summaryrefslogtreecommitdiff
path: root/vendor/golang.org/x/net/webdav/internal/xml/typeinfo.go
blob: fdde288bc37cc1edfd862a67c3b60701130338fb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
// 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
	fCharData
	fInnerXml
	fComment
	fAny

	fOmitEmpty

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

var tinfoMap = make(map[reflect.Type]*typeInfo)
var tinfoLock sync.RWMutex

var nameType = reflect.TypeOf(Name{})

// getTypeInfo returns the typeInfo structure with details necessary
// for marshalling and unmarshalling typ.
func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
	tinfoLock.RLock()
	tinfo, ok := tinfoMap[typ]
	tinfoLock.RUnlock()
	if ok {
		return tinfo, 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.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
			}
		}
	}
	tinfoLock.Lock()
	tinfoMap[typ] = tinfo
	tinfoLock.Unlock()
	return tinfo, 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 "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, fCharData, fInnerXml, fComment, fAny:
			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
	}

	if finfo.xmlns == "" && finfo.flags&fAttr == 0 {
		// If it's an element no namespace specified, get the default
		// from the XMLName of enclosing struct if possible.
		if xmlname := lookupXMLName(typ); xmlname != nil {
			finfo.xmlns = xmlname.xmlns
		}
	}

	// 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 marshalling and unmarshalling
	// 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 finfo.name != "" && err == nil {
			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 unmarshalling 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
}