1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Package reflect implements run-time reflection, allowing a program to
6 // manipulate objects with arbitrary types. The typical use is to take a value
7 // with static type interface{} and extract its dynamic type information by
8 // calling TypeOf, which returns a Type.
10 // A call to ValueOf returns a Value representing the run-time data.
11 // Zero takes a Type and returns a Value representing a zero value
14 // See "The Laws of Reflection" for an introduction to reflection in Go:
15 // https://golang.org/doc/articles/laws_of_reflection.html
26 // Type is the representation of a Go type.
28 // Not all methods apply to all kinds of types. Restrictions,
29 // if any, are noted in the documentation for each method.
30 // Use the Kind method to find out the kind of type before
31 // calling kind-specific methods. Calling a method
32 // inappropriate to the kind of type causes a run-time panic.
34 // Type values are comparable, such as with the == operator.
35 // Two Type values are equal if they represent identical types.
37 // Methods applicable to all types.
39 // Align returns the alignment in bytes of a value of
40 // this type when allocated in memory.
43 // FieldAlign returns the alignment in bytes of a value of
44 // this type when used as a field in a struct.
47 // Method returns the i'th method in the type's method set.
48 // It panics if i is not in the range [0, NumMethod()).
50 // For a non-interface type T or *T, the returned Method's Type and Func
51 // fields describe a function whose first argument is the receiver.
53 // For an interface type, the returned Method's Type field gives the
54 // method signature, without a receiver, and the Func field is nil.
57 // MethodByName returns the method with that name in the type's
58 // method set and a boolean indicating if the method was found.
60 // For a non-interface type T or *T, the returned Method's Type and Func
61 // fields describe a function whose first argument is the receiver.
63 // For an interface type, the returned Method's Type field gives the
64 // method signature, without a receiver, and the Func field is nil.
65 MethodByName(string) (Method
, bool)
67 // NumMethod returns the number of exported methods in the type's method set.
70 // Name returns the type's name within its package.
71 // It returns an empty string for unnamed types.
74 // PkgPath returns a named type's package path, that is, the import path
75 // that uniquely identifies the package, such as "encoding/base64".
76 // If the type was predeclared (string, error) or unnamed (*T, struct{}, []int),
77 // the package path will be the empty string.
80 // Size returns the number of bytes needed to store
81 // a value of the given type; it is analogous to unsafe.Sizeof.
84 // String returns a string representation of the type.
85 // The string representation may use shortened package names
86 // (e.g., base64 instead of "encoding/base64") and is not
87 // guaranteed to be unique among types. To test for type identity,
88 // compare the Types directly.
91 // Used internally by gccgo--the string retaining quoting.
94 // Kind returns the specific kind of this type.
97 // Implements reports whether the type implements the interface type u.
98 Implements(u Type
) bool
100 // AssignableTo reports whether a value of the type is assignable to type u.
101 AssignableTo(u Type
) bool
103 // ConvertibleTo reports whether a value of the type is convertible to type u.
104 ConvertibleTo(u Type
) bool
106 // Comparable reports whether values of this type are comparable.
109 // Methods applicable only to some types, depending on Kind.
110 // The methods allowed for each kind are:
112 // Int*, Uint*, Float*, Complex*: Bits
114 // Chan: ChanDir, Elem
115 // Func: In, NumIn, Out, NumOut, IsVariadic.
119 // Struct: Field, FieldByIndex, FieldByName, FieldByNameFunc, NumField
121 // Bits returns the size of the type in bits.
122 // It panics if the type's Kind is not one of the
123 // sized or unsized Int, Uint, Float, or Complex kinds.
126 // ChanDir returns a channel type's direction.
127 // It panics if the type's Kind is not Chan.
130 // IsVariadic reports whether a function type's final input parameter
131 // is a "..." parameter. If so, t.In(t.NumIn() - 1) returns the parameter's
132 // implicit actual type []T.
134 // For concreteness, if t represents func(x int, y ... float64), then
137 // t.In(0) is the reflect.Type for "int"
138 // t.In(1) is the reflect.Type for "[]float64"
139 // t.IsVariadic() == true
141 // IsVariadic panics if the type's Kind is not Func.
144 // Elem returns a type's element type.
145 // It panics if the type's Kind is not Array, Chan, Map, Ptr, or Slice.
148 // Field returns a struct type's i'th field.
149 // It panics if the type's Kind is not Struct.
150 // It panics if i is not in the range [0, NumField()).
151 Field(i
int) StructField
153 // FieldByIndex returns the nested field corresponding
154 // to the index sequence. It is equivalent to calling Field
155 // successively for each index i.
156 // It panics if the type's Kind is not Struct.
157 FieldByIndex(index
[]int) StructField
159 // FieldByName returns the struct field with the given name
160 // and a boolean indicating if the field was found.
161 FieldByName(name
string) (StructField
, bool)
163 // FieldByNameFunc returns the struct field with a name
164 // that satisfies the match function and a boolean indicating if
165 // the field was found.
167 // FieldByNameFunc considers the fields in the struct itself
168 // and then the fields in any anonymous structs, in breadth first order,
169 // stopping at the shallowest nesting depth containing one or more
170 // fields satisfying the match function. If multiple fields at that depth
171 // satisfy the match function, they cancel each other
172 // and FieldByNameFunc returns no match.
173 // This behavior mirrors Go's handling of name lookup in
174 // structs containing anonymous fields.
175 FieldByNameFunc(match
func(string) bool) (StructField
, bool)
177 // In returns the type of a function type's i'th input parameter.
178 // It panics if the type's Kind is not Func.
179 // It panics if i is not in the range [0, NumIn()).
182 // Key returns a map type's key type.
183 // It panics if the type's Kind is not Map.
186 // Len returns an array type's length.
187 // It panics if the type's Kind is not Array.
190 // NumField returns a struct type's field count.
191 // It panics if the type's Kind is not Struct.
194 // NumIn returns a function type's input parameter count.
195 // It panics if the type's Kind is not Func.
198 // NumOut returns a function type's output parameter count.
199 // It panics if the type's Kind is not Func.
202 // Out returns the type of a function type's i'th output parameter.
203 // It panics if the type's Kind is not Func.
204 // It panics if i is not in the range [0, NumOut()).
208 uncommon() *uncommonType
211 // BUG(rsc): FieldByName and related functions consider struct field names to be equal
212 // if the names are equal, even if they are unexported names originating
213 // in different packages. The practical effect of this is that the result of
214 // t.FieldByName("x") is not well defined if the struct type t contains
215 // multiple fields named x (embedded from different packages).
216 // FieldByName may return one of the fields named x or may report that there are none.
217 // See golang.org/issue/4876 for more details.
220 * These data structures are known to the compiler (../../cmd/internal/gc/reflect.go).
221 * A few are known to ../runtime/type.go to convey to debuggers.
222 * They are also known to ../runtime/type.go.
225 // A Kind represents the specific kind of type that a Type represents.
226 // The zero Kind is not a valid kind.
259 // rtype is the common implementation of most values.
260 // It is embedded in other, public struct types, but always
261 // with a unique tag like `reflect:"array"` or `reflect:"ptr"`
262 // so that code cannot convert from, say, *arrayType to *ptrType.
264 // rtype must be kept in sync with ../runtime/type.go:/^type._type.
267 ptrdata
uintptr // size of memory prefix holding all pointers
268 hash
uint32 // hash of type; avoids computation in hash tables
269 kind
uint8 // enumeration for C
270 align
int8 // alignment of variable with this type
271 fieldAlign
uint8 // alignment of struct field with this type
272 _
uint8 // unused/padding
274 hashfn
func(unsafe
.Pointer
, uintptr) uintptr // hash function
275 equalfn
func(unsafe
.Pointer
, unsafe
.Pointer
) bool // equality function
277 gcdata
*byte // garbage collection data
278 string *string // string form; unnecessary but undeniably useful
279 *uncommonType
// (relatively) uncommon fields
280 ptrToThis
*rtype
// type for pointer to this type, if used in binary or has methods
283 // Method on non-interface type
285 name
*string // name of method
286 pkgPath
*string // nil for exported Names; otherwise import path
287 mtyp
*rtype
// method type (without receiver)
288 typ
*rtype
// .(*FuncType) underneath (with receiver)
289 tfn unsafe
.Pointer
// fn used for normal method call
292 // uncommonType is present only for types with names or methods
293 // (if T is a named type, the uncommonTypes for T and *T have methods).
294 // Using a pointer to this struct reduces the overall size required
295 // to describe an unnamed type with no methods.
296 type uncommonType
struct {
297 name
*string // name of type
298 pkgPath
*string // import path; nil for built-in types like int, string
299 methods
[]method
// methods associated with type
302 // ChanDir represents a channel type's direction.
306 RecvDir ChanDir
= 1 << iota // <-chan
308 BothDir
= RecvDir | SendDir
// chan
311 // arrayType represents a fixed array type.
312 type arrayType
struct {
313 rtype
`reflect:"array"`
314 elem
*rtype
// array element type
315 slice
*rtype
// slice type
319 // chanType represents a channel type.
320 type chanType
struct {
321 rtype
`reflect:"chan"`
322 elem
*rtype
// channel element type
323 dir
uintptr // channel direction (ChanDir)
326 // funcType represents a function type.
327 type funcType
struct {
328 rtype
`reflect:"func"`
329 dotdotdot
bool // last input parameter is ...
330 in
[]*rtype
// input parameter types
331 out
[]*rtype
// output parameter types
334 // imethod represents a method on an interface type
335 type imethod
struct {
336 name
*string // name of method
337 pkgPath
*string // nil for exported Names; otherwise import path
338 typ
*rtype
// .(*FuncType) underneath
341 // interfaceType represents an interface type.
342 type interfaceType
struct {
343 rtype
`reflect:"interface"`
344 methods
[]imethod
// sorted by hash
347 // mapType represents a map type.
348 type mapType
struct {
349 rtype
`reflect:"map"`
350 key
*rtype
// map key type
351 elem
*rtype
// map element (value) type
352 bucket
*rtype
// internal bucket structure
353 hmap
*rtype
// internal map header
354 keysize
uint8 // size of key slot
355 indirectkey
uint8 // store ptr to key instead of key itself
356 valuesize
uint8 // size of value slot
357 indirectvalue
uint8 // store ptr to value instead of value itself
358 bucketsize
uint16 // size of bucket
359 reflexivekey
bool // true if k==k for all keys
360 needkeyupdate
bool // true if we need to update key on an overwrite
363 // ptrType represents a pointer type.
364 type ptrType
struct {
365 rtype
`reflect:"ptr"`
366 elem
*rtype
// pointer element (pointed at) type
369 // sliceType represents a slice type.
370 type sliceType
struct {
371 rtype
`reflect:"slice"`
372 elem
*rtype
// slice element type
376 type structField
struct {
377 name
*string // name is always non-empty
378 pkgPath
*string // nil for exported Names; otherwise import path
379 typ
*rtype
// type of field
380 tag
*string // nil if no tag
381 offsetAnon
uintptr // byte offset of field<<1 | isAnonymous
384 func (f
*structField
) offset() uintptr {
385 return f
.offsetAnon
>> 1
388 func (f
*structField
) anon() bool {
389 return f
.offsetAnon
&1 != 0
392 // structType represents a struct type.
393 type structType
struct {
394 rtype
`reflect:"struct"`
395 fields
[]structField
// sorted by offset
399 * The compiler knows the exact layout of all the data structures above.
400 * The compiler does not know about the data structures and methods below.
403 // Method represents a single method.
405 // Name is the method name.
406 // PkgPath is the package path that qualifies a lower case (unexported)
407 // method name. It is empty for upper case (exported) method names.
408 // The combination of PkgPath and Name uniquely identifies a method
410 // See https://golang.org/ref/spec#Uniqueness_of_identifiers
414 Type Type
// method type
415 Func Value
// func with receiver as first argument
416 Index
int // index for Type.Method
420 kindDirectIface
= 1 << 5
421 kindGCProg
= 1 << 6 // Type.gc points to GC program
422 kindNoPointers
= 1 << 7
423 kindMask
= (1 << 5) - 1
426 func (k Kind
) String() string {
427 if int(k
) < len(kindNames
) {
430 return "kind" + strconv
.Itoa(int(k
))
433 var kindNames
= []string{
449 Complex64
: "complex64",
450 Complex128
: "complex128",
454 Interface
: "interface",
460 UnsafePointer
: "unsafe.Pointer",
463 func (t
*uncommonType
) uncommon() *uncommonType
{
467 func (t
*uncommonType
) PkgPath() string {
468 if t
== nil || t
.pkgPath
== nil {
474 func (t
*uncommonType
) Name() string {
475 if t
== nil || t
.name
== nil {
481 func (t
*rtype
) rawString() string { return *t
.string }
483 func (t
*rtype
) String() string {
484 // For gccgo, strip out quoted strings.
487 r
:= make([]byte, len(s
))
489 for i
:= 0; i
< len(s
); i
++ {
500 func (t
*rtype
) Size() uintptr { return t
.size
}
502 func (t
*rtype
) Bits() int {
504 panic("reflect: Bits of nil Type")
507 if k
< Int || k
> Complex128
{
508 panic("reflect: Bits of non-arithmetic Type " + t
.String())
510 return int(t
.size
) * 8
513 func (t
*rtype
) Align() int { return int(t
.align
) }
515 func (t
*rtype
) FieldAlign() int { return int(t
.fieldAlign
) }
517 func (t
*rtype
) Kind() Kind
{ return Kind(t
.kind
& kindMask
) }
519 func (t
*rtype
) pointers() bool { return t
.kind
&kindNoPointers
== 0 }
521 func (t
*rtype
) common() *rtype
{ return t
}
523 var methodCache sync
.Map
// map[*rtype][]method
525 func (t
*rtype
) exportedMethods() []method
{
526 methodsi
, found
:= methodCache
.Load(t
)
528 return methodsi
.([]method
)
537 for _
, m
:= range allm
{
538 if m
.pkgPath
!= nil {
547 methods
= make([]method
, 0, len(allm
))
548 for _
, m
:= range allm
{
549 if m
.pkgPath
== nil {
550 methods
= append(methods
, m
)
553 methods
= methods
[:len(methods
):len(methods
)]
556 methodsi
, _
= methodCache
.LoadOrStore(t
, methods
)
557 return methodsi
.([]method
)
560 func (t
*rtype
) NumMethod() int {
561 if t
.Kind() == Interface
{
562 tt
:= (*interfaceType
)(unsafe
.Pointer(t
))
563 return tt
.NumMethod()
565 if t
.uncommonType
== nil {
566 return 0 // avoid methodCache synchronization
568 return len(t
.exportedMethods())
571 func (t
*rtype
) Method(i
int) (m Method
) {
572 if t
.Kind() == Interface
{
573 tt
:= (*interfaceType
)(unsafe
.Pointer(t
))
576 methods
:= t
.exportedMethods()
577 if i
< 0 || i
>= len(methods
) {
578 panic("reflect: Method index out of range")
587 x
:= new(unsafe
.Pointer
)
588 *x
= unsafe
.Pointer(&p
.tfn
)
589 m
.Func
= Value
{mt
, unsafe
.Pointer(x
), fl | flagIndir | flagMethodFn
}
594 func (t
*rtype
) MethodByName(name
string) (m Method
, ok
bool) {
595 if t
.Kind() == Interface
{
596 tt
:= (*interfaceType
)(unsafe
.Pointer(t
))
597 return tt
.MethodByName(name
)
601 return Method
{}, false
603 for i
:= range ut
.methods
{
605 if p
.pkgPath
== nil && p
.name
!= nil && *p
.name
== name
{
606 return t
.Method(i
), true
609 return Method
{}, false
612 func (t
*rtype
) PkgPath() string {
613 return t
.uncommonType
.PkgPath()
616 func (t
*rtype
) Name() string {
617 return t
.uncommonType
.Name()
620 func (t
*rtype
) ChanDir() ChanDir
{
621 if t
.Kind() != Chan
{
622 panic("reflect: ChanDir of non-chan type")
624 tt
:= (*chanType
)(unsafe
.Pointer(t
))
625 return ChanDir(tt
.dir
)
628 func (t
*rtype
) IsVariadic() bool {
629 if t
.Kind() != Func
{
630 panic("reflect: IsVariadic of non-func type")
632 tt
:= (*funcType
)(unsafe
.Pointer(t
))
636 func (t
*rtype
) Elem() Type
{
639 tt
:= (*arrayType
)(unsafe
.Pointer(t
))
640 return toType(tt
.elem
)
642 tt
:= (*chanType
)(unsafe
.Pointer(t
))
643 return toType(tt
.elem
)
645 tt
:= (*mapType
)(unsafe
.Pointer(t
))
646 return toType(tt
.elem
)
648 tt
:= (*ptrType
)(unsafe
.Pointer(t
))
649 return toType(tt
.elem
)
651 tt
:= (*sliceType
)(unsafe
.Pointer(t
))
652 return toType(tt
.elem
)
654 panic("reflect: Elem of invalid type")
657 func (t
*rtype
) Field(i
int) StructField
{
658 if t
.Kind() != Struct
{
659 panic("reflect: Field of non-struct type")
661 tt
:= (*structType
)(unsafe
.Pointer(t
))
665 func (t
*rtype
) FieldByIndex(index
[]int) StructField
{
666 if t
.Kind() != Struct
{
667 panic("reflect: FieldByIndex of non-struct type")
669 tt
:= (*structType
)(unsafe
.Pointer(t
))
670 return tt
.FieldByIndex(index
)
673 func (t
*rtype
) FieldByName(name
string) (StructField
, bool) {
674 if t
.Kind() != Struct
{
675 panic("reflect: FieldByName of non-struct type")
677 tt
:= (*structType
)(unsafe
.Pointer(t
))
678 return tt
.FieldByName(name
)
681 func (t
*rtype
) FieldByNameFunc(match
func(string) bool) (StructField
, bool) {
682 if t
.Kind() != Struct
{
683 panic("reflect: FieldByNameFunc of non-struct type")
685 tt
:= (*structType
)(unsafe
.Pointer(t
))
686 return tt
.FieldByNameFunc(match
)
689 func (t
*rtype
) In(i
int) Type
{
690 if t
.Kind() != Func
{
691 panic("reflect: In of non-func type")
693 tt
:= (*funcType
)(unsafe
.Pointer(t
))
694 return toType(tt
.in
[i
])
697 func (t
*rtype
) Key() Type
{
699 panic("reflect: Key of non-map type")
701 tt
:= (*mapType
)(unsafe
.Pointer(t
))
702 return toType(tt
.key
)
705 func (t
*rtype
) Len() int {
706 if t
.Kind() != Array
{
707 panic("reflect: Len of non-array type")
709 tt
:= (*arrayType
)(unsafe
.Pointer(t
))
713 func (t
*rtype
) NumField() int {
714 if t
.Kind() != Struct
{
715 panic("reflect: NumField of non-struct type")
717 tt
:= (*structType
)(unsafe
.Pointer(t
))
718 return len(tt
.fields
)
721 func (t
*rtype
) NumIn() int {
722 if t
.Kind() != Func
{
723 panic("reflect: NumIn of non-func type")
725 tt
:= (*funcType
)(unsafe
.Pointer(t
))
729 func (t
*rtype
) NumOut() int {
730 if t
.Kind() != Func
{
731 panic("reflect: NumOut of non-func type")
733 tt
:= (*funcType
)(unsafe
.Pointer(t
))
737 func (t
*rtype
) Out(i
int) Type
{
738 if t
.Kind() != Func
{
739 panic("reflect: Out of non-func type")
741 tt
:= (*funcType
)(unsafe
.Pointer(t
))
742 return toType(tt
.out
[i
])
745 func (d ChanDir
) String() string {
754 return "ChanDir" + strconv
.Itoa(int(d
))
757 // Method returns the i'th method in the type's method set.
758 func (t
*interfaceType
) Method(i
int) (m Method
) {
759 if i
< 0 || i
>= len(t
.methods
) {
764 if p
.pkgPath
!= nil {
765 m
.PkgPath
= *p
.pkgPath
767 m
.Type
= toType(p
.typ
)
772 // NumMethod returns the number of interface methods in the type's method set.
773 func (t
*interfaceType
) NumMethod() int { return len(t
.methods
) }
775 // MethodByName method with the given name in the type's method set.
776 func (t
*interfaceType
) MethodByName(name
string) (m Method
, ok
bool) {
781 for i
:= range t
.methods
{
784 return t
.Method(i
), true
790 // A StructField describes a single field in a struct.
791 type StructField
struct {
792 // Name is the field name.
794 // PkgPath is the package path that qualifies a lower case (unexported)
795 // field name. It is empty for upper case (exported) field names.
796 // See https://golang.org/ref/spec#Uniqueness_of_identifiers
799 Type Type
// field type
800 Tag StructTag
// field tag string
801 Offset
uintptr // offset within struct, in bytes
802 Index
[]int // index sequence for Type.FieldByIndex
803 Anonymous
bool // is an embedded field
806 // A StructTag is the tag string in a struct field.
808 // By convention, tag strings are a concatenation of
809 // optionally space-separated key:"value" pairs.
810 // Each key is a non-empty string consisting of non-control
811 // characters other than space (U+0020 ' '), quote (U+0022 '"'),
812 // and colon (U+003A ':'). Each value is quoted using U+0022 '"'
813 // characters and Go string literal syntax.
814 type StructTag
string
816 // Get returns the value associated with key in the tag string.
817 // If there is no such key in the tag, Get returns the empty string.
818 // If the tag does not have the conventional format, the value
819 // returned by Get is unspecified. To determine whether a tag is
820 // explicitly set to the empty string, use Lookup.
821 func (tag StructTag
) Get(key
string) string {
822 v
, _
:= tag
.Lookup(key
)
826 // Lookup returns the value associated with key in the tag string.
827 // If the key is present in the tag the value (which may be empty)
828 // is returned. Otherwise the returned value will be the empty string.
829 // The ok return value reports whether the value was explicitly set in
830 // the tag string. If the tag does not have the conventional format,
831 // the value returned by Lookup is unspecified.
832 func (tag StructTag
) Lookup(key
string) (value
string, ok
bool) {
833 // When modifying this code, also update the validateStructTag code
834 // in cmd/vet/structtag.go.
837 // Skip leading space.
839 for i
< len(tag
) && tag
[i
] == ' ' {
847 // Scan to colon. A space, a quote or a control character is a syntax error.
848 // Strictly speaking, control chars include the range [0x7f, 0x9f], not just
849 // [0x00, 0x1f], but in practice, we ignore the multi-byte control characters
850 // as it is simpler to inspect the tag's bytes than the tag's runes.
852 for i
< len(tag
) && tag
[i
] > ' ' && tag
[i
] != ':' && tag
[i
] != '"' && tag
[i
] != 0x7f {
855 if i
== 0 || i
+1 >= len(tag
) || tag
[i
] != ':' || tag
[i
+1] != '"' {
858 name
:= string(tag
[:i
])
861 // Scan quoted string to find value.
863 for i
< len(tag
) && tag
[i
] != '"' {
872 qvalue
:= string(tag
[:i
+1])
876 value
, err
:= strconv
.Unquote(qvalue
)
886 // Field returns the i'th struct field.
887 func (t
*structType
) Field(i
int) (f StructField
) {
888 if i
< 0 || i
>= len(t
.fields
) {
889 panic("reflect: Field index out of bounds")
892 f
.Type
= toType(p
.typ
)
894 f
.Anonymous
= p
.anon()
895 if p
.pkgPath
!= nil {
896 f
.PkgPath
= *p
.pkgPath
899 f
.Tag
= StructTag(*p
.tag
)
901 f
.Offset
= p
.offset()
903 // NOTE(rsc): This is the only allocation in the interface
904 // presented by a reflect.Type. It would be nice to avoid,
905 // at least in the common cases, but we need to make sure
906 // that misbehaving clients of reflect cannot affect other
907 // uses of reflect. One possibility is CL 5371098, but we
908 // postponed that ugliness until there is a demonstrated
909 // need for the performance. This is issue 2320.
914 // TODO(gri): Should there be an error/bool indicator if the index
915 // is wrong for FieldByIndex?
917 // FieldByIndex returns the nested field corresponding to index.
918 func (t
*structType
) FieldByIndex(index
[]int) (f StructField
) {
919 f
.Type
= toType(&t
.rtype
)
920 for i
, x
:= range index
{
923 if ft
.Kind() == Ptr
&& ft
.Elem().Kind() == Struct
{
933 // A fieldScan represents an item on the fieldByNameFunc scan work list.
934 type fieldScan
struct {
939 // FieldByNameFunc returns the struct field with a name that satisfies the
940 // match function and a boolean to indicate if the field was found.
941 func (t
*structType
) FieldByNameFunc(match
func(string) bool) (result StructField
, ok
bool) {
942 // This uses the same condition that the Go language does: there must be a unique instance
943 // of the match at a given depth level. If there are multiple instances of a match at the
944 // same depth, they annihilate each other and inhibit any possible match at a lower level.
945 // The algorithm is breadth first search, one depth level at a time.
947 // The current and next slices are work queues:
948 // current lists the fields to visit on this depth level,
949 // and next lists the fields on the next lower level.
950 current
:= []fieldScan
{}
951 next
:= []fieldScan
{{typ
: t
}}
953 // nextCount records the number of times an embedded type has been
954 // encountered and considered for queueing in the 'next' slice.
955 // We only queue the first one, but we increment the count on each.
956 // If a struct type T can be reached more than once at a given depth level,
957 // then it annihilates itself and need not be considered at all when we
958 // process that next depth level.
959 var nextCount
map[*structType
]int
961 // visited records the structs that have been considered already.
962 // Embedded pointer fields can create cycles in the graph of
963 // reachable embedded types; visited avoids following those cycles.
964 // It also avoids duplicated effort: if we didn't find the field in an
965 // embedded type T at level 2, we won't find it in one at level 4 either.
966 visited
:= map[*structType
]bool{}
969 current
, next
= next
, current
[:0]
973 // Process all the fields at this depth, now listed in 'current'.
974 // The loop queues embedded fields found in 'next', for processing during the next
975 // iteration. The multiplicity of the 'current' field counts is recorded
976 // in 'count'; the multiplicity of the 'next' field counts is recorded in 'nextCount'.
977 for _
, scan
:= range current
{
980 // We've looked through this type before, at a higher level.
981 // That higher level would shadow the lower level we're now at,
982 // so this one can't be useful to us. Ignore it.
986 for i
:= range t
.fields
{
988 // Find name and (for anonymous field) type for field f.
992 // Anonymous field of type T or *T.
994 if ntyp
.Kind() == Ptr
{
995 ntyp
= ntyp
.Elem().common()
1002 if count
[t
] > 1 || ok
{
1003 // Name appeared multiple times at this level: annihilate.
1004 return StructField
{}, false
1008 result
.Index
= append(result
.Index
, scan
.index
...)
1009 result
.Index
= append(result
.Index
, i
)
1014 // Queue embedded struct fields for processing with next level,
1015 // but only if we haven't seen a match yet at this level and only
1016 // if the embedded types haven't already been queued.
1017 if ok || ntyp
== nil || ntyp
.Kind() != Struct
{
1020 ntyp
= toType(ntyp
).common()
1021 styp
:= (*structType
)(unsafe
.Pointer(ntyp
))
1022 if nextCount
[styp
] > 0 {
1023 nextCount
[styp
] = 2 // exact multiple doesn't matter
1026 if nextCount
== nil {
1027 nextCount
= map[*structType
]int{}
1031 nextCount
[styp
] = 2 // exact multiple doesn't matter
1034 index
= append(index
, scan
.index
...)
1035 index
= append(index
, i
)
1036 next
= append(next
, fieldScan
{styp
, index
})
1046 // FieldByName returns the struct field with the given name
1047 // and a boolean to indicate if the field was found.
1048 func (t
*structType
) FieldByName(name
string) (f StructField
, present
bool) {
1049 // Quick check for top-level name, or struct without anonymous fields.
1052 for i
:= range t
.fields
{
1054 if *tf
.name
== name
{
1055 return t
.Field(i
), true
1065 return t
.FieldByNameFunc(func(s
string) bool { return s
== name
})
1068 // TypeOf returns the reflection Type that represents the dynamic type of i.
1069 // If i is a nil interface value, TypeOf returns nil.
1070 func TypeOf(i
interface{}) Type
{
1071 eface
:= *(*emptyInterface
)(unsafe
.Pointer(&i
))
1072 return toType(eface
.typ
)
1075 // ptrMap is the cache for PtrTo.
1076 var ptrMap sync
.Map
// map[*rtype]*ptrType
1078 // PtrTo returns the pointer type with element t.
1079 // For example, if t represents type Foo, PtrTo(t) represents *Foo.
1080 func PtrTo(t Type
) Type
{
1081 return t
.(*rtype
).ptrTo()
1084 func (t
*rtype
) ptrTo() *rtype
{
1085 if p
:= t
.ptrToThis
; p
!= nil {
1090 if pi
, ok
:= ptrMap
.Load(t
); ok
{
1091 return &pi
.(*ptrType
).rtype
1094 s
:= "*" + *t
.string
1096 canonicalTypeLock
.RLock()
1097 r
, ok
:= canonicalType
[s
]
1098 canonicalTypeLock
.RUnlock()
1100 p
:= (*ptrType
)(unsafe
.Pointer(r
.(*rtype
)))
1101 pi
, _
:= ptrMap
.LoadOrStore(t
, p
)
1102 return &pi
.(*ptrType
).rtype
1105 // Create a new ptrType starting with the description
1106 // of an *unsafe.Pointer.
1107 var iptr
interface{} = (*unsafe
.Pointer
)(nil)
1108 prototype
:= *(**ptrType
)(unsafe
.Pointer(&iptr
))
1114 // For the type structures linked into the binary, the
1115 // compiler provides a good hash of the string.
1116 // Create a good hash for the new string by using
1117 // the FNV-1 hash's mixing function to combine the
1118 // old hash and the new "*".
1119 // p.hash = fnv1(t.hash, '*')
1120 // This is the gccgo version.
1121 pp
.hash
= (t
.hash
<< 4) + 9
1123 pp
.uncommonType
= nil
1127 q
:= canonicalize(&pp
.rtype
)
1128 p
:= (*ptrType
)(unsafe
.Pointer(q
.(*rtype
)))
1130 pi
, _
:= ptrMap
.LoadOrStore(t
, p
)
1131 return &pi
.(*ptrType
).rtype
1134 // fnv1 incorporates the list of bytes into the hash x using the FNV-1 hash function.
1135 func fnv1(x
uint32, list
...byte) uint32 {
1136 for _
, b
:= range list
{
1137 x
= x
*16777619 ^ uint32(b
)
1142 func (t
*rtype
) Implements(u Type
) bool {
1144 panic("reflect: nil type passed to Type.Implements")
1146 if u
.Kind() != Interface
{
1147 panic("reflect: non-interface type passed to Type.Implements")
1149 return implements(u
.(*rtype
), t
)
1152 func (t
*rtype
) AssignableTo(u Type
) bool {
1154 panic("reflect: nil type passed to Type.AssignableTo")
1157 return directlyAssignable(uu
, t
) ||
implements(uu
, t
)
1160 func (t
*rtype
) ConvertibleTo(u Type
) bool {
1162 panic("reflect: nil type passed to Type.ConvertibleTo")
1165 return convertOp(uu
, t
) != nil
1168 func (t
*rtype
) Comparable() bool {
1170 case Bool
, Int
, Int8
, Int16
, Int32
, Int64
,
1171 Uint
, Uint8
, Uint16
, Uint32
, Uint64
, Uintptr
,
1172 Float32
, Float64
, Complex64
, Complex128
,
1173 Chan
, Interface
, Ptr
, String
, UnsafePointer
:
1176 case Func
, Map
, Slice
:
1180 return (*arrayType
)(unsafe
.Pointer(t
)).elem
.Comparable()
1183 tt
:= (*structType
)(unsafe
.Pointer(t
))
1184 for i
:= range tt
.fields
{
1185 if !tt
.fields
[i
].typ
.Comparable() {
1192 panic("reflect: impossible")
1196 // implements reports whether the type V implements the interface type T.
1197 func implements(T
, V
*rtype
) bool {
1198 if T
.Kind() != Interface
{
1201 t
:= (*interfaceType
)(unsafe
.Pointer(T
))
1202 if len(t
.methods
) == 0 {
1206 // The same algorithm applies in both cases, but the
1207 // method tables for an interface type and a concrete type
1208 // are different, so the code is duplicated.
1209 // In both cases the algorithm is a linear scan over the two
1210 // lists - T's methods and V's methods - simultaneously.
1211 // Since method tables are stored in a unique sorted order
1212 // (alphabetical, with no duplicate method names), the scan
1213 // through V's methods must hit a match for each of T's
1214 // methods along the way, or else V does not implement T.
1215 // This lets us run the scan in overall linear time instead of
1216 // the quadratic time a naive search would require.
1217 // See also ../runtime/iface.go.
1218 if V
.Kind() == Interface
{
1219 v
:= (*interfaceType
)(unsafe
.Pointer(V
))
1221 for j
:= 0; j
< len(v
.methods
); j
++ {
1224 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() {
1225 if i
++; i
>= len(t
.methods
) {
1238 for j
:= 0; j
< len(v
.methods
); j
++ {
1241 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() {
1242 if i
++; i
>= len(t
.methods
) {
1250 // directlyAssignable reports whether a value x of type V can be directly
1251 // assigned (using memmove) to a value of type T.
1252 // https://golang.org/doc/go_spec.html#Assignability
1253 // Ignoring the interface rules (implemented elsewhere)
1254 // and the ideal constant rules (no ideal constants at run time).
1255 func directlyAssignable(T
, V
*rtype
) bool {
1256 // x's type V is identical to T?
1261 // Otherwise at least one of T and V must be unnamed
1262 // and they must have the same kind.
1263 if T
.Name() != "" && V
.Name() != "" || T
.Kind() != V
.Kind() {
1267 // x's type T and V must have identical underlying types.
1268 return haveIdenticalUnderlyingType(T
, V
, true)
1271 func haveIdenticalType(T
, V Type
, cmpTags
bool) bool {
1276 if T
.Name() != V
.Name() || T
.Kind() != V
.Kind() {
1280 return haveIdenticalUnderlyingType(T
.common(), V
.common(), false)
1283 func haveIdenticalUnderlyingType(T
, V
*rtype
, cmpTags
bool) bool {
1289 if kind
!= V
.Kind() {
1293 // Non-composite types of equal kind have same underlying type
1294 // (the predefined instance of the type).
1295 if Bool
<= kind
&& kind
<= Complex128 || kind
== String || kind
== UnsafePointer
{
1302 return T
.Len() == V
.Len() && haveIdenticalType(T
.Elem(), V
.Elem(), cmpTags
)
1306 // x is a bidirectional channel value, T is a channel type,
1307 // and x's type V and T have identical element types.
1308 if V
.ChanDir() == BothDir
&& haveIdenticalType(T
.Elem(), V
.Elem(), cmpTags
) {
1312 // Otherwise continue test for identical underlying type.
1313 return V
.ChanDir() == T
.ChanDir() && haveIdenticalType(T
.Elem(), V
.Elem(), cmpTags
)
1316 t
:= (*funcType
)(unsafe
.Pointer(T
))
1317 v
:= (*funcType
)(unsafe
.Pointer(V
))
1318 if t
.dotdotdot
!= v
.dotdotdot ||
len(t
.in
) != len(v
.in
) ||
len(t
.out
) != len(v
.out
) {
1321 for i
, typ
:= range t
.in
{
1322 if !haveIdenticalType(typ
, v
.in
[i
], cmpTags
) {
1326 for i
, typ
:= range t
.out
{
1327 if !haveIdenticalType(typ
, v
.out
[i
], cmpTags
) {
1334 t
:= (*interfaceType
)(unsafe
.Pointer(T
))
1335 v
:= (*interfaceType
)(unsafe
.Pointer(V
))
1336 if len(t
.methods
) == 0 && len(v
.methods
) == 0 {
1339 // Might have the same methods but still
1340 // need a run time conversion.
1344 return haveIdenticalType(T
.Key(), V
.Key(), cmpTags
) && haveIdenticalType(T
.Elem(), V
.Elem(), cmpTags
)
1347 return haveIdenticalType(T
.Elem(), V
.Elem(), cmpTags
)
1350 t
:= (*structType
)(unsafe
.Pointer(T
))
1351 v
:= (*structType
)(unsafe
.Pointer(V
))
1352 if len(t
.fields
) != len(v
.fields
) {
1355 for i
:= range t
.fields
{
1358 if tf
.name
!= vf
.name
&& (tf
.name
== nil || vf
.name
== nil ||
*tf
.name
!= *vf
.name
) {
1361 if tf
.pkgPath
!= vf
.pkgPath
&& (tf
.pkgPath
== nil || vf
.pkgPath
== nil ||
*tf
.pkgPath
!= *vf
.pkgPath
) {
1364 if !haveIdenticalType(tf
.typ
, vf
.typ
, cmpTags
) {
1367 if cmpTags
&& tf
.tag
!= vf
.tag
&& (tf
.tag
== nil || vf
.tag
== nil ||
*tf
.tag
!= *vf
.tag
) {
1370 if tf
.offsetAnon
!= vf
.offsetAnon
{
1380 // The lookupCache caches ArrayOf, ChanOf, MapOf and SliceOf lookups.
1381 var lookupCache sync
.Map
// map[cacheKey]*rtype
1383 // A cacheKey is the key for use in the lookupCache.
1384 // Four values describe any of the types we are looking for:
1385 // type kind, one or two subtypes, and an extra integer.
1386 type cacheKey
struct {
1393 // The funcLookupCache caches FuncOf lookups.
1394 // FuncOf does not share the common lookupCache since cacheKey is not
1395 // sufficient to represent functions unambiguously.
1396 var funcLookupCache
struct {
1397 sync
.Mutex
// Guards stores (but not loads) on m.
1399 // m is a map[uint32][]*rtype keyed by the hash calculated in FuncOf.
1400 // Elements of m are append-only and thus safe for concurrent reading.
1404 // ChanOf returns the channel type with the given direction and element type.
1405 // For example, if t represents int, ChanOf(RecvDir, t) represents <-chan int.
1407 // The gc runtime imposes a limit of 64 kB on channel element types.
1408 // If t's size is equal to or exceeds this limit, ChanOf panics.
1409 func ChanOf(dir ChanDir
, t Type
) Type
{
1413 ckey
:= cacheKey
{Chan
, typ
, nil, uintptr(dir
)}
1414 if ch
, ok
:= lookupCache
.Load(ckey
); ok
{
1418 // This restriction is imposed by the gc compiler and the runtime.
1419 if typ
.size
>= 1<<16 {
1420 panic("reflect.ChanOf: element size too large")
1423 // Look in known types.
1424 // TODO: Precedence when constructing string.
1428 panic("reflect.ChanOf: invalid dir")
1430 s
= "chan<- " + *typ
.string
1432 s
= "<-chan " + *typ
.string
1434 s
= "chan " + *typ
.string
1437 // Make a channel type.
1438 var ichan
interface{} = (chan unsafe
.Pointer
)(nil)
1439 prototype
:= *(**chanType
)(unsafe
.Pointer(&ichan
))
1441 ch
.dir
= uintptr(dir
)
1444 // gccgo uses a different hash.
1445 // ch.hash = fnv1(typ.hash, 'c', byte(dir))
1447 if dir
&SendDir
!= 0 {
1450 if dir
&RecvDir
!= 0 {
1453 ch
.hash
+= typ
.hash
<< 2
1458 ch
.uncommonType
= nil
1461 ti
, _
:= lookupCache
.LoadOrStore(ckey
, &ch
.rtype
)
1465 func ismapkey(*rtype
) bool // implemented in runtime
1467 // MapOf returns the map type with the given key and element types.
1468 // For example, if k represents int and e represents string,
1469 // MapOf(k, e) represents map[int]string.
1471 // If the key type is not a valid map key type (that is, if it does
1472 // not implement Go's == operator), MapOf panics.
1473 func MapOf(key
, elem Type
) Type
{
1474 ktyp
:= key
.(*rtype
)
1475 etyp
:= elem
.(*rtype
)
1477 if !ismapkey(ktyp
) {
1478 panic("reflect.MapOf: invalid key type " + ktyp
.String())
1482 ckey
:= cacheKey
{Map
, ktyp
, etyp
, 0}
1483 if mt
, ok
:= lookupCache
.Load(ckey
); ok
{
1487 // Look in known types.
1488 s
:= "map[" + *ktyp
.string + "]" + *etyp
.string
1491 var imap
interface{} = (map[unsafe
.Pointer
]unsafe
.Pointer
)(nil)
1492 mt
:= **(**mapType
)(unsafe
.Pointer(&imap
))
1495 // gccgo uses a different hash
1496 // mt.hash = fnv1(etyp.hash, 'm', byte(ktyp.hash>>24), byte(ktyp.hash>>16), byte(ktyp.hash>>8), byte(ktyp.hash))
1497 mt
.hash
= ktyp
.hash
+ etyp
.hash
+ 2 + 14
1501 mt
.uncommonType
= nil
1504 mt
.bucket
= bucketOf(ktyp
, etyp
)
1505 if ktyp
.size
> maxKeySize
{
1506 mt
.keysize
= uint8(ptrSize
)
1509 mt
.keysize
= uint8(ktyp
.size
)
1512 if etyp
.size
> maxValSize
{
1513 mt
.valuesize
= uint8(ptrSize
)
1514 mt
.indirectvalue
= 1
1516 mt
.valuesize
= uint8(etyp
.size
)
1517 mt
.indirectvalue
= 0
1519 mt
.bucketsize
= uint16(mt
.bucket
.size
)
1520 mt
.reflexivekey
= isReflexive(ktyp
)
1521 mt
.needkeyupdate
= needKeyUpdate(ktyp
)
1523 ti
, _
:= lookupCache
.LoadOrStore(ckey
, &mt
.rtype
)
1527 // FuncOf returns the function type with the given argument and result types.
1528 // For example if k represents int and e represents string,
1529 // FuncOf([]Type{k}, []Type{e}, false) represents func(int) string.
1531 // The variadic argument controls whether the function is variadic. FuncOf
1532 // panics if the in[len(in)-1] does not represent a slice and variadic is
1534 func FuncOf(in
, out
[]Type
, variadic
bool) Type
{
1535 if variadic
&& (len(in
) == 0 || in
[len(in
)-1].Kind() != Slice
) {
1536 panic("reflect.FuncOf: last arg of variadic func must be slice")
1539 // Make a func type.
1540 var ifunc
interface{} = (func())(nil)
1541 prototype
:= *(**funcType
)(unsafe
.Pointer(&ifunc
))
1545 // Build a hash and minimally populate ft.
1547 var fin
, fout
[]*rtype
1549 for _
, in
:= range in
{
1551 fin
= append(fin
, t
)
1552 hash
+= t
.hash
<< shift
1556 for _
, out
:= range out
{
1558 fout
= append(fout
, t
)
1559 hash
+= t
.hash
<< shift
1570 ft
.dotdotdot
= variadic
1573 if ts
, ok
:= funcLookupCache
.m
.Load(hash
); ok
{
1574 for _
, t
:= range ts
.([]*rtype
) {
1575 if haveIdenticalUnderlyingType(&ft
.rtype
, t
, true) {
1581 // Not in cache, lock and retry.
1582 funcLookupCache
.Lock()
1583 defer funcLookupCache
.Unlock()
1584 if ts
, ok
:= funcLookupCache
.m
.Load(hash
); ok
{
1585 for _
, t
:= range ts
.([]*rtype
) {
1586 if haveIdenticalUnderlyingType(&ft
.rtype
, t
, true) {
1592 addToCache
:= func(tt
*rtype
) Type
{
1594 if rti
, ok
:= funcLookupCache
.m
.Load(hash
); ok
{
1595 rts
= rti
.([]*rtype
)
1597 funcLookupCache
.m
.Store(hash
, append(rts
, tt
))
1603 // Populate the remaining fields of ft and store in cache.
1605 ft
.uncommonType
= nil
1607 return addToCache(&ft
.rtype
)
1610 // funcStr builds a string representation of a funcType.
1611 func funcStr(ft
*funcType
) string {
1612 repr
:= make([]byte, 0, 64)
1613 repr
= append(repr
, "func("...)
1614 for i
, t
:= range ft
.in
{
1616 repr
= append(repr
, ", "...)
1618 if ft
.dotdotdot
&& i
== len(ft
.in
)-1 {
1619 repr
= append(repr
, "..."...)
1620 repr
= append(repr
, *(*sliceType
)(unsafe
.Pointer(t
)).elem
.string...)
1622 repr
= append(repr
, *t
.string...)
1625 repr
= append(repr
, ')')
1626 if l
:= len(ft
.out
); l
== 1 {
1627 repr
= append(repr
, ' ')
1629 repr
= append(repr
, " ("...)
1631 for i
, t
:= range ft
.out
{
1633 repr
= append(repr
, ", "...)
1635 repr
= append(repr
, *t
.string...)
1637 if len(ft
.out
) > 1 {
1638 repr
= append(repr
, ')')
1643 // isReflexive reports whether the == operation on the type is reflexive.
1644 // That is, x == x for all values x of type t.
1645 func isReflexive(t
*rtype
) bool {
1647 case Bool
, Int
, Int8
, Int16
, Int32
, Int64
, Uint
, Uint8
, Uint16
, Uint32
, Uint64
, Uintptr
, Chan
, Ptr
, String
, UnsafePointer
:
1649 case Float32
, Float64
, Complex64
, Complex128
, Interface
:
1652 tt
:= (*arrayType
)(unsafe
.Pointer(t
))
1653 return isReflexive(tt
.elem
)
1655 tt
:= (*structType
)(unsafe
.Pointer(t
))
1656 for _
, f
:= range tt
.fields
{
1657 if !isReflexive(f
.typ
) {
1663 // Func, Map, Slice, Invalid
1664 panic("isReflexive called on non-key type " + t
.String())
1668 // needKeyUpdate reports whether map overwrites require the key to be copied.
1669 func needKeyUpdate(t
*rtype
) bool {
1671 case Bool
, Int
, Int8
, Int16
, Int32
, Int64
, Uint
, Uint8
, Uint16
, Uint32
, Uint64
, Uintptr
, Chan
, Ptr
, UnsafePointer
:
1673 case Float32
, Float64
, Complex64
, Complex128
, Interface
, String
:
1674 // Float keys can be updated from +0 to -0.
1675 // String keys can be updated to use a smaller backing store.
1676 // Interfaces might have floats of strings in them.
1679 tt
:= (*arrayType
)(unsafe
.Pointer(t
))
1680 return needKeyUpdate(tt
.elem
)
1682 tt
:= (*structType
)(unsafe
.Pointer(t
))
1683 for _
, f
:= range tt
.fields
{
1684 if needKeyUpdate(f
.typ
) {
1690 // Func, Map, Slice, Invalid
1691 panic("needKeyUpdate called on non-key type " + t
.String())
1695 // Make sure these routines stay in sync with ../../runtime/hashmap.go!
1696 // These types exist only for GC, so we only fill out GC relevant info.
1697 // Currently, that's just size and the GC program. We also fill in string
1698 // for possible debugging use.
1700 bucketSize
uintptr = 8
1701 maxKeySize
uintptr = 128
1702 maxValSize
uintptr = 128
1705 func bucketOf(ktyp
, etyp
*rtype
) *rtype
{
1706 // See comment on hmap.overflow in ../runtime/hashmap.go.
1708 if ktyp
.kind
&kindNoPointers
!= 0 && etyp
.kind
&kindNoPointers
!= 0 &&
1709 ktyp
.size
<= maxKeySize
&& etyp
.size
<= maxValSize
{
1710 kind
= kindNoPointers
1713 if ktyp
.size
> maxKeySize
{
1714 ktyp
= PtrTo(ktyp
).(*rtype
)
1716 if etyp
.size
> maxValSize
{
1717 etyp
= PtrTo(etyp
).(*rtype
)
1720 // Prepare GC data if any.
1721 // A bucket is at most bucketSize*(1+maxKeySize+maxValSize)+2*ptrSize bytes,
1722 // or 2072 bytes, or 259 pointer-size words, or 33 bytes of pointer bitmap.
1723 // Note that since the key and value are known to be <= 128 bytes,
1724 // they're guaranteed to have bitmaps instead of GC programs.
1729 size
= align(size
, uintptr(ktyp
.fieldAlign
))
1730 size
+= bucketSize
* ktyp
.size
1731 size
= align(size
, uintptr(etyp
.fieldAlign
))
1732 size
+= bucketSize
* etyp
.size
1734 maxAlign
:= uintptr(ktyp
.fieldAlign
)
1735 if maxAlign
< uintptr(etyp
.fieldAlign
) {
1736 maxAlign
= uintptr(etyp
.fieldAlign
)
1738 if maxAlign
> ptrSize
{
1739 size
= align(size
, maxAlign
)
1740 size
+= align(ptrSize
, maxAlign
) - ptrSize
1741 } else if maxAlign
< ptrSize
{
1742 size
= align(size
, ptrSize
)
1749 if kind
!= kindNoPointers
{
1750 nptr
:= size
/ ptrSize
1751 mask
:= make([]byte, (nptr
+7)/8)
1753 psize
= align(psize
, uintptr(ktyp
.fieldAlign
))
1754 base
:= psize
/ ptrSize
1756 if ktyp
.kind
&kindNoPointers
== 0 {
1757 if ktyp
.kind
&kindGCProg
!= 0 {
1758 panic("reflect: unexpected GC program in MapOf")
1760 kmask
:= (*[16]byte)(unsafe
.Pointer(ktyp
.gcdata
))
1761 for i
:= uintptr(0); i
< ktyp
.ptrdata
/ptrSize
; i
++ {
1762 if (kmask
[i
/8]>>(i%8
))&1 != 0 {
1763 for j
:= uintptr(0); j
< bucketSize
; j
++ {
1764 word
:= base
+ j
*ktyp
.size
/ptrSize
+ i
1765 mask
[word
/8] |
= 1 << (word
% 8)
1770 psize
+= bucketSize
* ktyp
.size
1771 psize
= align(psize
, uintptr(etyp
.fieldAlign
))
1772 base
= psize
/ ptrSize
1774 if etyp
.kind
&kindNoPointers
== 0 {
1775 if etyp
.kind
&kindGCProg
!= 0 {
1776 panic("reflect: unexpected GC program in MapOf")
1778 emask
:= (*[16]byte)(unsafe
.Pointer(etyp
.gcdata
))
1779 for i
:= uintptr(0); i
< etyp
.ptrdata
/ptrSize
; i
++ {
1780 if (emask
[i
/8]>>(i%8
))&1 != 0 {
1781 for j
:= uintptr(0); j
< bucketSize
; j
++ {
1782 word
:= base
+ j
*etyp
.size
/ptrSize
+ i
1783 mask
[word
/8] |
= 1 << (word
% 8)
1789 word
:= ovoff
/ ptrSize
1790 mask
[word
/8] |
= 1 << (word
% 8)
1792 ptrdata
= (word
+ 1) * ptrSize
1794 // overflow word must be last
1795 if ptrdata
!= size
{
1796 panic("reflect: bad layout computation in MapOf")
1801 align
: int8(maxAlign
),
1802 fieldAlign
: uint8(maxAlign
),
1808 s
:= "bucket(" + *ktyp
.string + "," + *etyp
.string + ")"
1813 // SliceOf returns the slice type with element type t.
1814 // For example, if t represents int, SliceOf(t) represents []int.
1815 func SliceOf(t Type
) Type
{
1819 ckey
:= cacheKey
{Slice
, typ
, nil, 0}
1820 if slice
, ok
:= lookupCache
.Load(ckey
); ok
{
1824 // Look in known types.
1825 s
:= "[]" + *typ
.string
1827 // Make a slice type.
1828 var islice
interface{} = ([]unsafe
.Pointer
)(nil)
1829 prototype
:= *(**sliceType
)(unsafe
.Pointer(&islice
))
1833 // gccgo uses a different hash.
1834 // slice.hash = fnv1(typ.hash, '[')
1835 slice
.hash
= typ
.hash
+ 1 + 13
1838 slice
.uncommonType
= nil
1839 slice
.ptrToThis
= nil
1841 ti
, _
:= lookupCache
.LoadOrStore(ckey
, &slice
.rtype
)
1845 // The structLookupCache caches StructOf lookups.
1846 // StructOf does not share the common lookupCache since we need to pin
1847 // the memory associated with *structTypeFixedN.
1848 var structLookupCache
struct {
1849 sync
.Mutex
// Guards stores (but not loads) on m.
1851 // m is a map[uint32][]Type keyed by the hash calculated in StructOf.
1852 // Elements in m are append-only and thus safe for concurrent reading.
1856 // isLetter returns true if a given 'rune' is classified as a Letter.
1857 func isLetter(ch rune
) bool {
1858 return 'a' <= ch
&& ch
<= 'z' ||
'A' <= ch
&& ch
<= 'Z' || ch
== '_' || ch
>= utf8
.RuneSelf
&& unicode
.IsLetter(ch
)
1861 // isValidFieldName checks if a string is a valid (struct) field name or not.
1863 // According to the language spec, a field name should be an identifier.
1865 // identifier = letter { letter | unicode_digit } .
1866 // letter = unicode_letter | "_" .
1867 func isValidFieldName(fieldName
string) bool {
1868 for i
, c
:= range fieldName
{
1869 if i
== 0 && !isLetter(c
) {
1873 if !(isLetter(c
) || unicode
.IsDigit(c
)) {
1878 return len(fieldName
) > 0
1881 // StructOf returns the struct type containing fields.
1882 // The Offset and Index fields are ignored and computed as they would be
1885 // StructOf currently does not generate wrapper methods for embedded fields.
1886 // This limitation may be lifted in a future version.
1887 func StructOf(fields
[]StructField
) Type
{
1895 fs
= make([]structField
, len(fields
))
1896 repr
= make([]byte, 0, 64)
1897 fset
= map[string]struct{}{} // fields' names
1899 hasPtr
= false // records whether at least one struct-field is a pointer
1900 hasGCProg
= false // records whether a struct-field type has a GCProg
1903 lastzero
:= uintptr(0)
1904 repr
= append(repr
, "struct {"...)
1905 for i
, field
:= range fields
{
1906 if field
.Name
== "" {
1907 panic("reflect.StructOf: field " + strconv
.Itoa(i
) + " has no name")
1909 if !isValidFieldName(field
.Name
) {
1910 panic("reflect.StructOf: field " + strconv
.Itoa(i
) + " has invalid name")
1912 if field
.Type
== nil {
1913 panic("reflect.StructOf: field " + strconv
.Itoa(i
) + " has no type")
1915 f
:= runtimeStructField(field
)
1917 if ft
.kind
&kindGCProg
!= 0 {
1924 // Update string and hash
1926 hash
= (hash
<< 1) + ft
.hash
1928 repr
= append(repr
, (" " + name
)...)
1931 repr
= append(repr
, " ?"...)
1932 if f
.typ
.Kind() == Ptr
{
1933 // Embedded ** and *interface{} are illegal
1935 if k
:= elem
.Kind(); k
== Ptr || k
== Interface
{
1936 panic("reflect.StructOf: illegal anonymous field type " + ft
.String())
1938 name
= elem
.String()
1943 switch f
.typ
.Kind() {
1945 ift
:= (*interfaceType
)(unsafe
.Pointer(ft
))
1946 if len(ift
.methods
) > 0 {
1947 panic("reflect.StructOf: embedded field with methods not implemented")
1950 ptr
:= (*ptrType
)(unsafe
.Pointer(ft
))
1951 if unt
:= ptr
.uncommon(); unt
!= nil {
1952 if len(unt
.methods
) > 0 {
1953 panic("reflect.StructOf: embedded field with methods not implemented")
1956 if unt
:= ptr
.elem
.uncommon(); unt
!= nil {
1957 if len(unt
.methods
) > 0 {
1958 panic("reflect.StructOf: embedded field with methods not implemented")
1962 if unt
:= ft
.uncommon(); unt
!= nil {
1963 if len(unt
.methods
) > 0 {
1964 panic("reflect.StructOf: embedded field with methods not implemented")
1969 if _
, dup
:= fset
[name
]; dup
{
1970 panic("reflect.StructOf: duplicate field " + name
)
1972 fset
[name
] = struct{}{}
1974 repr
= append(repr
, (" " + ft
.String())...)
1976 repr
= append(repr
, (" " + strconv
.Quote(*f
.tag
))...)
1978 if i
< len(fields
)-1 {
1979 repr
= append(repr
, ';')
1982 comparable
= comparable
&& (ft
.equalfn
!= nil)
1983 hashable
= hashable
&& (ft
.hashfn
!= nil)
1985 offset
:= align(size
, uintptr(ft
.fieldAlign
))
1986 if int8(ft
.fieldAlign
) > typalign
{
1987 typalign
= int8(ft
.fieldAlign
)
1989 size
= offset
+ ft
.size
1990 f
.offsetAnon |
= offset
<< 1
1999 if size
> 0 && lastzero
== size
{
2000 // This is a non-zero sized struct that ends in a
2001 // zero-sized field. We add an extra byte of padding,
2002 // to ensure that taking the address of the final
2003 // zero-sized field can't manufacture a pointer to the
2004 // next object in the heap. See issue 9401.
2009 repr
= append(repr
, ' ')
2011 repr
= append(repr
, '}')
2015 // Round the size up to be a multiple of the alignment.
2016 size
= align(size
, uintptr(typalign
))
2018 // Make the struct type.
2019 var istruct
interface{} = struct{}{}
2020 prototype
:= *(**structType
)(unsafe
.Pointer(&istruct
))
2021 typ
:= new(structType
)
2026 if ts
, ok
:= structLookupCache
.m
.Load(hash
); ok
{
2027 for _
, st
:= range ts
.([]Type
) {
2029 if haveIdenticalUnderlyingType(&typ
.rtype
, t
, true) {
2035 // Not in cache, lock and retry.
2036 structLookupCache
.Lock()
2037 defer structLookupCache
.Unlock()
2038 if ts
, ok
:= structLookupCache
.m
.Load(hash
); ok
{
2039 for _
, st
:= range ts
.([]Type
) {
2041 if haveIdenticalUnderlyingType(&typ
.rtype
, t
, true) {
2047 addToCache
:= func(t Type
) Type
{
2049 if ti
, ok
:= structLookupCache
.m
.Load(hash
); ok
{
2052 structLookupCache
.m
.Store(hash
, append(ts
, t
))
2059 typ
.align
= typalign
2060 typ
.fieldAlign
= uint8(typalign
)
2062 typ
.kind |
= kindNoPointers
2064 typ
.kind
&^= kindNoPointers
2069 for i
, ft
:= range fs
{
2070 if ft
.typ
.pointers() {
2074 prog
:= []byte{0, 0, 0, 0} // will be length of prog
2075 for i
, ft
:= range fs
{
2076 if i
> lastPtrField
{
2077 // gcprog should not include anything for any field after
2078 // the last field that contains pointer data
2081 // FIXME(sbinet) handle padding, fields smaller than a word
2082 elemGC
:= (*[1 << 30]byte)(unsafe
.Pointer(ft
.typ
.gcdata
))[:]
2083 elemPtrs
:= ft
.typ
.ptrdata
/ ptrSize
2085 case ft
.typ
.kind
&kindGCProg
== 0 && ft
.typ
.ptrdata
!= 0:
2086 // Element is small with pointer mask; use as literal bits.
2088 // Emit 120-bit chunks of full bytes (max is 127 but we avoid using partial bytes).
2090 for n
:= elemPtrs
; n
> 120; n
-= 120 {
2091 prog
= append(prog
, 120)
2092 prog
= append(prog
, mask
[:15]...)
2095 prog
= append(prog
, byte(n
))
2096 prog
= append(prog
, mask
[:(n
+7)/8]...)
2097 case ft
.typ
.kind
&kindGCProg
!= 0:
2098 // Element has GC program; emit one element.
2099 elemProg
:= elemGC
[4 : 4+*(*uint32)(unsafe
.Pointer(&elemGC
[0]))-1]
2100 prog
= append(prog
, elemProg
...)
2102 // Pad from ptrdata to size.
2103 elemWords
:= ft
.typ
.size
/ ptrSize
2104 if elemPtrs
< elemWords
{
2105 // Emit literal 0 bit, then repeat as needed.
2106 prog
= append(prog
, 0x01, 0x00)
2107 if elemPtrs
+1 < elemWords
{
2108 prog
= append(prog
, 0x81)
2109 prog
= appendVarint(prog
, elemWords
-elemPtrs
-1)
2113 *(*uint32)(unsafe
.Pointer(&prog
[0])) = uint32(len(prog
) - 4)
2114 typ
.kind |
= kindGCProg
2115 typ
.gcdata
= &prog
[0]
2117 typ
.kind
&^= kindGCProg
2118 bv
:= new(bitVector
)
2119 addTypeBits(bv
, 0, typ
.common())
2120 if len(bv
.data
) > 0 {
2121 typ
.gcdata
= &bv
.data
[0]
2124 typ
.ptrdata
= typeptrdata(typ
.common())
2127 typ
.hashfn
= func(p unsafe
.Pointer
, seed
uintptr) uintptr {
2129 for _
, ft
:= range typ
.fields
{
2130 pi
:= unsafe
.Pointer(uintptr(p
) + ft
.offset())
2131 o
= ft
.typ
.hashfn(pi
, o
)
2140 typ
.equalfn
= func(p
, q unsafe
.Pointer
) bool {
2141 for _
, ft
:= range typ
.fields
{
2142 pi
:= unsafe
.Pointer(uintptr(p
) + ft
.offset())
2143 qi
:= unsafe
.Pointer(uintptr(q
) + ft
.offset())
2144 if !ft
.typ
.equalfn(pi
, qi
) {
2154 typ
.kind
&^= kindDirectIface
2155 typ
.uncommonType
= nil
2158 return addToCache(&typ
.rtype
)
2161 func runtimeStructField(field StructField
) structField
{
2162 if field
.PkgPath
!= "" {
2163 panic("reflect.StructOf: StructOf does not allow unexported fields")
2166 // Best-effort check for misuse.
2167 // Since PkgPath is empty, not much harm done if Unicode lowercase slips through.
2169 if 'a' <= c
&& c
<= 'z' || c
== '_' {
2170 panic("reflect.StructOf: field \"" + field
.Name
+ "\" is unexported but missing PkgPath")
2173 offsetAnon
:= uintptr(0)
2174 if field
.Anonymous
{
2182 if field
.Tag
!= "" {
2183 st
:= string(field
.Tag
)
2190 typ
: field
.Type
.common(),
2192 offsetAnon
: offsetAnon
,
2196 // typeptrdata returns the length in bytes of the prefix of t
2197 // containing pointer data. Anything after this offset is scalar data.
2198 // keep in sync with ../cmd/compile/internal/gc/reflect.go
2199 func typeptrdata(t
*rtype
) uintptr {
2205 st
:= (*structType
)(unsafe
.Pointer(t
))
2206 // find the last field that has pointers.
2208 for i
:= range st
.fields
{
2209 ft
:= st
.fields
[i
].typ
2214 f
:= st
.fields
[field
]
2215 return f
.offset() + f
.typ
.ptrdata
2218 panic("reflect.typeptrdata: unexpected type, " + t
.String())
2222 // See cmd/compile/internal/gc/reflect.go for derivation of constant.
2223 const maxPtrmaskBytes
= 2048
2225 // ArrayOf returns the array type with the given count and element type.
2226 // For example, if t represents int, ArrayOf(5, t) represents [5]int.
2228 // If the resulting type would be larger than the available address space,
2230 func ArrayOf(count
int, elem Type
) Type
{
2231 typ
:= elem
.(*rtype
)
2234 ckey
:= cacheKey
{Array
, typ
, nil, uintptr(count
)}
2235 if array
, ok
:= lookupCache
.Load(ckey
); ok
{
2239 // Look in known types.
2240 s
:= "[" + strconv
.Itoa(count
) + "]" + *typ
.string
2242 // Make an array type.
2243 var iarray
interface{} = [1]unsafe
.Pointer
{}
2244 prototype
:= *(**arrayType
)(unsafe
.Pointer(&iarray
))
2248 // gccgo uses a different hash.
2249 // array.hash = fnv1(typ.hash, '[')
2250 // for n := uint32(count); n > 0; n >>= 8 {
2251 // array.hash = fnv1(array.hash, byte(n))
2253 // array.hash = fnv1(array.hash, ']')
2254 array
.hash
= typ
.hash
+ 1 + 13
2257 array
.ptrToThis
= nil
2259 max
:= ^uintptr(0) / typ
.size
2260 if uintptr(count
) > max
{
2261 panic("reflect.ArrayOf: array size would exceed virtual address space")
2264 array
.size
= typ
.size
* uintptr(count
)
2265 if count
> 0 && typ
.ptrdata
!= 0 {
2266 array
.ptrdata
= typ
.size
*uintptr(count
-1) + typ
.ptrdata
2268 array
.align
= typ
.align
2269 array
.fieldAlign
= typ
.fieldAlign
2270 array
.uncommonType
= nil
2271 array
.len = uintptr(count
)
2272 array
.slice
= SliceOf(elem
).(*rtype
)
2274 array
.kind
&^= kindNoPointers
2276 case typ
.kind
&kindNoPointers
!= 0 || array
.size
== 0:
2278 array
.kind |
= kindNoPointers
2283 // In memory, 1-element array looks just like the element.
2284 array
.kind |
= typ
.kind
& kindGCProg
2285 array
.gcdata
= typ
.gcdata
2286 array
.ptrdata
= typ
.ptrdata
2288 case typ
.kind
&kindGCProg
== 0 && array
.size
<= maxPtrmaskBytes
*8*ptrSize
:
2289 // Element is small with pointer mask; array is still small.
2290 // Create direct pointer mask by turning each 1 bit in elem
2291 // into count 1 bits in larger mask.
2292 mask
:= make([]byte, (array
.ptrdata
/ptrSize
+7)/8)
2293 elemMask
:= (*[1 << 30]byte)(unsafe
.Pointer(typ
.gcdata
))[:]
2294 elemWords
:= typ
.size
/ ptrSize
2295 for j
:= uintptr(0); j
< typ
.ptrdata
/ptrSize
; j
++ {
2296 if (elemMask
[j
/8]>>(j%8
))&1 != 0 {
2297 for i
:= uintptr(0); i
< array
.len; i
++ {
2298 k
:= i
*elemWords
+ j
2299 mask
[k
/8] |
= 1 << (k
% 8)
2303 array
.gcdata
= &mask
[0]
2306 // Create program that emits one element
2307 // and then repeats to make the array.
2308 prog
:= []byte{0, 0, 0, 0} // will be length of prog
2309 elemGC
:= (*[1 << 30]byte)(unsafe
.Pointer(typ
.gcdata
))[:]
2310 elemPtrs
:= typ
.ptrdata
/ ptrSize
2311 if typ
.kind
&kindGCProg
== 0 {
2312 // Element is small with pointer mask; use as literal bits.
2314 // Emit 120-bit chunks of full bytes (max is 127 but we avoid using partial bytes).
2316 for n
= elemPtrs
; n
> 120; n
-= 120 {
2317 prog
= append(prog
, 120)
2318 prog
= append(prog
, mask
[:15]...)
2321 prog
= append(prog
, byte(n
))
2322 prog
= append(prog
, mask
[:(n
+7)/8]...)
2324 // Element has GC program; emit one element.
2325 elemProg
:= elemGC
[4 : 4+*(*uint32)(unsafe
.Pointer(&elemGC
[0]))-1]
2326 prog
= append(prog
, elemProg
...)
2328 // Pad from ptrdata to size.
2329 elemWords
:= typ
.size
/ ptrSize
2330 if elemPtrs
< elemWords
{
2331 // Emit literal 0 bit, then repeat as needed.
2332 prog
= append(prog
, 0x01, 0x00)
2333 if elemPtrs
+1 < elemWords
{
2334 prog
= append(prog
, 0x81)
2335 prog
= appendVarint(prog
, elemWords
-elemPtrs
-1)
2338 // Repeat count-1 times.
2339 if elemWords
< 0x80 {
2340 prog
= append(prog
, byte(elemWords|
0x80))
2342 prog
= append(prog
, 0x80)
2343 prog
= appendVarint(prog
, elemWords
)
2345 prog
= appendVarint(prog
, uintptr(count
)-1)
2346 prog
= append(prog
, 0)
2347 *(*uint32)(unsafe
.Pointer(&prog
[0])) = uint32(len(prog
) - 4)
2348 array
.kind |
= kindGCProg
2349 array
.gcdata
= &prog
[0]
2350 array
.ptrdata
= array
.size
// overestimate but ok; must match program
2353 array
.kind
&^= kindDirectIface
2357 if typ
.equalfn
== nil {
2360 eequal
:= typ
.equalfn
2361 array
.equalfn
= func(p
, q unsafe
.Pointer
) bool {
2362 for i
:= 0; i
< count
; i
++ {
2363 pi
:= arrayAt(p
, i
, esize
)
2364 qi
:= arrayAt(q
, i
, esize
)
2365 if !eequal(pi
, qi
) {
2373 if typ
.hashfn
== nil {
2377 array
.hashfn
= func(ptr unsafe
.Pointer
, seed
uintptr) uintptr {
2379 for i
:= 0; i
< count
; i
++ {
2380 o
= ehash(arrayAt(ptr
, i
, esize
), o
)
2386 ti
, _
:= lookupCache
.LoadOrStore(ckey
, &array
.rtype
)
2390 func appendVarint(x
[]byte, v
uintptr) []byte {
2391 for ; v
>= 0x80; v
>>= 7 {
2392 x
= append(x
, byte(v|
0x80))
2394 x
= append(x
, byte(v
))
2398 // toType converts from a *rtype to a Type that can be returned
2399 // to the client of package reflect. In gc, the only concern is that
2400 // a nil *rtype must be replaced by a nil Type, but in gccgo this
2401 // function takes care of ensuring that multiple *rtype for the same
2402 // type are coalesced into a single Type.
2403 var canonicalType
= make(map[string]Type
)
2405 var canonicalTypeLock sync
.RWMutex
2407 func canonicalize(t Type
) Type
{
2412 canonicalTypeLock
.RLock()
2413 if r
, ok
:= canonicalType
[s
]; ok
{
2414 canonicalTypeLock
.RUnlock()
2417 canonicalTypeLock
.RUnlock()
2418 canonicalTypeLock
.Lock()
2419 if r
, ok
:= canonicalType
[s
]; ok
{
2420 canonicalTypeLock
.Unlock()
2423 canonicalType
[s
] = t
2424 canonicalTypeLock
.Unlock()
2428 func toType(p
*rtype
) Type
{
2432 return canonicalize(p
)
2435 // ifaceIndir reports whether t is stored indirectly in an interface value.
2436 func ifaceIndir(t
*rtype
) bool {
2437 return t
.kind
&kindDirectIface
== 0
2440 // Layout matches runtime.gobitvector (well enough).
2441 type bitVector
struct {
2442 n
uint32 // number of bits
2446 // append a bit to the bitmap.
2447 func (bv
*bitVector
) append(bit
uint8) {
2449 bv
.data
= append(bv
.data
, 0)
2451 bv
.data
[bv
.n
/8] |
= bit
<< (bv
.n
% 8)
2455 func addTypeBits(bv
*bitVector
, offset
uintptr, t
*rtype
) {
2456 if t
.kind
&kindNoPointers
!= 0 {
2460 switch Kind(t
.kind
& kindMask
) {
2461 case Chan
, Func
, Map
, Ptr
, Slice
, String
, UnsafePointer
:
2462 // 1 pointer at start of representation
2463 for bv
.n
< uint32(offset
/uintptr(ptrSize
)) {
2470 for bv
.n
< uint32(offset
/uintptr(ptrSize
)) {
2477 // repeat inner type
2478 tt
:= (*arrayType
)(unsafe
.Pointer(t
))
2479 for i
:= 0; i
< int(tt
.len); i
++ {
2480 addTypeBits(bv
, offset
+uintptr(i
)*tt
.elem
.size
, tt
.elem
)
2485 tt
:= (*structType
)(unsafe
.Pointer(t
))
2486 for i
:= range tt
.fields
{
2488 addTypeBits(bv
, offset
+f
.offset(), f
.typ
)