// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package xml
import (
"bytes"
"encoding"
"errors"
"fmt"
"reflect"
"strconv"
"strings"
)
// BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
// an XML element is an order-dependent collection of anonymous
// values, while a data structure is an order-independent collection
// of named values.
// See package json for a textual representation more suitable
// to data structures.
// Unmarshal parses the XML-encoded data and stores the result in
// the value pointed to by v, which must be an arbitrary struct,
// slice, or string. Well-formed data that does not fit into v is
// discarded.
//
// Because Unmarshal uses the reflect package, it can only assign
// to exported (upper case) fields. Unmarshal uses a case-sensitive
// comparison to match XML element names to tag values and struct
// field names.
//
// Unmarshal maps an XML element to a struct using the following rules.
// In the rules, the tag of a field refers to the value associated with the
// key 'xml' in the struct field's tag (see the example above).
//
// * If the struct has a field of type []byte or string with tag
// ",innerxml", Unmarshal accumulates the raw XML nested inside the
// element in that field. The rest of the rules still apply.
//
// * If the struct has a field named XMLName of type Name,
// Unmarshal records the element name in that field.
//
// * If the XMLName field has an associated tag of the form
// "name" or "namespace-URL name", the XML element must have
// the given name (and, optionally, name space) or else Unmarshal
// returns an error.
//
// * If the XML element has an attribute whose name matches a
// struct field name with an associated tag containing ",attr" or
// the explicit name in a struct field tag of the form "name,attr",
// Unmarshal records the attribute value in that field.
//
// * If the XML element has an attribute not handled by the previous
// rule and the struct has a field with an associated tag containing
// ",any,attr", Unmarshal records the attribute value in the first
// such field.
//
// * If the XML element contains character data, that data is
// accumulated in the first struct field that has tag ",chardata".
// The struct field may have type []byte or string.
// If there is no such field, the character data is discarded.
//
// * If the XML element contains comments, they are accumulated in
// the first struct field that has tag ",comment". The struct
// field may have type []byte or string. If there is no such
// field, the comments are discarded.
//
// * If the XML element contains a sub-element whose name matches
// the prefix of a tag formatted as "a" or "a>b>c", unmarshal
// will descend into the XML structure looking for elements with the
// given names, and will map the innermost elements to that struct
// field. A tag starting with ">" is equivalent to one starting
// with the field name followed by ">".
//
// * If the XML element contains a sub-element whose name matches
// a struct field's XMLName tag and the struct field has no
// explicit name tag as per the previous rule, unmarshal maps
// the sub-element to that struct field.
//
// * If the XML element contains a sub-element whose name matches a
// field without any mode flags (",attr", ",chardata", etc), Unmarshal
// maps the sub-element to that struct field.
//
// * If the XML element contains a sub-element that hasn't matched any
// of the above rules and the struct has a field with tag ",any",
// unmarshal maps the sub-element to that struct field.
//
// * An anonymous struct field is handled as if the fields of its
// value were part of the outer struct.
//
// * A struct field with tag "-" is never unmarshaled into.
//
// If Unmarshal encounters a field type that implements the Unmarshaler
// interface, Unmarshal calls its UnmarshalXML method to produce the value from
// the XML element. Otherwise, if the value implements
// encoding.TextUnmarshaler, Unmarshal calls that value's UnmarshalText method.
//
// Unmarshal maps an XML element to a string or []byte by saving the
// concatenation of that element's character data in the string or
// []byte. The saved []byte is never nil.
//
// Unmarshal maps an attribute value to a string or []byte by saving
// the value in the string or slice.
//
// Unmarshal maps an attribute value to an Attr by saving the attribute,
// including its name, in the Attr.
//
// Unmarshal maps an XML element or attribute value to a slice by
// extending the length of the slice and mapping the element or attribute
// to the newly created value.
//
// Unmarshal maps an XML element or attribute value to a bool by
// setting it to the boolean value represented by the string. Whitespace
// is trimmed and ignored.
//
// Unmarshal maps an XML element or attribute value to an integer or
// floating-point field by setting the field to the result of
// interpreting the string value in decimal. There is no check for
// overflow. Whitespace is trimmed and ignored.
//
// Unmarshal maps an XML element to a Name by recording the element
// name.
//
// Unmarshal maps an XML element to a pointer by setting the pointer
// to a freshly allocated value and then mapping the element to that value.
//
// A missing element or empty attribute value will be unmarshaled as a zero value.
// If the field is a slice, a zero value will be appended to the field. Otherwise, the
// field will be set to its zero value.
func Unmarshal(data []byte, v interface{}) error {
return NewDecoder(bytes.NewReader(data)).Decode(v)
}
// Decode works like Unmarshal, except it reads the decoder
// stream to find the start element.
func (d *Decoder) Decode(v interface{}) error {
return d.DecodeElement(v, nil)
}
// DecodeElement works like Unmarshal except that it takes
// a pointer to the start XML element to decode into v.
// It is useful when a client reads some raw XML tokens itself
// but also wants to defer to Unmarshal for some elements.
func (d *Decoder) DecodeElement(v interface{}, start *StartElement) error {
val := reflect.ValueOf(v)
if val.Kind() != reflect.Ptr {
return errors.New("non-pointer passed to Unmarshal")
}
return d.unmarshal(val.Elem(), start)
}
// An UnmarshalError represents an error in the unmarshaling process.
type UnmarshalError string
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.
// start is the opening tag of the element.
func (d *Decoder) unmarshalInterface(val Unmarshaler, start *StartElement) error {
// Record that decoder must stop at end tag corresponding to start.
d.pushEOF()
d.unmarshalDepth++
err := val.UnmarshalXML(d, *start)
d.unmarshalDepth--
if err != nil {
d.popEOF()
return err
}
if !d.popEOF() {
return fmt.Errorf("xml: %s.UnmarshalXML did not consume entire <%s> element", receiverType(val), start.Name.Local)
}
return nil
}
// unmarshalTextInterface unmarshals a single XML element into val.
// The chardata contained in the element (but not its children)
// is passed to the text unmarshaler.
func (d *Decoder) unmarshalTextInterface(val encoding.TextUnmarshaler) error {
var buf []byte
depth := 1
for depth > 0 {
t, err := d.Token()
if err != nil {
return err
}
switch t := t.(type) {
case CharData:
if depth == 1 {
buf = append(buf, t...)
}
case StartElement:
depth++
case EndElement:
depth--
}
}
return val.UnmarshalText(buf)
}
// unmarshalAttr unmarshals a single XML attribute into val.
func (d *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 := d.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))
}
var (
attrType = reflect.TypeOf(Attr{})
unmarshalerType = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
unmarshalerAttrType = reflect.TypeOf((*UnmarshalerAttr)(nil)).Elem()
textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
)
// Unmarshal a single XML element into val.
func (d *Decoder) unmarshal(val reflect.Value, start *StartElement) error {
// Find start element if we need it.
if start == nil {
for {
tok, err := d.Token()
if err != nil {
return err
}
if t, ok := tok.(StartElement); ok {
start = &t
break
}
}
}
// Load value from interface, but only if the result will be
// usefully addressable.
if val.Kind() == reflect.Interface && !val.IsNil() {
e := val.Elem()
if e.Kind() == reflect.Ptr && !e.IsNil() {
val = e
}
}
if val.Kind() == reflect.Ptr {
if val.IsNil() {
val.Set(reflect.New(val.Type().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 d.unmarshalInterface(val.Interface().(Unmarshaler), start)
}
if val.CanAddr() {
pv := val.Addr()
if pv.CanInterface() && pv.Type().Implements(unmarshalerType) {
return d.unmarshalInterface(pv.Interface().(Unmarshaler), start)
}
}
if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
return d.unmarshalTextInterface(val.Interface().(encoding.TextUnmarshaler))
}
if val.CanAddr() {
pv := val.Addr()
if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
return d.unmarshalTextInterface(pv.Interface().(encoding.TextUnmarshaler))
}
}
var (
data []byte
saveData reflect.Value
comment []byte
saveComment reflect.Value
saveXML reflect.Value
saveXMLIndex int
saveXMLData []byte
saveAny reflect.Value
sv reflect.Value
tinfo *typeInfo
err error
)
switch v := val; v.Kind() {
default:
return errors.New("unknown type " + v.Type().String())
case reflect.Interface:
// TODO: For now, simply ignore the field. In the near
// future we may choose to unmarshal the start
// element on it, if not nil.
return d.Skip()
case reflect.Slice:
typ := v.Type()
if typ.Elem().Kind() == reflect.Uint8 {
// []byte
saveData = v
break
}
// Slice of element values.
// Grow slice.
n := v.Len()
v.Set(reflect.Append(val, reflect.Zero(v.Type().Elem())))
// Recur to read element into slice.
if err := d.unmarshal(v.Index(n), start); err != nil {
v.SetLen(n)
return err
}
return nil
case reflect.Bool, reflect.Float32, reflect.Float64, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr, reflect.String:
saveData = v
case reflect.Struct:
typ := v.Type()
if typ == nameType {
v.Set(reflect.ValueOf(start.Name))
break
}
sv = v
tinfo, err = getTypeInfo(typ)
if err != nil {
return err
}
// Validate and assign element name.
if tinfo.xmlname != nil {
finfo := tinfo.xmlname
if finfo.name != "" && finfo.name != start.Name.Local {
return UnmarshalError("expected element type <" + finfo.name + "> but have <" + start.Name.Local + ">")
}
if finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
e := "expected element <" + finfo.name + "> in name space " + finfo.xmlns + " but have "
if start.Name.Space == "" {
e += "no name space"
} else {
e += start.Name.Space
}
return UnmarshalError(e)
}
fv := finfo.value(sv)
if _, ok := fv.Interface().(Name); ok {
fv.Set(reflect.ValueOf(start.Name))
}
}
// Assign attributes.
for _, a := range start.Attr {
handled := false
any := -1
for i := range tinfo.fields {
finfo := &tinfo.fields[i]
switch finfo.flags & fMode {
case fAttr:
strv := finfo.value(sv)
if a.Name.Local == finfo.name && (finfo.xmlns == "" || finfo.xmlns == a.Name.Space) {
if err := d.unmarshalAttr(strv, a); err != nil {
return err
}
handled = true
}
case fAny | fAttr:
if any == -1 {
any = i
}
}
}
if !handled && any >= 0 {
finfo := &tinfo.fields[any]
strv := finfo.value(sv)
if err := d.unmarshalAttr(strv, a); err != nil {
return err
}
}
}
// Determine whether we need to save character data or comments.
for i := range tinfo.fields {
finfo := &tinfo.fields[i]
switch finfo.flags & fMode {
case fCDATA, fCharData:
if !saveData.IsValid() {
saveData = finfo.value(sv)
}
case fComment:
if !saveComment.IsValid() {
saveComment = finfo.value(sv)
}
case fAny, fAny | fElement:
if !saveAny.IsValid() {
saveAny = finfo.value(sv)
}
case fInnerXml:
if !saveXML.IsValid() {
saveXML = finfo.value(sv)
if d.saved == nil {
saveXMLIndex = 0
d.saved = new(bytes.Buffer)
} else {
saveXMLIndex = d.savedOffset()
}
}
}
}
}
// Find end element.
// Process sub-elements along the way.
Loop:
for {
var savedOffset int
if saveXML.IsValid() {
savedOffset = d.savedOffset()
}
tok, err := d.Token()
if err != nil {
return err
}
switch t := tok.(type) {
case StartElement:
consumed := false
if sv.IsValid() {
consumed, err = d.unmarshalPath(tinfo, sv, nil, &t)
if err != nil {
return err
}
if !consumed && saveAny.IsValid() {
consumed = true
if err := d.unmarshal(saveAny, &t); err != nil {
return err
}
}
}
if !consumed {
if err := d.Skip(); err != nil {
return err
}
}
case EndElement:
if saveXML.IsValid() {
saveXMLData = d.saved.Bytes()[saveXMLIndex:savedOffset]
if saveXMLIndex == 0 {
d.saved = nil
}
}
break Loop
case CharData:
if saveData.IsValid() {
data = append(data, t...)
}
case Comment:
if saveComment.IsValid() {
comment = append(comment, t...)
}
}
}
if saveData.IsValid() && saveData.CanInterface() && saveData.Type().Implements(textUnmarshalerType) {
if err := saveData.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
return err
}
saveData = reflect.Value{}
}
if saveData.IsValid() && saveData.CanAddr() {
pv := saveData.Addr()
if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
if err := pv.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
return err
}
saveData = reflect.Value{}
}
}
if err := copyValue(saveData, data); err != nil {
return err
}
switch t := saveComment; t.Kind() {
case reflect.String:
t.SetString(string(comment))
case reflect.Slice:
t.Set(reflect.ValueOf(comment))
}
switch t := saveXML; t.Kind() {
case reflect.String:
t.SetString(string(saveXMLData))
case reflect.Slice:
if t.Type().Elem().Kind() == reflect.Uint8 {
t.Set(reflect.ValueOf(saveXMLData))
}
}
return nil
}
func copyValue(dst reflect.Value, src []byte) (err error) {
dst0 := dst
if dst.Kind() == reflect.Ptr {
if dst.IsNil() {
dst.Set(reflect.New(dst.Type().Elem()))
}
dst = dst.Elem()
}
// Save accumulated data.
switch dst.Kind() {
case reflect.Invalid:
// Probably a comment.
default:
return errors.New("cannot unmarshal into " + dst0.Type().String())
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
if len(src) == 0 {
dst.SetInt(0)
return nil
}
itmp, err := strconv.ParseInt(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
if err != nil {
return err
}
dst.SetInt(itmp)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
if len(src) == 0 {
dst.SetUint(0)
return nil
}
utmp, err := strconv.ParseUint(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
if err != nil {
return err
}
dst.SetUint(utmp)
case reflect.Float32, reflect.Float64:
if len(src) == 0 {
dst.SetFloat(0)
return nil
}
ftmp, err := strconv.ParseFloat(strings.TrimSpace(string(src)), dst.Type().Bits())
if err != nil {
return err
}
dst.SetFloat(ftmp)
case reflect.Bool:
if len(src) == 0 {
dst.SetBool(false)
return nil
}
value, err := strconv.ParseBool(strings.TrimSpace(string(src)))
if err != nil {
return err
}
dst.SetBool(value)
case reflect.String:
dst.SetString(string(src))
case reflect.Slice:
if len(src) == 0 {
// non-nil to flag presence
src = []byte{}
}
dst.SetBytes(src)
}
return nil
}
// unmarshalPath walks down an XML structure looking for wanted
// paths, and calls unmarshal on them.
// The consumed result tells whether XML elements have been consumed
// from the Decoder until start's matching end element, or if it's
// still untouched because start is uninteresting for sv's fields.
func (d *Decoder) unmarshalPath(tinfo *typeInfo, sv reflect.Value, parents []string, start *StartElement) (consumed bool, err error) {
recurse := false
Loop:
for i := range tinfo.fields {
finfo := &tinfo.fields[i]
if finfo.flags&fElement == 0 || len(finfo.parents) < len(parents) || finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
continue
}
for j := range parents {
if parents[j] != finfo.parents[j] {
continue Loop
}
}
if len(finfo.parents) == len(parents) && finfo.name == start.Name.Local {
// It's a perfect match, unmarshal the field.
return true, d.unmarshal(finfo.value(sv), start)
}
if len(finfo.parents) > len(parents) && finfo.parents[len(parents)] == start.Name.Local {
// It's a prefix for the field. Break and recurse
// since it's not ok for one field path to be itself
// the prefix for another field path.
recurse = true
// We can reuse the same slice as long as we
// don't try to append to it.
parents = finfo.parents[:len(parents)+1]
break
}
}
if !recurse {
// We have no business with this element.
return false, nil
}
// The element is not a perfect match for any field, but one
// or more fields have the path to this element as a parent
// prefix. Recurse and attempt to match these.
for {
var tok Token
tok, err = d.Token()
if err != nil {
return true, err
}
switch t := tok.(type) {
case StartElement:
consumed2, err := d.unmarshalPath(tinfo, sv, parents, &t)
if err != nil {
return true, err
}
if !consumed2 {
if err := d.Skip(); err != nil {
return true, err
}
}
case EndElement:
return true, nil
}
}
}
// Skip reads tokens until it has consumed the end element
// matching the most recent start element already consumed.
// It recurs if it encounters a start element, so it can be used to
// skip nested structures.
// It returns nil if it finds an end element matching the start
// element; otherwise it returns an error describing the problem.
func (d *Decoder) Skip() error {
for {
tok, err := d.Token()
if err != nil {
return err
}
switch tok.(type) {
case StartElement:
if err := d.Skip(); err != nil {
return err
}
case EndElement:
return nil
}
}
}
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