Golang StructValue.Field方法代码示例

// Generic struct printer.
// Doesn't care about the string tag "domain-name",
// but does look for an "ipv4" tag on uint32 variables
// and the "ipv6" tag on array variables,
// printing them as IP addresses.
func printStructValue(val *reflect.StructValue) string {
	s := "{"
	for i := 0; i < val.NumField(); i++ {
		if i > 0 {
			s += ", "
		}
		f := val.Type().(*reflect.StructType).Field(i)
		if !f.Anonymous {
			s += f.Name + "="
		}
		fval := val.Field(i)
		if fv, ok := fval.(*reflect.StructValue); ok {
			s += printStructValue(fv)
		} else if fv, ok := fval.(*reflect.UintValue); ok && f.Tag == "ipv4" {
			i := fv.Get()
			s += IPv4(byte(i>>24), byte(i>>16), byte(i>>8), byte(i)).String()
		} else if fv, ok := fval.(*reflect.ArrayValue); ok && f.Tag == "ipv6" {
			i := fv.Interface().([]byte)
			s += IP(i).String()
		} else {
			s += fmt.Sprint(fval.Interface())
		}
	}
	s += "}"
	return s
}

func writeStruct(w io.Writer, val *reflect.StructValue) (err os.Error) {
	if _, err = fmt.Fprint(w, "{"); err != nil {
		return
	}

	typ := val.Type().(*reflect.StructType)

	for i := 0; i < val.NumField(); i++ {
		fieldValue := val.Field(i)
		if _, err = fmt.Fprintf(w, "%s:", Quote(typ.Field(i).Name)); err != nil {
			return
		}
		if err = writeValue(w, fieldValue); err != nil {
			return
		}
		if i < val.NumField()-1 {
			if _, err = fmt.Fprint(w, ","); err != nil {
				return
			}
		}
	}

	_, err = fmt.Fprint(w, "}")
	return
}

func enc_struct(val *reflect.StructValue, typ *reflect.StructType, buffer *bytes.Buffer) os.Error {
	buffer.WriteString("{")
	first := true
	for i := 0; i < typ.NumField(); i++ {
		f := typ.Field(i)
		if f.Tag == "" {
			continue
		}
		tags := strings.Split(f.Tag[3:len(f.Tag)-1], ",", -1)
		l := buffer.Len()
		if first {
			buffer.WriteString(fmt.Sprintf("\"%v\":", tags[1]))
		} else {
			buffer.WriteString(fmt.Sprintf(",\"%v\":", tags[1]))
		}
		written, err := enc(val.Field(i), f.Type, buffer, tags[2] == "req")
		if err != nil {
			return err
		}
		if !written {
			buffer.Truncate(l)
		} else {
			first = false
		}
	}
	buffer.WriteString("}")
	return nil
}

func writeStruct(w io.Writer, val *reflect.StructValue) (err os.Error) {
	_, err = fmt.Fprint(w, "d")
	if err != nil {
		return
	}

	typ := val.Type().(*reflect.StructType)

	numFields := val.NumField()
	svList := make(StringValueArray, numFields)

	for i := 0; i < numFields; i++ {
		field := typ.Field(i)
		key := field.Name
		if len(field.Tag) > 0 {
			key = field.Tag
		}
		svList[i].key = key
		svList[i].value = val.Field(i)
	}

	err = writeSVList(w, svList)
	if err != nil {
		return
	}

	_, err = fmt.Fprint(w, "e")
	if err != nil {
		return
	}
	return
}

// Get the i'th arg of the struct value.
// If the arg itself is an interface, return a value for
// the thing inside the interface, not the interface itself.
func getField(v *reflect.StructValue, i int) reflect.Value {
	val := v.Field(i)
	if i, ok := val.(*reflect.InterfaceValue); ok {
		if inter := i.Interface(); inter != nil {
			return reflect.NewValue(inter)
		}
	}
	return val
}

func encodeStruct(w io.Writer, v *reflect.StructValue) (err os.Error) {
	n := v.NumField()
	if err = printfLine(w, "*%d", n); err != nil {
		return
	}
	for i := 0; i < n; i++ {
		if err = encode(w, v.Field(i).Interface()); err != nil {
			return
		}
	}
	return nil
}

func fuzzyEqualStruct(a *reflect.StructValue, b *reflect.StructValue) bool {
	numA, numB := a.NumField(), b.NumField()
	if numA != numB {
		return false
	}

	for i := 0; i < numA; i++ {
		if !fuzzyEqualValue(a.Field(i), b.Field(i)) {
			return false
		}
	}
	return true
}

// TODO(rsc): Move into generic library?
// Unpack a reflect.StructValue from msg.
// Same restrictions as packStructValue.
func unpackStructValue(val *reflect.StructValue, msg []byte, off int) (off1 int, ok bool) {
	for i := 0; i < val.NumField(); i++ {
		f := val.Type().(*reflect.StructType).Field(i)
		switch fv := val.Field(i).(type) {
		default:
		BadType:
			fmt.Fprintf(os.Stderr, "net: dns: unknown packing type %v", f.Type)
			return len(msg), false
		case *reflect.StructValue:
			off, ok = unpackStructValue(fv, msg, off)
		case *reflect.UintValue:
			switch fv.Type().Kind() {
			default:
				goto BadType
			case reflect.Uint16:
				if off+2 > len(msg) {
					return len(msg), false
				}
				i := uint16(msg[off])<<8 | uint16(msg[off+1])
				fv.Set(uint64(i))
				off += 2
			case reflect.Uint32:
				if off+4 > len(msg) {
					return len(msg), false
				}
				i := uint32(msg[off])<<24 | uint32(msg[off+1])<<16 | uint32(msg[off+2])<<8 | uint32(msg[off+3])
				fv.Set(uint64(i))
				off += 4
			}
		case *reflect.StringValue:
			var s string
			switch f.Tag {
			default:
				fmt.Fprintf(os.Stderr, "net: dns: unknown string tag %v", f.Tag)
				return len(msg), false
			case "domain-name":
				s, off, ok = unpackDomainName(msg, off)
				if !ok {
					return len(msg), false
				}
			case "":
				if off >= len(msg) || off+1+int(msg[off]) > len(msg) {
					return len(msg), false
				}
				n := int(msg[off])
				off++
				b := make([]byte, n)
				for i := 0; i < n; i++ {
					b[i] = msg[off+i]
				}
				off += n
				s = string(b)
			}
			fv.Set(s)
		}
	}
	return off, true
}

// TODO(rsc): Move into generic library?
// Pack a reflect.StructValue into msg.  Struct members can only be uint16, uint32, string,
// and other (often anonymous) structs.
func packStructValue(val *reflect.StructValue, msg []byte, off int) (off1 int, ok bool) {
	for i := 0; i < val.NumField(); i++ {
		f := val.Type().(*reflect.StructType).Field(i)
		switch fv := val.Field(i).(type) {
		default:
		BadType:
			fmt.Fprintf(os.Stderr, "net: dns: unknown packing type %v", f.Type)
			return len(msg), false
		case *reflect.StructValue:
			off, ok = packStructValue(fv, msg, off)
		case *reflect.UintValue:
			i := fv.Get()
			switch fv.Type().Kind() {
			default:
				goto BadType
			case reflect.Uint16:
				if off+2 > len(msg) {
					return len(msg), false
				}
				msg[off] = byte(i >> 8)
				msg[off+1] = byte(i)
				off += 2
			case reflect.Uint32:
				if off+4 > len(msg) {
					return len(msg), false
				}
				msg[off] = byte(i >> 24)
				msg[off+1] = byte(i >> 16)
				msg[off+2] = byte(i >> 8)
				msg[off+3] = byte(i)
				off += 4
			}
		case *reflect.StringValue:
			// There are multiple string encodings.
			// The tag distinguishes ordinary strings from domain names.
			s := fv.Get()
			switch f.Tag {
			default:
				fmt.Fprintf(os.Stderr, "net: dns: unknown string tag %v", f.Tag)
				return len(msg), false
			case "domain-name":
				off, ok = packDomainName(s, msg, off)
				if !ok {
					return len(msg), false
				}
			case "":
				// Counted string: 1 byte length.
				if len(s) > 255 || off+1+len(s) > len(msg) {
					return len(msg), false
				}
				msg[off] = byte(len(s))
				off++
				off += copy(msg[off:], s)
			}
		}
	}
	return off, true
}

func writeStruct(w io.Writer, val *reflect.StructValue) os.Error {
	fmt.Fprint(w, "{")

	typ := val.Type().(*reflect.StructType)

	for i := 0; i < val.NumField(); i++ {
		fieldValue := val.Field(i)
		fmt.Fprintf(w, "%q:", typ.Field(i).Name)
		if err := writeValue(w, fieldValue); err != nil {
			return err
		}
		if i < val.NumField()-1 {
			fmt.Fprint(w, ",")
		}
	}

	fmt.Fprint(w, "}")
	return nil
}

func dec_struct(val *reflect.StructValue, typ *reflect.StructType, json map[string]interface{}) os.Error {
	for i := 0; i < typ.NumField(); i++ {
		f := typ.Field(i)
		if f.Tag == "" {
			continue
		}
		tags := strings.Split(f.Tag[3:len(f.Tag)-1], ",", -1)
		j, ok := json[tags[1]]
		if !ok {
			if tags[2] == "req" {
				return os.NewError("Field " + f.Name + " is missing")
			}
			continue
		}
		err := dec(val.Field(i), f.Type, j)
		if err != nil {
			return err
		}
	}
	return nil
}

// TODO: document me
//
func GetByteArrayAtIndex(v *reflect.StructValue, i int) (arr []byte, ok bool) {
	field := v.Field(i)
	return GetByteArray(field)
}

// object consumes an object from d.data[d.off-1:], decoding into the value v.
// the first byte of the object ('{') has been read already.
func (d *decodeState) object(v reflect.Value) {
	// Check for unmarshaler.
	unmarshaler, pv := d.indirect(v, false)
	if unmarshaler != nil {
		d.off--
		err := unmarshaler.UnmarshalJSON(d.next())
		if err != nil {
			d.error(err)
		}
		return
	}
	v = pv

	// Decoding into nil interface?  Switch to non-reflect code.
	iv, ok := v.(*reflect.InterfaceValue)
	if ok {
		iv.Set(reflect.NewValue(d.objectInterface()))
		return
	}

	// Check type of target: struct or map[string]T
	var (
		mv *reflect.MapValue
		sv *reflect.StructValue
	)
	switch v := v.(type) {
	case *reflect.MapValue:
		// map must have string type
		t := v.Type().(*reflect.MapType)
		if t.Key() != reflect.Typeof("") {
			d.saveError(&UnmarshalTypeError{"object", v.Type()})
			break
		}
		mv = v
		if mv.IsNil() {
			mv.SetValue(reflect.MakeMap(t))
		}
	case *reflect.StructValue:
		sv = v
	default:
		d.saveError(&UnmarshalTypeError{"object", v.Type()})
	}

	if mv == nil && sv == nil {
		d.off--
		d.next() // skip over { } in input
		return
	}

	for {
		// Read opening " of string key or closing }.
		op := d.scanWhile(scanSkipSpace)
		if op == scanEndObject {
			// closing } - can only happen on first iteration.
			break
		}
		if op != scanBeginLiteral {
			d.error(errPhase)
		}

		// Read string key.
		start := d.off - 1
		op = d.scanWhile(scanContinue)
		item := d.data[start : d.off-1]
		key, ok := unquote(item)
		if !ok {
			d.error(errPhase)
		}

		// Figure out field corresponding to key.
		var subv reflect.Value
		if mv != nil {
			subv = reflect.MakeZero(mv.Type().(*reflect.MapType).Elem())
		} else {
			// First try for field with that tag.
			for i := 0; i < sv.NumField(); i++ {
				f := sv.Type().(*reflect.StructType).Field(i)
				if f.Tag == key {
					subv = sv.Field(i)
					break
				}
			}
			if subv == nil {
				// Second, exact match.
				subv = sv.FieldByName(key)
				if subv == nil {
					// Third, case-insensitive match.
					subv = sv.FieldByNameFunc(func(s string) bool { return matchName(key, s) })
				}
			}
		}

		// Read : before value.
		if op == scanSkipSpace {
			op = d.scanWhile(scanSkipSpace)
		}
		if op != scanObjectKey {
			d.error(errPhase)
//.........这里部分代码省略.........