min-dev-java/src/main/java/packet/CPacket.java

package packet;

import component.ComponentException;
import component.IdentifierWrapper;
import component.Payload;
import component.TTL;
import encoding.*;

/*
 * @Author: Wang Feng
 * @Description:
 * @Version: 1.0.0
 * @Date: 22:07 2021/3/13
 * @Copyright: MIN-Group；国家重大科技基础设施——未来网络北大实验室；深圳市信息论与未来网络重点实验室
 */
//
// 表示一个通用的MIN推式包
//
// @Description:
//	1. 包格式定义如下：
//		CPacket = 5 TLV-LENGTH
//             { CommonIdentifier }          => 标识区
//             { Signature }                 => 签名区
//             {                             => 只读区
//                 <Payload>
//             }
//             {                             => 可变区
//                 {                         => 受保护区
//                     "Empty"
//                 }
//                 {                         => 非受保护区
//                     [TTL]
//                 }
//             }
//
public class CPacket implements InteractWithField, IEncodingAble {
    private MINPacket minPacket;
    private TTL ttl;
    private Payload payload;
    private String flatIdentifier; // 推式包拥有一个扁平的标识

    public  CPacket(){
        minPacket=new MINPacket();
        ttl=new TTL();
        payload=new Payload();
    }

    /**
     * 将 CPacket 的各项属性填充到 MINPacket 中定义的对应分区当中
     * @Description:
     * //	1. 主要填充标识区、只读区和可变区
     * @return
     */
    @Override
    public boolean fillDataToFields() throws PacketException {
        // 可变区 => 受保护区（无）

        // 填充可变区 => 非受保护区
        // 首先清除所有的Block
        this.minPacket.mutableField.mutableDangerousField.clearBlocks();
        Block block= null;
        try {
            block = new SelfEncodingBase().selfWireEncode(this.ttl);
        } catch (EncoderException | BlockException | ComponentException e) {
            throw new PacketException("CPacket.fillDataToFields: "+e.getMessage());
        }
        if(block==null){
            return false;
        }
        this.minPacket.mutableField.mutableDangerousField.addBlock(block);

        // 填充只读区
        // 首先清除所有的Block
        this.minPacket.readOnlyField.clearBlocks();
        try {
            block=new SelfEncodingBase().selfWireEncode(this.payload);
        } catch (EncoderException | BlockException | ComponentException e) {
            throw new PacketException("CPacket.fillDataToFields: "+e.getMessage());
        }
        if(block==null){
            return false;
        }
        this.minPacket.readOnlyField.addBlock(block);

        // 填充标识区
        // 首先清除所有的标识
        this.minPacket.identifierField.clearIdentifiers();
        IdentifierWrapper identifierWrapper=
                new IdentifierWrapper().createCommonIdentifierByString(this.flatIdentifier);
        if(identifierWrapper==null){
            return false;
        }
        this.minPacket.identifierField.addIdentifier(identifierWrapper);

        return true;
    }

    /**
     * 从 MINPacket 的分区当中提取出 CPacket 的各项属性
     * @return
     */
    @Override
    public boolean extraDataFromFields() throws PacketException {
        // 提取 Payload
        Block payloadBlock=this.minPacket.readOnlyField.getBlockByType(new VlInt(TLV.TlvPayload));
        if(payloadBlock==null){
            return false;
        }
        if(this.payload.wireDecode(payloadBlock)){
            return false;
        }

        // 提取 TTL
        Block ttlBlock=this.minPacket.mutableField.mutableDangerousField.getBlockByType(new VlInt(TLV.TlvTTL));
        if(ttlBlock==null){
            return false;
        }
        try {
            if(this.ttl.wireDecode(ttlBlock)){
                return false;
            }
        } catch (ComponentException e) {
            throw new PacketException("CPacket.extraDataFromFields: "+e.getMessage());
        }

        // 提取标识
        IdentifierWrapper commonIdentifier=this.minPacket.identifierField.getIdentifierByType(new VlInt(TLV.TlvIdentifierCommon));
        if(commonIdentifier==null){
            return false;
        }
        String identifierString=commonIdentifier.toUri();
        if((identifierString.length()>0)&&(identifierString.startsWith("/"))){
            this.flatIdentifier=identifierString.substring(1);
        }

        return true;
    }

    /**
     * 将 CPacket 编码成 TLV
     * @param encoder
     * @return
     */
    @Override
    public int wireEncode(Encoder encoder) throws PacketException {
        // 首先将属性填充到分区当中
        if(!this.fillDataToFields()){
            return 0;
        }

        // 指定包类型
        this.minPacket.packetType=new VlInt(TLV.TlvPacketMINCommon);

        return this.minPacket.wireEncode(encoder);
    }

    /**
     * 从 TLV Block 中解码出一个 CPacket
     * @param block
     * @return
     */
    @Override
    public boolean wireDecode(Block block) throws PacketException {
        if(!this.minPacket.wireDecode(block)){
            return false;
        }
        return this.extraDataFromFields();
    }

    /**
     * 展示平面标识
     * @return
     */
    public String toUri(){
        return this.flatIdentifier;
    }

    /**
     * 设置推式包的平面标识，eg: asdfsvnjweivnjsdcs
     * @param identifier
     */
    public void setIdentifier(String identifier){
        this.flatIdentifier=identifier;
    }

    /**
     * 获取推式包的平面标识
     * @return
     */
    public String getIdentifier(){
        return this.flatIdentifier;
    }

    /**
     * 得到 TTL
     * @return
     */
    public TTL getTtl() {
        return ttl;
    }

    /**
     * 设置 TTL
     * @param ttl
     */
    public void setTtl(TTL ttl) {
        this.ttl = ttl;
    }
}