1
//
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// Copyright (c) 2011-2019 Canonical Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//     http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
15

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package yaml
17

18
import (
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	"encoding"
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	"encoding/base64"
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	"fmt"
22
	"io"
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	"math"
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	"reflect"
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	"strconv"
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	"time"
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)
28

29
// ----------------------------------------------------------------------------
30
// Parser, produces a node tree out of a libyaml event stream.
31

32
type parser struct {
33
	parser   yaml_parser_t
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	event    yaml_event_t
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	doc      *Node
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	anchors  map[string]*Node
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	doneInit bool
38
	textless bool
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}
40

41
func newParser(b []byte) *parser {
42
	p := parser{}
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	if !yaml_parser_initialize(&p.parser) {
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		panic("failed to initialize YAML emitter")
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	}
46
	if len(b) == 0 {
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		b = []byte{'\n'}
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	}
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	yaml_parser_set_input_string(&p.parser, b)
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	return &p
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}
52

53
func newParserFromReader(r io.Reader) *parser {
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	p := parser{}
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	if !yaml_parser_initialize(&p.parser) {
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		panic("failed to initialize YAML emitter")
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	}
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	yaml_parser_set_input_reader(&p.parser, r)
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	return &p
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}
61

62
func (p *parser) init() {
63
	if p.doneInit {
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		return
65
	}
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	p.anchors = make(map[string]*Node)
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	p.expect(yaml_STREAM_START_EVENT)
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	p.doneInit = true
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}
70

71
func (p *parser) destroy() {
72
	if p.event.typ != yaml_NO_EVENT {
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		yaml_event_delete(&p.event)
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	}
75
	yaml_parser_delete(&p.parser)
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}
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78
// expect consumes an event from the event stream and
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// checks that it's of the expected type.
80
func (p *parser) expect(e yaml_event_type_t) {
81
	if p.event.typ == yaml_NO_EVENT {
82
		if !yaml_parser_parse(&p.parser, &p.event) {
83
			p.fail()
84
		}
85
	}
86
	if p.event.typ == yaml_STREAM_END_EVENT {
87
		failf("attempted to go past the end of stream; corrupted value?")
88
	}
89
	if p.event.typ != e {
90
		p.parser.problem = fmt.Sprintf("expected %s event but got %s", e, p.event.typ)
91
		p.fail()
92
	}
93
	yaml_event_delete(&p.event)
94
	p.event.typ = yaml_NO_EVENT
95
}
96

97
// peek peeks at the next event in the event stream,
98
// puts the results into p.event and returns the event type.
99
func (p *parser) peek() yaml_event_type_t {
100
	if p.event.typ != yaml_NO_EVENT {
101
		return p.event.typ
102
	}
103
	// It's curious choice from the underlying API to generally return a
104
	// positive result on success, but on this case return true in an error
105
	// scenario. This was the source of bugs in the past (issue #666).
106
	if !yaml_parser_parse(&p.parser, &p.event) || p.parser.error != yaml_NO_ERROR {
107
		p.fail()
108
	}
109
	return p.event.typ
110
}
111

112
func (p *parser) fail() {
113
	var where string
114
	var line int
115
	if p.parser.context_mark.line != 0 {
116
		line = p.parser.context_mark.line
117
		// Scanner errors don't iterate line before returning error
118
		if p.parser.error == yaml_SCANNER_ERROR {
119
			line++
120
		}
121
	} else if p.parser.problem_mark.line != 0 {
122
		line = p.parser.problem_mark.line
123
		// Scanner errors don't iterate line before returning error
124
		if p.parser.error == yaml_SCANNER_ERROR {
125
			line++
126
		}
127
	}
128
	if line != 0 {
129
		where = "line " + strconv.Itoa(line) + ": "
130
	}
131
	var msg string
132
	if len(p.parser.problem) > 0 {
133
		msg = p.parser.problem
134
	} else {
135
		msg = "unknown problem parsing YAML content"
136
	}
137
	failf("%s%s", where, msg)
138
}
139

140
func (p *parser) anchor(n *Node, anchor []byte) {
141
	if anchor != nil {
142
		n.Anchor = string(anchor)
143
		p.anchors[n.Anchor] = n
144
	}
145
}
146

147
func (p *parser) parse() *Node {
148
	p.init()
149
	switch p.peek() {
150
	case yaml_SCALAR_EVENT:
151
		return p.scalar()
152
	case yaml_ALIAS_EVENT:
153
		return p.alias()
154
	case yaml_MAPPING_START_EVENT:
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		return p.mapping()
156
	case yaml_SEQUENCE_START_EVENT:
157
		return p.sequence()
158
	case yaml_DOCUMENT_START_EVENT:
159
		return p.document()
160
	case yaml_STREAM_END_EVENT:
161
		// Happens when attempting to decode an empty buffer.
162
		return nil
163
	case yaml_TAIL_COMMENT_EVENT:
164
		panic("internal error: unexpected tail comment event (please report)")
165
	default:
166
		panic("internal error: attempted to parse unknown event (please report): " + p.event.typ.String())
167
	}
168
}
169

170
func (p *parser) node(kind Kind, defaultTag, tag, value string) *Node {
171
	var style Style
172
	if tag != "" && tag != "!" {
173
		tag = shortTag(tag)
174
		style = TaggedStyle
175
	} else if defaultTag != "" {
176
		tag = defaultTag
177
	} else if kind == ScalarNode {
178
		tag, _ = resolve("", value)
179
	}
180
	n := &Node{
181
		Kind:  kind,
182
		Tag:   tag,
183
		Value: value,
184
		Style: style,
185
	}
186
	if !p.textless {
187
		n.Line = p.event.start_mark.line + 1
188
		n.Column = p.event.start_mark.column + 1
189
		n.HeadComment = string(p.event.head_comment)
190
		n.LineComment = string(p.event.line_comment)
191
		n.FootComment = string(p.event.foot_comment)
192
	}
193
	return n
194
}
195

196
func (p *parser) parseChild(parent *Node) *Node {
197
	child := p.parse()
198
	parent.Content = append(parent.Content, child)
199
	return child
200
}
201

202
func (p *parser) document() *Node {
203
	n := p.node(DocumentNode, "", "", "")
204
	p.doc = n
205
	p.expect(yaml_DOCUMENT_START_EVENT)
206
	p.parseChild(n)
207
	if p.peek() == yaml_DOCUMENT_END_EVENT {
208
		n.FootComment = string(p.event.foot_comment)
209
	}
210
	p.expect(yaml_DOCUMENT_END_EVENT)
211
	return n
212
}
213

214
func (p *parser) alias() *Node {
215
	n := p.node(AliasNode, "", "", string(p.event.anchor))
216
	n.Alias = p.anchors[n.Value]
217
	if n.Alias == nil {
218
		failf("unknown anchor '%s' referenced", n.Value)
219
	}
220
	p.expect(yaml_ALIAS_EVENT)
221
	return n
222
}
223

224
func (p *parser) scalar() *Node {
225
	var parsedStyle = p.event.scalar_style()
226
	var nodeStyle Style
227
	switch {
228
	case parsedStyle&yaml_DOUBLE_QUOTED_SCALAR_STYLE != 0:
229
		nodeStyle = DoubleQuotedStyle
230
	case parsedStyle&yaml_SINGLE_QUOTED_SCALAR_STYLE != 0:
231
		nodeStyle = SingleQuotedStyle
232
	case parsedStyle&yaml_LITERAL_SCALAR_STYLE != 0:
233
		nodeStyle = LiteralStyle
234
	case parsedStyle&yaml_FOLDED_SCALAR_STYLE != 0:
235
		nodeStyle = FoldedStyle
236
	}
237
	var nodeValue = string(p.event.value)
238
	var nodeTag = string(p.event.tag)
239
	var defaultTag string
240
	if nodeStyle == 0 {
241
		if nodeValue == "<<" {
242
			defaultTag = mergeTag
243
		}
244
	} else {
245
		defaultTag = strTag
246
	}
247
	n := p.node(ScalarNode, defaultTag, nodeTag, nodeValue)
248
	n.Style |= nodeStyle
249
	p.anchor(n, p.event.anchor)
250
	p.expect(yaml_SCALAR_EVENT)
251
	return n
252
}
253

254
func (p *parser) sequence() *Node {
255
	n := p.node(SequenceNode, seqTag, string(p.event.tag), "")
256
	if p.event.sequence_style()&yaml_FLOW_SEQUENCE_STYLE != 0 {
257
		n.Style |= FlowStyle
258
	}
259
	p.anchor(n, p.event.anchor)
260
	p.expect(yaml_SEQUENCE_START_EVENT)
261
	for p.peek() != yaml_SEQUENCE_END_EVENT {
262
		p.parseChild(n)
263
	}
264
	n.LineComment = string(p.event.line_comment)
265
	n.FootComment = string(p.event.foot_comment)
266
	p.expect(yaml_SEQUENCE_END_EVENT)
267
	return n
268
}
269

270
func (p *parser) mapping() *Node {
271
	n := p.node(MappingNode, mapTag, string(p.event.tag), "")
272
	block := true
273
	if p.event.mapping_style()&yaml_FLOW_MAPPING_STYLE != 0 {
274
		block = false
275
		n.Style |= FlowStyle
276
	}
277
	p.anchor(n, p.event.anchor)
278
	p.expect(yaml_MAPPING_START_EVENT)
279
	for p.peek() != yaml_MAPPING_END_EVENT {
280
		k := p.parseChild(n)
281
		if block && k.FootComment != "" {
282
			// Must be a foot comment for the prior value when being dedented.
283
			if len(n.Content) > 2 {
284
				n.Content[len(n.Content)-3].FootComment = k.FootComment
285
				k.FootComment = ""
286
			}
287
		}
288
		v := p.parseChild(n)
289
		if k.FootComment == "" && v.FootComment != "" {
290
			k.FootComment = v.FootComment
291
			v.FootComment = ""
292
		}
293
		if p.peek() == yaml_TAIL_COMMENT_EVENT {
294
			if k.FootComment == "" {
295
				k.FootComment = string(p.event.foot_comment)
296
			}
297
			p.expect(yaml_TAIL_COMMENT_EVENT)
298
		}
299
	}
300
	n.LineComment = string(p.event.line_comment)
301
	n.FootComment = string(p.event.foot_comment)
302
	if n.Style&FlowStyle == 0 && n.FootComment != "" && len(n.Content) > 1 {
303
		n.Content[len(n.Content)-2].FootComment = n.FootComment
304
		n.FootComment = ""
305
	}
306
	p.expect(yaml_MAPPING_END_EVENT)
307
	return n
308
}
309

310
// ----------------------------------------------------------------------------
311
// Decoder, unmarshals a node into a provided value.
312

313
type decoder struct {
314
	doc     *Node
315
	aliases map[*Node]bool
316
	terrors []string
317

318
	stringMapType  reflect.Type
319
	generalMapType reflect.Type
320

321
	knownFields bool
322
	uniqueKeys  bool
323
	decodeCount int
324
	aliasCount  int
325
	aliasDepth  int
326

327
	mergedFields map[interface{}]bool
328
}
329

330
var (
331
	nodeType       = reflect.TypeOf(Node{})
332
	durationType   = reflect.TypeOf(time.Duration(0))
333
	stringMapType  = reflect.TypeOf(map[string]interface{}{})
334
	generalMapType = reflect.TypeOf(map[interface{}]interface{}{})
335
	ifaceType      = generalMapType.Elem()
336
	timeType       = reflect.TypeOf(time.Time{})
337
	ptrTimeType    = reflect.TypeOf(&time.Time{})
338
)
339

340
func newDecoder() *decoder {
341
	d := &decoder{
342
		stringMapType:  stringMapType,
343
		generalMapType: generalMapType,
344
		uniqueKeys:     true,
345
	}
346
	d.aliases = make(map[*Node]bool)
347
	return d
348
}
349

350
func (d *decoder) terror(n *Node, tag string, out reflect.Value) {
351
	if n.Tag != "" {
352
		tag = n.Tag
353
	}
354
	value := n.Value
355
	if tag != seqTag && tag != mapTag {
356
		if len(value) > 10 {
357
			value = " `" + value[:7] + "...`"
358
		} else {
359
			value = " `" + value + "`"
360
		}
361
	}
362
	d.terrors = append(d.terrors, fmt.Sprintf("line %d: cannot unmarshal %s%s into %s", n.Line, shortTag(tag), value, out.Type()))
363
}
364

365
func (d *decoder) callUnmarshaler(n *Node, u Unmarshaler) (good bool) {
366
	err := u.UnmarshalYAML(n)
367
	if e, ok := err.(*TypeError); ok {
368
		d.terrors = append(d.terrors, e.Errors...)
369
		return false
370
	}
371
	if err != nil {
372
		fail(err)
373
	}
374
	return true
375
}
376

377
func (d *decoder) callObsoleteUnmarshaler(n *Node, u obsoleteUnmarshaler) (good bool) {
378
	terrlen := len(d.terrors)
379
	err := u.UnmarshalYAML(func(v interface{}) (err error) {
380
		defer handleErr(&err)
381
		d.unmarshal(n, reflect.ValueOf(v))
382
		if len(d.terrors) > terrlen {
383
			issues := d.terrors[terrlen:]
384
			d.terrors = d.terrors[:terrlen]
385
			return &TypeError{issues}
386
		}
387
		return nil
388
	})
389
	if e, ok := err.(*TypeError); ok {
390
		d.terrors = append(d.terrors, e.Errors...)
391
		return false
392
	}
393
	if err != nil {
394
		fail(err)
395
	}
396
	return true
397
}
398

399
// d.prepare initializes and dereferences pointers and calls UnmarshalYAML
400
// if a value is found to implement it.
401
// It returns the initialized and dereferenced out value, whether
402
// unmarshalling was already done by UnmarshalYAML, and if so whether
403
// its types unmarshalled appropriately.
404
//
405
// If n holds a null value, prepare returns before doing anything.
406
func (d *decoder) prepare(n *Node, out reflect.Value) (newout reflect.Value, unmarshaled, good bool) {
407
	if n.ShortTag() == nullTag {
408
		return out, false, false
409
	}
410
	again := true
411
	for again {
412
		again = false
413
		if out.Kind() == reflect.Ptr {
414
			if out.IsNil() {
415
				out.Set(reflect.New(out.Type().Elem()))
416
			}
417
			out = out.Elem()
418
			again = true
419
		}
420
		if out.CanAddr() {
421
			outi := out.Addr().Interface()
422
			if u, ok := outi.(Unmarshaler); ok {
423
				good = d.callUnmarshaler(n, u)
424
				return out, true, good
425
			}
426
			if u, ok := outi.(obsoleteUnmarshaler); ok {
427
				good = d.callObsoleteUnmarshaler(n, u)
428
				return out, true, good
429
			}
430
		}
431
	}
432
	return out, false, false
433
}
434

435
func (d *decoder) fieldByIndex(n *Node, v reflect.Value, index []int) (field reflect.Value) {
436
	if n.ShortTag() == nullTag {
437
		return reflect.Value{}
438
	}
439
	for _, num := range index {
440
		for {
441
			if v.Kind() == reflect.Ptr {
442
				if v.IsNil() {
443
					v.Set(reflect.New(v.Type().Elem()))
444
				}
445
				v = v.Elem()
446
				continue
447
			}
448
			break
449
		}
450
		v = v.Field(num)
451
	}
452
	return v
453
}
454

455
const (
456
	// 400,000 decode operations is ~500kb of dense object declarations, or
457
	// ~5kb of dense object declarations with 10000% alias expansion
458
	alias_ratio_range_low = 400000
459

460
	// 4,000,000 decode operations is ~5MB of dense object declarations, or
461
	// ~4.5MB of dense object declarations with 10% alias expansion
462
	alias_ratio_range_high = 4000000
463

464
	// alias_ratio_range is the range over which we scale allowed alias ratios
465
	alias_ratio_range = float64(alias_ratio_range_high - alias_ratio_range_low)
466
)
467

468
func allowedAliasRatio(decodeCount int) float64 {
469
	switch {
470
	case decodeCount <= alias_ratio_range_low:
471
		// allow 99% to come from alias expansion for small-to-medium documents
472
		return 0.99
473
	case decodeCount >= alias_ratio_range_high:
474
		// allow 10% to come from alias expansion for very large documents
475
		return 0.10
476
	default:
477
		// scale smoothly from 99% down to 10% over the range.
478
		// this maps to 396,000 - 400,000 allowed alias-driven decodes over the range.
479
		// 400,000 decode operations is ~100MB of allocations in worst-case scenarios (single-item maps).
480
		return 0.99 - 0.89*(float64(decodeCount-alias_ratio_range_low)/alias_ratio_range)
481
	}
482
}
483

484
func (d *decoder) unmarshal(n *Node, out reflect.Value) (good bool) {
485
	d.decodeCount++
486
	if d.aliasDepth > 0 {
487
		d.aliasCount++
488
	}
489
	if d.aliasCount > 100 && d.decodeCount > 1000 && float64(d.aliasCount)/float64(d.decodeCount) > allowedAliasRatio(d.decodeCount) {
490
		failf("document contains excessive aliasing")
491
	}
492
	if out.Type() == nodeType {
493
		out.Set(reflect.ValueOf(n).Elem())
494
		return true
495
	}
496
	switch n.Kind {
497
	case DocumentNode:
498
		return d.document(n, out)
499
	case AliasNode:
500
		return d.alias(n, out)
501
	}
502
	out, unmarshaled, good := d.prepare(n, out)
503
	if unmarshaled {
504
		return good
505
	}
506
	switch n.Kind {
507
	case ScalarNode:
508
		good = d.scalar(n, out)
509
	case MappingNode:
510
		good = d.mapping(n, out)
511
	case SequenceNode:
512
		good = d.sequence(n, out)
513
	case 0:
514
		if n.IsZero() {
515
			return d.null(out)
516
		}
517
		fallthrough
518
	default:
519
		failf("cannot decode node with unknown kind %d", n.Kind)
520
	}
521
	return good
522
}
523

524
func (d *decoder) document(n *Node, out reflect.Value) (good bool) {
525
	if len(n.Content) == 1 {
526
		d.doc = n
527
		d.unmarshal(n.Content[0], out)
528
		return true
529
	}
530
	return false
531
}
532

533
func (d *decoder) alias(n *Node, out reflect.Value) (good bool) {
534
	if d.aliases[n] {
535
		// TODO this could actually be allowed in some circumstances.
536
		failf("anchor '%s' value contains itself", n.Value)
537
	}
538
	d.aliases[n] = true
539
	d.aliasDepth++
540
	good = d.unmarshal(n.Alias, out)
541
	d.aliasDepth--
542
	delete(d.aliases, n)
543
	return good
544
}
545

546
var zeroValue reflect.Value
547

548
func resetMap(out reflect.Value) {
549
	for _, k := range out.MapKeys() {
550
		out.SetMapIndex(k, zeroValue)
551
	}
552
}
553

554
func (d *decoder) null(out reflect.Value) bool {
555
	if out.CanAddr() {
556
		switch out.Kind() {
557
		case reflect.Interface, reflect.Ptr, reflect.Map, reflect.Slice:
558
			out.Set(reflect.Zero(out.Type()))
559
			return true
560
		}
561
	}
562
	return false
563
}
564

565
func (d *decoder) scalar(n *Node, out reflect.Value) bool {
566
	var tag string
567
	var resolved interface{}
568
	if n.indicatedString() {
569
		tag = strTag
570
		resolved = n.Value
571
	} else {
572
		tag, resolved = resolve(n.Tag, n.Value)
573
		if tag == binaryTag {
574
			data, err := base64.StdEncoding.DecodeString(resolved.(string))
575
			if err != nil {
576
				failf("!!binary value contains invalid base64 data")
577
			}
578
			resolved = string(data)
579
		}
580
	}
581
	if resolved == nil {
582
		return d.null(out)
583
	}
584
	if resolvedv := reflect.ValueOf(resolved); out.Type() == resolvedv.Type() {
585
		// We've resolved to exactly the type we want, so use that.
586
		out.Set(resolvedv)
587
		return true
588
	}
589
	// Perhaps we can use the value as a TextUnmarshaler to
590
	// set its value.
591
	if out.CanAddr() {
592
		u, ok := out.Addr().Interface().(encoding.TextUnmarshaler)
593
		if ok {
594
			var text []byte
595
			if tag == binaryTag {
596
				text = []byte(resolved.(string))
597
			} else {
598
				// We let any value be unmarshaled into TextUnmarshaler.
599
				// That might be more lax than we'd like, but the
600
				// TextUnmarshaler itself should bowl out any dubious values.
601
				text = []byte(n.Value)
602
			}
603
			err := u.UnmarshalText(text)
604
			if err != nil {
605
				fail(err)
606
			}
607
			return true
608
		}
609
	}
610
	switch out.Kind() {
611
	case reflect.String:
612
		if tag == binaryTag {
613
			out.SetString(resolved.(string))
614
			return true
615
		}
616
		out.SetString(n.Value)
617
		return true
618
	case reflect.Interface:
619
		out.Set(reflect.ValueOf(resolved))
620
		return true
621
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
622
		// This used to work in v2, but it's very unfriendly.
623
		isDuration := out.Type() == durationType
624

625
		switch resolved := resolved.(type) {
626
		case int:
627
			if !isDuration && !out.OverflowInt(int64(resolved)) {
628
				out.SetInt(int64(resolved))
629
				return true
630
			}
631
		case int64:
632
			if !isDuration && !out.OverflowInt(resolved) {
633
				out.SetInt(resolved)
634
				return true
635
			}
636
		case uint64:
637
			if !isDuration && resolved <= math.MaxInt64 && !out.OverflowInt(int64(resolved)) {
638
				out.SetInt(int64(resolved))
639
				return true
640
			}
641
		case float64:
642
			if !isDuration && resolved <= math.MaxInt64 && !out.OverflowInt(int64(resolved)) {
643
				out.SetInt(int64(resolved))
644
				return true
645
			}
646
		case string:
647
			if out.Type() == durationType {
648
				d, err := time.ParseDuration(resolved)
649
				if err == nil {
650
					out.SetInt(int64(d))
651
					return true
652
				}
653
			}
654
		}
655
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
656
		switch resolved := resolved.(type) {
657
		case int:
658
			if resolved >= 0 && !out.OverflowUint(uint64(resolved)) {
659
				out.SetUint(uint64(resolved))
660
				return true
661
			}
662
		case int64:
663
			if resolved >= 0 && !out.OverflowUint(uint64(resolved)) {
664
				out.SetUint(uint64(resolved))
665
				return true
666
			}
667
		case uint64:
668
			if !out.OverflowUint(uint64(resolved)) {
669
				out.SetUint(uint64(resolved))
670
				return true
671
			}
672
		case float64:
673
			if resolved <= math.MaxUint64 && !out.OverflowUint(uint64(resolved)) {
674
				out.SetUint(uint64(resolved))
675
				return true
676
			}
677
		}
678
	case reflect.Bool:
679
		switch resolved := resolved.(type) {
680
		case bool:
681
			out.SetBool(resolved)
682
			return true
683
		case string:
684
			// This offers some compatibility with the 1.1 spec (https://yaml.org/type/bool.html).
685
			// It only works if explicitly attempting to unmarshal into a typed bool value.
686
			switch resolved {
687
			case "y", "Y", "yes", "Yes", "YES", "on", "On", "ON":
688
				out.SetBool(true)
689
				return true
690
			case "n", "N", "no", "No", "NO", "off", "Off", "OFF":
691
				out.SetBool(false)
692
				return true
693
			}
694
		}
695
	case reflect.Float32, reflect.Float64:
696
		switch resolved := resolved.(type) {
697
		case int:
698
			out.SetFloat(float64(resolved))
699
			return true
700
		case int64:
701
			out.SetFloat(float64(resolved))
702
			return true
703
		case uint64:
704
			out.SetFloat(float64(resolved))
705
			return true
706
		case float64:
707
			out.SetFloat(resolved)
708
			return true
709
		}
710
	case reflect.Struct:
711
		if resolvedv := reflect.ValueOf(resolved); out.Type() == resolvedv.Type() {
712
			out.Set(resolvedv)
713
			return true
714
		}
715
	case reflect.Ptr:
716
		panic("yaml internal error: please report the issue")
717
	}
718
	d.terror(n, tag, out)
719
	return false
720
}
721

722
func settableValueOf(i interface{}) reflect.Value {
723
	v := reflect.ValueOf(i)
724
	sv := reflect.New(v.Type()).Elem()
725
	sv.Set(v)
726
	return sv
727
}
728

729
func (d *decoder) sequence(n *Node, out reflect.Value) (good bool) {
730
	l := len(n.Content)
731

732
	var iface reflect.Value
733
	switch out.Kind() {
734
	case reflect.Slice:
735
		out.Set(reflect.MakeSlice(out.Type(), l, l))
736
	case reflect.Array:
737
		if l != out.Len() {
738
			failf("invalid array: want %d elements but got %d", out.Len(), l)
739
		}
740
	case reflect.Interface:
741
		// No type hints. Will have to use a generic sequence.
742
		iface = out
743
		out = settableValueOf(make([]interface{}, l))
744
	default:
745
		d.terror(n, seqTag, out)
746
		return false
747
	}
748
	et := out.Type().Elem()
749

750
	j := 0
751
	for i := 0; i < l; i++ {
752
		e := reflect.New(et).Elem()
753
		if ok := d.unmarshal(n.Content[i], e); ok {
754
			out.Index(j).Set(e)
755
			j++
756
		}
757
	}
758
	if out.Kind() != reflect.Array {
759
		out.Set(out.Slice(0, j))
760
	}
761
	if iface.IsValid() {
762
		iface.Set(out)
763
	}
764
	return true
765
}
766

767
func (d *decoder) mapping(n *Node, out reflect.Value) (good bool) {
768
	l := len(n.Content)
769
	if d.uniqueKeys {
770
		nerrs := len(d.terrors)
771
		for i := 0; i < l; i += 2 {
772
			ni := n.Content[i]
773
			for j := i + 2; j < l; j += 2 {
774
				nj := n.Content[j]
775
				if ni.Kind == nj.Kind && ni.Value == nj.Value {
776
					d.terrors = append(d.terrors, fmt.Sprintf("line %d: mapping key %#v already defined at line %d", nj.Line, nj.Value, ni.Line))
777
				}
778
			}
779
		}
780
		if len(d.terrors) > nerrs {
781
			return false
782
		}
783
	}
784
	switch out.Kind() {
785
	case reflect.Struct:
786
		return d.mappingStruct(n, out)
787
	case reflect.Map:
788
		// okay
789
	case reflect.Interface:
790
		iface := out
791
		if isStringMap(n) {
792
			out = reflect.MakeMap(d.stringMapType)
793
		} else {
794
			out = reflect.MakeMap(d.generalMapType)
795
		}
796
		iface.Set(out)
797
	default:
798
		d.terror(n, mapTag, out)
799
		return false
800
	}
801

802
	outt := out.Type()
803
	kt := outt.Key()
804
	et := outt.Elem()
805

806
	stringMapType := d.stringMapType
807
	generalMapType := d.generalMapType
808
	if outt.Elem() == ifaceType {
809
		if outt.Key().Kind() == reflect.String {
810
			d.stringMapType = outt
811
		} else if outt.Key() == ifaceType {
812
			d.generalMapType = outt
813
		}
814
	}
815

816
	mergedFields := d.mergedFields
817
	d.mergedFields = nil
818

819
	var mergeNode *Node
820

821
	mapIsNew := false
822
	if out.IsNil() {
823
		out.Set(reflect.MakeMap(outt))
824
		mapIsNew = true
825
	}
826
	for i := 0; i < l; i += 2 {
827
		if isMerge(n.Content[i]) {
828
			mergeNode = n.Content[i+1]
829
			continue
830
		}
831
		k := reflect.New(kt).Elem()
832
		if d.unmarshal(n.Content[i], k) {
833
			if mergedFields != nil {
834
				ki := k.Interface()
835
				if mergedFields[ki] {
836
					continue
837
				}
838
				mergedFields[ki] = true
839
			}
840
			kkind := k.Kind()
841
			if kkind == reflect.Interface {
842
				kkind = k.Elem().Kind()
843
			}
844
			if kkind == reflect.Map || kkind == reflect.Slice {
845
				failf("invalid map key: %#v", k.Interface())
846
			}
847
			e := reflect.New(et).Elem()
848
			if d.unmarshal(n.Content[i+1], e) || n.Content[i+1].ShortTag() == nullTag && (mapIsNew || !out.MapIndex(k).IsValid()) {
849
				out.SetMapIndex(k, e)
850
			}
851
		}
852
	}
853

854
	d.mergedFields = mergedFields
855
	if mergeNode != nil {
856
		d.merge(n, mergeNode, out)
857
	}
858

859
	d.stringMapType = stringMapType
860
	d.generalMapType = generalMapType
861
	return true
862
}
863

864
func isStringMap(n *Node) bool {
865
	if n.Kind != MappingNode {
866
		return false
867
	}
868
	l := len(n.Content)
869
	for i := 0; i < l; i += 2 {
870
		shortTag := n.Content[i].ShortTag()
871
		if shortTag != strTag && shortTag != mergeTag {
872
			return false
873
		}
874
	}
875
	return true
876
}
877

878
func (d *decoder) mappingStruct(n *Node, out reflect.Value) (good bool) {
879
	sinfo, err := getStructInfo(out.Type())
880
	if err != nil {
881
		panic(err)
882
	}
883

884
	var inlineMap reflect.Value
885
	var elemType reflect.Type
886
	if sinfo.InlineMap != -1 {
887
		inlineMap = out.Field(sinfo.InlineMap)
888
		elemType = inlineMap.Type().Elem()
889
	}
890

891
	for _, index := range sinfo.InlineUnmarshalers {
892
		field := d.fieldByIndex(n, out, index)
893
		d.prepare(n, field)
894
	}
895

896
	mergedFields := d.mergedFields
897
	d.mergedFields = nil
898
	var mergeNode *Node
899
	var doneFields []bool
900
	if d.uniqueKeys {
901
		doneFields = make([]bool, len(sinfo.FieldsList))
902
	}
903
	name := settableValueOf("")
904
	l := len(n.Content)
905
	for i := 0; i < l; i += 2 {
906
		ni := n.Content[i]
907
		if isMerge(ni) {
908
			mergeNode = n.Content[i+1]
909
			continue
910
		}
911
		if !d.unmarshal(ni, name) {
912
			continue
913
		}
914
		sname := name.String()
915
		if mergedFields != nil {
916
			if mergedFields[sname] {
917
				continue
918
			}
919
			mergedFields[sname] = true
920
		}
921
		if info, ok := sinfo.FieldsMap[sname]; ok {
922
			if d.uniqueKeys {
923
				if doneFields[info.Id] {
924
					d.terrors = append(d.terrors, fmt.Sprintf("line %d: field %s already set in type %s", ni.Line, name.String(), out.Type()))
925
					continue
926
				}
927
				doneFields[info.Id] = true
928
			}
929
			var field reflect.Value
930
			if info.Inline == nil {
931
				field = out.Field(info.Num)
932
			} else {
933
				field = d.fieldByIndex(n, out, info.Inline)
934
			}
935
			d.unmarshal(n.Content[i+1], field)
936
		} else if sinfo.InlineMap != -1 {
937
			if inlineMap.IsNil() {
938
				inlineMap.Set(reflect.MakeMap(inlineMap.Type()))
939
			}
940
			value := reflect.New(elemType).Elem()
941
			d.unmarshal(n.Content[i+1], value)
942
			inlineMap.SetMapIndex(name, value)
943
		} else if d.knownFields {
944
			d.terrors = append(d.terrors, fmt.Sprintf("line %d: field %s not found in type %s", ni.Line, name.String(), out.Type()))
945
		}
946
	}
947

948
	d.mergedFields = mergedFields
949
	if mergeNode != nil {
950
		d.merge(n, mergeNode, out)
951
	}
952
	return true
953
}
954

955
func failWantMap() {
956
	failf("map merge requires map or sequence of maps as the value")
957
}
958

959
func (d *decoder) merge(parent *Node, merge *Node, out reflect.Value) {
960
	mergedFields := d.mergedFields
961
	if mergedFields == nil {
962
		d.mergedFields = make(map[interface{}]bool)
963
		for i := 0; i < len(parent.Content); i += 2 {
964
			k := reflect.New(ifaceType).Elem()
965
			if d.unmarshal(parent.Content[i], k) {
966
				d.mergedFields[k.Interface()] = true
967
			}
968
		}
969
	}
970

971
	switch merge.Kind {
972
	case MappingNode:
973
		d.unmarshal(merge, out)
974
	case AliasNode:
975
		if merge.Alias != nil && merge.Alias.Kind != MappingNode {
976
			failWantMap()
977
		}
978
		d.unmarshal(merge, out)
979
	case SequenceNode:
980
		for i := 0; i < len(merge.Content); i++ {
981
			ni := merge.Content[i]
982
			if ni.Kind == AliasNode {
983
				if ni.Alias != nil && ni.Alias.Kind != MappingNode {
984
					failWantMap()
985
				}
986
			} else if ni.Kind != MappingNode {
987
				failWantMap()
988
			}
989
			d.unmarshal(ni, out)
990
		}
991
	default:
992
		failWantMap()
993
	}
994

995
	d.mergedFields = mergedFields
996
}
997

998
func isMerge(n *Node) bool {
999
	return n.Kind == ScalarNode && n.Value == "<<" && (n.Tag == "" || n.Tag == "!" || shortTag(n.Tag) == mergeTag)
1000
}
1001

1002