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
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
|
// Copyright 2009 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 reflect implements run-time reflection, allowing a program to
// manipulate objects with arbitrary types. The typical use is to take a value
// with static type interface{} and extract its dynamic type information by
// calling TypeOf, which returns a Type.
//
// A call to ValueOf returns a Value representing the run-time data.
// Zero takes a Type and returns a Value representing a zero value
// for that type.
//
// See "The Laws of Reflection" for an introduction to reflection in Go:
// http://blog.golang.org/2011/09/laws-of-reflection.html
package reflect
import (
"runtime"
"strconv"
"sync"
"unsafe"
)
// Type is the representation of a Go type.
//
// Not all methods apply to all kinds of types. Restrictions,
// if any, are noted in the documentation for each method.
// Use the Kind method to find out the kind of type before
// calling kind-specific methods. Calling a method
// inappropriate to the kind of type causes a run-time panic.
type Type interface {
// Methods applicable to all types.
// Align returns the alignment in bytes of a value of
// this type when allocated in memory.
Align() int
// FieldAlign returns the alignment in bytes of a value of
// this type when used as a field in a struct.
FieldAlign() int
// Method returns the i'th method in the type's method set.
// It panics if i is not in the range [0, NumMethod()).
//
// For a non-interface type T or *T, the returned Method's Type and Func
// fields describe a function whose first argument is the receiver.
//
// For an interface type, the returned Method's Type field gives the
// method signature, without a receiver, and the Func field is nil.
Method(int) Method
// MethodByName returns the method with that name in the type's
// method set and a boolean indicating if the method was found.
//
// For a non-interface type T or *T, the returned Method's Type and Func
// fields describe a function whose first argument is the receiver.
//
// For an interface type, the returned Method's Type field gives the
// method signature, without a receiver, and the Func field is nil.
MethodByName(string) (Method, bool)
// NumMethod returns the number of methods in the type's method set.
NumMethod() int
// Name returns the type's name within its package.
// It returns an empty string for unnamed types.
Name() string
// PkgPath returns the type's package path.
// The package path is a full package import path like "encoding/base64".
// PkgPath returns an empty string for unnamed or predeclared types.
PkgPath() string
// Size returns the number of bytes needed to store
// a value of the given type; it is analogous to unsafe.Sizeof.
Size() uintptr
// String returns a string representation of the type.
// The string representation may use shortened package names
// (e.g., base64 instead of "encoding/base64") and is not
// guaranteed to be unique among types. To test for equality,
// compare the Types directly.
String() string
// Kind returns the specific kind of this type.
Kind() Kind
// Implements returns true if the type implements the interface type u.
Implements(u Type) bool
// AssignableTo returns true if a value of the type is assignable to type u.
AssignableTo(u Type) bool
// Methods applicable only to some types, depending on Kind.
// The methods allowed for each kind are:
//
// Int*, Uint*, Float*, Complex*: Bits
// Array: Elem, Len
// Chan: ChanDir, Elem
// Func: In, NumIn, Out, NumOut, IsVariadic.
// Map: Key, Elem
// Ptr: Elem
// Slice: Elem
// Struct: Field, FieldByIndex, FieldByName, FieldByNameFunc, NumField
// Bits returns the size of the type in bits.
// It panics if the type's Kind is not one of the
// sized or unsized Int, Uint, Float, or Complex kinds.
Bits() int
// ChanDir returns a channel type's direction.
// It panics if the type's Kind is not Chan.
ChanDir() ChanDir
// IsVariadic returns true if a function type's final input parameter
// is a "..." parameter. If so, t.In(t.NumIn() - 1) returns the parameter's
// implicit actual type []T.
//
// For concreteness, if t represents func(x int, y ... float64), then
//
// t.NumIn() == 2
// t.In(0) is the reflect.Type for "int"
// t.In(1) is the reflect.Type for "[]float64"
// t.IsVariadic() == true
//
// IsVariadic panics if the type's Kind is not Func.
IsVariadic() bool
// Elem returns a type's element type.
// It panics if the type's Kind is not Array, Chan, Map, Ptr, or Slice.
Elem() Type
// Field returns a struct type's i'th field.
// It panics if the type's Kind is not Struct.
// It panics if i is not in the range [0, NumField()).
Field(i int) StructField
// FieldByIndex returns the nested field corresponding
// to the index sequence. It is equivalent to calling Field
// successively for each index i.
// It panics if the type's Kind is not Struct.
FieldByIndex(index []int) StructField
// FieldByName returns the struct field with the given name
// and a boolean indicating if the field was found.
FieldByName(name string) (StructField, bool)
// FieldByNameFunc returns the first struct field with a name
// that satisfies the match function and a boolean indicating if
// the field was found.
FieldByNameFunc(match func(string) bool) (StructField, bool)
// In returns the type of a function type's i'th input parameter.
// It panics if the type's Kind is not Func.
// It panics if i is not in the range [0, NumIn()).
In(i int) Type
// Key returns a map type's key type.
// It panics if the type's Kind is not Map.
Key() Type
// Len returns an array type's length.
// It panics if the type's Kind is not Array.
Len() int
// NumField returns a struct type's field count.
// It panics if the type's Kind is not Struct.
NumField() int
// NumIn returns a function type's input parameter count.
// It panics if the type's Kind is not Func.
NumIn() int
// NumOut returns a function type's output parameter count.
// It panics if the type's Kind is not Func.
NumOut() int
// Out returns the type of a function type's i'th output parameter.
// It panics if the type's Kind is not Func.
// It panics if i is not in the range [0, NumOut()).
Out(i int) Type
runtimeType() *runtime.Type
common() *commonType
uncommon() *uncommonType
}
// A Kind represents the specific kind of type that a Type represents.
// The zero Kind is not a valid kind.
type Kind uint
const (
Invalid Kind = iota
Bool
Int
Int8
Int16
Int32
Int64
Uint
Uint8
Uint16
Uint32
Uint64
Uintptr
Float32
Float64
Complex64
Complex128
Array
Chan
Func
Interface
Map
Ptr
Slice
String
Struct
UnsafePointer
)
/*
* Copy of data structures from ../runtime/type.go.
* For comments, see the ones in that file.
*
* These data structures are known to the compiler and the runtime.
*
* Putting these types in runtime instead of reflect means that
* reflect doesn't need to be autolinked into every binary, which
* simplifies bootstrapping and package dependencies.
* Unfortunately, it also means that reflect needs its own
* copy in order to access the private fields.
*/
// commonType is the common implementation of most values.
// It is embedded in other, public struct types, but always
// with a unique tag like `reflect:"array"` or `reflect:"ptr"`
// so that code cannot convert from, say, *arrayType to *ptrType.
type commonType struct {
kind uint8
align int8
fieldAlign uint8
size uintptr
hash uint32
hashfn func(unsafe.Pointer, uintptr)
equalfn func(unsafe.Pointer, unsafe.Pointer, uintptr)
string *string
*uncommonType
ptrToThis *runtime.Type
}
type method struct {
name *string
pkgPath *string
mtyp *runtime.Type
typ *runtime.Type
tfn unsafe.Pointer
}
type uncommonType struct {
name *string
pkgPath *string
methods []method
}
// ChanDir represents a channel type's direction.
type ChanDir int
const (
RecvDir ChanDir = 1 << iota
SendDir
BothDir = RecvDir | SendDir
)
// arrayType represents a fixed array type.
type arrayType struct {
commonType `reflect:"array"`
elem *runtime.Type
slice *runtime.Type
len uintptr
}
// chanType represents a channel type.
type chanType struct {
commonType `reflect:"chan"`
elem *runtime.Type
dir uintptr
}
// funcType represents a function type.
type funcType struct {
commonType `reflect:"func"`
dotdotdot bool
in []*runtime.Type
out []*runtime.Type
}
// imethod represents a method on an interface type
type imethod struct {
name *string
pkgPath *string
typ *runtime.Type
}
// interfaceType represents an interface type.
type interfaceType struct {
commonType `reflect:"interface"`
methods []imethod
}
// mapType represents a map type.
type mapType struct {
commonType `reflect:"map"`
key *runtime.Type
elem *runtime.Type
}
// ptrType represents a pointer type.
type ptrType struct {
commonType `reflect:"ptr"`
elem *runtime.Type
}
// sliceType represents a slice type.
type sliceType struct {
commonType `reflect:"slice"`
elem *runtime.Type
}
// Struct field
type structField struct {
name *string
pkgPath *string
typ *runtime.Type
tag *string
offset uintptr
}
// structType represents a struct type.
type structType struct {
commonType `reflect:"struct"`
fields []structField
}
/*
* The compiler knows the exact layout of all the data structures above.
* The compiler does not know about the data structures and methods below.
*/
// Method represents a single method.
type Method struct {
PkgPath string // empty for uppercase Name
Name string
Type Type
Func Value
Index int
}
// High bit says whether type has
// embedded pointers,to help garbage collector.
const kindMask = 0x7f
func (k Kind) String() string {
if int(k) < len(kindNames) {
return kindNames[k]
}
return "kind" + strconv.Itoa(int(k))
}
var kindNames = []string{
Invalid: "invalid",
Bool: "bool",
Int: "int",
Int8: "int8",
Int16: "int16",
Int32: "int32",
Int64: "int64",
Uint: "uint",
Uint8: "uint8",
Uint16: "uint16",
Uint32: "uint32",
Uint64: "uint64",
Uintptr: "uintptr",
Float32: "float32",
Float64: "float64",
Complex64: "complex64",
Complex128: "complex128",
Array: "array",
Chan: "chan",
Func: "func",
Interface: "interface",
Map: "map",
Ptr: "ptr",
Slice: "slice",
String: "string",
Struct: "struct",
UnsafePointer: "unsafe.Pointer",
}
func (t *uncommonType) uncommon() *uncommonType {
return t
}
func (t *uncommonType) PkgPath() string {
if t == nil || t.pkgPath == nil {
return ""
}
return *t.pkgPath
}
func (t *uncommonType) Name() string {
if t == nil || t.name == nil {
return ""
}
return *t.name
}
func (t *commonType) toType() Type {
if t == nil {
return nil
}
return canonicalize(t)
}
func (t *commonType) String() string { return *t.string }
func (t *commonType) Size() uintptr { return t.size }
func (t *commonType) Bits() int {
if t == nil {
panic("reflect: Bits of nil Type")
}
k := t.Kind()
if k < Int || k > Complex128 {
panic("reflect: Bits of non-arithmetic Type " + t.String())
}
return int(t.size) * 8
}
func (t *commonType) Align() int { return int(t.align) }
func (t *commonType) FieldAlign() int { return int(t.fieldAlign) }
func (t *commonType) Kind() Kind { return Kind(t.kind & kindMask) }
func (t *commonType) common() *commonType { return t }
func (t *uncommonType) Method(i int) (m Method) {
if t == nil || i < 0 || i >= len(t.methods) {
panic("reflect: Method index out of range")
}
p := &t.methods[i]
if p.name != nil {
m.Name = *p.name
}
fl := flag(Func) << flagKindShift
if p.pkgPath != nil {
m.PkgPath = *p.pkgPath
fl |= flagRO
}
mt := toCommonType(p.typ)
m.Type = mt.toType()
x := new(unsafe.Pointer)
*x = p.tfn
m.Func = Value{mt, unsafe.Pointer(x), fl | flagIndir}
m.Index = i
return
}
func (t *uncommonType) NumMethod() int {
if t == nil {
return 0
}
return len(t.methods)
}
func (t *uncommonType) MethodByName(name string) (m Method, ok bool) {
if t == nil {
return
}
var p *method
for i := range t.methods {
p = &t.methods[i]
if p.name != nil && *p.name == name {
return t.Method(i), true
}
}
return
}
// TODO(rsc): 6g supplies these, but they are not
// as efficient as they could be: they have commonType
// as the receiver instead of *commonType.
func (t *commonType) NumMethod() int {
if t.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(t))
return tt.NumMethod()
}
return t.uncommonType.NumMethod()
}
func (t *commonType) Method(i int) (m Method) {
if t.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(t))
return tt.Method(i)
}
return t.uncommonType.Method(i)
}
func (t *commonType) MethodByName(name string) (m Method, ok bool) {
if t.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(t))
return tt.MethodByName(name)
}
return t.uncommonType.MethodByName(name)
}
func (t *commonType) PkgPath() string {
return t.uncommonType.PkgPath()
}
func (t *commonType) Name() string {
return t.uncommonType.Name()
}
func (t *commonType) ChanDir() ChanDir {
if t.Kind() != Chan {
panic("reflect: ChanDir of non-chan type")
}
tt := (*chanType)(unsafe.Pointer(t))
return ChanDir(tt.dir)
}
func (t *commonType) IsVariadic() bool {
if t.Kind() != Func {
panic("reflect: IsVariadic of non-func type")
}
tt := (*funcType)(unsafe.Pointer(t))
return tt.dotdotdot
}
func (t *commonType) Elem() Type {
switch t.Kind() {
case Array:
tt := (*arrayType)(unsafe.Pointer(t))
return toType(tt.elem)
case Chan:
tt := (*chanType)(unsafe.Pointer(t))
return toType(tt.elem)
case Map:
tt := (*mapType)(unsafe.Pointer(t))
return toType(tt.elem)
case Ptr:
tt := (*ptrType)(unsafe.Pointer(t))
return toType(tt.elem)
case Slice:
tt := (*sliceType)(unsafe.Pointer(t))
return toType(tt.elem)
}
panic("reflect; Elem of invalid type")
}
func (t *commonType) Field(i int) StructField {
if t.Kind() != Struct {
panic("reflect: Field of non-struct type")
}
tt := (*structType)(unsafe.Pointer(t))
return tt.Field(i)
}
func (t *commonType) FieldByIndex(index []int) StructField {
if t.Kind() != Struct {
panic("reflect: FieldByIndex of non-struct type")
}
tt := (*structType)(unsafe.Pointer(t))
return tt.FieldByIndex(index)
}
func (t *commonType) FieldByName(name string) (StructField, bool) {
if t.Kind() != Struct {
panic("reflect: FieldByName of non-struct type")
}
tt := (*structType)(unsafe.Pointer(t))
return tt.FieldByName(name)
}
func (t *commonType) FieldByNameFunc(match func(string) bool) (StructField, bool) {
if t.Kind() != Struct {
panic("reflect: FieldByNameFunc of non-struct type")
}
tt := (*structType)(unsafe.Pointer(t))
return tt.FieldByNameFunc(match)
}
func (t *commonType) In(i int) Type {
if t.Kind() != Func {
panic("reflect: In of non-func type")
}
tt := (*funcType)(unsafe.Pointer(t))
return toType(tt.in[i])
}
func (t *commonType) Key() Type {
if t.Kind() != Map {
panic("reflect: Key of non-map type")
}
tt := (*mapType)(unsafe.Pointer(t))
return toType(tt.key)
}
func (t *commonType) Len() int {
if t.Kind() != Array {
panic("reflect: Len of non-array type")
}
tt := (*arrayType)(unsafe.Pointer(t))
return int(tt.len)
}
func (t *commonType) NumField() int {
if t.Kind() != Struct {
panic("reflect: NumField of non-struct type")
}
tt := (*structType)(unsafe.Pointer(t))
return len(tt.fields)
}
func (t *commonType) NumIn() int {
if t.Kind() != Func {
panic("reflect; NumIn of non-func type")
}
tt := (*funcType)(unsafe.Pointer(t))
return len(tt.in)
}
func (t *commonType) NumOut() int {
if t.Kind() != Func {
panic("reflect; NumOut of non-func type")
}
tt := (*funcType)(unsafe.Pointer(t))
return len(tt.out)
}
func (t *commonType) Out(i int) Type {
if t.Kind() != Func {
panic("reflect: Out of non-func type")
}
tt := (*funcType)(unsafe.Pointer(t))
return toType(tt.out[i])
}
func (d ChanDir) String() string {
switch d {
case SendDir:
return "chan<-"
case RecvDir:
return "<-chan"
case BothDir:
return "chan"
}
return "ChanDir" + strconv.Itoa(int(d))
}
// Method returns the i'th method in the type's method set.
func (t *interfaceType) Method(i int) (m Method) {
if i < 0 || i >= len(t.methods) {
return
}
p := &t.methods[i]
m.Name = *p.name
if p.pkgPath != nil {
m.PkgPath = *p.pkgPath
}
m.Type = toType(p.typ)
m.Index = i
return
}
// NumMethod returns the number of interface methods in the type's method set.
func (t *interfaceType) NumMethod() int { return len(t.methods) }
// MethodByName method with the given name in the type's method set.
func (t *interfaceType) MethodByName(name string) (m Method, ok bool) {
if t == nil {
return
}
var p *imethod
for i := range t.methods {
p = &t.methods[i]
if *p.name == name {
return t.Method(i), true
}
}
return
}
type StructField struct {
PkgPath string // empty for uppercase Name
Name string
Type Type
Tag StructTag
Offset uintptr
Index []int
Anonymous bool
}
// A StructTag is the tag string in a struct field.
//
// By convention, tag strings are a concatenation of
// optionally space-separated key:"value" pairs.
// Each key is a non-empty string consisting of non-control
// characters other than space (U+0020 ' '), quote (U+0022 '"'),
// and colon (U+003A ':'). Each value is quoted using U+0022 '"'
// characters and Go string literal syntax.
type StructTag string
// Get returns the value associated with key in the tag string.
// If there is no such key in the tag, Get returns the empty string.
// If the tag does not have the conventional format, the value
// returned by Get is unspecified.
func (tag StructTag) Get(key string) string {
for tag != "" {
// skip leading space
i := 0
for i < len(tag) && tag[i] == ' ' {
i++
}
tag = tag[i:]
if tag == "" {
break
}
// scan to colon.
// a space or a quote is a syntax error
i = 0
for i < len(tag) && tag[i] != ' ' && tag[i] != ':' && tag[i] != '"' {
i++
}
if i+1 >= len(tag) || tag[i] != ':' || tag[i+1] != '"' {
break
}
name := string(tag[:i])
tag = tag[i+1:]
// scan quoted string to find value
i = 1
for i < len(tag) && tag[i] != '"' {
if tag[i] == '\\' {
i++
}
i++
}
if i >= len(tag) {
break
}
qvalue := string(tag[:i+1])
tag = tag[i+1:]
if key == name {
value, _ := strconv.Unquote(qvalue)
return value
}
}
return ""
}
// Field returns the i'th struct field.
func (t *structType) Field(i int) (f StructField) {
if i < 0 || i >= len(t.fields) {
return
}
p := &t.fields[i]
f.Type = toType(p.typ)
if p.name != nil {
f.Name = *p.name
} else {
t := f.Type
if t.Kind() == Ptr {
t = t.Elem()
}
f.Name = t.Name()
f.Anonymous = true
}
if p.pkgPath != nil {
f.PkgPath = *p.pkgPath
}
if p.tag != nil {
f.Tag = StructTag(*p.tag)
}
f.Offset = p.offset
f.Index = []int{i}
return
}
// TODO(gri): Should there be an error/bool indicator if the index
// is wrong for FieldByIndex?
// FieldByIndex returns the nested field corresponding to index.
func (t *structType) FieldByIndex(index []int) (f StructField) {
f.Type = Type(t.toType())
for i, x := range index {
if i > 0 {
ft := f.Type
if ft.Kind() == Ptr && ft.Elem().Kind() == Struct {
ft = ft.Elem()
}
f.Type = ft
}
f = f.Type.Field(x)
}
return
}
const inf = 1 << 30 // infinity - no struct has that many nesting levels
func (t *structType) fieldByNameFunc(match func(string) bool, mark map[*structType]bool, depth int) (ff StructField, fd int) {
fd = inf // field depth
if mark[t] {
// Struct already seen.
return
}
mark[t] = true
var fi int // field index
n := 0 // number of matching fields at depth fd
L:
for i := range t.fields {
f := t.Field(i)
d := inf
switch {
case match(f.Name):
// Matching top-level field.
d = depth
case f.Anonymous:
ft := f.Type
if ft.Kind() == Ptr {
ft = ft.Elem()
}
switch {
case match(ft.Name()):
// Matching anonymous top-level field.
d = depth
case fd > depth:
// No top-level field yet; look inside nested structs.
if ft.Kind() == Struct {
st := (*structType)(unsafe.Pointer(ft.(*commonType)))
f, d = st.fieldByNameFunc(match, mark, depth+1)
}
}
}
switch {
case d < fd:
// Found field at shallower depth.
ff, fi, fd = f, i, d
n = 1
case d == fd:
// More than one matching field at the same depth (or d, fd == inf).
// Same as no field found at this depth.
n++
if d == depth {
// Impossible to find a field at lower depth.
break L
}
}
}
if n == 1 {
// Found matching field.
if depth >= len(ff.Index) {
ff.Index = make([]int, depth+1)
}
if len(ff.Index) > 1 {
ff.Index[depth] = fi
}
} else {
// None or more than one matching field found.
fd = inf
}
delete(mark, t)
return
}
// FieldByName returns the struct field with the given name
// and a boolean to indicate if the field was found.
func (t *structType) FieldByName(name string) (f StructField, present bool) {
return t.FieldByNameFunc(func(s string) bool { return s == name })
}
// FieldByNameFunc returns the struct field with a name that satisfies the
// match function and a boolean to indicate if the field was found.
func (t *structType) FieldByNameFunc(match func(string) bool) (f StructField, present bool) {
if ff, fd := t.fieldByNameFunc(match, make(map[*structType]bool), 0); fd < inf {
ff.Index = ff.Index[0 : fd+1]
f, present = ff, true
}
return
}
// Convert runtime type to reflect type.
func toCommonType(p *runtime.Type) *commonType {
if p == nil {
return nil
}
x := unsafe.Pointer(p)
return (*commonType)(x)
}
// Canonicalize a Type.
var canonicalType = make(map[string]Type)
var canonicalTypeLock sync.RWMutex
func canonicalize(t Type) Type {
if t == nil {
return nil
}
u := t.uncommon()
var s string
if u == nil || u.PkgPath() == "" {
s = t.String()
} else {
s = u.PkgPath() + "." + u.Name()
}
canonicalTypeLock.RLock()
if r, ok := canonicalType[s]; ok {
canonicalTypeLock.RUnlock()
return r
}
canonicalTypeLock.RUnlock()
canonicalTypeLock.Lock()
if r, ok := canonicalType[s]; ok {
canonicalTypeLock.Unlock()
return r
}
canonicalType[s] = t
canonicalTypeLock.Unlock()
return t
}
func toType(p *runtime.Type) Type {
if p == nil {
return nil
}
return toCommonType(p).toType()
}
// TypeOf returns the reflection Type of the value in the interface{}.
func TypeOf(i interface{}) Type {
eface := *(*emptyInterface)(unsafe.Pointer(&i))
return toType(eface.typ)
}
// ptrMap is the cache for PtrTo.
var ptrMap struct {
sync.RWMutex
m map[*commonType]*ptrType
}
func (t *commonType) runtimeType() *runtime.Type {
return (*runtime.Type)(unsafe.Pointer(t))
}
// PtrTo returns the pointer type with element t.
// For example, if t represents type Foo, PtrTo(t) represents *Foo.
func PtrTo(t Type) Type {
return t.(*commonType).ptrTo()
}
func (ct *commonType) ptrTo() *commonType {
if p := ct.ptrToThis; p != nil {
return toCommonType(p)
}
// Otherwise, synthesize one.
// This only happens for pointers with no methods.
// We keep the mapping in a map on the side, because
// this operation is rare and a separate map lets us keep
// the type structures in read-only memory.
ptrMap.RLock()
if m := ptrMap.m; m != nil {
if p := m[ct]; p != nil {
ptrMap.RUnlock()
return &p.commonType
}
}
ptrMap.RUnlock()
ptrMap.Lock()
if ptrMap.m == nil {
ptrMap.m = make(map[*commonType]*ptrType)
}
p := ptrMap.m[ct]
if p != nil {
// some other goroutine won the race and created it
ptrMap.Unlock()
return &p.commonType
}
rp := new(runtime.PtrType)
// initialize p using *byte's ptrType as a prototype.
// have to do assignment as ptrType, not runtime.PtrType,
// in order to write to unexported fields.
p = (*ptrType)(unsafe.Pointer(rp))
bp := (*ptrType)(unsafe.Pointer(unsafe.Typeof((*byte)(nil)).(*runtime.PtrType)))
*p = *bp
s := "*" + *ct.string
p.string = &s
// For the type structures linked into the binary, the
// compiler provides a good hash of the string.
// Create a good hash for the new string by using
// the FNV-1 hash's mixing function to combine the
// old hash and the new "*".
p.hash = ct.hash*16777619 ^ '*'
p.uncommonType = nil
p.ptrToThis = nil
p.elem = (*runtime.Type)(unsafe.Pointer(ct))
ptrMap.m[ct] = p
ptrMap.Unlock()
return &p.commonType
}
func (t *commonType) Implements(u Type) bool {
if u == nil {
panic("reflect: nil type passed to Type.Implements")
}
if u.Kind() != Interface {
panic("reflect: non-interface type passed to Type.Implements")
}
return implements(u.(*commonType), t)
}
func (t *commonType) AssignableTo(u Type) bool {
if u == nil {
panic("reflect: nil type passed to Type.AssignableTo")
}
uu := u.(*commonType)
return directlyAssignable(uu, t) || implements(uu, t)
}
// implements returns true if the type V implements the interface type T.
func implements(T, V *commonType) bool {
if T.Kind() != Interface {
return false
}
t := (*interfaceType)(unsafe.Pointer(T))
if len(t.methods) == 0 {
return true
}
// The same algorithm applies in both cases, but the
// method tables for an interface type and a concrete type
// are different, so the code is duplicated.
// In both cases the algorithm is a linear scan over the two
// lists - T's methods and V's methods - simultaneously.
// Since method tables are stored in a unique sorted order
// (alphabetical, with no duplicate method names), the scan
// through V's methods must hit a match for each of T's
// methods along the way, or else V does not implement T.
// This lets us run the scan in overall linear time instead of
// the quadratic time a naive search would require.
// See also ../runtime/iface.c.
if V.Kind() == Interface {
v := (*interfaceType)(unsafe.Pointer(V))
i := 0
for j := 0; j < len(v.methods); j++ {
tm := &t.methods[i]
vm := &v.methods[j]
if *vm.name == *tm.name && (vm.pkgPath == tm.pkgPath || (vm.pkgPath != nil && tm.pkgPath != nil && *vm.pkgPath == *tm.pkgPath)) && toType(vm.typ).common() == toType(tm.typ).common() {
if i++; i >= len(t.methods) {
return true
}
}
}
return false
}
v := V.uncommon()
if v == nil {
return false
}
i := 0
for j := 0; j < len(v.methods); j++ {
tm := &t.methods[i]
vm := &v.methods[j]
if *vm.name == *tm.name && (vm.pkgPath == tm.pkgPath || (vm.pkgPath != nil && tm.pkgPath != nil && *vm.pkgPath == *tm.pkgPath)) && toType(vm.mtyp).common() == toType(tm.typ).common() {
if i++; i >= len(t.methods) {
return true
}
}
}
return false
}
// directlyAssignable returns true if a value x of type V can be directly
// assigned (using memmove) to a value of type T.
// http://golang.org/doc/go_spec.html#Assignability
// Ignoring the interface rules (implemented elsewhere)
// and the ideal constant rules (no ideal constants at run time).
func directlyAssignable(T, V *commonType) bool {
// x's type V is identical to T?
if T == V {
return true
}
// Otherwise at least one of T and V must be unnamed
// and they must have the same kind.
if T.Name() != "" && V.Name() != "" || T.Kind() != V.Kind() {
return false
}
// x's type T and V have identical underlying types.
// Since at least one is unnamed, only the composite types
// need to be considered.
switch T.Kind() {
case Array:
return T.Elem() == V.Elem() && T.Len() == V.Len()
case Chan:
// Special case:
// x is a bidirectional channel value, T is a channel type,
// and x's type V and T have identical element types.
if V.ChanDir() == BothDir && T.Elem() == V.Elem() {
return true
}
// Otherwise continue test for identical underlying type.
return V.ChanDir() == T.ChanDir() && T.Elem() == V.Elem()
case Func:
t := (*funcType)(unsafe.Pointer(T))
v := (*funcType)(unsafe.Pointer(V))
if t.dotdotdot != v.dotdotdot || len(t.in) != len(v.in) || len(t.out) != len(v.out) {
return false
}
for i, typ := range t.in {
if typ != v.in[i] {
return false
}
}
for i, typ := range t.out {
if typ != v.out[i] {
return false
}
}
return true
case Interface:
t := (*interfaceType)(unsafe.Pointer(T))
v := (*interfaceType)(unsafe.Pointer(V))
if len(t.methods) == 0 && len(v.methods) == 0 {
return true
}
// Might have the same methods but still
// need a run time conversion.
return false
case Map:
return T.Key() == V.Key() && T.Elem() == V.Elem()
case Ptr, Slice:
return T.Elem() == V.Elem()
case Struct:
t := (*structType)(unsafe.Pointer(T))
v := (*structType)(unsafe.Pointer(V))
if len(t.fields) != len(v.fields) {
return false
}
for i := range t.fields {
tf := &t.fields[i]
vf := &v.fields[i]
if tf.name != vf.name || tf.pkgPath != vf.pkgPath ||
tf.typ != vf.typ || tf.tag != vf.tag || tf.offset != vf.offset {
return false
}
}
return true
}
return false
}
|