AbstractBinaryMemcacheDecoder.java
/*
* Copyright 2013 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.
*/
package io.netty.handler.codec.memcache.binary;
import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.DecoderResult;
import io.netty.handler.codec.memcache.AbstractMemcacheObjectDecoder;
import io.netty.handler.codec.memcache.DefaultLastMemcacheContent;
import io.netty.handler.codec.memcache.DefaultMemcacheContent;
import io.netty.handler.codec.memcache.LastMemcacheContent;
import io.netty.handler.codec.memcache.MemcacheContent;
import io.netty.util.internal.UnstableApi;
import java.util.List;
/**
* Decoder for both {@link BinaryMemcacheRequest} and {@link BinaryMemcacheResponse}.
* <p/>
* The difference in the protocols (header) is implemented by the subclasses.
*/
@UnstableApi
public abstract class AbstractBinaryMemcacheDecoder<M extends BinaryMemcacheMessage>
extends AbstractMemcacheObjectDecoder {
public static final int DEFAULT_MAX_CHUNK_SIZE = 8192;
private final int chunkSize;
private M currentMessage;
private int alreadyReadChunkSize;
private State state = State.READ_HEADER;
/**
* Create a new {@link AbstractBinaryMemcacheDecoder} with default settings.
*/
protected AbstractBinaryMemcacheDecoder() {
this(DEFAULT_MAX_CHUNK_SIZE);
}
/**
* Create a new {@link AbstractBinaryMemcacheDecoder} with custom settings.
*
* @param chunkSize the maximum chunk size of the payload.
*/
protected AbstractBinaryMemcacheDecoder(int chunkSize) {
checkPositiveOrZero(chunkSize, "chunkSize");
this.chunkSize = chunkSize;
}
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
switch (state) {
case READ_HEADER: try {
if (in.readableBytes() < 24) {
return;
}
resetDecoder();
currentMessage = decodeHeader(in);
state = State.READ_EXTRAS;
} catch (Exception e) {
resetDecoder();
out.add(invalidMessage(e));
return;
}
case READ_EXTRAS: try {
byte extrasLength = currentMessage.extrasLength();
if (extrasLength > 0) {
if (in.readableBytes() < extrasLength) {
return;
}
currentMessage.setExtras(in.readRetainedSlice(extrasLength));
}
state = State.READ_KEY;
} catch (Exception e) {
resetDecoder();
out.add(invalidMessage(e));
return;
}
case READ_KEY: try {
short keyLength = currentMessage.keyLength();
if (keyLength > 0) {
if (in.readableBytes() < keyLength) {
return;
}
currentMessage.setKey(in.readRetainedSlice(keyLength));
}
out.add(currentMessage.retain());
state = State.READ_CONTENT;
} catch (Exception e) {
resetDecoder();
out.add(invalidMessage(e));
return;
}
case READ_CONTENT: try {
int valueLength = currentMessage.totalBodyLength()
- currentMessage.keyLength()
- currentMessage.extrasLength();
int toRead = in.readableBytes();
if (valueLength > 0) {
if (toRead == 0) {
return;
}
if (toRead > chunkSize) {
toRead = chunkSize;
}
int remainingLength = valueLength - alreadyReadChunkSize;
if (toRead > remainingLength) {
toRead = remainingLength;
}
ByteBuf chunkBuffer = in.readRetainedSlice(toRead);
MemcacheContent chunk;
if ((alreadyReadChunkSize += toRead) >= valueLength) {
chunk = new DefaultLastMemcacheContent(chunkBuffer);
} else {
chunk = new DefaultMemcacheContent(chunkBuffer);
}
out.add(chunk);
if (alreadyReadChunkSize < valueLength) {
return;
}
} else {
out.add(LastMemcacheContent.EMPTY_LAST_CONTENT);
}
resetDecoder();
state = State.READ_HEADER;
return;
} catch (Exception e) {
resetDecoder();
out.add(invalidChunk(e));
return;
}
case BAD_MESSAGE:
in.skipBytes(actualReadableBytes());
return;
default:
throw new Error("Unknown state reached: " + state);
}
}
/**
* Helper method to create a message indicating a invalid decoding result.
*
* @param cause the cause of the decoding failure.
* @return a valid message indicating failure.
*/
private M invalidMessage(Exception cause) {
state = State.BAD_MESSAGE;
M message = buildInvalidMessage();
message.setDecoderResult(DecoderResult.failure(cause));
return message;
}
/**
* Helper method to create a content chunk indicating a invalid decoding result.
*
* @param cause the cause of the decoding failure.
* @return a valid content chunk indicating failure.
*/
private MemcacheContent invalidChunk(Exception cause) {
state = State.BAD_MESSAGE;
MemcacheContent chunk = new DefaultLastMemcacheContent(Unpooled.EMPTY_BUFFER);
chunk.setDecoderResult(DecoderResult.failure(cause));
return chunk;
}
/**
* When the channel goes inactive, release all frames to prevent data leaks.
*
* @param ctx handler context
* @throws Exception
*/
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
super.channelInactive(ctx);
resetDecoder();
}
/**
* Prepare for next decoding iteration.
*/
protected void resetDecoder() {
if (currentMessage != null) {
currentMessage.release();
currentMessage = null;
}
alreadyReadChunkSize = 0;
}
/**
* Decode and return the parsed {@link BinaryMemcacheMessage}.
*
* @param in the incoming buffer.
* @return the decoded header.
*/
protected abstract M decodeHeader(ByteBuf in);
/**
* Helper method to create a upstream message when the incoming parsing did fail.
*
* @return a message indicating a decoding failure.
*/
protected abstract M buildInvalidMessage();
/**
* Contains all states this decoder can possibly be in.
* <p/>
* Note that most of the states can be optional, the only one required is reading
* the header ({@link #READ_HEADER}. All other steps depend on the length fields
* in the header and will be executed conditionally.
*/
enum State {
/**
* Currently reading the header portion.
*/
READ_HEADER,
/**
* Currently reading the extras portion (optional).
*/
READ_EXTRAS,
/**
* Currently reading the key portion (optional).
*/
READ_KEY,
/**
* Currently reading the value chunks (optional).
*/
READ_CONTENT,
/**
* Something went wrong while decoding the message or chunks.
*/
BAD_MESSAGE
}
}