467 lines
12 KiB
Go
467 lines
12 KiB
Go
// Copyright 2011 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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"bufio"
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"bytes"
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"fmt"
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"io"
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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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const (
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// A generic XML header suitable for use with the output of Marshal.
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// This is not automatically added to any output of this package,
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// it is provided as a convenience.
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Header = `<?xml version="1.0" encoding="UTF-8"?>` + "\n"
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)
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// Marshal returns the XML encoding of v.
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//
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// Marshal handles an array or slice by marshalling each of the elements.
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// Marshal handles a pointer by marshalling the value it points at or, if the
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// pointer is nil, by writing nothing. Marshal handles an interface value by
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// marshalling the value it contains or, if the interface value is nil, by
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// writing nothing. Marshal handles all other data by writing one or more XML
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// elements containing the data.
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//
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// The name for the XML elements is taken from, in order of preference:
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// - the tag on the XMLName field, if the data is a struct
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// - the value of the XMLName field of type xml.Name
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// - the tag of the struct field used to obtain the data
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// - the name of the struct field used to obtain the data
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// - the name of the marshalled type
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//
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// The XML element for a struct contains marshalled elements for each of the
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// exported fields of the struct, with these exceptions:
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// - the XMLName field, described above, is omitted.
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// - a field with tag "-" is omitted.
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// - a field with tag "name,attr" becomes an attribute with
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// the given name in the XML element.
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// - a field with tag ",attr" becomes an attribute with the
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// field name in the XML element.
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// - a field with tag ",chardata" is written as character data,
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// not as an XML element.
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// - a field with tag ",innerxml" is written verbatim, not subject
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// to the usual marshalling procedure.
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// - a field with tag ",comment" is written as an XML comment, not
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// subject to the usual marshalling procedure. It must not contain
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// the "--" string within it.
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// - a field with a tag including the "omitempty" option is omitted
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// if the field value is empty. The empty values are false, 0, any
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// nil pointer or interface value, and any array, slice, map, or
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// string of length zero.
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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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// If a field uses a tag "a>b>c", then the element c will be nested inside
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// parent elements a and b. Fields that appear next to each other that name
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// the same parent will be enclosed in one XML element.
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//
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// See MarshalIndent for an example.
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//
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// Marshal will return an error if asked to marshal a channel, function, or map.
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func Marshal(v interface{}) ([]byte, error) {
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var b bytes.Buffer
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if err := NewEncoder(&b).Encode(v); err != nil {
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return nil, err
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}
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return b.Bytes(), nil
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}
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// MarshalIndent works like Marshal, but each XML element begins on a new
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// indented line that starts with prefix and is followed by one or more
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// copies of indent according to the nesting depth.
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func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error) {
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var b bytes.Buffer
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enc := NewEncoder(&b)
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enc.prefix = prefix
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enc.indent = indent
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if err := enc.Encode(v); err != nil {
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return nil, err
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}
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return b.Bytes(), nil
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}
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// An Encoder writes XML data to an output stream.
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type Encoder struct {
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printer
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}
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// NewEncoder returns a new encoder that writes to w.
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func NewEncoder(w io.Writer) *Encoder {
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return &Encoder{printer{Writer: bufio.NewWriter(w)}}
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}
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// Encode writes the XML encoding of v to the stream.
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//
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// See the documentation for Marshal for details about the conversion
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// of Go values to XML.
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func (enc *Encoder) Encode(v interface{}) error {
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err := enc.marshalValue(reflect.ValueOf(v), nil)
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if err != nil {
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return err
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}
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return enc.Flush()
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}
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type printer struct {
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*bufio.Writer
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indent string
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prefix string
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depth int
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indentedIn bool
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}
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// marshalValue writes one or more XML elements representing val.
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// If val was obtained from a struct field, finfo must have its details.
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func (p *printer) marshalValue(val reflect.Value, finfo *fieldInfo) error {
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if !val.IsValid() {
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return nil
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}
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if finfo != nil && finfo.flags&fOmitEmpty != 0 && isEmptyValue(val) {
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return nil
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}
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kind := val.Kind()
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typ := val.Type()
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// Drill into pointers/interfaces
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if kind == reflect.Ptr || kind == reflect.Interface {
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if val.IsNil() {
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return nil
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}
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return p.marshalValue(val.Elem(), finfo)
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}
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// Slices and arrays iterate over the elements. They do not have an enclosing tag.
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if (kind == reflect.Slice || kind == reflect.Array) && typ.Elem().Kind() != reflect.Uint8 {
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for i, n := 0, val.Len(); i < n; i++ {
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if err := p.marshalValue(val.Index(i), finfo); err != nil {
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return err
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}
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}
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return nil
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}
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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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// Precedence for the XML element name is:
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// 1. XMLName field in underlying struct;
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// 2. field name/tag in the struct field; and
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// 3. type name
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var xmlns, name string
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if tinfo.xmlname != nil {
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xmlname := tinfo.xmlname
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if xmlname.name != "" {
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xmlns, name = xmlname.xmlns, xmlname.name
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} else if v, ok := xmlname.value(val).Interface().(Name); ok && v.Local != "" {
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xmlns, name = v.Space, v.Local
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}
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}
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if name == "" && finfo != nil {
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xmlns, name = finfo.xmlns, finfo.name
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}
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if name == "" {
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name = typ.Name()
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if name == "" {
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return &UnsupportedTypeError{typ}
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}
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}
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p.writeIndent(1)
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p.WriteByte('<')
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p.WriteString(name)
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if xmlns != "" {
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p.WriteString(` xmlns="`)
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// TODO: EscapeString, to avoid the allocation.
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Escape(p, []byte(xmlns))
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p.WriteByte('"')
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}
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// Attributes
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for i := range tinfo.fields {
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finfo := &tinfo.fields[i]
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if finfo.flags&fAttr == 0 {
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continue
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}
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fv := finfo.value(val)
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if finfo.flags&fOmitEmpty != 0 && isEmptyValue(fv) {
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continue
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}
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p.WriteByte(' ')
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p.WriteString(finfo.name)
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p.WriteString(`="`)
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if err := p.marshalSimple(fv.Type(), fv); err != nil {
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return err
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}
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p.WriteByte('"')
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}
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p.WriteByte('>')
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if val.Kind() == reflect.Struct {
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err = p.marshalStruct(tinfo, val)
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} else {
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err = p.marshalSimple(typ, val)
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}
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if err != nil {
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return err
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}
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p.writeIndent(-1)
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p.WriteByte('<')
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p.WriteByte('/')
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p.WriteString(name)
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p.WriteByte('>')
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return p.cachedWriteError()
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}
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var timeType = reflect.TypeOf(time.Time{})
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func (p *printer) marshalSimple(typ reflect.Type, val reflect.Value) error {
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// Normally we don't see structs, but this can happen for an attribute.
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if val.Type() == timeType {
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p.WriteString(val.Interface().(time.Time).Format(time.RFC3339Nano))
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return nil
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}
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switch val.Kind() {
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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p.WriteString(strconv.FormatInt(val.Int(), 10))
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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p.WriteString(strconv.FormatUint(val.Uint(), 10))
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case reflect.Float32, reflect.Float64:
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p.WriteString(strconv.FormatFloat(val.Float(), 'g', -1, val.Type().Bits()))
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case reflect.String:
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// TODO: Add EscapeString.
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Escape(p, []byte(val.String()))
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case reflect.Bool:
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p.WriteString(strconv.FormatBool(val.Bool()))
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case reflect.Array:
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// will be [...]byte
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bytes := make([]byte, val.Len())
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for i := range bytes {
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bytes[i] = val.Index(i).Interface().(byte)
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}
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Escape(p, bytes)
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case reflect.Slice:
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// will be []byte
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Escape(p, val.Bytes())
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default:
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return &UnsupportedTypeError{typ}
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}
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return p.cachedWriteError()
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}
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var ddBytes = []byte("--")
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func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
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if val.Type() == timeType {
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_, err := p.WriteString(val.Interface().(time.Time).Format(time.RFC3339Nano))
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return err
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}
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s := parentStack{printer: p}
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for i := range tinfo.fields {
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finfo := &tinfo.fields[i]
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if finfo.flags&(fAttr) != 0 {
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continue
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}
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vf := finfo.value(val)
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switch finfo.flags & fMode {
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case fCharData:
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var scratch [64]byte
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switch vf.Kind() {
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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Escape(p, strconv.AppendInt(scratch[:0], vf.Int(), 10))
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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Escape(p, strconv.AppendUint(scratch[:0], vf.Uint(), 10))
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case reflect.Float32, reflect.Float64:
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Escape(p, strconv.AppendFloat(scratch[:0], vf.Float(), 'g', -1, vf.Type().Bits()))
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case reflect.Bool:
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Escape(p, strconv.AppendBool(scratch[:0], vf.Bool()))
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case reflect.String:
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Escape(p, []byte(vf.String()))
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case reflect.Slice:
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if elem, ok := vf.Interface().([]byte); ok {
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Escape(p, elem)
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}
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case reflect.Struct:
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if vf.Type() == timeType {
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Escape(p, []byte(vf.Interface().(time.Time).Format(time.RFC3339Nano)))
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}
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}
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continue
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case fComment:
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k := vf.Kind()
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if !(k == reflect.String || k == reflect.Slice && vf.Type().Elem().Kind() == reflect.Uint8) {
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return fmt.Errorf("xml: bad type for comment field of %s", val.Type())
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}
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if vf.Len() == 0 {
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continue
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}
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p.writeIndent(0)
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p.WriteString("<!--")
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dashDash := false
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dashLast := false
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switch k {
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case reflect.String:
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s := vf.String()
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dashDash = strings.Index(s, "--") >= 0
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dashLast = s[len(s)-1] == '-'
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if !dashDash {
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p.WriteString(s)
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}
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case reflect.Slice:
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b := vf.Bytes()
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dashDash = bytes.Index(b, ddBytes) >= 0
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dashLast = b[len(b)-1] == '-'
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if !dashDash {
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p.Write(b)
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}
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default:
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panic("can't happen")
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}
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if dashDash {
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return fmt.Errorf(`xml: comments must not contain "--"`)
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}
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if dashLast {
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// "--->" is invalid grammar. Make it "- -->"
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p.WriteByte(' ')
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}
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p.WriteString("-->")
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continue
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case fInnerXml:
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iface := vf.Interface()
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switch raw := iface.(type) {
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case []byte:
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p.Write(raw)
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continue
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case string:
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p.WriteString(raw)
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continue
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}
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case fElement, fElement | fAny:
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s.trim(finfo.parents)
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if len(finfo.parents) > len(s.stack) {
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if vf.Kind() != reflect.Ptr && vf.Kind() != reflect.Interface || !vf.IsNil() {
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s.push(finfo.parents[len(s.stack):])
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}
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}
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}
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if err := p.marshalValue(vf, finfo); err != nil {
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return err
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}
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}
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s.trim(nil)
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return p.cachedWriteError()
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}
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// return the bufio Writer's cached write error
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func (p *printer) cachedWriteError() error {
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_, err := p.Write(nil)
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return err
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}
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func (p *printer) writeIndent(depthDelta int) {
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if len(p.prefix) == 0 && len(p.indent) == 0 {
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return
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}
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if depthDelta < 0 {
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p.depth--
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if p.indentedIn {
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p.indentedIn = false
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return
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}
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p.indentedIn = false
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}
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p.WriteByte('\n')
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if len(p.prefix) > 0 {
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p.WriteString(p.prefix)
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}
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if len(p.indent) > 0 {
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for i := 0; i < p.depth; i++ {
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p.WriteString(p.indent)
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}
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}
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if depthDelta > 0 {
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p.depth++
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p.indentedIn = true
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}
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}
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type parentStack struct {
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*printer
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stack []string
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}
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// trim updates the XML context to match the longest common prefix of the stack
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// and the given parents. A closing tag will be written for every parent
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// popped. Passing a zero slice or nil will close all the elements.
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func (s *parentStack) trim(parents []string) {
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split := 0
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for ; split < len(parents) && split < len(s.stack); split++ {
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if parents[split] != s.stack[split] {
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break
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}
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}
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for i := len(s.stack) - 1; i >= split; i-- {
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s.writeIndent(-1)
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s.WriteString("</")
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s.WriteString(s.stack[i])
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s.WriteByte('>')
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}
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s.stack = parents[:split]
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}
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// push adds parent elements to the stack and writes open tags.
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func (s *parentStack) push(parents []string) {
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for i := 0; i < len(parents); i++ {
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s.writeIndent(1)
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s.WriteByte('<')
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s.WriteString(parents[i])
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s.WriteByte('>')
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}
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s.stack = append(s.stack, parents...)
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}
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// A MarshalXMLError is returned when Marshal encounters a type
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// that cannot be converted into XML.
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type UnsupportedTypeError struct {
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Type reflect.Type
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}
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func (e *UnsupportedTypeError) Error() string {
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return "xml: unsupported type: " + e.Type.String()
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}
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func isEmptyValue(v reflect.Value) bool {
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switch v.Kind() {
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case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
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return v.Len() == 0
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case reflect.Bool:
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return !v.Bool()
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return v.Int() == 0
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return v.Uint() == 0
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case reflect.Float32, reflect.Float64:
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return v.Float() == 0
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case reflect.Interface, reflect.Ptr:
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return v.IsNil()
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}
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return false
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}
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