be47d6ecef
From-SVN: r200974
520 lines
14 KiB
Go
520 lines
14 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package xml
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import (
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"bytes"
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"errors"
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"reflect"
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"strconv"
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"strings"
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"time"
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)
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// BUG(rsc): Mapping between XML elements and data structures is inherently flawed:
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// an XML element is an order-dependent collection of anonymous
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// values, while a data structure is an order-independent collection
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// of named values.
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// See package json for a textual representation more suitable
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// to data structures.
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// Unmarshal parses the XML-encoded data and stores the result in
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// the value pointed to by v, which must be an arbitrary struct,
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// slice, or string. Well-formed data that does not fit into v is
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// discarded.
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//
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// Because Unmarshal uses the reflect package, it can only assign
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// to exported (upper case) fields. Unmarshal uses a case-sensitive
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// comparison to match XML element names to tag values and struct
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// field names.
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//
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// Unmarshal maps an XML element to a struct using the following rules.
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// In the rules, the tag of a field refers to the value associated with the
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// key 'xml' in the struct field's tag (see the example above).
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//
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// * If the struct has a field of type []byte or string with tag
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// ",innerxml", Unmarshal accumulates the raw XML nested inside the
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// element in that field. The rest of the rules still apply.
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//
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// * If the struct has a field named XMLName of type xml.Name,
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// Unmarshal records the element name in that field.
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//
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// * If the XMLName field has an associated tag of the form
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// "name" or "namespace-URL name", the XML element must have
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// the given name (and, optionally, name space) or else Unmarshal
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// returns an error.
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//
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// * If the XML element has an attribute whose name matches a
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// struct field name with an associated tag containing ",attr" or
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// the explicit name in a struct field tag of the form "name,attr",
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// Unmarshal records the attribute value in that field.
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//
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// * If the XML element contains character data, that data is
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// accumulated in the first struct field that has tag "chardata".
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// The struct field may have type []byte or string.
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// If there is no such field, the character data is discarded.
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//
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// * If the XML element contains comments, they are accumulated in
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// the first struct field that has tag ",comments". The struct
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// field may have type []byte or string. If there is no such
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// field, the comments are discarded.
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//
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// * If the XML element contains a sub-element whose name matches
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// the prefix of a tag formatted as "a" or "a>b>c", unmarshal
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// will descend into the XML structure looking for elements with the
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// given names, and will map the innermost elements to that struct
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// field. A tag starting with ">" is equivalent to one starting
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// with the field name followed by ">".
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//
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// * If the XML element contains a sub-element whose name matches
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// a struct field's XMLName tag and the struct field has no
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// explicit name tag as per the previous rule, unmarshal maps
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// the sub-element to that struct field.
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//
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// * If the XML element contains a sub-element whose name matches a
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// field without any mode flags (",attr", ",chardata", etc), Unmarshal
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// maps the sub-element to that struct field.
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//
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// * If the XML element contains a sub-element that hasn't matched any
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// of the above rules and the struct has a field with tag ",any",
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// unmarshal maps the sub-element to that struct field.
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//
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// * An anonymous struct field is handled as if the fields of its
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// value were part of the outer struct.
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//
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// * A struct field with tag "-" is never unmarshalled into.
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//
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// Unmarshal maps an XML element to a string or []byte by saving the
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// concatenation of that element's character data in the string or
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// []byte. The saved []byte is never nil.
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//
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// Unmarshal maps an attribute value to a string or []byte by saving
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// the value in the string or slice.
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//
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// Unmarshal maps an XML element to a slice by extending the length of
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// the slice and mapping the element to the newly created value.
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//
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// Unmarshal maps an XML element or attribute value to a bool by
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// setting it to the boolean value represented by the string.
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//
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// Unmarshal maps an XML element or attribute value to an integer or
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// floating-point field by setting the field to the result of
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// interpreting the string value in decimal. There is no check for
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// overflow.
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//
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// Unmarshal maps an XML element to an xml.Name by recording the
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// element name.
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//
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// Unmarshal maps an XML element to a pointer by setting the pointer
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// to a freshly allocated value and then mapping the element to that value.
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//
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func Unmarshal(data []byte, v interface{}) error {
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return NewDecoder(bytes.NewBuffer(data)).Decode(v)
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}
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// Decode works like xml.Unmarshal, except it reads the decoder
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// stream to find the start element.
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func (d *Decoder) Decode(v interface{}) error {
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return d.DecodeElement(v, nil)
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}
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// DecodeElement works like xml.Unmarshal except that it takes
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// a pointer to the start XML element to decode into v.
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// It is useful when a client reads some raw XML tokens itself
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// but also wants to defer to Unmarshal for some elements.
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func (d *Decoder) DecodeElement(v interface{}, start *StartElement) error {
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val := reflect.ValueOf(v)
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if val.Kind() != reflect.Ptr {
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return errors.New("non-pointer passed to Unmarshal")
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}
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return d.unmarshal(val.Elem(), start)
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}
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// An UnmarshalError represents an error in the unmarshalling process.
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type UnmarshalError string
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func (e UnmarshalError) Error() string { return string(e) }
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// Unmarshal a single XML element into val.
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func (p *Decoder) unmarshal(val reflect.Value, start *StartElement) error {
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// Find start element if we need it.
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if start == nil {
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for {
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tok, err := p.Token()
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if err != nil {
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return err
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}
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if t, ok := tok.(StartElement); ok {
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start = &t
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break
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}
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}
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}
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if pv := val; pv.Kind() == reflect.Ptr {
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if pv.IsNil() {
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pv.Set(reflect.New(pv.Type().Elem()))
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}
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val = pv.Elem()
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}
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var (
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data []byte
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saveData reflect.Value
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comment []byte
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saveComment reflect.Value
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saveXML reflect.Value
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saveXMLIndex int
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saveXMLData []byte
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saveAny reflect.Value
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sv reflect.Value
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tinfo *typeInfo
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err error
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)
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switch v := val; v.Kind() {
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default:
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return errors.New("unknown type " + v.Type().String())
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case reflect.Interface:
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// TODO: For now, simply ignore the field. In the near
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// future we may choose to unmarshal the start
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// element on it, if not nil.
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return p.Skip()
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case reflect.Slice:
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typ := v.Type()
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if typ.Elem().Kind() == reflect.Uint8 {
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// []byte
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saveData = v
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break
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}
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// Slice of element values.
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// Grow slice.
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n := v.Len()
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if n >= v.Cap() {
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ncap := 2 * n
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if ncap < 4 {
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ncap = 4
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}
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new := reflect.MakeSlice(typ, n, ncap)
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reflect.Copy(new, v)
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v.Set(new)
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}
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v.SetLen(n + 1)
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// Recur to read element into slice.
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if err := p.unmarshal(v.Index(n), start); err != nil {
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v.SetLen(n)
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return err
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}
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return nil
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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:
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saveData = v
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case reflect.Struct:
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typ := v.Type()
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if typ == nameType {
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v.Set(reflect.ValueOf(start.Name))
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break
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}
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if typ == timeType {
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saveData = v
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break
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}
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sv = v
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tinfo, err = getTypeInfo(typ)
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if err != nil {
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return err
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}
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// Validate and assign element name.
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if tinfo.xmlname != nil {
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finfo := tinfo.xmlname
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if finfo.name != "" && finfo.name != start.Name.Local {
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return UnmarshalError("expected element type <" + finfo.name + "> but have <" + start.Name.Local + ">")
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}
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if finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
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e := "expected element <" + finfo.name + "> in name space " + finfo.xmlns + " but have "
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if start.Name.Space == "" {
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e += "no name space"
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} else {
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e += start.Name.Space
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}
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return UnmarshalError(e)
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}
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fv := finfo.value(sv)
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if _, ok := fv.Interface().(Name); ok {
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fv.Set(reflect.ValueOf(start.Name))
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}
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}
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// Assign attributes.
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// Also, determine whether we need to save character data or comments.
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for i := range tinfo.fields {
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finfo := &tinfo.fields[i]
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switch finfo.flags & fMode {
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case fAttr:
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strv := finfo.value(sv)
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// Look for attribute.
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for _, a := range start.Attr {
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if a.Name.Local == finfo.name && (finfo.xmlns == "" || finfo.xmlns == a.Name.Space) {
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copyValue(strv, []byte(a.Value))
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break
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}
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}
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case fCharData:
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if !saveData.IsValid() {
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saveData = finfo.value(sv)
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}
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case fComment:
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if !saveComment.IsValid() {
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saveComment = finfo.value(sv)
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}
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case fAny, fAny | fElement:
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if !saveAny.IsValid() {
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saveAny = finfo.value(sv)
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}
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case fInnerXml:
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if !saveXML.IsValid() {
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saveXML = finfo.value(sv)
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if p.saved == nil {
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saveXMLIndex = 0
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p.saved = new(bytes.Buffer)
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} else {
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saveXMLIndex = p.savedOffset()
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}
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}
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}
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}
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}
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// Find end element.
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// Process sub-elements along the way.
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Loop:
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for {
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var savedOffset int
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if saveXML.IsValid() {
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savedOffset = p.savedOffset()
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}
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tok, err := p.Token()
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if err != nil {
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return err
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}
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switch t := tok.(type) {
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case StartElement:
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consumed := false
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if sv.IsValid() {
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consumed, err = p.unmarshalPath(tinfo, sv, nil, &t)
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if err != nil {
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return err
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}
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if !consumed && saveAny.IsValid() {
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consumed = true
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if err := p.unmarshal(saveAny, &t); err != nil {
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return err
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}
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}
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}
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if !consumed {
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if err := p.Skip(); err != nil {
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return err
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}
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}
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case EndElement:
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if saveXML.IsValid() {
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saveXMLData = p.saved.Bytes()[saveXMLIndex:savedOffset]
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if saveXMLIndex == 0 {
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p.saved = nil
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}
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}
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break Loop
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case CharData:
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if saveData.IsValid() {
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data = append(data, t...)
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}
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case Comment:
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if saveComment.IsValid() {
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comment = append(comment, t...)
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}
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}
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}
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if err := copyValue(saveData, data); err != nil {
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return err
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}
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switch t := saveComment; t.Kind() {
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case reflect.String:
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t.SetString(string(comment))
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case reflect.Slice:
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t.Set(reflect.ValueOf(comment))
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}
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switch t := saveXML; t.Kind() {
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case reflect.String:
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t.SetString(string(saveXMLData))
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case reflect.Slice:
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t.Set(reflect.ValueOf(saveXMLData))
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}
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return nil
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}
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func copyValue(dst reflect.Value, src []byte) (err error) {
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if dst.Kind() == reflect.Ptr {
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if dst.IsNil() {
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dst.Set(reflect.New(dst.Type().Elem()))
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}
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dst = dst.Elem()
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}
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// Save accumulated data.
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switch dst.Kind() {
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case reflect.Invalid:
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// Probably a commendst.
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default:
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return errors.New("cannot happen: unknown type " + dst.Type().String())
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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itmp, err := strconv.ParseInt(string(src), 10, dst.Type().Bits())
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if err != nil {
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return err
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}
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dst.SetInt(itmp)
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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utmp, err := strconv.ParseUint(string(src), 10, dst.Type().Bits())
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if err != nil {
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return err
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}
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dst.SetUint(utmp)
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case reflect.Float32, reflect.Float64:
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ftmp, err := strconv.ParseFloat(string(src), dst.Type().Bits())
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if err != nil {
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return err
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}
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dst.SetFloat(ftmp)
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case reflect.Bool:
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value, err := strconv.ParseBool(strings.TrimSpace(string(src)))
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if err != nil {
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return err
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}
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dst.SetBool(value)
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case reflect.String:
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dst.SetString(string(src))
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case reflect.Slice:
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if len(src) == 0 {
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// non-nil to flag presence
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src = []byte{}
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}
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dst.SetBytes(src)
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case reflect.Struct:
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if dst.Type() == timeType {
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tv, err := time.Parse(time.RFC3339, string(src))
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if err != nil {
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return err
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}
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dst.Set(reflect.ValueOf(tv))
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}
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}
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return nil
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}
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// unmarshalPath walks down an XML structure looking for wanted
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// paths, and calls unmarshal on them.
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// The consumed result tells whether XML elements have been consumed
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// from the Decoder until start's matching end element, or if it's
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// still untouched because start is uninteresting for sv's fields.
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func (p *Decoder) unmarshalPath(tinfo *typeInfo, sv reflect.Value, parents []string, start *StartElement) (consumed bool, err error) {
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recurse := false
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Loop:
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for i := range tinfo.fields {
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finfo := &tinfo.fields[i]
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if finfo.flags&fElement == 0 || len(finfo.parents) < len(parents) || finfo.xmlns != "" && finfo.xmlns != start.Name.Space {
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continue
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}
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for j := range parents {
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if parents[j] != finfo.parents[j] {
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continue Loop
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}
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}
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if len(finfo.parents) == len(parents) && finfo.name == start.Name.Local {
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// It's a perfect match, unmarshal the field.
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return true, p.unmarshal(finfo.value(sv), start)
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}
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if len(finfo.parents) > len(parents) && finfo.parents[len(parents)] == start.Name.Local {
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// It's a prefix for the field. Break and recurse
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// since it's not ok for one field path to be itself
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// the prefix for another field path.
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recurse = true
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// We can reuse the same slice as long as we
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// don't try to append to it.
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parents = finfo.parents[:len(parents)+1]
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break
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}
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}
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if !recurse {
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// We have no business with this element.
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return false, nil
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}
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// The element is not a perfect match for any field, but one
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// or more fields have the path to this element as a parent
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// prefix. Recurse and attempt to match these.
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for {
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var tok Token
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tok, err = p.Token()
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if err != nil {
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return true, err
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}
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switch t := tok.(type) {
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case StartElement:
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consumed2, err := p.unmarshalPath(tinfo, sv, parents, &t)
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if err != nil {
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return true, err
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}
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if !consumed2 {
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if err := p.Skip(); err != nil {
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return true, err
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}
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}
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case EndElement:
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return true, nil
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}
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}
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}
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// Skip reads tokens until it has consumed the end element
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// matching the most recent start element already consumed.
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// It recurs if it encounters a start element, so it can be used to
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// skip nested structures.
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// It returns nil if it finds an end element matching the start
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// element; otherwise it returns an error describing the problem.
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func (d *Decoder) Skip() error {
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for {
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tok, err := d.Token()
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if err != nil {
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return err
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}
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switch tok.(type) {
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case StartElement:
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if err := d.Skip(); err != nil {
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return err
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}
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case EndElement:
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return nil
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}
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}
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}
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