func marshalStruct()

in ssh/messages.go [502:581]
76 lines of code
22 McCabe index (conditional complexity)

func marshalStruct(out []byte, msg interface{}) []byte {
	v := reflect.Indirect(reflect.ValueOf(msg))
	msgTypes := typeTags(v.Type())
	if len(msgTypes) > 0 {
		out = append(out, msgTypes[0])
	}

	for i, n := 0, v.NumField(); i < n; i++ {
		field := v.Field(i)
		switch t := field.Type(); t.Kind() {
		case reflect.Bool:
			var v uint8
			if field.Bool() {
				v = 1
			}
			out = append(out, v)
		case reflect.Array:
			if t.Elem().Kind() != reflect.Uint8 {
				panic(fmt.Sprintf("array of non-uint8 in field %d: %T", i, field.Interface()))
			}
			for j, l := 0, t.Len(); j < l; j++ {
				out = append(out, uint8(field.Index(j).Uint()))
			}
		case reflect.Uint32:
			out = appendU32(out, uint32(field.Uint()))
		case reflect.Uint64:
			out = appendU64(out, uint64(field.Uint()))
		case reflect.Uint8:
			out = append(out, uint8(field.Uint()))
		case reflect.String:
			s := field.String()
			out = appendInt(out, len(s))
			out = append(out, s...)
		case reflect.Slice:
			switch t.Elem().Kind() {
			case reflect.Uint8:
				if v.Type().Field(i).Tag.Get("ssh") != "rest" {
					out = appendInt(out, field.Len())
				}
				out = append(out, field.Bytes()...)
			case reflect.String:
				offset := len(out)
				out = appendU32(out, 0)
				if n := field.Len(); n > 0 {
					for j := 0; j < n; j++ {
						f := field.Index(j)
						if j != 0 {
							out = append(out, ',')
						}
						out = append(out, f.String()...)
					}
					// overwrite length value
					binary.BigEndian.PutUint32(out[offset:], uint32(len(out)-offset-4))
				}
			default:
				panic(fmt.Sprintf("slice of unknown type in field %d: %T", i, field.Interface()))
			}
		case reflect.Ptr:
			if t == bigIntType {
				var n *big.Int
				nValue := reflect.ValueOf(&n)
				nValue.Elem().Set(field)
				needed := intLength(n)
				oldLength := len(out)

				if cap(out)-len(out) < needed {
					newOut := make([]byte, len(out), 2*(len(out)+needed))
					copy(newOut, out)
					out = newOut
				}
				out = out[:oldLength+needed]
				marshalInt(out[oldLength:], n)
			} else {
				panic(fmt.Sprintf("pointer to unknown type in field %d: %T", i, field.Interface()))
			}
		}
	}

	return out
}