gcc/libgo/go/encoding/xml/read.go
Ian Lance Taylor be47d6ecef libgo: Update to Go 1.1.1.
From-SVN: r200974
2013-07-16 06:54:42 +00:00

520 lines
14 KiB
Go

// 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"
"errors"
"reflect"
"strconv"
"strings"
"time"
)
// 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 xml.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 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 ",comments". 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 unmarshalled into.
//
// 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 XML element to a slice by extending the length of
// the slice and mapping the element 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.
//
// 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.
//
// Unmarshal maps an XML element to an xml.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.
//
func Unmarshal(data []byte, v interface{}) error {
return NewDecoder(bytes.NewBuffer(data)).Decode(v)
}
// Decode works like xml.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 xml.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 unmarshalling process.
type UnmarshalError string
func (e UnmarshalError) Error() string { return string(e) }
// Unmarshal a single XML element into val.
func (p *Decoder) unmarshal(val reflect.Value, start *StartElement) error {
// Find start element if we need it.
if start == nil {
for {
tok, err := p.Token()
if err != nil {
return err
}
if t, ok := tok.(StartElement); ok {
start = &t
break
}
}
}
if pv := val; pv.Kind() == reflect.Ptr {
if pv.IsNil() {
pv.Set(reflect.New(pv.Type().Elem()))
}
val = pv.Elem()
}
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 p.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()
if n >= v.Cap() {
ncap := 2 * n
if ncap < 4 {
ncap = 4
}
new := reflect.MakeSlice(typ, n, ncap)
reflect.Copy(new, v)
v.Set(new)
}
v.SetLen(n + 1)
// Recur to read element into slice.
if err := p.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
}
if typ == timeType {
saveData = v
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.
// Also, determine whether we need to save character data or comments.
for i := range tinfo.fields {
finfo := &tinfo.fields[i]
switch finfo.flags & fMode {
case fAttr:
strv := finfo.value(sv)
// 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))
break
}
}
case 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 p.saved == nil {
saveXMLIndex = 0
p.saved = new(bytes.Buffer)
} else {
saveXMLIndex = p.savedOffset()
}
}
}
}
}
// Find end element.
// Process sub-elements along the way.
Loop:
for {
var savedOffset int
if saveXML.IsValid() {
savedOffset = p.savedOffset()
}
tok, err := p.Token()
if err != nil {
return err
}
switch t := tok.(type) {
case StartElement:
consumed := false
if sv.IsValid() {
consumed, err = p.unmarshalPath(tinfo, sv, nil, &t)
if err != nil {
return err
}
if !consumed && saveAny.IsValid() {
consumed = true
if err := p.unmarshal(saveAny, &t); err != nil {
return err
}
}
}
if !consumed {
if err := p.Skip(); err != nil {
return err
}
}
case EndElement:
if saveXML.IsValid() {
saveXMLData = p.saved.Bytes()[saveXMLIndex:savedOffset]
if saveXMLIndex == 0 {
p.saved = nil
}
}
break Loop
case CharData:
if saveData.IsValid() {
data = append(data, t...)
}
case Comment:
if saveComment.IsValid() {
comment = append(comment, t...)
}
}
}
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:
t.Set(reflect.ValueOf(saveXMLData))
}
return nil
}
func copyValue(dst reflect.Value, src []byte) (err error) {
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 commendst.
default:
return errors.New("cannot happen: unknown type " + dst.Type().String())
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
itmp, err := strconv.ParseInt(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:
utmp, err := strconv.ParseUint(string(src), 10, dst.Type().Bits())
if err != nil {
return err
}
dst.SetUint(utmp)
case reflect.Float32, reflect.Float64:
ftmp, err := strconv.ParseFloat(string(src), dst.Type().Bits())
if err != nil {
return err
}
dst.SetFloat(ftmp)
case reflect.Bool:
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)
case reflect.Struct:
if dst.Type() == timeType {
tv, err := time.Parse(time.RFC3339, string(src))
if err != nil {
return err
}
dst.Set(reflect.ValueOf(tv))
}
}
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 (p *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, p.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 = p.Token()
if err != nil {
return true, err
}
switch t := tok.(type) {
case StartElement:
consumed2, err := p.unmarshalPath(tinfo, sv, parents, &t)
if err != nil {
return true, err
}
if !consumed2 {
if err := p.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
}
}
}