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// Copyright 2011 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 (
"bufio"
"io"
"os"
"reflect"
"strconv"
"strings"
)
const (
// A generic XML header suitable for use with the output of Marshal and MarshalIndent.
// This is not automatically added to any output of this package, it is provided as a
// convenience.
Header = `<?xml version="1.0" encoding="UTF-8">\n`
)
// A Marshaler can produce well-formatted XML representing its internal state.
// It is used by both Marshal and MarshalIndent.
type Marshaler interface {
MarshalXML() ([]byte, os.Error)
}
type printer struct {
*bufio.Writer
}
// Marshal writes an XML-formatted representation of v to w.
//
// If v implements Marshaler, then Marshal calls its MarshalXML method.
// Otherwise, Marshal uses the following procedure to create the XML.
//
// Marshal handles an array or slice by marshalling each of the elements.
// Marshal handles a pointer by marshalling the value it points at or, if the
// pointer is nil, by writing nothing. Marshal handles an interface value by
// marshalling the value it contains or, if the interface value is nil, by
// writing nothing. Marshal handles all other data by writing a single XML
// element containing the data.
//
// The name of that XML element is taken from, in order of preference:
// - the tag on an XMLName field, if the data is a struct
// - the value of an XMLName field of type xml.Name
// - the tag of the struct field used to obtain the data
// - the name of the struct field used to obtain the data
// - the name '???'.
//
// The XML element for a struct contains marshalled elements for each of the
// exported fields of the struct, with these exceptions:
// - the XMLName field, described above, is omitted.
// - a field with tag "attr" becomes an attribute in the XML element.
// - a field with tag "chardata" is written as character data,
// not as an XML element.
// - a field with tag "innerxml" is written verbatim,
// not subject to the usual marshalling procedure.
//
// Marshal will return an error if asked to marshal a channel, function, or map.
func Marshal(w io.Writer, v interface{}) (err os.Error) {
p := &printer{bufio.NewWriter(w)}
err = p.marshalValue(reflect.ValueOf(v), "???")
p.Flush()
return err
}
func (p *printer) marshalValue(val reflect.Value, name string) os.Error {
if !val.IsValid() {
return nil
}
kind := val.Kind()
typ := val.Type()
// Try Marshaler
if typ.NumMethod() > 0 {
if marshaler, ok := val.Interface().(Marshaler); ok {
bytes, err := marshaler.MarshalXML()
if err != nil {
return err
}
p.Write(bytes)
return nil
}
}
// Drill into pointers/interfaces
if kind == reflect.Ptr || kind == reflect.Interface {
if val.IsNil() {
return nil
}
return p.marshalValue(val.Elem(), name)
}
// Slices and arrays iterate over the elements. They do not have an enclosing tag.
if (kind == reflect.Slice || kind == reflect.Array) && typ.Elem().Kind() != reflect.Uint8 {
for i, n := 0, val.Len(); i < n; i++ {
if err := p.marshalValue(val.Index(i), name); err != nil {
return err
}
}
return nil
}
// Find XML name
xmlns := ""
if kind == reflect.Struct {
if f, ok := typ.FieldByName("XMLName"); ok {
if tag := f.Tag.Get("xml"); tag != "" {
if i := strings.Index(tag, " "); i >= 0 {
xmlns, name = tag[:i], tag[i+1:]
} else {
name = tag
}
} else if v, ok := val.FieldByIndex(f.Index).Interface().(Name); ok && v.Local != "" {
xmlns, name = v.Space, v.Local
}
}
}
p.WriteByte('<')
p.WriteString(name)
// Attributes
if kind == reflect.Struct {
if len(xmlns) > 0 {
p.WriteString(` xmlns="`)
Escape(p, []byte(xmlns))
p.WriteByte('"')
}
for i, n := 0, typ.NumField(); i < n; i++ {
if f := typ.Field(i); f.PkgPath == "" && f.Tag.Get("xml") == "attr" {
if f.Type.Kind() == reflect.String {
if str := val.Field(i).String(); str != "" {
p.WriteByte(' ')
p.WriteString(strings.ToLower(f.Name))
p.WriteString(`="`)
Escape(p, []byte(str))
p.WriteByte('"')
}
}
}
}
}
p.WriteByte('>')
switch k := val.Kind(); k {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
p.WriteString(strconv.Itoa64(val.Int()))
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
p.WriteString(strconv.Uitoa64(val.Uint()))
case reflect.Float32, reflect.Float64:
p.WriteString(strconv.Ftoa64(val.Float(), 'g', -1))
case reflect.String:
Escape(p, []byte(val.String()))
case reflect.Bool:
p.WriteString(strconv.Btoa(val.Bool()))
case reflect.Array:
// will be [...]byte
bytes := make([]byte, val.Len())
for i := range bytes {
bytes[i] = val.Index(i).Interface().(byte)
}
Escape(p, bytes)
case reflect.Slice:
// will be []byte
bytes := val.Interface().([]byte)
Escape(p, bytes)
case reflect.Struct:
for i, n := 0, val.NumField(); i < n; i++ {
if f := typ.Field(i); f.Name != "XMLName" && f.PkgPath == "" {
name := f.Name
switch tag := f.Tag.Get("xml"); tag {
case "":
case "chardata":
if tk := f.Type.Kind(); tk == reflect.String {
p.Write([]byte(val.Field(i).String()))
} else if tk == reflect.Slice {
if elem, ok := val.Field(i).Interface().([]byte); ok {
Escape(p, elem)
}
}
continue
case "innerxml":
iface := val.Field(i).Interface()
switch raw := iface.(type) {
case []byte:
p.Write(raw)
continue
case string:
p.WriteString(raw)
continue
}
case "attr":
continue
default:
name = tag
}
if err := p.marshalValue(val.Field(i), name); err != nil {
return err
}
}
}
default:
return &UnsupportedTypeError{typ}
}
p.WriteByte('<')
p.WriteByte('/')
p.WriteString(name)
p.WriteByte('>')
return nil
}
// A MarshalXMLError is returned when Marshal or MarshalIndent encounter a type
// that cannot be converted into XML.
type UnsupportedTypeError struct {
Type reflect.Type
}
func (e *UnsupportedTypeError) String() string {
return "xml: unsupported type: " + e.Type.String()
}