src/encoding/xml/typeinfo.go - go - Git at Google

 // 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 (
 	"fmt"
 	"reflect"
 	"strings"
 	"sync"
 )

 // typeInfo holds details for the xml representation of a type.
 type typeInfo struct {
 	xmlname *fieldInfo
 	fields  []fieldInfo
 }

 // fieldInfo holds details for the xml representation of a single field.
 type fieldInfo struct {
 	idx     []int
 	name    string
 	xmlns   string
 	flags   fieldFlags
 	parents []string
 }

 type fieldFlags int

 const (
 	fElement fieldFlags = 1 << iota
 	fAttr
 	fCDATA
 	fCharData
 	fInnerXml
 	fComment
 	fAny

 	fOmitEmpty

 	fMode = fElement | fAttr | fCDATA | fCharData | fInnerXml | fComment | fAny

 	xmlName = "XMLName"
 )

 var tinfoMap sync.Map // map[reflect.Type]*typeInfo

 var nameType = reflect.TypeOf(Name{})

 // getTypeInfo returns the typeInfo structure with details necessary
 // for marshaling and unmarshaling typ.
 func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
 	if ti, ok := tinfoMap.Load(typ); ok {
 		return ti.(*typeInfo), nil
 	}

 	tinfo := &typeInfo{}
 	if typ.Kind() == reflect.Struct && typ != nameType {
 		n := typ.NumField()
 		for i := 0; i < n; i++ {
 			f := typ.Field(i)
 			if (f.PkgPath != "" && !f.Anonymous) || f.Tag.Get("xml") == "-" {
 				continue // Private field
 			}

 			// For embedded structs, embed its fields.
 			if f.Anonymous {
 				t := f.Type
 				if t.Kind() == reflect.Ptr {
 					t = t.Elem()
 				}
 				if t.Kind() == reflect.Struct {
 					inner, err := getTypeInfo(t)
 					if err != nil {
 						return nil, err
 					}
 					if tinfo.xmlname == nil {
 						tinfo.xmlname = inner.xmlname
 					}
 					for _, finfo := range inner.fields {
 						finfo.idx = append([]int{i}, finfo.idx...)
 						if err := addFieldInfo(typ, tinfo, &finfo); err != nil {
 							return nil, err
 						}
 					}
 					continue
 				}
 			}

 			finfo, err := structFieldInfo(typ, &f)
 			if err != nil {
 				return nil, err
 			}

 			if f.Name == xmlName {
 				tinfo.xmlname = finfo
 				continue
 			}

 			// Add the field if it doesn't conflict with other fields.
 			if err := addFieldInfo(typ, tinfo, finfo); err != nil {
 				return nil, err
 			}
 		}
 	}

 	ti, _ := tinfoMap.LoadOrStore(typ, tinfo)
 	return ti.(*typeInfo), nil
 }

 // structFieldInfo builds and returns a fieldInfo for f.
 func structFieldInfo(typ reflect.Type, f *reflect.StructField) (*fieldInfo, error) {
 	finfo := &fieldInfo{idx: f.Index}

 	// Split the tag from the xml namespace if necessary.
 	tag := f.Tag.Get("xml")
 	if i := strings.Index(tag, " "); i >= 0 {
 		finfo.xmlns, tag = tag[:i], tag[i+1:]
 	}

 	// Parse flags.
 	tokens := strings.Split(tag, ",")
 	if len(tokens) == 1 {
 		finfo.flags = fElement
 	} else {
 		tag = tokens[0]
 		for _, flag := range tokens[1:] {
 			switch flag {
 			case "attr":
 				finfo.flags |= fAttr
 			case "cdata":
 				finfo.flags |= fCDATA
 			case "chardata":
 				finfo.flags |= fCharData
 			case "innerxml":
 				finfo.flags |= fInnerXml
 			case "comment":
 				finfo.flags |= fComment
 			case "any":
 				finfo.flags |= fAny
 			case "omitempty":
 				finfo.flags |= fOmitEmpty
 			}
 		}

 		// Validate the flags used.
 		valid := true
 		switch mode := finfo.flags & fMode; mode {
 		case 0:
 			finfo.flags |= fElement
 		case fAttr, fCDATA, fCharData, fInnerXml, fComment, fAny, fAny | fAttr:
 			if f.Name == xmlName || tag != "" && mode != fAttr {
 				valid = false
 			}
 		default:
 			// This will also catch multiple modes in a single field.
 			valid = false
 		}
 		if finfo.flags&fMode == fAny {
 			finfo.flags |= fElement
 		}
 		if finfo.flags&fOmitEmpty != 0 && finfo.flags&(fElement|fAttr) == 0 {
 			valid = false
 		}
 		if !valid {
 			return nil, fmt.Errorf("xml: invalid tag in field %s of type %s: %q",
 				f.Name, typ, f.Tag.Get("xml"))
 		}
 	}

 	// Use of xmlns without a name is not allowed.
 	if finfo.xmlns != "" && tag == "" {
 		return nil, fmt.Errorf("xml: namespace without name in field %s of type %s: %q",
 			f.Name, typ, f.Tag.Get("xml"))
 	}

 	if f.Name == xmlName {
 		// The XMLName field records the XML element name. Don't
 		// process it as usual because its name should default to
 		// empty rather than to the field name.
 		finfo.name = tag
 		return finfo, nil
 	}

 	if tag == "" {
 		// If the name part of the tag is completely empty, get
 		// default from XMLName of underlying struct if feasible,
 		// or field name otherwise.
 		if xmlname := lookupXMLName(f.Type); xmlname != nil {
 			finfo.xmlns, finfo.name = xmlname.xmlns, xmlname.name
 		} else {
 			finfo.name = f.Name
 		}
 		return finfo, nil
 	}

 	// Prepare field name and parents.
 	parents := strings.Split(tag, ">")
 	if parents[0] == "" {
 		parents[0] = f.Name
 	}
 	if parents[len(parents)-1] == "" {
 		return nil, fmt.Errorf("xml: trailing '>' in field %s of type %s", f.Name, typ)
 	}
 	finfo.name = parents[len(parents)-1]
 	if len(parents) > 1 {
 		if (finfo.flags & fElement) == 0 {
 			return nil, fmt.Errorf("xml: %s chain not valid with %s flag", tag, strings.Join(tokens[1:], ","))
 		}
 		finfo.parents = parents[:len(parents)-1]
 	}

 	// If the field type has an XMLName field, the names must match
 	// so that the behavior of both marshaling and unmarshaling
 	// is straightforward and unambiguous.
 	if finfo.flags&fElement != 0 {
 		ftyp := f.Type
 		xmlname := lookupXMLName(ftyp)
 		if xmlname != nil && xmlname.name != finfo.name {
 			return nil, fmt.Errorf("xml: name %q in tag of %s.%s conflicts with name %q in %s.XMLName",
 				finfo.name, typ, f.Name, xmlname.name, ftyp)
 		}
 	}
 	return finfo, nil
 }

 // lookupXMLName returns the fieldInfo for typ's XMLName field
 // in case it exists and has a valid xml field tag, otherwise
 // it returns nil.
 func lookupXMLName(typ reflect.Type) (xmlname *fieldInfo) {
 	for typ.Kind() == reflect.Ptr {
 		typ = typ.Elem()
 	}
 	if typ.Kind() != reflect.Struct {
 		return nil
 	}
 	for i, n := 0, typ.NumField(); i < n; i++ {
 		f := typ.Field(i)
 		if f.Name != xmlName {
 			continue
 		}
 		finfo, err := structFieldInfo(typ, &f)
 		if err == nil && finfo.name != "" {
 			return finfo
 		}
 		// Also consider errors as a non-existent field tag
 		// and let getTypeInfo itself report the error.
 		break
 	}
 	return nil
 }

 func min(a, b int) int {
 	if a <= b {
 		return a
 	}
 	return b
 }

 // addFieldInfo adds finfo to tinfo.fields if there are no
 // conflicts, or if conflicts arise from previous fields that were
 // obtained from deeper embedded structures than finfo. In the latter
 // case, the conflicting entries are dropped.
 // A conflict occurs when the path (parent + name) to a field is
 // itself a prefix of another path, or when two paths match exactly.
 // It is okay for field paths to share a common, shorter prefix.
 func addFieldInfo(typ reflect.Type, tinfo *typeInfo, newf *fieldInfo) error {
 	var conflicts []int
 Loop:
 	// First, figure all conflicts. Most working code will have none.
 	for i := range tinfo.fields {
 		oldf := &tinfo.fields[i]
 		if oldf.flags&fMode != newf.flags&fMode {
 			continue
 		}
 		if oldf.xmlns != "" && newf.xmlns != "" && oldf.xmlns != newf.xmlns {
 			continue
 		}
 		minl := min(len(newf.parents), len(oldf.parents))
 		for p := 0; p < minl; p++ {
 			if oldf.parents[p] != newf.parents[p] {
 				continue Loop
 			}
 		}
 		if len(oldf.parents) > len(newf.parents) {
 			if oldf.parents[len(newf.parents)] == newf.name {
 				conflicts = append(conflicts, i)
 			}
 		} else if len(oldf.parents) < len(newf.parents) {
 			if newf.parents[len(oldf.parents)] == oldf.name {
 				conflicts = append(conflicts, i)
 			}
 		} else {
 			if newf.name == oldf.name {
 				conflicts = append(conflicts, i)
 			}
 		}
 	}
 	// Without conflicts, add the new field and return.
 	if conflicts == nil {
 		tinfo.fields = append(tinfo.fields, *newf)
 		return nil
 	}

 	// If any conflict is shallower, ignore the new field.
 	// This matches the Go field resolution on embedding.
 	for _, i := range conflicts {
 		if len(tinfo.fields[i].idx) < len(newf.idx) {
 			return nil
 		}
 	}

 	// Otherwise, if any of them is at the same depth level, it's an error.
 	for _, i := range conflicts {
 		oldf := &tinfo.fields[i]
 		if len(oldf.idx) == len(newf.idx) {
 			f1 := typ.FieldByIndex(oldf.idx)
 			f2 := typ.FieldByIndex(newf.idx)
 			return &TagPathError{typ, f1.Name, f1.Tag.Get("xml"), f2.Name, f2.Tag.Get("xml")}
 		}
 	}

 	// Otherwise, the new field is shallower, and thus takes precedence,
 	// so drop the conflicting fields from tinfo and append the new one.
 	for c := len(conflicts) - 1; c >= 0; c-- {
 		i := conflicts[c]
 		copy(tinfo.fields[i:], tinfo.fields[i+1:])
 		tinfo.fields = tinfo.fields[:len(tinfo.fields)-1]
 	}
 	tinfo.fields = append(tinfo.fields, *newf)
 	return nil
 }

 // A TagPathError represents an error in the unmarshaling process
 // caused by the use of field tags with conflicting paths.
 type TagPathError struct {
 	Struct       reflect.Type
 	Field1, Tag1 string
 	Field2, Tag2 string
 }

 func (e *TagPathError) Error() string {
 	return fmt.Sprintf("%s field %q with tag %q conflicts with field %q with tag %q", e.Struct, e.Field1, e.Tag1, e.Field2, e.Tag2)
 }

 // value returns v's field value corresponding to finfo.
 // It's equivalent to v.FieldByIndex(finfo.idx), but initializes
 // and dereferences pointers as necessary.
 func (finfo *fieldInfo) value(v reflect.Value) reflect.Value {
 	for i, x := range finfo.idx {
 		if i > 0 {
 			t := v.Type()
 			if t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Struct {
 				if v.IsNil() {
 					v.Set(reflect.New(v.Type().Elem()))
 				}
 				v = v.Elem()
 			}
 		}
 		v = v.Field(x)
 	}
 	return v
 }
	// 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 (
	"fmt"
	"reflect"
	"strings"
	"sync"
	)

	// typeInfo holds details for the xml representation of a type.
	type typeInfo struct {
	xmlname *fieldInfo
	fields []fieldInfo
	}

	// fieldInfo holds details for the xml representation of a single field.
	type fieldInfo struct {
	idx []int
	name string
	xmlns string
	flags fieldFlags
	parents []string
	}

	type fieldFlags int

	const (
	fElement fieldFlags = 1 << iota
	fAttr
	fCDATA
	fCharData
	fInnerXml
	fComment
	fAny

	fOmitEmpty

	fMode = fElement \| fAttr \| fCDATA \| fCharData \| fInnerXml \| fComment \| fAny

	xmlName = "XMLName"
	)

	var tinfoMap sync.Map // map[reflect.Type]*typeInfo

	var nameType = reflect.TypeOf(Name{})

	// getTypeInfo returns the typeInfo structure with details necessary
	// for marshaling and unmarshaling typ.
	func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
	if ti, ok := tinfoMap.Load(typ); ok {
	return ti.(*typeInfo), nil
	}

	tinfo := &typeInfo{}
	if typ.Kind() == reflect.Struct && typ != nameType {
	n := typ.NumField()
	for i := 0; i < n; i++ {
	f := typ.Field(i)
	if (f.PkgPath != "" && !f.Anonymous) \|\| f.Tag.Get("xml") == "-" {
	continue // Private field
	}

	// For embedded structs, embed its fields.
	if f.Anonymous {
	t := f.Type
	if t.Kind() == reflect.Ptr {
	t = t.Elem()
	}
	if t.Kind() == reflect.Struct {
	inner, err := getTypeInfo(t)
	if err != nil {
	return nil, err
	}
	if tinfo.xmlname == nil {
	tinfo.xmlname = inner.xmlname
	}
	for _, finfo := range inner.fields {
	finfo.idx = append([]int{i}, finfo.idx...)
	if err := addFieldInfo(typ, tinfo, &finfo); err != nil {
	return nil, err
	}
	}
	continue
	}
	}

	finfo, err := structFieldInfo(typ, &f)
	if err != nil {
	return nil, err
	}

	if f.Name == xmlName {
	tinfo.xmlname = finfo
	continue
	}

	// Add the field if it doesn't conflict with other fields.
	if err := addFieldInfo(typ, tinfo, finfo); err != nil {
	return nil, err
	}
	}
	}

	ti, _ := tinfoMap.LoadOrStore(typ, tinfo)
	return ti.(*typeInfo), nil
	}

	// structFieldInfo builds and returns a fieldInfo for f.
	func structFieldInfo(typ reflect.Type, f reflect.StructField) (fieldInfo, error) {
	finfo := &fieldInfo{idx: f.Index}

	// Split the tag from the xml namespace if necessary.
	tag := f.Tag.Get("xml")
	if i := strings.Index(tag, " "); i >= 0 {
	finfo.xmlns, tag = tag[:i], tag[i+1:]
	}

	// Parse flags.
	tokens := strings.Split(tag, ",")
	if len(tokens) == 1 {
	finfo.flags = fElement
	} else {
	tag = tokens[0]
	for _, flag := range tokens[1:] {
	switch flag {
	case "attr":
	finfo.flags \|= fAttr
	case "cdata":
	finfo.flags \|= fCDATA
	case "chardata":
	finfo.flags \|= fCharData
	case "innerxml":
	finfo.flags \|= fInnerXml
	case "comment":
	finfo.flags \|= fComment
	case "any":
	finfo.flags \|= fAny
	case "omitempty":
	finfo.flags \|= fOmitEmpty
	}
	}

	// Validate the flags used.
	valid := true
	switch mode := finfo.flags & fMode; mode {
	case 0:
	finfo.flags \|= fElement
	case fAttr, fCDATA, fCharData, fInnerXml, fComment, fAny, fAny \| fAttr:
	if f.Name == xmlName \|\| tag != "" && mode != fAttr {
	valid = false
	}
	default:
	// This will also catch multiple modes in a single field.
	valid = false
	}
	if finfo.flags&fMode == fAny {
	finfo.flags \|= fElement
	}
	if finfo.flags&fOmitEmpty != 0 && finfo.flags&(fElement\|fAttr) == 0 {
	valid = false
	}
	if !valid {
	return nil, fmt.Errorf("xml: invalid tag in field %s of type %s: %q",
	f.Name, typ, f.Tag.Get("xml"))
	}
	}

	// Use of xmlns without a name is not allowed.
	if finfo.xmlns != "" && tag == "" {
	return nil, fmt.Errorf("xml: namespace without name in field %s of type %s: %q",
	f.Name, typ, f.Tag.Get("xml"))
	}

	if f.Name == xmlName {
	// The XMLName field records the XML element name. Don't
	// process it as usual because its name should default to
	// empty rather than to the field name.
	finfo.name = tag
	return finfo, nil
	}

	if tag == "" {
	// If the name part of the tag is completely empty, get
	// default from XMLName of underlying struct if feasible,
	// or field name otherwise.
	if xmlname := lookupXMLName(f.Type); xmlname != nil {
	finfo.xmlns, finfo.name = xmlname.xmlns, xmlname.name
	} else {
	finfo.name = f.Name
	}
	return finfo, nil
	}

	// Prepare field name and parents.
	parents := strings.Split(tag, ">")
	if parents[0] == "" {
	parents[0] = f.Name
	}
	if parents[len(parents)-1] == "" {
	return nil, fmt.Errorf("xml: trailing '>' in field %s of type %s", f.Name, typ)
	}
	finfo.name = parents[len(parents)-1]
	if len(parents) > 1 {
	if (finfo.flags & fElement) == 0 {
	return nil, fmt.Errorf("xml: %s chain not valid with %s flag", tag, strings.Join(tokens[1:], ","))
	}
	finfo.parents = parents[:len(parents)-1]
	}

	// If the field type has an XMLName field, the names must match
	// so that the behavior of both marshaling and unmarshaling
	// is straightforward and unambiguous.
	if finfo.flags&fElement != 0 {
	ftyp := f.Type
	xmlname := lookupXMLName(ftyp)
	if xmlname != nil && xmlname.name != finfo.name {
	return nil, fmt.Errorf("xml: name %q in tag of %s.%s conflicts with name %q in %s.XMLName",
	finfo.name, typ, f.Name, xmlname.name, ftyp)
	}
	}
	return finfo, nil
	}

	// lookupXMLName returns the fieldInfo for typ's XMLName field
	// in case it exists and has a valid xml field tag, otherwise
	// it returns nil.
	func lookupXMLName(typ reflect.Type) (xmlname *fieldInfo) {
	for typ.Kind() == reflect.Ptr {
	typ = typ.Elem()
	}
	if typ.Kind() != reflect.Struct {
	return nil
	}
	for i, n := 0, typ.NumField(); i < n; i++ {
	f := typ.Field(i)
	if f.Name != xmlName {
	continue
	}
	finfo, err := structFieldInfo(typ, &f)
	if err == nil && finfo.name != "" {
	return finfo
	}
	// Also consider errors as a non-existent field tag
	// and let getTypeInfo itself report the error.
	break
	}
	return nil
	}

	func min(a, b int) int {
	if a <= b {
	return a
	}
	return b
	}

	// addFieldInfo adds finfo to tinfo.fields if there are no
	// conflicts, or if conflicts arise from previous fields that were
	// obtained from deeper embedded structures than finfo. In the latter
	// case, the conflicting entries are dropped.
	// A conflict occurs when the path (parent + name) to a field is
	// itself a prefix of another path, or when two paths match exactly.
	// It is okay for field paths to share a common, shorter prefix.
	func addFieldInfo(typ reflect.Type, tinfo typeInfo, newf fieldInfo) error {
	var conflicts []int
	Loop:
	// First, figure all conflicts. Most working code will have none.
	for i := range tinfo.fields {
	oldf := &tinfo.fields[i]
	if oldf.flags&fMode != newf.flags&fMode {
	continue
	}
	if oldf.xmlns != "" && newf.xmlns != "" && oldf.xmlns != newf.xmlns {
	continue
	}
	minl := min(len(newf.parents), len(oldf.parents))
	for p := 0; p < minl; p++ {
	if oldf.parents[p] != newf.parents[p] {
	continue Loop
	}
	}
	if len(oldf.parents) > len(newf.parents) {
	if oldf.parents[len(newf.parents)] == newf.name {
	conflicts = append(conflicts, i)
	}
	} else if len(oldf.parents) < len(newf.parents) {
	if newf.parents[len(oldf.parents)] == oldf.name {
	conflicts = append(conflicts, i)
	}
	} else {
	if newf.name == oldf.name {
	conflicts = append(conflicts, i)
	}
	}
	}
	// Without conflicts, add the new field and return.
	if conflicts == nil {
	tinfo.fields = append(tinfo.fields, *newf)
	return nil
	}

	// If any conflict is shallower, ignore the new field.
	// This matches the Go field resolution on embedding.
	for _, i := range conflicts {
	if len(tinfo.fields[i].idx) < len(newf.idx) {
	return nil
	}
	}

	// Otherwise, if any of them is at the same depth level, it's an error.
	for _, i := range conflicts {
	oldf := &tinfo.fields[i]
	if len(oldf.idx) == len(newf.idx) {
	f1 := typ.FieldByIndex(oldf.idx)
	f2 := typ.FieldByIndex(newf.idx)
	return &TagPathError{typ, f1.Name, f1.Tag.Get("xml"), f2.Name, f2.Tag.Get("xml")}
	}
	}

	// Otherwise, the new field is shallower, and thus takes precedence,
	// so drop the conflicting fields from tinfo and append the new one.
	for c := len(conflicts) - 1; c >= 0; c-- {
	i := conflicts[c]
	copy(tinfo.fields[i:], tinfo.fields[i+1:])
	tinfo.fields = tinfo.fields[:len(tinfo.fields)-1]
	}
	tinfo.fields = append(tinfo.fields, *newf)
	return nil
	}

	// A TagPathError represents an error in the unmarshaling process
	// caused by the use of field tags with conflicting paths.
	type TagPathError struct {
	Struct reflect.Type
	Field1, Tag1 string
	Field2, Tag2 string
	}

	func (e *TagPathError) Error() string {
	return fmt.Sprintf("%s field %q with tag %q conflicts with field %q with tag %q", e.Struct, e.Field1, e.Tag1, e.Field2, e.Tag2)
	}

	// value returns v's field value corresponding to finfo.
	// It's equivalent to v.FieldByIndex(finfo.idx), but initializes
	// and dereferences pointers as necessary.
	func (finfo *fieldInfo) value(v reflect.Value) reflect.Value {
	for i, x := range finfo.idx {
	if i > 0 {
	t := v.Type()
	if t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Struct {
	if v.IsNil() {
	v.Set(reflect.New(v.Type().Elem()))
	}
	v = v.Elem()
	}
	}
	v = v.Field(x)
	}
	return v
	}