asn1

This is a minor fork of the encoding/asn1 package. It adds in two tags for TLV data into structs:

• littleendian for little endian data
• class for explicit specification of expected class of tag (see wiki article for more details).

For example:

type Info struct {
    FirmwareVersion    []byte `asn1:"tag:64,class:1"`
    SerialNumber       []byte `asn1:"tag:65,class:1"`
    PartNumber         []byte `asn1:"tag:66,class:1"`
    AccelSampleRate    int    `asn1:"tag:67,class:1,littleendian"`
    MagsenseSampleRate int    `asn1:"tag:68,class:1,littleendian"`
    AccelFFTSize       int    `asn1:"tag:69,class:1,littleendian"`
    MagsenseFFTSize    int    `asn1:"tag:70,class:1,littleendian"`
}

func main() {
    // 3 indicates Private specification
    // 0 indicates Primitive (octets directly encode data)
    // 5c is the number of bytes to follow 
    // the rest is described in the struct tags
    bytes, _ := hex.DecodeString("305c" + "5f402373696c766572676c6164652f6663635f76302e302e322d37342d6736636639636134005f410e554e494e495449414c495a4544005f420e554e494e495449414c495a4544005f430200195f440220035f450200085f46028000")

    var info Info

    _, err := Unmarshal(bytes, &info)

    if err != nil {
        panic(err)
    }

    fmt.Printf("%+v\n", info)
    fmt.Println(string(info.FirmwareVersion))
    fmt.Println(string(info.SerialNumber))
    fmt.Println(string(info.PartNumber))

    marshaledBytes, err := Marshal(info)

    if err != nil {
        panic(err)
    }

    if hex.EncodeToString(marshaledBytes) != byteString {
        panic("Remarshaling did not match\n%s\n%s", byteString, hex.EncodeToString(marshaledBytes))
    }
}