Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF 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 org.apache.cassandra.transport; import java.lang.reflect.Array; import java.util.EnumMap; import java.util.Map; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import org.apache.cassandra.utils.Pair; public class OptionCodec<T extends Enum<T> & OptionCodec.Codecable<T>> { public interface Codecable<T extends Enum<T>> { public int getId(int version); public Object readValue(ByteBuf cb, int version); public void writeValue(Object value, ByteBuf cb, int version); public int serializedValueSize(Object obj, int version); } private final Class<T> klass; private final T[] ids; @SuppressWarnings({ "unchecked" }) public OptionCodec(Class<T> klass) { this.klass = klass; T[] values = klass.getEnumConstants(); int maxId = -1; for (T opt : values) maxId = Math.max(maxId, opt.getId(Server.CURRENT_VERSION)); ids = (T[]) Array.newInstance(klass, maxId + 1); for (T opt : values) { if (ids[opt.getId(Server.CURRENT_VERSION)] != null) throw new IllegalStateException( String.format("Duplicate option id %d", opt.getId(Server.CURRENT_VERSION))); ids[opt.getId(Server.CURRENT_VERSION)] = opt; } } private T fromId(int id) { T opt = ids[id]; if (opt == null) throw new ProtocolException(String.format("Unknown option id %d", id)); return opt; } public Map<T, Object> decode(ByteBuf body, int version) { EnumMap<T, Object> options = new EnumMap<T, Object>(klass); int n = body.readUnsignedShort(); for (int i = 0; i < n; i++) { T opt = fromId(body.readUnsignedShort()); Object value = opt.readValue(body, version); if (options.containsKey(opt)) throw new ProtocolException(String.format("Duplicate option %s in message", opt.name())); options.put(opt, value); } return options; } public ByteBuf encode(Map<T, Object> options, int version) { int optLength = 2; for (Map.Entry<T, Object> entry : options.entrySet()) optLength += 2 + entry.getKey().serializedValueSize(entry.getValue(), version); ByteBuf cb = Unpooled.buffer(optLength); cb.writeShort(options.size()); for (Map.Entry<T, Object> entry : options.entrySet()) { T opt = entry.getKey(); cb.writeShort(opt.getId(version)); opt.writeValue(entry.getValue(), cb, version); } return cb; } public Pair<T, Object> decodeOne(ByteBuf body, int version) { T opt = fromId(body.readUnsignedShort()); Object value = opt.readValue(body, version); return Pair.create(opt, value); } public void writeOne(Pair<T, Object> option, ByteBuf dest, int version) { T opt = option.left; Object obj = option.right; dest.writeShort(opt.getId(version)); opt.writeValue(obj, dest, version); } public int oneSerializedSize(Pair<T, Object> option, int version) { T opt = option.left; Object obj = option.right; return 2 + opt.serializedValueSize(obj, version); } }