go - 如何执行动态解码

Question

任何人都可以帮助我根据从 Diameter 客户端收到的消息类型执行动态解码。在下面的代码中，我必须使用两个结构来表示直径服务器接收到的两条不同消息。我想修改将请求解码到结构 var req HandleDERRequest 的当前代码，以便对 var req HandleDERRequest 或 var 动态完成解码challreq HandleChallRequest，取决于接收到的与特定结构匹配的消息。我试图用下面的代码来实现，但它没有按预期工作。所有答案都同时返回，这不是我所期望的。

func HandleDER(settings sm.Settings) diam.HandlerFunc {

    // If received AVP messages are of this struct format, Unmarshal message to this structure

    type HandleDERRequest struct {
        SessionID         datatype.UTF8String       `avp:"Session-Id"`
        OriginHost        datatype.DiameterIdentity `avp:"Origin-Host"`
        OriginRealm       datatype.DiameterIdentity `avp:"Origin-Realm"`
        DestinationHost   datatype.DiameterIdentity `avp:"Destination-Host"`
        DestinationRealm  datatype.DiameterIdentity `avp:"Destination-Realm"`
        UserName          datatype.UTF8String       `avp:"User-Name"`
        AuthSessionState  datatype.Enumerated       `avp:"Auth-Session-State"`
        AuthApplicationID datatype.Unsigned32       `avp:"Auth-Application-Id"`
        AuthRequestType   datatype.Enumerated       `avp:"Auth-Request-Type"`
        EAPPayload        datatype.OctetString      `avp:"EAP-Payload"`
        RATType           datatype.Enumerated       `avp:"RAT-Type"`
        ANID              datatype.UTF8String       `avp:"ANID"`
    }

    // If received AVP messages are of this struct format, Unmarshal message to this structure

    type HandleChallRequest struct {
        SessionID        datatype.UTF8String       `avp:"Session-Id"`
        OriginHost       datatype.DiameterIdentity `avp:"Origin-Host"`
        OriginRealm      datatype.DiameterIdentity `avp:"Origin-Realm"`
        DestinationHost  datatype.DiameterIdentity `avp:"Destination-Host"`
        DestinationRealm datatype.DiameterIdentity `avp:"Destination-Realm"`
        EAPPayload       datatype.OctetString      `avp:"EAP-Payload"`
    }

    return func(c diam.Conn, m *diam.Message) {

        var err error = nil
        var req HandleDERRequest

        var code uint32 = diam.Success
        err = m.Unmarshal(&req)
        if err != nil {
            err = fmt.Errorf("Unmarshal failed: %s", err)
            code = diam.UnableToComply
            log.Printf("Invalid DER(%d): %s\n", code, err.Error())
        }
        a := m.Answer(code)
        a.NewAVP(avp.SessionID, avp.Mbit, 0, req.SessionID)
        a.NewAVP(avp.OriginHost, avp.Mbit, 0, req.DestinationHost)
        a.NewAVP(avp.OriginRealm, avp.Mbit, 0, req.DestinationRealm)
        a.NewAVP(avp.OriginStateID, avp.Mbit, 0, settings.OriginStateID)
        _, err = AKA_Challenge_Request(settings, c, a)
        if err != nil {
            log.Printf("Failed to send AAA challenge request: %s", err.Error())
        }

        var challreq HandleChallageRequest
        err = m.Unmarshal(&challreq)
        if err != nil {
            err = fmt.Errorf("Unmarshal failed: %s", err)
            code = diam.UnableToComply
            log.Printf("Invalid DER(%d): %s\n", code, err.Error())
        }
        a = m.Answer(code)
        a.NewAVP(avp.SessionID, avp.Mbit, 0, req.SessionID)
        a.NewAVP(avp.OriginHost, avp.Mbit, 0, req.DestinationHost)
        a.NewAVP(avp.OriginRealm, avp.Mbit, 0, req.DestinationRealm)
        a.NewAVP(avp.OriginStateID, avp.Mbit, 0, settings.OriginStateID)
        _, err = AKA_Success_Notification(settings, c, a)
        if err != nil {
           log.Printf("Failed to send Success Notification: %s", err.Error())
       }
    }
}

func AKA_Challenge_Request(settings sm.Settings, w io.Writer, m *diam.Message) (n int64, err error) {
    PayloadSlice := []byte(`RAND, AUTHN, MAC, RESULT_ID`)
    m.NewAVP(avp.EAPPayload, avp.Mbit, 0, datatype.OctetString(PayloadSlice))
    return m.WriteTo(w)
}

func AKA_Success_Notification(settings sm.Settings, w io.Writer, m *diam.Message) (n int64, err error) {
    EAPSlice := []byte(`EAP_Success`)
    MSKSlice := []byte(`EAP-Master-Session-Key`)
    m.NewAVP(avp.EAPPayload, avp.Mbit, 0, datatype.OctetString(EAPSlice))
    m.NewAVP(avp.EAPMasterSessionKey, avp.Mbit, 0, datatype.OctetString(MSKSlice))
    return m.WriteTo(w)
}

我知道返回函数应该有一个if条件，但我不知道如何开始。请知道如何去做。

Answer 1

我会说此时不需要 HandleChallRequest 类型。如果我正确阅读了字段，两种类型都具有相同的基本属性，但 HandleDERRequest 类型具有更多属性，这些属性是否可以在未编码类型中只是 nil 值？

然后你可以做一些 nil 检查来确定一个数据集与另一个数据集，或者更优选的是创建一个具有所有字段和一组通用方法的接口(interface)，这样你就可以创建两种类型实现这个接口(interface)，选择就变成了创建哪个接口(interface)。

编辑 1.

再次抱歉，如果我没有捕获要点，但我仍然看不到不同类型的必要性，在我看来它们只是数据容器，具有不同的数据。

这是我在单一数据类型方面的想法。

func HandleDER(settings sm.Settings) diam.HandlerFunc {

// If received AVP messages are of this struct format, Unmarshal message to this structure

type HandleRequest struct {
    SessionID         datatype.UTF8String       `avp:"Session-Id"`
    OriginHost        datatype.DiameterIdentity `avp:"Origin-Host"`
    OriginRealm       datatype.DiameterIdentity `avp:"Origin-Realm"`
    DestinationHost   datatype.DiameterIdentity `avp:"Destination-Host"`
    DestinationRealm  datatype.DiameterIdentity `avp:"Destination-Realm"`
    UserName          datatype.UTF8String       `avp:"User-Name"`
    AuthSessionState  datatype.Enumerated       `avp:"Auth-Session-State"`
    AuthApplicationID datatype.Unsigned32       `avp:"Auth-Application-Id"`
    AuthRequestType   datatype.Enumerated       `avp:"Auth-Request-Type"`
    EAPPayload        datatype.OctetString      `avp:"EAP-Payload"`
    RATType           datatype.Enumerated       `avp:"RAT-Type"`
    ANID              datatype.UTF8String       `avp:"ANID"`
}

// If received AVP messages are of this struct format, Unmarshal message to this structure

return func(c diam.Conn, m *diam.Message) {

    var err error = nil
    var req HandleRequest

    var code uint32 = diam.Success

    err = m.Unmarshal(&req)
    if err != nil {
        err = fmt.Errorf("Unmarshal failed: %s", err)
        code = diam.UnableToComply
        log.Printf("Invalid DER(%d): %s\n", code, err.Error())
    }
    a := m.Answer(code)
    a.NewAVP(avp.SessionID, avp.Mbit, 0, req.SessionID)
    a.NewAVP(avp.OriginHost, avp.Mbit, 0, req.DestinationHost)
    a.NewAVP(avp.OriginRealm, avp.Mbit, 0, req.DestinationRealm)
    a.NewAVP(avp.OriginStateID, avp.Mbit, 0, settings.OriginStateID)

    if ("messagetype" == "first message type") {
        _, err = AKA_Challenge_Request(settings, c, a)
        if err != nil {
            log.Printf("Failed to send AAA challenge request: %s", err.Error())
        }
    } else {
        _, err = AKA_Success_Notification(settings, c, a)
        if err != nil {
            log.Printf("Failed to send Success Notification: %s", err.Error())
        }
    }
}