1 /*
2 * Copyright 2015 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.handler.codec.protobuf;
17
18 import com.google.protobuf.CodedOutputStream;
19 import com.google.protobuf.nano.CodedOutputByteBufferNano;
20 import io.netty.buffer.ByteBuf;
21 import io.netty.channel.ChannelHandler.Sharable;
22 import io.netty.channel.ChannelHandlerContext;
23 import io.netty.handler.codec.MessageToByteEncoder;
24
25 /**
26 * An encoder that prepends the Google Protocol Buffers
27 * <a href="https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints">Base
28 * 128 Varints</a> integer length field. For example:
29 * <pre>
30 * BEFORE ENCODE (300 bytes) AFTER ENCODE (302 bytes)
31 * +---------------+ +--------+---------------+
32 * | Protobuf Data |-------------->| Length | Protobuf Data |
33 * | (300 bytes) | | 0xAC02 | (300 bytes) |
34 * +---------------+ +--------+---------------+
35 * </pre> *
36 *
37 * @see CodedOutputStream
38 * @see CodedOutputByteBufferNano
39 */
40 @Sharable
41 public class ProtobufVarint32LengthFieldPrepender extends MessageToByteEncoder<ByteBuf> {
42
43 public ProtobufVarint32LengthFieldPrepender() {
44 super(ByteBuf.class);
45 }
46
47 @Override
48 protected void encode(
49 ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception {
50 int bodyLen = msg.readableBytes();
51 int headerLen = computeRawVarint32Size(bodyLen);
52 out.ensureWritable(headerLen + bodyLen);
53 writeRawVarint32(out, bodyLen);
54 out.writeBytes(msg, msg.readerIndex(), bodyLen);
55 }
56
57 /**
58 * Writes protobuf varint32 to (@link ByteBuf).
59 * @param out to be written to
60 * @param value to be written
61 */
62 static void writeRawVarint32(ByteBuf out, int value) {
63 while (true) {
64 if ((value & ~0x7F) == 0) {
65 out.writeByte(value);
66 return;
67 } else {
68 out.writeByte((value & 0x7F) | 0x80);
69 value >>>= 7;
70 }
71 }
72 }
73
74 /**
75 * Computes size of protobuf varint32 after encoding.
76 * @param value which is to be encoded.
77 * @return size of value encoded as protobuf varint32.
78 */
79 static int computeRawVarint32Size(final int value) {
80 if ((value & (0xffffffff << 7)) == 0) {
81 return 1;
82 }
83 if ((value & (0xffffffff << 14)) == 0) {
84 return 2;
85 }
86 if ((value & (0xffffffff << 21)) == 0) {
87 return 3;
88 }
89 if ((value & (0xffffffff << 28)) == 0) {
90 return 4;
91 }
92 return 5;
93 }
94 }