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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:
 *
 *   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 io.netty.handler.codec.protobuf;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import io.netty.handler.codec.CorruptedFrameException;

import java.util.List;

import com.google.protobuf.CodedInputStream;

/**
 * A decoder that splits the received {@link ByteBuf}s dynamically by the
 * value of the Google Protocol Buffers
 * Base
 * 128 Varints integer length field in the message.  For example:
 * 
 * BEFORE DECODE (302 bytes)       AFTER DECODE (300 bytes)
 * +--------+---------------+      +---------------+
 * | Length | Protobuf Data |----->| Protobuf Data |
 * | 0xAC02 |  (300 bytes)  |      |  (300 bytes)  |
 * +--------+---------------+      +---------------+
 * 
* * @see CodedInputStream */ public class ProtobufVarint32FrameDecoder extends ByteToMessageDecoder { // TODO maxFrameLength + safe skip + fail-fast option // (just like LengthFieldBasedFrameDecoder) @Override protected void decode(ChannelHandlerContext ctx, ByteBuf in, List out) throws Exception { in.markReaderIndex(); final byte[] buf = new byte[5]; for (int i = 0; i < buf.length; i ++) { if (!in.isReadable()) { in.resetReaderIndex(); return; } buf[i] = in.readByte(); if (buf[i] >= 0) { int length = CodedInputStream.newInstance(buf, 0, i + 1).readRawVarint32(); if (length < 0) { throw new CorruptedFrameException("negative length: " + length); } if (in.readableBytes() < length) { in.resetReaderIndex(); return; } else { out.add(in.readSlice(length).retain()); return; } } } // Couldn't find the byte whose MSB is off. throw new CorruptedFrameException("length wider than 32-bit"); } }