existing buffer type
* to add convenient accessors. The custom buffer type still implements
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} interface rather than
* introducing an incompatible type.
*
*
Transparent Zero Copy
*
* To lift up the performance of a network application to the extreme, you need
* to reduce the number of memory copy operation. You might have a set of
* buffers that could be sliced and combined to compose a whole message. Netty
* provides a composite buffer which allows you to create a new buffer from the
* arbitrary number of existing buffers with no memory copy. For example, a
* message could be composed of two parts; header and body. In a modularized
* application, the two parts could be produced by different modules and
* assembled later when the message is sent out.
*
* If {@link java.nio.ByteBuffer} were used, you would have to create a new big
* buffer and copy the two parts into the new buffer. Alternatively, you can
* perform a gathering write operation in NIO, but it restricts you to represent
* the composite of buffers as an array of {@link java.nio.ByteBuffer}s rather
* than a single buffer, breaking the abstraction and introducing complicated
* state management. Moreover, it's of no use if you are not going to read or
* write from an NIO channel.
*
* // The composite type is incompatible with the component type.
* ByteBuffer[] message = new ByteBuffer[] { header, body };
*
* By contrast, {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} does not have such
* caveats because it is fully extensible and has a built-in composite buffer
* type.
*
* // The composite type is compatible with the component type.
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} message = {@link org.apache.pulsar.shade.io.netty.buffer.Unpooled}.wrappedBuffer(header, body);
*
* // Therefore, you can even create a composite by mixing a composite and an
* // ordinary buffer.
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} messageWithFooter = {@link org.apache.pulsar.shade.io.netty.buffer.Unpooled}.wrappedBuffer(message, footer);
*
* // Because the composite is still a {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf}, you can access its content
* // easily, and the accessor method will behave just like it's a single buffer
* // even if the region you want to access spans over multiple components. The
* // unsigned integer being read here is located across body and footer.
* messageWithFooter.getUnsignedInt(
* messageWithFooter.readableBytes() - footer.readableBytes() - 1);
*
*
*
Automatic Capacity Extension
*
* Many protocols define variable length messages, which means there's no way to
* determine the length of a message until you construct the message or it is
* difficult and inconvenient to calculate the length precisely. It is just
* like when you build a {@link java.lang.String}. You often estimate the length
* of the resulting string and let {@link java.lang.StringBuffer} expand itself
* on demand.
*
* // A new dynamic buffer is created. Internally, the actual buffer is created
* // lazily to avoid potentially wasted memory space.
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} b = {@link org.apache.pulsar.shade.io.netty.buffer.Unpooled}.buffer(4);
*
* // When the first write attempt is made, the internal buffer is created with
* // the specified initial capacity (4).
* b.writeByte('1');
*
* b.writeByte('2');
* b.writeByte('3');
* b.writeByte('4');
*
* // When the number of written bytes exceeds the initial capacity (4), the
* // internal buffer is reallocated automatically with a larger capacity.
* b.writeByte('5');
*
*
*
Better Performance
*
* Most frequently used buffer implementation of
* {@link org.apache.pulsar.shade.io.netty.buffer.ByteBuf} is a very thin wrapper of a
* byte array (i.e. {@code byte[]}). Unlike {@link java.nio.ByteBuffer}, it has
* no complicated boundary check and index compensation, and therefore it is
* easier for a JVM to optimize the buffer access. More complicated buffer
* implementation is used only for sliced or composite buffers, and it performs
* as well as {@link java.nio.ByteBuffer}.
*/
package org.apache.pulsar.shade.io.netty.buffer;
