Java tutorial
/* * Copyright (c) 2015 Huawei, Inc and others. All rights reserved. * * This program and the accompanying materials are made available under the * terms of the Eclipse Public License v1.0 which accompanies this distribution, * and is available at http://www.eclipse.org/legal/epl-v10.html */ package org.opendaylight.usc.protocol; import java.io.IOException; import org.opendaylight.usc.protocol.UscHeader.OperationType; import io.netty.buffer.ByteBuf; /** * Base class of a UscFrame packet. */ public abstract class UscFrame { private final UscHeader header; /** * Constructs a new UscFrame * * @param operationType * @param port * @param sessionId * @param payloadLength */ public UscFrame(OperationType operationType, int port, int sessionId, int payloadLength) { this.header = new UscHeader(UscHeader.USC_VERSION, operationType, port, sessionId, payloadLength); } /** * Returns the USC header * * @return the USC header */ public UscHeader getHeader() { return header; } /** * Length of the frame in bytes, inclusive of both the header and the. * payload * * @return Length of the frame in bytes. */ public int length() { return header.length() + header.getPayloadLength(); } /** * To be implemented by subclasses to return the payload as a ByteBuf. * * @return payload as a buffer */ public abstract ByteBuf getPayload(); /** * Decodes a ByteBuf into a UscFrame * * @param buf * @return * @throws IOException */ public static UscFrame getFromByteBuf(ByteBuf buf) throws IOException { final UscHeader header = UscHeader.fromByteBuffer(buf.nioBuffer(0, UscHeader.HEADER_LENGTH)); buf.readerIndex(UscHeader.HEADER_LENGTH); final int port = header.getApplicationPort(); final int sessionId = header.getSessionId(); final UscFrame result; switch (header.getOperationType()) { case DATA: result = new UscData(port, sessionId, buf.copy()); break; case CONTROL: result = new UscControl(port, sessionId, buf.readUnsignedShort()); break; case ERROR: result = new UscError(port, sessionId, buf.readUnsignedShort()); break; default: result = null; throw new IOException("Invalid operation type"); } return result; } }