0e4c073bcf
Motivation: ByteToMessageDecoder requires using an intermediate List to put results into. This intermediate list adds overhead (memory/CPU) which grows as the number of objects increases. This overhead can be avoided by directly propagating events through the ChannelPipeline via ctx.fireChannelRead(...). This also makes the semantics more clear and allows us to keep track if we need to call ctx.read() in all cases. Modifications: - Remove List from the method signature of ByteToMessageDecoder.decode(...) and decodeLast(...) - Adjust all sub-classes - Adjust unit tests - Fix javadocs. Result: Adjust ByteToMessageDecoder as noted in https://github.com/netty/netty/issues/8525.
115 lines
3.9 KiB
Java
115 lines
3.9 KiB
Java
/*
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* Copyright 2015 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.handler.codec.dns;
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import io.netty.buffer.ByteBuf;
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import io.netty.channel.ChannelHandler;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.channel.socket.DatagramPacket;
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import io.netty.handler.codec.CorruptedFrameException;
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import io.netty.handler.codec.MessageToMessageDecoder;
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import io.netty.util.internal.UnstableApi;
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import static java.util.Objects.requireNonNull;
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/**
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* Decodes a {@link DatagramPacket} into a {@link DatagramDnsQuery}.
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*/
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@UnstableApi
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@ChannelHandler.Sharable
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public class DatagramDnsQueryDecoder extends MessageToMessageDecoder<DatagramPacket> {
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private final DnsRecordDecoder recordDecoder;
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/**
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* Creates a new decoder with {@linkplain DnsRecordDecoder#DEFAULT the default record decoder}.
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*/
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public DatagramDnsQueryDecoder() {
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this(DnsRecordDecoder.DEFAULT);
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}
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/**
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* Creates a new decoder with the specified {@code recordDecoder}.
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*/
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public DatagramDnsQueryDecoder(DnsRecordDecoder recordDecoder) {
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this.recordDecoder = requireNonNull(recordDecoder, "recordDecoder");
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}
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@Override
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protected void decode(ChannelHandlerContext ctx, DatagramPacket packet) throws Exception {
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final ByteBuf buf = packet.content();
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DnsQuery query = newQuery(packet, buf);
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try {
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final int questionCount = buf.readUnsignedShort();
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final int answerCount = buf.readUnsignedShort();
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final int authorityRecordCount = buf.readUnsignedShort();
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final int additionalRecordCount = buf.readUnsignedShort();
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decodeQuestions(query, buf, questionCount);
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decodeRecords(query, DnsSection.ANSWER, buf, answerCount);
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decodeRecords(query, DnsSection.AUTHORITY, buf, authorityRecordCount);
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decodeRecords(query, DnsSection.ADDITIONAL, buf, additionalRecordCount);
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DnsQuery q = query;
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query = null;
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ctx.fireChannelRead(q);
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} finally {
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if (query != null) {
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query.release();
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}
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}
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}
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private static DnsQuery newQuery(DatagramPacket packet, ByteBuf buf) {
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final int id = buf.readUnsignedShort();
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final int flags = buf.readUnsignedShort();
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if (flags >> 15 == 1) {
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throw new CorruptedFrameException("not a query");
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}
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final DnsQuery query =
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new DatagramDnsQuery(
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packet.sender(),
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packet.recipient(),
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id,
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DnsOpCode.valueOf((byte) (flags >> 11 & 0xf)));
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query.setRecursionDesired((flags >> 8 & 1) == 1);
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query.setZ(flags >> 4 & 0x7);
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return query;
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}
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private void decodeQuestions(DnsQuery query, ByteBuf buf, int questionCount) throws Exception {
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for (int i = questionCount; i > 0; i--) {
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query.addRecord(DnsSection.QUESTION, recordDecoder.decodeQuestion(buf));
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}
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}
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private void decodeRecords(
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DnsQuery query, DnsSection section, ByteBuf buf, int count) throws Exception {
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for (int i = count; i > 0; i--) {
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final DnsRecord r = recordDecoder.decodeRecord(buf);
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if (r == null) {
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// Truncated response
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break;
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}
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query.addRecord(section, r);
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}
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}
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}
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