/*
* 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:
*
* 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 com.facebook.presto.jdbc.internal.netty.handler.codec.frame;
import com.facebook.presto.jdbc.internal.netty.buffer.ChannelBuffer;
import com.facebook.presto.jdbc.internal.netty.buffer.ChannelBufferFactory;
import com.facebook.presto.jdbc.internal.netty.channel.Channel;
import com.facebook.presto.jdbc.internal.netty.channel.ChannelHandlerContext;
/**
* A decoder that splits the received {@link ChannelBuffer}s by the fixed number
* of bytes. For example, if you received the following four fragmented packets:
* <pre>
* +---+----+------+----+
* | A | BC | DEFG | HI |
* +---+----+------+----+
* </pre>
* A {@link FixedLengthFrameDecoder}{@code (3)} will decode them into the
* following three packets with the fixed length:
* <pre>
* +-----+-----+-----+
* | ABC | DEF | GHI |
* +-----+-----+-----+
* </pre>
*/
public class FixedLengthFrameDecoder extends FrameDecoder {
private final int frameLength;
private final boolean allocateFullBuffer;
/**
* Calls {@link #FixedLengthFrameDecoder(int, boolean)} with {@code false}
*/
public FixedLengthFrameDecoder(int frameLength) {
this(frameLength, false);
}
/**
* Creates a new instance.
*
* @param frameLength
* the length of the frame
* @param allocateFullBuffer
* {@code true} if the cumulative {@link ChannelBuffer} should use the
* {@link #frameLength} as its initial size
*/
public FixedLengthFrameDecoder(int frameLength, boolean allocateFullBuffer) {
if (frameLength <= 0) {
throw new IllegalArgumentException(
"frameLength must be a positive integer: " + frameLength);
}
this.frameLength = frameLength;
this.allocateFullBuffer = allocateFullBuffer;
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
if (buffer.readableBytes() < frameLength) {
return null;
} else {
ChannelBuffer frame = extractFrame(buffer, buffer.readerIndex(), frameLength);
buffer.skipBytes(frameLength);
return frame;
}
}
@Override
protected ChannelBuffer newCumulationBuffer(ChannelHandlerContext ctx, int minimumCapacity) {
ChannelBufferFactory factory = ctx.getChannel().getConfig().getBufferFactory();
if (allocateFullBuffer) {
return factory.getBuffer(frameLength);
}
return super.newCumulationBuffer(ctx, minimumCapacity);
}
}