Source file src/encoding/xml/read.go

Documentation: encoding/xml

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package xml
     6  
     7  import (
     8  	"bytes"
     9  	"encoding"
    10  	"errors"
    11  	"fmt"
    12  	"reflect"
    13  	"runtime"
    14  	"strconv"
    15  	"strings"
    16  )
    17  
    18  // BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
    19  // an XML element is an order-dependent collection of anonymous
    20  // values, while a data structure is an order-independent collection
    21  // of named values.
    22  // See package json for a textual representation more suitable
    23  // to data structures.
    24  
    25  // Unmarshal parses the XML-encoded data and stores the result in
    26  // the value pointed to by v, which must be an arbitrary struct,
    27  // slice, or string. Well-formed data that does not fit into v is
    28  // discarded.
    29  //
    30  // Because Unmarshal uses the reflect package, it can only assign
    31  // to exported (upper case) fields. Unmarshal uses a case-sensitive
    32  // comparison to match XML element names to tag values and struct
    33  // field names.
    34  //
    35  // Unmarshal maps an XML element to a struct using the following rules.
    36  // In the rules, the tag of a field refers to the value associated with the
    37  // key 'xml' in the struct field's tag (see the example above).
    38  //
    39  //   - If the struct has a field of type []byte or string with tag
    40  //     ",innerxml", Unmarshal accumulates the raw XML nested inside the
    41  //     element in that field. The rest of the rules still apply.
    42  //
    43  //   - If the struct has a field named XMLName of type Name,
    44  //     Unmarshal records the element name in that field.
    45  //
    46  //   - If the XMLName field has an associated tag of the form
    47  //     "name" or "namespace-URL name", the XML element must have
    48  //     the given name (and, optionally, name space) or else Unmarshal
    49  //     returns an error.
    50  //
    51  //   - If the XML element has an attribute whose name matches a
    52  //     struct field name with an associated tag containing ",attr" or
    53  //     the explicit name in a struct field tag of the form "name,attr",
    54  //     Unmarshal records the attribute value in that field.
    55  //
    56  //   - If the XML element has an attribute not handled by the previous
    57  //     rule and the struct has a field with an associated tag containing
    58  //     ",any,attr", Unmarshal records the attribute value in the first
    59  //     such field.
    60  //
    61  //   - If the XML element contains character data, that data is
    62  //     accumulated in the first struct field that has tag ",chardata".
    63  //     The struct field may have type []byte or string.
    64  //     If there is no such field, the character data is discarded.
    65  //
    66  //   - If the XML element contains comments, they are accumulated in
    67  //     the first struct field that has tag ",comment".  The struct
    68  //     field may have type []byte or string. If there is no such
    69  //     field, the comments are discarded.
    70  //
    71  //   - If the XML element contains a sub-element whose name matches
    72  //     the prefix of a tag formatted as "a" or "a>b>c", unmarshal
    73  //     will descend into the XML structure looking for elements with the
    74  //     given names, and will map the innermost elements to that struct
    75  //     field. A tag starting with ">" is equivalent to one starting
    76  //     with the field name followed by ">".
    77  //
    78  //   - If the XML element contains a sub-element whose name matches
    79  //     a struct field's XMLName tag and the struct field has no
    80  //     explicit name tag as per the previous rule, unmarshal maps
    81  //     the sub-element to that struct field.
    82  //
    83  //   - If the XML element contains a sub-element whose name matches a
    84  //     field without any mode flags (",attr", ",chardata", etc), Unmarshal
    85  //     maps the sub-element to that struct field.
    86  //
    87  //   - If the XML element contains a sub-element that hasn't matched any
    88  //     of the above rules and the struct has a field with tag ",any",
    89  //     unmarshal maps the sub-element to that struct field.
    90  //
    91  //   - An anonymous struct field is handled as if the fields of its
    92  //     value were part of the outer struct.
    93  //
    94  //   - A struct field with tag "-" is never unmarshaled into.
    95  //
    96  // If Unmarshal encounters a field type that implements the Unmarshaler
    97  // interface, Unmarshal calls its UnmarshalXML method to produce the value from
    98  // the XML element.  Otherwise, if the value implements
    99  // encoding.TextUnmarshaler, Unmarshal calls that value's UnmarshalText method.
   100  //
   101  // Unmarshal maps an XML element to a string or []byte by saving the
   102  // concatenation of that element's character data in the string or
   103  // []byte. The saved []byte is never nil.
   104  //
   105  // Unmarshal maps an attribute value to a string or []byte by saving
   106  // the value in the string or slice.
   107  //
   108  // Unmarshal maps an attribute value to an Attr by saving the attribute,
   109  // including its name, in the Attr.
   110  //
   111  // Unmarshal maps an XML element or attribute value to a slice by
   112  // extending the length of the slice and mapping the element or attribute
   113  // to the newly created value.
   114  //
   115  // Unmarshal maps an XML element or attribute value to a bool by
   116  // setting it to the boolean value represented by the string. Whitespace
   117  // is trimmed and ignored.
   118  //
   119  // Unmarshal maps an XML element or attribute value to an integer or
   120  // floating-point field by setting the field to the result of
   121  // interpreting the string value in decimal. There is no check for
   122  // overflow. Whitespace is trimmed and ignored.
   123  //
   124  // Unmarshal maps an XML element to a Name by recording the element
   125  // name.
   126  //
   127  // Unmarshal maps an XML element to a pointer by setting the pointer
   128  // to a freshly allocated value and then mapping the element to that value.
   129  //
   130  // A missing element or empty attribute value will be unmarshaled as a zero value.
   131  // If the field is a slice, a zero value will be appended to the field. Otherwise, the
   132  // field will be set to its zero value.
   133  func Unmarshal(data []byte, v any) error {
   134  	return NewDecoder(bytes.NewReader(data)).Decode(v)
   135  }
   136  
   137  // Decode works like Unmarshal, except it reads the decoder
   138  // stream to find the start element.
   139  func (d *Decoder) Decode(v any) error {
   140  	return d.DecodeElement(v, nil)
   141  }
   142  
   143  // DecodeElement works like Unmarshal except that it takes
   144  // a pointer to the start XML element to decode into v.
   145  // It is useful when a client reads some raw XML tokens itself
   146  // but also wants to defer to Unmarshal for some elements.
   147  func (d *Decoder) DecodeElement(v any, start *StartElement) error {
   148  	val := reflect.ValueOf(v)
   149  	if val.Kind() != reflect.Pointer {
   150  		return errors.New("non-pointer passed to Unmarshal")
   151  	}
   152  
   153  	if val.IsNil() {
   154  		return errors.New("nil pointer passed to Unmarshal")
   155  	}
   156  	return d.unmarshal(val.Elem(), start, 0)
   157  }
   158  
   159  // An UnmarshalError represents an error in the unmarshaling process.
   160  type UnmarshalError string
   161  
   162  func (e UnmarshalError) Error() string { return string(e) }
   163  
   164  // Unmarshaler is the interface implemented by objects that can unmarshal
   165  // an XML element description of themselves.
   166  //
   167  // UnmarshalXML decodes a single XML element
   168  // beginning with the given start element.
   169  // If it returns an error, the outer call to Unmarshal stops and
   170  // returns that error.
   171  // UnmarshalXML must consume exactly one XML element.
   172  // One common implementation strategy is to unmarshal into
   173  // a separate value with a layout matching the expected XML
   174  // using d.DecodeElement, and then to copy the data from
   175  // that value into the receiver.
   176  // Another common strategy is to use d.Token to process the
   177  // XML object one token at a time.
   178  // UnmarshalXML may not use d.RawToken.
   179  type Unmarshaler interface {
   180  	UnmarshalXML(d *Decoder, start StartElement) error
   181  }
   182  
   183  // UnmarshalerAttr is the interface implemented by objects that can unmarshal
   184  // an XML attribute description of themselves.
   185  //
   186  // UnmarshalXMLAttr decodes a single XML attribute.
   187  // If it returns an error, the outer call to Unmarshal stops and
   188  // returns that error.
   189  // UnmarshalXMLAttr is used only for struct fields with the
   190  // "attr" option in the field tag.
   191  type UnmarshalerAttr interface {
   192  	UnmarshalXMLAttr(attr Attr) error
   193  }
   194  
   195  // receiverType returns the receiver type to use in an expression like "%s.MethodName".
   196  func receiverType(val any) string {
   197  	t := reflect.TypeOf(val)
   198  	if t.Name() != "" {
   199  		return t.String()
   200  	}
   201  	return "(" + t.String() + ")"
   202  }
   203  
   204  // unmarshalInterface unmarshals a single XML element into val.
   205  // start is the opening tag of the element.
   206  func (d *Decoder) unmarshalInterface(val Unmarshaler, start *StartElement) error {
   207  	// Record that decoder must stop at end tag corresponding to start.
   208  	d.pushEOF()
   209  
   210  	d.unmarshalDepth++
   211  	err := val.UnmarshalXML(d, *start)
   212  	d.unmarshalDepth--
   213  	if err != nil {
   214  		d.popEOF()
   215  		return err
   216  	}
   217  
   218  	if !d.popEOF() {
   219  		return fmt.Errorf("xml: %s.UnmarshalXML did not consume entire <%s> element", receiverType(val), start.Name.Local)
   220  	}
   221  
   222  	return nil
   223  }
   224  
   225  // unmarshalTextInterface unmarshals a single XML element into val.
   226  // The chardata contained in the element (but not its children)
   227  // is passed to the text unmarshaler.
   228  func (d *Decoder) unmarshalTextInterface(val encoding.TextUnmarshaler) error {
   229  	var buf []byte
   230  	depth := 1
   231  	for depth > 0 {
   232  		t, err := d.Token()
   233  		if err != nil {
   234  			return err
   235  		}
   236  		switch t := t.(type) {
   237  		case CharData:
   238  			if depth == 1 {
   239  				buf = append(buf, t...)
   240  			}
   241  		case StartElement:
   242  			depth++
   243  		case EndElement:
   244  			depth--
   245  		}
   246  	}
   247  	return val.UnmarshalText(buf)
   248  }
   249  
   250  // unmarshalAttr unmarshals a single XML attribute into val.
   251  func (d *Decoder) unmarshalAttr(val reflect.Value, attr Attr) error {
   252  	if val.Kind() == reflect.Pointer {
   253  		if val.IsNil() {
   254  			val.Set(reflect.New(val.Type().Elem()))
   255  		}
   256  		val = val.Elem()
   257  	}
   258  	if val.CanInterface() && val.Type().Implements(unmarshalerAttrType) {
   259  		// This is an unmarshaler with a non-pointer receiver,
   260  		// so it's likely to be incorrect, but we do what we're told.
   261  		return val.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
   262  	}
   263  	if val.CanAddr() {
   264  		pv := val.Addr()
   265  		if pv.CanInterface() && pv.Type().Implements(unmarshalerAttrType) {
   266  			return pv.Interface().(UnmarshalerAttr).UnmarshalXMLAttr(attr)
   267  		}
   268  	}
   269  
   270  	// Not an UnmarshalerAttr; try encoding.TextUnmarshaler.
   271  	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
   272  		// This is an unmarshaler with a non-pointer receiver,
   273  		// so it's likely to be incorrect, but we do what we're told.
   274  		return val.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
   275  	}
   276  	if val.CanAddr() {
   277  		pv := val.Addr()
   278  		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
   279  			return pv.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
   280  		}
   281  	}
   282  
   283  	if val.Type().Kind() == reflect.Slice && val.Type().Elem().Kind() != reflect.Uint8 {
   284  		// Slice of element values.
   285  		// Grow slice.
   286  		n := val.Len()
   287  		val.Set(reflect.Append(val, reflect.Zero(val.Type().Elem())))
   288  
   289  		// Recur to read element into slice.
   290  		if err := d.unmarshalAttr(val.Index(n), attr); err != nil {
   291  			val.SetLen(n)
   292  			return err
   293  		}
   294  		return nil
   295  	}
   296  
   297  	if val.Type() == attrType {
   298  		val.Set(reflect.ValueOf(attr))
   299  		return nil
   300  	}
   301  
   302  	return copyValue(val, []byte(attr.Value))
   303  }
   304  
   305  var (
   306  	attrType            = reflect.TypeOf(Attr{})
   307  	unmarshalerType     = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
   308  	unmarshalerAttrType = reflect.TypeOf((*UnmarshalerAttr)(nil)).Elem()
   309  	textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
   310  )
   311  
   312  const (
   313  	maxUnmarshalDepth     = 10000
   314  	maxUnmarshalDepthWasm = 5000 // go.dev/issue/56498
   315  )
   316  
   317  var errUnmarshalDepth = errors.New("exceeded max depth")
   318  
   319  // Unmarshal a single XML element into val.
   320  func (d *Decoder) unmarshal(val reflect.Value, start *StartElement, depth int) error {
   321  	if depth >= maxUnmarshalDepth || runtime.GOARCH == "wasm" && depth >= maxUnmarshalDepthWasm {
   322  		return errUnmarshalDepth
   323  	}
   324  	// Find start element if we need it.
   325  	if start == nil {
   326  		for {
   327  			tok, err := d.Token()
   328  			if err != nil {
   329  				return err
   330  			}
   331  			if t, ok := tok.(StartElement); ok {
   332  				start = &t
   333  				break
   334  			}
   335  		}
   336  	}
   337  
   338  	// Load value from interface, but only if the result will be
   339  	// usefully addressable.
   340  	if val.Kind() == reflect.Interface && !val.IsNil() {
   341  		e := val.Elem()
   342  		if e.Kind() == reflect.Pointer && !e.IsNil() {
   343  			val = e
   344  		}
   345  	}
   346  
   347  	if val.Kind() == reflect.Pointer {
   348  		if val.IsNil() {
   349  			val.Set(reflect.New(val.Type().Elem()))
   350  		}
   351  		val = val.Elem()
   352  	}
   353  
   354  	if val.CanInterface() && val.Type().Implements(unmarshalerType) {
   355  		// This is an unmarshaler with a non-pointer receiver,
   356  		// so it's likely to be incorrect, but we do what we're told.
   357  		return d.unmarshalInterface(val.Interface().(Unmarshaler), start)
   358  	}
   359  
   360  	if val.CanAddr() {
   361  		pv := val.Addr()
   362  		if pv.CanInterface() && pv.Type().Implements(unmarshalerType) {
   363  			return d.unmarshalInterface(pv.Interface().(Unmarshaler), start)
   364  		}
   365  	}
   366  
   367  	if val.CanInterface() && val.Type().Implements(textUnmarshalerType) {
   368  		return d.unmarshalTextInterface(val.Interface().(encoding.TextUnmarshaler))
   369  	}
   370  
   371  	if val.CanAddr() {
   372  		pv := val.Addr()
   373  		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
   374  			return d.unmarshalTextInterface(pv.Interface().(encoding.TextUnmarshaler))
   375  		}
   376  	}
   377  
   378  	var (
   379  		data         []byte
   380  		saveData     reflect.Value
   381  		comment      []byte
   382  		saveComment  reflect.Value
   383  		saveXML      reflect.Value
   384  		saveXMLIndex int
   385  		saveXMLData  []byte
   386  		saveAny      reflect.Value
   387  		sv           reflect.Value
   388  		tinfo        *typeInfo
   389  		err          error
   390  	)
   391  
   392  	switch v := val; v.Kind() {
   393  	default:
   394  		return errors.New("unknown type " + v.Type().String())
   395  
   396  	case reflect.Interface:
   397  		// TODO: For now, simply ignore the field. In the near
   398  		//       future we may choose to unmarshal the start
   399  		//       element on it, if not nil.
   400  		return d.Skip()
   401  
   402  	case reflect.Slice:
   403  		typ := v.Type()
   404  		if typ.Elem().Kind() == reflect.Uint8 {
   405  			// []byte
   406  			saveData = v
   407  			break
   408  		}
   409  
   410  		// Slice of element values.
   411  		// Grow slice.
   412  		n := v.Len()
   413  		v.Set(reflect.Append(val, reflect.Zero(v.Type().Elem())))
   414  
   415  		// Recur to read element into slice.
   416  		if err := d.unmarshal(v.Index(n), start, depth+1); err != nil {
   417  			v.SetLen(n)
   418  			return err
   419  		}
   420  		return nil
   421  
   422  	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:
   423  		saveData = v
   424  
   425  	case reflect.Struct:
   426  		typ := v.Type()
   427  		if typ == nameType {
   428  			v.Set(reflect.ValueOf(start.Name))
   429  			break
   430  		}
   431  
   432  		sv = v
   433  		tinfo, err = getTypeInfo(typ)
   434  		if err != nil {
   435  			return err
   436  		}
   437  
   438  		// Validate and assign element name.
   439  		if tinfo.xmlname != nil {
   440  			finfo := tinfo.xmlname
   441  			if finfo.name != "" && finfo.name != start.Name.Local {
   442  				return UnmarshalError("expected element type <" + finfo.name + "> but have <" + start.Name.Local + ">")
   443  			}
   444  			if finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
   445  				e := "expected element <" + finfo.name + "> in name space " + finfo.xmlns + " but have "
   446  				if start.Name.Space == "" {
   447  					e += "no name space"
   448  				} else {
   449  					e += start.Name.Space
   450  				}
   451  				return UnmarshalError(e)
   452  			}
   453  			fv := finfo.value(sv, initNilPointers)
   454  			if _, ok := fv.Interface().(Name); ok {
   455  				fv.Set(reflect.ValueOf(start.Name))
   456  			}
   457  		}
   458  
   459  		// Assign attributes.
   460  		for _, a := range start.Attr {
   461  			handled := false
   462  			any := -1
   463  			for i := range tinfo.fields {
   464  				finfo := &tinfo.fields[i]
   465  				switch finfo.flags & fMode {
   466  				case fAttr:
   467  					strv := finfo.value(sv, initNilPointers)
   468  					if a.Name.Local == finfo.name && (finfo.xmlns == "" || finfo.xmlns == a.Name.Space) {
   469  						if err := d.unmarshalAttr(strv, a); err != nil {
   470  							return err
   471  						}
   472  						handled = true
   473  					}
   474  
   475  				case fAny | fAttr:
   476  					if any == -1 {
   477  						any = i
   478  					}
   479  				}
   480  			}
   481  			if !handled && any >= 0 {
   482  				finfo := &tinfo.fields[any]
   483  				strv := finfo.value(sv, initNilPointers)
   484  				if err := d.unmarshalAttr(strv, a); err != nil {
   485  					return err
   486  				}
   487  			}
   488  		}
   489  
   490  		// Determine whether we need to save character data or comments.
   491  		for i := range tinfo.fields {
   492  			finfo := &tinfo.fields[i]
   493  			switch finfo.flags & fMode {
   494  			case fCDATA, fCharData:
   495  				if !saveData.IsValid() {
   496  					saveData = finfo.value(sv, initNilPointers)
   497  				}
   498  
   499  			case fComment:
   500  				if !saveComment.IsValid() {
   501  					saveComment = finfo.value(sv, initNilPointers)
   502  				}
   503  
   504  			case fAny, fAny | fElement:
   505  				if !saveAny.IsValid() {
   506  					saveAny = finfo.value(sv, initNilPointers)
   507  				}
   508  
   509  			case fInnerXML:
   510  				if !saveXML.IsValid() {
   511  					saveXML = finfo.value(sv, initNilPointers)
   512  					if d.saved == nil {
   513  						saveXMLIndex = 0
   514  						d.saved = new(bytes.Buffer)
   515  					} else {
   516  						saveXMLIndex = d.savedOffset()
   517  					}
   518  				}
   519  			}
   520  		}
   521  	}
   522  
   523  	// Find end element.
   524  	// Process sub-elements along the way.
   525  Loop:
   526  	for {
   527  		var savedOffset int
   528  		if saveXML.IsValid() {
   529  			savedOffset = d.savedOffset()
   530  		}
   531  		tok, err := d.Token()
   532  		if err != nil {
   533  			return err
   534  		}
   535  		switch t := tok.(type) {
   536  		case StartElement:
   537  			consumed := false
   538  			if sv.IsValid() {
   539  				// unmarshalPath can call unmarshal, so we need to pass the depth through so that
   540  				// we can continue to enforce the maximum recursion limit.
   541  				consumed, err = d.unmarshalPath(tinfo, sv, nil, &t, depth)
   542  				if err != nil {
   543  					return err
   544  				}
   545  				if !consumed && saveAny.IsValid() {
   546  					consumed = true
   547  					if err := d.unmarshal(saveAny, &t, depth+1); err != nil {
   548  						return err
   549  					}
   550  				}
   551  			}
   552  			if !consumed {
   553  				if err := d.Skip(); err != nil {
   554  					return err
   555  				}
   556  			}
   557  
   558  		case EndElement:
   559  			if saveXML.IsValid() {
   560  				saveXMLData = d.saved.Bytes()[saveXMLIndex:savedOffset]
   561  				if saveXMLIndex == 0 {
   562  					d.saved = nil
   563  				}
   564  			}
   565  			break Loop
   566  
   567  		case CharData:
   568  			if saveData.IsValid() {
   569  				data = append(data, t...)
   570  			}
   571  
   572  		case Comment:
   573  			if saveComment.IsValid() {
   574  				comment = append(comment, t...)
   575  			}
   576  		}
   577  	}
   578  
   579  	if saveData.IsValid() && saveData.CanInterface() && saveData.Type().Implements(textUnmarshalerType) {
   580  		if err := saveData.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
   581  			return err
   582  		}
   583  		saveData = reflect.Value{}
   584  	}
   585  
   586  	if saveData.IsValid() && saveData.CanAddr() {
   587  		pv := saveData.Addr()
   588  		if pv.CanInterface() && pv.Type().Implements(textUnmarshalerType) {
   589  			if err := pv.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
   590  				return err
   591  			}
   592  			saveData = reflect.Value{}
   593  		}
   594  	}
   595  
   596  	if err := copyValue(saveData, data); err != nil {
   597  		return err
   598  	}
   599  
   600  	switch t := saveComment; t.Kind() {
   601  	case reflect.String:
   602  		t.SetString(string(comment))
   603  	case reflect.Slice:
   604  		t.Set(reflect.ValueOf(comment))
   605  	}
   606  
   607  	switch t := saveXML; t.Kind() {
   608  	case reflect.String:
   609  		t.SetString(string(saveXMLData))
   610  	case reflect.Slice:
   611  		if t.Type().Elem().Kind() == reflect.Uint8 {
   612  			t.Set(reflect.ValueOf(saveXMLData))
   613  		}
   614  	}
   615  
   616  	return nil
   617  }
   618  
   619  func copyValue(dst reflect.Value, src []byte) (err error) {
   620  	dst0 := dst
   621  
   622  	if dst.Kind() == reflect.Pointer {
   623  		if dst.IsNil() {
   624  			dst.Set(reflect.New(dst.Type().Elem()))
   625  		}
   626  		dst = dst.Elem()
   627  	}
   628  
   629  	// Save accumulated data.
   630  	switch dst.Kind() {
   631  	case reflect.Invalid:
   632  		// Probably a comment.
   633  	default:
   634  		return errors.New("cannot unmarshal into " + dst0.Type().String())
   635  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   636  		if len(src) == 0 {
   637  			dst.SetInt(0)
   638  			return nil
   639  		}
   640  		itmp, err := strconv.ParseInt(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
   641  		if err != nil {
   642  			return err
   643  		}
   644  		dst.SetInt(itmp)
   645  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
   646  		if len(src) == 0 {
   647  			dst.SetUint(0)
   648  			return nil
   649  		}
   650  		utmp, err := strconv.ParseUint(strings.TrimSpace(string(src)), 10, dst.Type().Bits())
   651  		if err != nil {
   652  			return err
   653  		}
   654  		dst.SetUint(utmp)
   655  	case reflect.Float32, reflect.Float64:
   656  		if len(src) == 0 {
   657  			dst.SetFloat(0)
   658  			return nil
   659  		}
   660  		ftmp, err := strconv.ParseFloat(strings.TrimSpace(string(src)), dst.Type().Bits())
   661  		if err != nil {
   662  			return err
   663  		}
   664  		dst.SetFloat(ftmp)
   665  	case reflect.Bool:
   666  		if len(src) == 0 {
   667  			dst.SetBool(false)
   668  			return nil
   669  		}
   670  		value, err := strconv.ParseBool(strings.TrimSpace(string(src)))
   671  		if err != nil {
   672  			return err
   673  		}
   674  		dst.SetBool(value)
   675  	case reflect.String:
   676  		dst.SetString(string(src))
   677  	case reflect.Slice:
   678  		if len(src) == 0 {
   679  			// non-nil to flag presence
   680  			src = []byte{}
   681  		}
   682  		dst.SetBytes(src)
   683  	}
   684  	return nil
   685  }
   686  
   687  // unmarshalPath walks down an XML structure looking for wanted
   688  // paths, and calls unmarshal on them.
   689  // The consumed result tells whether XML elements have been consumed
   690  // from the Decoder until start's matching end element, or if it's
   691  // still untouched because start is uninteresting for sv's fields.
   692  func (d *Decoder) unmarshalPath(tinfo *typeInfo, sv reflect.Value, parents []string, start *StartElement, depth int) (consumed bool, err error) {
   693  	recurse := false
   694  Loop:
   695  	for i := range tinfo.fields {
   696  		finfo := &tinfo.fields[i]
   697  		if finfo.flags&fElement == 0 || len(finfo.parents) < len(parents) || finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
   698  			continue
   699  		}
   700  		for j := range parents {
   701  			if parents[j] != finfo.parents[j] {
   702  				continue Loop
   703  			}
   704  		}
   705  		if len(finfo.parents) == len(parents) && finfo.name == start.Name.Local {
   706  			// It's a perfect match, unmarshal the field.
   707  			return true, d.unmarshal(finfo.value(sv, initNilPointers), start, depth+1)
   708  		}
   709  		if len(finfo.parents) > len(parents) && finfo.parents[len(parents)] == start.Name.Local {
   710  			// It's a prefix for the field. Break and recurse
   711  			// since it's not ok for one field path to be itself
   712  			// the prefix for another field path.
   713  			recurse = true
   714  
   715  			// We can reuse the same slice as long as we
   716  			// don't try to append to it.
   717  			parents = finfo.parents[:len(parents)+1]
   718  			break
   719  		}
   720  	}
   721  	if !recurse {
   722  		// We have no business with this element.
   723  		return false, nil
   724  	}
   725  	// The element is not a perfect match for any field, but one
   726  	// or more fields have the path to this element as a parent
   727  	// prefix. Recurse and attempt to match these.
   728  	for {
   729  		var tok Token
   730  		tok, err = d.Token()
   731  		if err != nil {
   732  			return true, err
   733  		}
   734  		switch t := tok.(type) {
   735  		case StartElement:
   736  			// the recursion depth of unmarshalPath is limited to the path length specified
   737  			// by the struct field tag, so we don't increment the depth here.
   738  			consumed2, err := d.unmarshalPath(tinfo, sv, parents, &t, depth)
   739  			if err != nil {
   740  				return true, err
   741  			}
   742  			if !consumed2 {
   743  				if err := d.Skip(); err != nil {
   744  					return true, err
   745  				}
   746  			}
   747  		case EndElement:
   748  			return true, nil
   749  		}
   750  	}
   751  }
   752  
   753  // Skip reads tokens until it has consumed the end element
   754  // matching the most recent start element already consumed,
   755  // skipping nested structures.
   756  // It returns nil if it finds an end element matching the start
   757  // element; otherwise it returns an error describing the problem.
   758  func (d *Decoder) Skip() error {
   759  	var depth int64
   760  	for {
   761  		tok, err := d.Token()
   762  		if err != nil {
   763  			return err
   764  		}
   765  		switch tok.(type) {
   766  		case StartElement:
   767  			depth++
   768  		case EndElement:
   769  			if depth == 0 {
   770  				return nil
   771  			}
   772  			depth--
   773  		}
   774  	}
   775  }
   776  

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