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Unified Diff: src/pkg/encoding/xml/read.go

Issue 12556043: code review 12556043: encoding/xml: add, support Unmarshaler interface (Closed)
Patch Set: diff -r 117ed8ab3db0 https://code.google.com/p/go/ Created 10 years, 7 months ago
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Index: src/pkg/encoding/xml/read.go
===================================================================
--- a/src/pkg/encoding/xml/read.go
+++ b/src/pkg/encoding/xml/read.go
@@ -7,6 +7,7 @@
import (
"bytes"
"errors"
+ "fmt"
"reflect"
"strconv"
"strings"
@@ -137,6 +138,100 @@
func (e UnmarshalError) Error() string { return string(e) }
+// Unmarshaler is the interface implemented by objects that can unmarshal
+// an XML element description of themselves.
+//
+// UnmarshalXML decodes a single XML element
+// beginning with the given start element.
+// If it returns an error, the outer call to Unmarshal stops and
+// returns that error.
+// UnmarshalXML must consume exactly one XML element.
+// One common implementation strategy is to unmarshal into
+// a separate value with a layout matching the expected XML
+// using d.DecodeElement, and then to copy the data from
+// that value into the receiver.
+// Another common strategy is to use d.Token to process the
+// XML object one token at a time.
+// UnmarshalXML may not use d.RawToken.
+type Unmarshaler interface {
+ UnmarshalXML(d *Decoder, start StartElement) error
+}
+
+// UnmarshalerAttr is the interface implemented by objects that can unmarshal
+// an XML attribute description of themselves.
+//
+// UnmarshalXMLAttr decodes a single XML attribute.
+// If it returns an error, the outer call to Unmarshal stops and
+// returns that error.
+// UnmarshalXMLAttr is used only for struct fields with the
+// "attr" option in the field tag.
+type UnmarshalerAttr interface {
+ UnmarshalXMLAttr(attr Attr) error
+}
+
+// receiverType returns the receiver type to use in an expression like "%s.MethodName".
+func receiverType(val interface{}) string {
+ t := reflect.TypeOf(val)
+ if t.Name() != "" {
+ return t.String()
+ }
+ return "(" + t.String() + ")"
+}
+
+// unmarshalInterface unmarshals a single XML element into val,
+// which is known to implement Unmarshaler.
+// start is the opening tag of the element.
+func (p *Decoder) unmarshalInterface(val Unmarshaler, start *StartElement) error {
+ // Record that decoder must stop at end tag corresponding to start.
+ p.pushEOF()
+
+ p.unmarshalDepth++
+ err := val.UnmarshalXML(p, *start)
+ p.unmarshalDepth--
+ if err != nil {
+ p.popEOF()
+ return err
+ }
+
+ if !p.popEOF() {
+ return fmt.Errorf("xml: %s.UnmarshalXML did not consume entire <%s> element", receiverType(val), start.Name.Local)
+ }
+
+ return nil
+}
+
+// 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)
+ }
+ }
+
+ // TODO: Check for and use encoding.TextUnmarshaler.
+
+ copyValue(val, []byte(attr.Value))
+ return nil
+}
+
+var (
+ unmarshalerType = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
+ unmarshalerAttrType = reflect.TypeOf((*UnmarshalerAttr)(nil)).Elem()
+)
+
// Unmarshal a single XML element into val.
func (p *Decoder) unmarshal(val reflect.Value, start *StartElement) error {
// Find start element if we need it.
@@ -153,13 +248,28 @@
}
}
- if pv := val; pv.Kind() == reflect.Ptr {
- if pv.IsNil() {
- pv.Set(reflect.New(pv.Type().Elem()))
+ if val.Kind() == reflect.Ptr {
+ if val.IsNil() {
+ val.Set(reflect.New(val.Type().Elem()))
}
- val = pv.Elem()
+ val = val.Elem()
}
+ if val.CanInterface() && val.Type().Implements(unmarshalerType) {
+ // This is an unmarshaler with a non-pointer receiver,
+ // so it's likely to be incorrect, but we do what we're told.
+ return p.unmarshalInterface(val.Interface().(Unmarshaler), start)
+ }
+
+ if val.CanAddr() {
+ pv := val.Addr()
+ if pv.CanInterface() && pv.Type().Implements(unmarshalerType) {
+ return p.unmarshalInterface(pv.Interface().(Unmarshaler), start)
+ }
+ }
+
+ // TODO: Check for and use encoding.TextUnmarshaler.
+
var (
data []byte
saveData reflect.Value
@@ -264,7 +374,9 @@
// Look for attribute.
for _, a := range start.Attr {
if a.Name.Local == finfo.name && (finfo.xmlns == "" || finfo.xmlns == a.Name.Space) {
- copyValue(strv, []byte(a.Value))
+ if err := p.unmarshalAttr(strv, a); err != nil {
+ return err
+ }
break
}
}
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