Golang Value.Len方法代码示例

func encodeArray(v reflect.Value) interface{} {
	n := node{}
	for i := 0; i < v.Len(); i++ {
		n[strconv.Itoa(i)] = encodeValue(v.Index(i))
	}
	return n
}

func (w *Writer) writeMap(v interface{}, rv reflect.Value) (err error) {
	w.setRef(v)
	s := w.Stream
	if err = s.WriteByte(TagMap); err == nil {
		if count := rv.Len(); count > 0 {
			if err = w.writeInt(count); err == nil {
				if err = s.WriteByte(TagOpenbrace); err == nil {
					keys := rv.MapKeys()
					for i := range keys {
						if err = w.WriteValue(keys[i]); err != nil {
							return err
						}
						if err = w.WriteValue(rv.MapIndex(keys[i])); err != nil {
							return err
						}
					}
					err = s.WriteByte(TagClosebrace)
				}
			}
		} else if err = s.WriteByte(TagOpenbrace); err == nil {
			err = s.WriteByte(TagClosebrace)
		}
	}
	return err
}

func (f *decFnInfo) kSlice(rv reflect.Value) {
	// A slice can be set from a map or array in stream.
	currEncodedType := f.dd.currentEncodedType()

	switch currEncodedType {
	case valueTypeBytes, valueTypeString:
		if f.ti.rtid == uint8SliceTypId || f.ti.rt.Elem().Kind() == reflect.Uint8 {
			if bs2, changed2 := f.dd.decodeBytes(rv.Bytes()); changed2 {
				rv.SetBytes(bs2)
			}
			return
		}
	}

	if shortCircuitReflectToFastPath && rv.CanAddr() {
		switch f.ti.rtid {
		case intfSliceTypId:
			f.d.decSliceIntf(rv.Addr().Interface().(*[]interface{}), currEncodedType, f.array)
			return
		case uint64SliceTypId:
			f.d.decSliceUint64(rv.Addr().Interface().(*[]uint64), currEncodedType, f.array)
			return
		case int64SliceTypId:
			f.d.decSliceInt64(rv.Addr().Interface().(*[]int64), currEncodedType, f.array)
			return
		case strSliceTypId:
			f.d.decSliceStr(rv.Addr().Interface().(*[]string), currEncodedType, f.array)
			return
		}
	}

	containerLen, containerLenS := decContLens(f.dd, currEncodedType)

	// an array can never return a nil slice. so no need to check f.array here.

	if rv.IsNil() {
		rv.Set(reflect.MakeSlice(f.ti.rt, containerLenS, containerLenS))
	}

	if containerLen == 0 {
		return
	}

	if rvcap, rvlen := rv.Len(), rv.Cap(); containerLenS > rvcap {
		if f.array { // !rv.CanSet()
			decErr(msgDecCannotExpandArr, rvcap, containerLenS)
		}
		rvn := reflect.MakeSlice(f.ti.rt, containerLenS, containerLenS)
		if rvlen > 0 {
			reflect.Copy(rvn, rv)
		}
		rv.Set(rvn)
	} else if containerLenS > rvlen {
		rv.SetLen(containerLenS)
	}

	for j := 0; j < containerLenS; j++ {
		f.d.decodeValue(rv.Index(j))
	}
}

func (e *encoder) addSlice(v reflect.Value) {
	vi := v.Interface()
	if d, ok := vi.(D); ok {
		for _, elem := range d {
			e.addElem(elem.Name, reflect.ValueOf(elem.Value), false)
		}
		return
	}
	if d, ok := vi.(RawD); ok {
		for _, elem := range d {
			e.addElem(elem.Name, reflect.ValueOf(elem.Value), false)
		}
		return
	}
	l := v.Len()
	et := v.Type().Elem()
	if et == typeDocElem {
		for i := 0; i < l; i++ {
			elem := v.Index(i).Interface().(DocElem)
			e.addElem(elem.Name, reflect.ValueOf(elem.Value), false)
		}
		return
	}
	if et == typeRawDocElem {
		for i := 0; i < l; i++ {
			elem := v.Index(i).Interface().(RawDocElem)
			e.addElem(elem.Name, reflect.ValueOf(elem.Value), false)
		}
		return
	}
	for i := 0; i < l; i++ {
		e.addElem(itoa(i), v.Index(i), false)
	}
}

func (d *decoder) readArrayDocTo(out reflect.Value) {
	end := int(d.readInt32())
	end += d.i - 4
	if end <= d.i || end > len(d.in) || d.in[end-1] != '\x00' {
		corrupted()
	}
	i := 0
	l := out.Len()
	for d.in[d.i] != '\x00' {
		if i >= l {
			panic("Length mismatch on array field")
		}
		kind := d.readByte()
		for d.i < end && d.in[d.i] != '\x00' {
			d.i++
		}
		if d.i >= end {
			corrupted()
		}
		d.i++
		d.readElemTo(out.Index(i), kind)
		if d.i >= end {
			corrupted()
		}
		i++
	}
	if i != l {
		panic("Length mismatch on array field")
	}
	d.i++ // '\x00'
	if d.i != end {
		corrupted()
	}
}

// callSliceRequired returns true if CallSlice is required instead of Call.
func callSliceRequired(param reflect.Type, val reflect.Value) bool {
	vt := val.Type()
	for param.Kind() == reflect.Slice {
		if val.Kind() == reflect.Interface {
			val = reflect.ValueOf(val.Interface())
			vt = val.Type()
		}

		if vt.Kind() != reflect.Slice {
			return false
		}

		vt = vt.Elem()
		if val.Kind() != reflect.Invalid {
			if val.Len() > 0 {
				val = val.Index(0)
			} else {
				val = reflect.Value{}
			}
		}
		param = param.Elem()
	}

	return true
}

func decodeSliceValue(d *Decoder, v reflect.Value) error {
	n, err := d.DecodeArrayLen()
	if err != nil {
		return err
	}

	if n == -1 {
		v.Set(reflect.Zero(v.Type()))
		return nil
	}
	if n == 0 && v.IsNil() {
		v.Set(reflect.MakeSlice(v.Type(), 0, 0))
		return nil
	}

	if v.Cap() >= n {
		v.Set(v.Slice(0, n))
	} else if v.Len() < v.Cap() {
		v.Set(v.Slice(0, v.Cap()))
	}

	for i := 0; i < n; i++ {
		if i >= v.Len() {
			v.Set(growSliceValue(v, n))
		}
		sv := v.Index(i)
		if err := d.DecodeValue(sv); err != nil {
			return err
		}
	}

	return nil
}

func encodeMap(val reflect.Value) ([]byte, error) {
	var t = val.Type()

	if t.Key().Kind() != reflect.String {
		return nil, fmt.Errorf("xmlrpc encode error: only maps with string keys are supported")
	}

	var b bytes.Buffer

	b.WriteString("<struct>")

	keys := val.MapKeys()

	for i := 0; i < val.Len(); i++ {
		key := keys[i]
		kval := val.MapIndex(key)

		b.WriteString("<member>")
		b.WriteString(fmt.Sprintf("<name>%s</name>", key.String()))

		p, err := encodeValue(kval)

		if err != nil {
			return nil, err
		}

		b.Write(p)
		b.WriteString("</member>")
	}

	b.WriteString("</struct>")

	return b.Bytes(), nil
}

// decodeArrayInterface decodes the source value into []interface{}
func decodeArrayInterface(s *decodeState, sv reflect.Value) []interface{} {
	arr := []interface{}{}
	for i := 0; i < sv.Len(); i++ {
		arr = append(arr, decodeInterface(s, sv.Index(i)))
	}
	return arr
}

// isZero reports whether the value is the zero of its type.
func isZero(val reflect.Value) bool {
	switch val.Kind() {
	case reflect.Array:
		for i := 0; i < val.Len(); i++ {
			if !isZero(val.Index(i)) {
				return false
			}
		}
		return true
	case reflect.Map, reflect.Slice, reflect.String:
		return val.Len() == 0
	case reflect.Bool:
		return !val.Bool()
	case reflect.Complex64, reflect.Complex128:
		return val.Complex() == 0
	case reflect.Chan, reflect.Func, reflect.Ptr:
		return val.IsNil()
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return val.Int() == 0
	case reflect.Float32, reflect.Float64:
		return val.Float() == 0
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		return val.Uint() == 0
	case reflect.Struct:
		for i := 0; i < val.NumField(); i++ {
			if !isZero(val.Field(i)) {
				return false
			}
		}
		return true
	}
	panic("unknown type in isZero " + val.Type().String())
}

// tomlArrayType returns the element type of a TOML array. The type returned
// may be nil if it cannot be determined (e.g., a nil slice or a zero length
// slize). This function may also panic if it finds a type that cannot be
// expressed in TOML (such as nil elements, heterogeneous arrays or directly
// nested arrays of tables).
func tomlArrayType(rv reflect.Value) tomlType {
	if isNil(rv) || !rv.IsValid() || rv.Len() == 0 {
		return nil
	}
	firstType := tomlTypeOfGo(rv.Index(0))
	if firstType == nil {
		encPanic(errArrayNilElement)
	}

	rvlen := rv.Len()
	for i := 1; i < rvlen; i++ {
		elem := rv.Index(i)
		switch elemType := tomlTypeOfGo(elem); {
		case elemType == nil:
			encPanic(errArrayNilElement)
		case !typeEqual(firstType, elemType):
			encPanic(errArrayMixedElementTypes)
		}
	}
	// If we have a nested array, then we must make sure that the nested
	// array contains ONLY primitives.
	// This checks arbitrarily nested arrays.
	if typeEqual(firstType, tomlArray) || typeEqual(firstType, tomlArrayHash) {
		nest := tomlArrayType(eindirect(rv.Index(0)))
		if typeEqual(nest, tomlHash) || typeEqual(nest, tomlArrayHash) {
			encPanic(errArrayNoTable)
		}
	}
	return firstType
}

// checkWhereArray handles the where-matching logic when the seqv value is an
// Array or Slice.
func checkWhereArray(
	seqv, kv, mv reflect.Value,
	path []string, op string) (interface{}, error) {

	rv := reflect.MakeSlice(seqv.Type(), 0, 0)
	for i := 0; i < seqv.Len(); i++ {
		var vvv reflect.Value
		rvv := seqv.Index(i)
		if kv.Kind() == reflect.String {
			vvv = rvv
			for _, elemName := range path {
				var err error
				vvv, err = evaluateSubElem(vvv, elemName)
				if err != nil {
					return nil, err
				}
			}
		} else {
			vv, _ := indirect(rvv)
			if vv.Kind() == reflect.Map &&
				kv.Type().AssignableTo(vv.Type().Key()) {
				vvv = vv.MapIndex(kv)
			}
		}

		if ok, err := checkCondition(vvv, mv, op); ok {
			rv = reflect.Append(rv, rvv)
		} else if err != nil {
			return nil, err
		}
	}
	return rv.Interface(), nil
}

func (e *encoder) slicev(tag string, in reflect.Value) {
	var ctag *C.yaml_char_t
	var free func()
	var cimplicit C.int
	if tag != "" {
		ctag, free = ystr(tag)
		defer free()
		cimplicit = 0
	} else {
		cimplicit = 1
	}

	cstyle := C.yaml_sequence_style_t(C.YAML_BLOCK_SEQUENCE_STYLE)
	if e.flow {
		e.flow = false
		cstyle = C.YAML_FLOW_SEQUENCE_STYLE
	}
	C.yaml_sequence_start_event_initialize(&e.event, nil, ctag, cimplicit,
		cstyle)
	e.emit()
	n := in.Len()
	for i := 0; i < n; i++ {
		e.marshal("", in.Index(i))
	}
	C.yaml_sequence_end_event_initialize(&e.event)
	e.emit()
}

// visit calls the visitor function for each string it finds, and will descend
// recursively into structures and slices. If any visitor returns an error then
// the search will stop and that error will be returned.
func visit(path string, v reflect.Value, t reflect.Type, fn visitor) error {
	switch v.Kind() {
	case reflect.String:
		return fn(path, v)
	case reflect.Struct:
		for i := 0; i < v.NumField(); i++ {
			vf := v.Field(i)
			tf := t.Field(i)
			newPath := fmt.Sprintf("%s.%s", path, tf.Name)
			if err := visit(newPath, vf, tf.Type, fn); err != nil {
				return err
			}
		}
	case reflect.Slice:
		for i := 0; i < v.Len(); i++ {
			vi := v.Index(i)
			ti := vi.Type()
			newPath := fmt.Sprintf("%s[%d]", path, i)
			if err := visit(newPath, vi, ti, fn); err != nil {
				return err
			}
		}
	}
	return nil
}

func encodeSliceContent(buf *bytes2.ChunkedWriter, val reflect.Value) {
	lenWriter := NewLenWriter(buf)
	for i := 0; i < val.Len(); i++ {
		encodeField(buf, Itoa(i), val.Index(i))
	}
	lenWriter.Close()
}