Function layerString

packet.go:255–313

layerString outputs, recursively, a layer in a "smart" way. See docs for LayerString for more details. Params: i - value to write out anonymous: if we're currently recursing an anonymous member of a struct writeSpace: if we've already written a value in a struct, and need to write a space before

(v reflect.Value, anonymous bool, writeSpace bool)

//     write a space before writing more.  This happens when we write various
//     anonymous values, and need to keep writing more.
func layerString(v reflect.Value, anonymous bool, writeSpace bool) string {
	// Let String() functions take precedence.
	if v.CanInterface() {
		if s, ok := v.Interface().(fmt.Stringer); ok {
			return s.String()
		}
	}
	// Reflect, and spit out all the exported fields as key=value.
	switch v.Type().Kind() {
	case reflect.Interface, reflect.Ptr:
		if v.IsNil() {
			return "nil"
		}
		r := v.Elem()
		return layerString(r, anonymous, writeSpace)
	case reflect.Struct:
		var b bytes.Buffer
		typ := v.Type()
		if !anonymous {
			b.WriteByte('{')
		}
		for i := 0; i < v.NumField(); i++ {
			// Check if this is upper-case.
			ftype := typ.Field(i)
			f := v.Field(i)
			if ftype.Anonymous {
				anonStr := layerString(f, true, writeSpace)
				writeSpace = writeSpace || anonStr != ""
				b.WriteString(anonStr)
			} else if ftype.PkgPath == "" { // exported
				if writeSpace {
					b.WriteByte(' ')
				}
				writeSpace = true
				fmt.Fprintf(&b, "%s=%s", typ.Field(i).Name, layerString(f, false, writeSpace))
			}
		}
		if !anonymous {
			b.WriteByte('}')
		}
		return b.String()
	case reflect.Slice:
		var b bytes.Buffer
		b.WriteByte('[')
		if v.Len() > 4 {
			fmt.Fprintf(&b, "..%d..", v.Len())
		} else {
			for j := 0; j < v.Len(); j++ {
				if j != 0 {
					b.WriteString(", ")
				}
				b.WriteString(layerString(v.Index(j), false, false))
			}
		}
		b.WriteByte(']')
		return b.String()
	}
	return fmt.Sprintf("%v", v.Interface())