Golang Value.SetLen方法代码示例

func decodeSlice(d *decodeState, kind int, v reflect.Value) {
	if kind != kindArray {
		d.saveErrorAndSkip(kind, v.Type())
		return
	}
	t := v.Type()
	offset := d.beginDoc()
	i := 0
	for {
		kind, _ := d.scanKindName()
		if kind == 0 {
			break
		}
		if i >= v.Cap() {
			newcap := v.Cap() + v.Cap()/2
			if newcap < 4 {
				newcap = 4
			}
			newv := reflect.MakeSlice(t, v.Len(), newcap)
			reflect.Copy(newv, v)
			v.Set(newv)
		}
		if i >= v.Len() {
			v.SetLen(i + 1)
		}
		d.decodeValue(kind, v.Index(i))
		i += 1
	}
	d.endDoc(offset)
}

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 setRepeated(field reflect.Value, vslice []Value, setElem setFunc) error {
	vlen := len(vslice)
	var flen int
	switch field.Type().Kind() {
	case reflect.Slice:
		// Make a slice of the right size, avoiding allocation if possible.
		switch {
		case field.Len() < vlen:
			field.Set(reflect.MakeSlice(field.Type(), vlen, vlen))
		case field.Len() > vlen:
			field.SetLen(vlen)
		}
		flen = vlen

	case reflect.Array:
		flen = field.Len()
		if flen > vlen {
			// Set extra elements to their zero value.
			z := reflect.Zero(field.Type().Elem())
			for i := vlen; i < flen; i++ {
				field.Index(i).Set(z)
			}
		}
	default:
		return fmt.Errorf("bigquery: impossible field type %s", field.Type())
	}
	for i, val := range vslice {
		if i < flen { // avoid writing past the end of a short array
			if err := setElem(field.Index(i), val); err != nil {
				return err
			}
		}
	}
	return nil
}

func (d *Decoder) decodeList(avList []*dynamodb.AttributeValue, v reflect.Value) error {
	switch v.Kind() {
	case reflect.Slice:
		// Make room for the slice elements if needed
		if v.IsNil() || v.Cap() < len(avList) {
			// What about if ignoring nil/empty values?
			v.Set(reflect.MakeSlice(v.Type(), 0, len(avList)))
		}
	case reflect.Array:
		// Limited to capacity of existing array.
	case reflect.Interface:
		s := make([]interface{}, len(avList))
		for i, av := range avList {
			if err := d.decode(av, reflect.ValueOf(&s[i]).Elem(), tag{}); err != nil {
				return err
			}
		}
		v.Set(reflect.ValueOf(s))
		return nil
	default:
		return &UnmarshalTypeError{Value: "list", Type: v.Type()}
	}

	// If v is not a slice, array
	for i := 0; i < v.Cap() && i < len(avList); i++ {
		v.SetLen(i + 1)
		if err := d.decode(avList[i], v.Index(i), tag{}); err != nil {
			return err
		}
	}

	return nil
}

func (d *Decoder) decodeBinary(b []byte, v reflect.Value) error {
	if v.Kind() == reflect.Interface {
		buf := make([]byte, len(b))
		copy(buf, b)
		v.Set(reflect.ValueOf(buf))
		return nil
	}

	switch v.Interface().(type) {
	case []byte:
		if v.IsNil() || v.Cap() < len(b) {
			v.Set(reflect.MakeSlice(byteSliceType, len(b), len(b)))
		} else if v.Len() != len(b) {
			v.SetLen(len(b))
		}
		copy(v.Interface().([]byte), b)
	default:
		if v.Kind() == reflect.Array && v.Type().Elem().Kind() == reflect.Uint8 {
			reflect.Copy(v, reflect.ValueOf(b))
			break
		}
		return &UnmarshalTypeError{Value: "binary", Type: v.Type()}
	}

	return nil
}

func (d *Decoder) decodeStringSet(ss []*string, v reflect.Value) error {
	switch v.Kind() {
	case reflect.Slice:
		// Make room for the slice elements if needed
		if v.IsNil() || v.Cap() < len(ss) {
			v.Set(reflect.MakeSlice(v.Type(), 0, len(ss)))
		}
	case reflect.Array:
		// Limited to capacity of existing array.
	case reflect.Interface:
		set := make([]string, len(ss))
		for i, s := range ss {
			if err := d.decodeString(s, reflect.ValueOf(&set[i]).Elem(), tag{}); err != nil {
				return err
			}
		}
		v.Set(reflect.ValueOf(set))
		return nil
	default:
		return &UnmarshalTypeError{Value: "string set", Type: v.Type()}
	}

	for i := 0; i < v.Cap() && i < len(ss); i++ {
		v.SetLen(i + 1)
		u, elem := indirect(v.Index(i), false)
		if u != nil {
			return u.UnmarshalDynamoDBAttributeValue(&dynamodb.AttributeValue{SS: ss})
		}
		if err := d.decodeString(ss[i], elem, tag{}); err != nil {
			return err
		}
	}

	return nil
}

// parse a value as the appropriate type and store it in the struct
func setSlice(dest reflect.Value, values []string) error {
	if !dest.CanSet() {
		return fmt.Errorf("field is not writable")
	}

	var ptr bool
	elem := dest.Type().Elem()
	if elem.Kind() == reflect.Ptr {
		ptr = true
		elem = elem.Elem()
	}

	// Truncate the dest slice in case default values exist
	if !dest.IsNil() {
		dest.SetLen(0)
	}

	for _, s := range values {
		v := reflect.New(elem)
		if err := setScalar(v.Elem(), s); err != nil {
			return err
		}
		if !ptr {
			v = v.Elem()
		}
		dest.Set(reflect.Append(dest, v))
	}
	return nil
}

func ensureLen(d reflect.Value, n int) {
	if n > d.Cap() {
		d.Set(reflect.MakeSlice(d.Type(), n, n))
	} else {
		d.SetLen(n)
	}
}

func (p *Decoder) unmarshalArray(pval *plistValue, val reflect.Value) {
	subvalues := pval.value.([]*plistValue)

	var n int
	if val.Kind() == reflect.Slice {
		// Slice of element values.
		// Grow slice.
		cnt := len(subvalues) + val.Len()
		if cnt >= val.Cap() {
			ncap := 2 * cnt
			if ncap < 4 {
				ncap = 4
			}
			new := reflect.MakeSlice(val.Type(), val.Len(), ncap)
			reflect.Copy(new, val)
			val.Set(new)
		}
		n = val.Len()
		val.SetLen(cnt)
	} else if val.Kind() == reflect.Array {
		if len(subvalues) > val.Cap() {
			panic(fmt.Errorf("plist: attempted to unmarshal %d values into an array of size %d", len(subvalues), val.Cap()))
		}
	} else {
		panic(&incompatibleDecodeTypeError{val.Type(), pval.kind})
	}

	// Recur to read element into slice.
	for _, sval := range subvalues {
		p.unmarshal(sval, val.Index(n))
		n++
	}
	return
}

func decodeSliceElems(s *Stream, val reflect.Value, elemdec decoder) error {
	i := 0
	for ; ; i++ {
		// grow slice if necessary
		if i >= val.Cap() {
			newcap := val.Cap() + val.Cap()/2
			if newcap < 4 {
				newcap = 4
			}
			newv := reflect.MakeSlice(val.Type(), val.Len(), newcap)
			reflect.Copy(newv, val)
			val.Set(newv)
		}
		if i >= val.Len() {
			val.SetLen(i + 1)
		}
		// decode into element
		if err := elemdec(s, val.Index(i)); err == EOL {
			break
		} else if err != nil {
			return addErrorContext(err, fmt.Sprint("[", i, "]"))
		}
	}
	if i < val.Len() {
		val.SetLen(i)
	}
	return nil
}

func (d *Decoder) decodeList(v reflect.Value) error {
	//if we have an interface, just put a []interface{} in it!
	if v.Kind() == reflect.Interface {
		var x []interface{}
		defer func(p reflect.Value) { p.Set(v) }(v)
		v = reflect.ValueOf(&x).Elem()
	}

	if v.Kind() != reflect.Array && v.Kind() != reflect.Slice {
		return fmt.Errorf("Cant store a []interface{} into %s", v.Type())
	}

	//read out the l that prefixes the list
	ch, err := d.readByte()
	if err != nil {
		return err
	}
	if ch != 'l' {
		panic("got something other than a list head after a peek")
	}

	for i := 0; ; i++ {
		//peek for the end token and read it out
		ch, err := d.peekByte()
		if err != nil {
			return err
		}
		switch ch {
		case 'e':
			_, err := d.readByte() //consume the end
			return err
		}

		//grow it if required
		if i >= v.Cap() && v.IsValid() {
			newcap := v.Cap() + v.Cap()/2
			if newcap < 4 {
				newcap = 4
			}
			newv := reflect.MakeSlice(v.Type(), v.Len(), newcap)
			reflect.Copy(newv, v)
			v.Set(newv)
		}

		//reslice into cap (its a slice now since it had to have grown)
		if i >= v.Len() && v.IsValid() {
			v.SetLen(i + 1)
		}

		//decode a value into the index
		if err := d.decodeInto(v.Index(i)); err != nil {
			return err
		}
	}

	panic("unreachable")
}

//FIXME: fix when v is invalid
// type(1) | name length(1) | item size(4) | raw name bytes | 0x00
// | element number(4) | element1 | ... | elementN
func (d *decodeState) array(v reflect.Value) {
	d.off += 1 // type

	klen := int(Int8(d.data[d.off:]))
	d.off += 1 // name length

	// vlen := int(Int32(d.data[d.off:]))
	d.off += 4 //  content length

	//var key string
	if klen > 0 {
		key := d.data[d.off : d.off+klen-1]
		d.off += klen
		v = fieldByTag(v, key)
		u, pv := d.indirect(v, false)
		if u != nil {
			d.off -= 1 + 1 + 4 + klen
			if err := u.UnmarshalMCPACK(d.next()); err != nil {
				d.error(err)
			}
			return
		}
		v = pv
	}

	n := int(Int32(d.data[d.off:]))
	d.off += 4 // member number

	if v.Kind() == reflect.Slice {
		if n > v.Cap() {
			newv := reflect.MakeSlice(v.Type(), n, n)
			v.Set(newv)
		}
		v.SetLen(n)
	}

	for i := 0; i < n; i++ {
		if i < v.Len() {
			d.value(v.Index(i))
		} else {
			d.value(reflect.Value{})
		}
	}

	if n < v.Len() {
		if v.Kind() == reflect.Array {
			z := reflect.Zero(v.Type().Elem())
			for i := 0; i < v.Len(); i++ {
				v.Index(i).Set(z)
			}
		}
	}

	if n == 0 && v.Kind() == reflect.Slice {
		v.Set(reflect.MakeSlice(v.Type(), 0, 0))
	}
}

func fixSliceLen(slice reflect.Value, lenslice int) reflect.Value {
	if slice.Len() != lenslice {
		if slice.Cap() >= lenslice {
			slice.SetLen(lenslice)
		} else {
			slice.Set(reflect.MakeSlice(slice.Type(), lenslice, lenslice))
		}
	}
	return slice
}

// unmarshalAttr unmarshals a single XML attribute into val.
func (p *Decoder) unmarshalAttr(val reflect.Value, attr Attr) error {
	if val.Kind() == reflect.Ptr {
		if val.IsNil() {
			val.Set(reflect.New(val.Type().Elem()))
		}
		val = val.Elem()
	}
	if val.CanInterface() && val.Type().Implements(unmarshalerAttrType) {
		// This is an unmarshaler with a non-pointer receiver,
		// so it's likely to be incorrect, but we do what we're told.
		return val.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
	}
	if val.CanAddr() {
		pv := val.Addr()
		if pv.CanInterface() && pv.Type().Implements(unmarshalerAttrType) {
			return pv.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
		}
	}

	// Not an UnmarshalerAttr; try encoding.TextUnmarshaler.
	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
		// This is an unmarshaler with a non-pointer receiver,
		// so it's likely to be incorrect, but we do what we're told.
		return val.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
	}
	if val.CanAddr() {
		pv := val.Addr()
		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
			return pv.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
		}
	}

	if val.Type().Kind() == reflect.Slice && val.Type().Elem().Kind() != reflect.Uint8 {
		// Slice of element values.
		// Grow slice.
		n := val.Len()
		val.Set(reflect.Append(val, reflect.Zero(val.Type().Elem())))

		// Recur to read element into slice.
		if err := p.unmarshalAttr(val.Index(n), attr); err != nil {
			val.SetLen(n)
			return err
		}
		return nil
	}

	if val.Type() == attrType {
		val.Set(reflect.ValueOf(attr))
		return nil
	}

	return copyValue(val, []byte(attr.Value))
}

func (md *MetaData) unifySlice(data interface{}, rv reflect.Value) error {
	datav := reflect.ValueOf(data)
	if datav.Kind() != reflect.Slice {
		return badtype("slice", data)
	}
	sliceLen := datav.Len()
	if rv.IsNil() || rv.Len() < datav.Len() {
		rv.Set(reflect.MakeSlice(rv.Type(), sliceLen, sliceLen))
	}
	rv.SetLen(datav.Len())
	return md.unifySliceArray(datav, rv)
}