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/*
 * Copyright 2015 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 com.google.protobuf.CodedOutputStream;
import com.google.protobuf.nano.CodedOutputByteBufferNano;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;

/**
 * An encoder that prepends the Google Protocol Buffers
 * Base
 * 128 Varints integer length field. For example:
 * 
 * BEFORE ENCODE (300 bytes)       AFTER ENCODE (302 bytes)
 * +---------------+               +--------+---------------+
 * | Protobuf Data |-------------->| Length | Protobuf Data |
 * |  (300 bytes)  |               | 0xAC02 |  (300 bytes)  |
 * +---------------+               +--------+---------------+
 * 
* * * @see CodedOutputStream * @see CodedOutputByteBufferNano */ @Sharable public class ProtobufVarint32LengthFieldPrepender extends MessageToByteEncoder { @Override protected void encode( ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception { int bodyLen = msg.readableBytes(); int headerLen = computeRawVarint32Size(bodyLen); out.ensureWritable(headerLen + bodyLen); writeRawVarint32(out, bodyLen); out.writeBytes(msg, msg.readerIndex(), bodyLen); } /** * Writes protobuf varint32 to (@link ByteBuf). * @param out to be written to * @param value to be written */ static void writeRawVarint32(ByteBuf out, int value) { while (true) { if ((value & ~0x7F) == 0) { out.writeByte(value); return; } else { out.writeByte((value & 0x7F) | 0x80); value >>>= 7; } } } /** * Computes size of protobuf varint32 after encoding. * @param value which is to be encoded. * @return size of value encoded as protobuf varint32. */ static int computeRawVarint32Size(final int value) { if ((value & (0xffffffff << 7)) == 0) { return 1; } if ((value & (0xffffffff << 14)) == 0) { return 2; } if ((value & (0xffffffff << 21)) == 0) { return 3; } if ((value & (0xffffffff << 28)) == 0) { return 4; } return 5; } }




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