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

561 lines
15 KiB
Go

// 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"
"bytes"
"fmt"
"io"
"reflect"
"strconv"
"strings"
"time"
)
const (
// A generic XML header suitable for use with the output of Marshal.
// 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"
)
// Marshal returns the XML encoding of v.
//
// 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 one or more XML
// elements containing the data.
//
// The name for the XML elements is taken from, in order of preference:
// - the tag on the XMLName field, if the data is a struct
// - the value of the 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 of the marshalled type
//
// 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 "-" is omitted.
// - a field with tag "name,attr" becomes an attribute with
// the given name in the XML element.
// - a field with tag ",attr" becomes an attribute with the
// field name 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.
// - a field with tag ",comment" is written as an XML comment, not
// subject to the usual marshalling procedure. It must not contain
// the "--" string within it.
// - a field with a tag including the "omitempty" option is omitted
// if the field value is empty. The empty values are false, 0, any
// nil pointer or interface value, and any array, slice, map, or
// string of length zero.
// - an anonymous struct field is handled as if the fields of its
// value were part of the outer struct.
//
// If a field uses a tag "a>b>c", then the element c will be nested inside
// parent elements a and b. Fields that appear next to each other that name
// the same parent will be enclosed in one XML element.
//
// See MarshalIndent for an example.
//
// Marshal will return an error if asked to marshal a channel, function, or map.
func Marshal(v interface{}) ([]byte, error) {
var b bytes.Buffer
if err := NewEncoder(&b).Encode(v); err != nil {
return nil, err
}
return b.Bytes(), nil
}
// MarshalIndent works like Marshal, but each XML element begins on a new
// indented line that starts with prefix and is followed by one or more
// copies of indent according to the nesting depth.
func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error) {
var b bytes.Buffer
enc := NewEncoder(&b)
enc.Indent(prefix, indent)
if err := enc.Encode(v); err != nil {
return nil, err
}
return b.Bytes(), nil
}
// An Encoder writes XML data to an output stream.
type Encoder struct {
printer
}
// NewEncoder returns a new encoder that writes to w.
func NewEncoder(w io.Writer) *Encoder {
return &Encoder{printer{Writer: bufio.NewWriter(w)}}
}
// Indent sets the encoder to generate XML in which each element
// begins on a new indented line that starts with prefix and is followed by
// one or more copies of indent according to the nesting depth.
func (enc *Encoder) Indent(prefix, indent string) {
enc.prefix = prefix
enc.indent = indent
}
// Encode writes the XML encoding of v to the stream.
//
// See the documentation for Marshal for details about the conversion
// of Go values to XML.
func (enc *Encoder) Encode(v interface{}) error {
err := enc.marshalValue(reflect.ValueOf(v), nil)
if err != nil {
return err
}
return enc.Flush()
}
type printer struct {
*bufio.Writer
seq int
indent string
prefix string
depth int
indentedIn bool
putNewline bool
attrNS map[string]string // map prefix -> name space
attrPrefix map[string]string // map name space -> prefix
}
// createAttrPrefix finds the name space prefix attribute to use for the given name space,
// defining a new prefix if necessary. It returns the prefix and whether it is new.
func (p *printer) createAttrPrefix(url string) (prefix string, isNew bool) {
if prefix = p.attrPrefix[url]; prefix != "" {
return prefix, false
}
// The "http://www.w3.org/XML/1998/namespace" name space is predefined as "xml"
// and must be referred to that way.
// (The "http://www.w3.org/2000/xmlns/" name space is also predefined as "xmlns",
// but users should not be trying to use that one directly - that's our job.)
if url == xmlURL {
return "xml", false
}
// Need to define a new name space.
if p.attrPrefix == nil {
p.attrPrefix = make(map[string]string)
p.attrNS = make(map[string]string)
}
// Pick a name. We try to use the final element of the path
// but fall back to _.
prefix = strings.TrimRight(url, "/")
if i := strings.LastIndex(prefix, "/"); i >= 0 {
prefix = prefix[i+1:]
}
if prefix == "" || !isName([]byte(prefix)) || strings.Contains(prefix, ":") {
prefix = "_"
}
if strings.HasPrefix(prefix, "xml") {
// xmlanything is reserved.
prefix = "_" + prefix
}
if p.attrNS[prefix] != "" {
// Name is taken. Find a better one.
for p.seq++; ; p.seq++ {
if id := prefix + "_" + strconv.Itoa(p.seq); p.attrNS[id] == "" {
prefix = id
break
}
}
}
p.attrPrefix[url] = prefix
p.attrNS[prefix] = url
p.WriteString(`xmlns:`)
p.WriteString(prefix)
p.WriteString(`="`)
EscapeText(p, []byte(url))
p.WriteString(`" `)
return prefix, true
}
// deleteAttrPrefix removes an attribute name space prefix.
func (p *printer) deleteAttrPrefix(prefix string) {
delete(p.attrPrefix, p.attrNS[prefix])
delete(p.attrNS, prefix)
}
// marshalValue writes one or more XML elements representing val.
// If val was obtained from a struct field, finfo must have its details.
func (p *printer) marshalValue(val reflect.Value, finfo *fieldInfo) error {
if !val.IsValid() {
return nil
}
if finfo != nil && finfo.flags&fOmitEmpty != 0 && isEmptyValue(val) {
return nil
}
kind := val.Kind()
typ := val.Type()
// Drill into pointers/interfaces
if kind == reflect.Ptr || kind == reflect.Interface {
if val.IsNil() {
return nil
}
return p.marshalValue(val.Elem(), finfo)
}
// 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), finfo); err != nil {
return err
}
}
return nil
}
tinfo, err := getTypeInfo(typ)
if err != nil {
return err
}
// Precedence for the XML element name is:
// 1. XMLName field in underlying struct;
// 2. field name/tag in the struct field; and
// 3. type name
var xmlns, name string
if tinfo.xmlname != nil {
xmlname := tinfo.xmlname
if xmlname.name != "" {
xmlns, name = xmlname.xmlns, xmlname.name
} else if v, ok := xmlname.value(val).Interface().(Name); ok && v.Local != "" {
xmlns, name = v.Space, v.Local
}
}
if name == "" && finfo != nil {
xmlns, name = finfo.xmlns, finfo.name
}
if name == "" {
name = typ.Name()
if name == "" {
return &UnsupportedTypeError{typ}
}
}
p.writeIndent(1)
p.WriteByte('<')
p.WriteString(name)
if xmlns != "" {
p.WriteString(` xmlns="`)
// TODO: EscapeString, to avoid the allocation.
if err := EscapeText(p, []byte(xmlns)); err != nil {
return err
}
p.WriteByte('"')
}
// Attributes
for i := range tinfo.fields {
finfo := &tinfo.fields[i]
if finfo.flags&fAttr == 0 {
continue
}
fv := finfo.value(val)
if finfo.flags&fOmitEmpty != 0 && isEmptyValue(fv) {
continue
}
p.WriteByte(' ')
if finfo.xmlns != "" {
prefix, created := p.createAttrPrefix(finfo.xmlns)
if created {
defer p.deleteAttrPrefix(prefix)
}
p.WriteString(prefix)
p.WriteByte(':')
}
p.WriteString(finfo.name)
p.WriteString(`="`)
if err := p.marshalSimple(fv.Type(), fv); err != nil {
return err
}
p.WriteByte('"')
}
p.WriteByte('>')
if val.Kind() == reflect.Struct {
err = p.marshalStruct(tinfo, val)
} else {
err = p.marshalSimple(typ, val)
}
if err != nil {
return err
}
p.writeIndent(-1)
p.WriteByte('<')
p.WriteByte('/')
p.WriteString(name)
p.WriteByte('>')
return p.cachedWriteError()
}
var timeType = reflect.TypeOf(time.Time{})
func (p *printer) marshalSimple(typ reflect.Type, val reflect.Value) error {
// Normally we don't see structs, but this can happen for an attribute.
if val.Type() == timeType {
p.WriteString(val.Interface().(time.Time).Format(time.RFC3339Nano))
return nil
}
switch val.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
p.WriteString(strconv.FormatInt(val.Int(), 10))
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
p.WriteString(strconv.FormatUint(val.Uint(), 10))
case reflect.Float32, reflect.Float64:
p.WriteString(strconv.FormatFloat(val.Float(), 'g', -1, val.Type().Bits()))
case reflect.String:
// TODO: Add EscapeString.
EscapeText(p, []byte(val.String()))
case reflect.Bool:
p.WriteString(strconv.FormatBool(val.Bool()))
case reflect.Array:
// will be [...]byte
var bytes []byte
if val.CanAddr() {
bytes = val.Slice(0, val.Len()).Bytes()
} else {
bytes = make([]byte, val.Len())
reflect.Copy(reflect.ValueOf(bytes), val)
}
EscapeText(p, bytes)
case reflect.Slice:
// will be []byte
EscapeText(p, val.Bytes())
default:
return &UnsupportedTypeError{typ}
}
return p.cachedWriteError()
}
var ddBytes = []byte("--")
func (p *printer) marshalStruct(tinfo *typeInfo, val reflect.Value) error {
if val.Type() == timeType {
_, err := p.WriteString(val.Interface().(time.Time).Format(time.RFC3339Nano))
return err
}
s := parentStack{printer: p}
for i := range tinfo.fields {
finfo := &tinfo.fields[i]
if finfo.flags&fAttr != 0 {
continue
}
vf := finfo.value(val)
switch finfo.flags & fMode {
case fCharData:
var scratch [64]byte
switch vf.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
Escape(p, strconv.AppendInt(scratch[:0], vf.Int(), 10))
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
Escape(p, strconv.AppendUint(scratch[:0], vf.Uint(), 10))
case reflect.Float32, reflect.Float64:
Escape(p, strconv.AppendFloat(scratch[:0], vf.Float(), 'g', -1, vf.Type().Bits()))
case reflect.Bool:
Escape(p, strconv.AppendBool(scratch[:0], vf.Bool()))
case reflect.String:
if err := EscapeText(p, []byte(vf.String())); err != nil {
return err
}
case reflect.Slice:
if elem, ok := vf.Interface().([]byte); ok {
if err := EscapeText(p, elem); err != nil {
return err
}
}
case reflect.Struct:
if vf.Type() == timeType {
Escape(p, []byte(vf.Interface().(time.Time).Format(time.RFC3339Nano)))
}
}
continue
case fComment:
k := vf.Kind()
if !(k == reflect.String || k == reflect.Slice && vf.Type().Elem().Kind() == reflect.Uint8) {
return fmt.Errorf("xml: bad type for comment field of %s", val.Type())
}
if vf.Len() == 0 {
continue
}
p.writeIndent(0)
p.WriteString("<!--")
dashDash := false
dashLast := false
switch k {
case reflect.String:
s := vf.String()
dashDash = strings.Index(s, "--") >= 0
dashLast = s[len(s)-1] == '-'
if !dashDash {
p.WriteString(s)
}
case reflect.Slice:
b := vf.Bytes()
dashDash = bytes.Index(b, ddBytes) >= 0
dashLast = b[len(b)-1] == '-'
if !dashDash {
p.Write(b)
}
default:
panic("can't happen")
}
if dashDash {
return fmt.Errorf(`xml: comments must not contain "--"`)
}
if dashLast {
// "--->" is invalid grammar. Make it "- -->"
p.WriteByte(' ')
}
p.WriteString("-->")
continue
case fInnerXml:
iface := vf.Interface()
switch raw := iface.(type) {
case []byte:
p.Write(raw)
continue
case string:
p.WriteString(raw)
continue
}
case fElement, fElement | fAny:
s.trim(finfo.parents)
if len(finfo.parents) > len(s.stack) {
if vf.Kind() != reflect.Ptr && vf.Kind() != reflect.Interface || !vf.IsNil() {
s.push(finfo.parents[len(s.stack):])
}
}
}
if err := p.marshalValue(vf, finfo); err != nil {
return err
}
}
s.trim(nil)
return p.cachedWriteError()
}
// return the bufio Writer's cached write error
func (p *printer) cachedWriteError() error {
_, err := p.Write(nil)
return err
}
func (p *printer) writeIndent(depthDelta int) {
if len(p.prefix) == 0 && len(p.indent) == 0 {
return
}
if depthDelta < 0 {
p.depth--
if p.indentedIn {
p.indentedIn = false
return
}
p.indentedIn = false
}
if p.putNewline {
p.WriteByte('\n')
} else {
p.putNewline = true
}
if len(p.prefix) > 0 {
p.WriteString(p.prefix)
}
if len(p.indent) > 0 {
for i := 0; i < p.depth; i++ {
p.WriteString(p.indent)
}
}
if depthDelta > 0 {
p.depth++
p.indentedIn = true
}
}
type parentStack struct {
*printer
stack []string
}
// trim updates the XML context to match the longest common prefix of the stack
// and the given parents. A closing tag will be written for every parent
// popped. Passing a zero slice or nil will close all the elements.
func (s *parentStack) trim(parents []string) {
split := 0
for ; split < len(parents) && split < len(s.stack); split++ {
if parents[split] != s.stack[split] {
break
}
}
for i := len(s.stack) - 1; i >= split; i-- {
s.writeIndent(-1)
s.WriteString("</")
s.WriteString(s.stack[i])
s.WriteByte('>')
}
s.stack = parents[:split]
}
// push adds parent elements to the stack and writes open tags.
func (s *parentStack) push(parents []string) {
for i := 0; i < len(parents); i++ {
s.writeIndent(1)
s.WriteByte('<')
s.WriteString(parents[i])
s.WriteByte('>')
}
s.stack = append(s.stack, parents...)
}
// A MarshalXMLError is returned when Marshal encounters a type
// that cannot be converted into XML.
type UnsupportedTypeError struct {
Type reflect.Type
}
func (e *UnsupportedTypeError) Error() string {
return "xml: unsupported type: " + e.Type.String()
}
func isEmptyValue(v reflect.Value) bool {
switch v.Kind() {
case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
return v.Len() == 0
case reflect.Bool:
return !v.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return v.Int() == 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return v.Uint() == 0
case reflect.Float32, reflect.Float64:
return v.Float() == 0
case reflect.Interface, reflect.Ptr:
return v.IsNil()
}
return false
}