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// 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:
// https://golang.org/doc/articles/laws_of_reflection.html
package reflect
import (
"internal/abi"
"internal/goarch"
"strconv"
"sync"
"unicode"
"unicode/utf8"
"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 values are comparable, such as with the == operator,
// so they can be used as map keys.
// Two Type values are equal if they represent identical types.
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,
// and only exported methods are accessible.
//
// For an interface type, the returned Method's Type field gives the
// method signature, without a receiver, and the Func field is nil.
//
// Methods are sorted in lexicographic order.
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 accessible using Method.
//
// For a non-interface type, it returns the number of exported methods.
//
// For an interface type, it returns the number of exported and unexported methods.
NumMethod() int
// Name returns the type's name within its package for a defined type.
// For other (non-defined) types it returns the empty string.
Name() string
// PkgPath returns a defined type's package path, that is, the import path
// that uniquely identifies the package, such as "encoding/base64".
// If the type was predeclared (string, error) or not defined (*T, struct{},
// []int, or A where A is an alias for a non-defined type), the package path
// will be the empty string.
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 type identity,
// compare the Types directly.
String() string
// Kind returns the specific kind of this type.
Kind() Kind
// Implements reports whether the type implements the interface type u.
Implements(u Type) bool
// AssignableTo reports whether a value of the type is assignable to type u.
AssignableTo(u Type) bool
// ConvertibleTo reports whether a value of the type is convertible to type u.
// Even if ConvertibleTo returns true, the conversion may still panic.
// For example, a slice of type []T is convertible to *[N]T,
// but the conversion will panic if its length is less than N.
ConvertibleTo(u Type) bool
// Comparable reports whether values of this type are comparable.
// Even if Comparable returns true, the comparison may still panic.
// For example, values of interface type are comparable,
// but the comparison will panic if their dynamic type is not comparable.
Comparable() 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
// Pointer: 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 reports whether 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, Pointer, 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.
// If the returned field is promoted from an embedded struct,
// then Offset in the returned StructField is the offset in
// the embedded struct.
FieldByName(name string) (StructField, bool)
// FieldByNameFunc returns the struct field with a name
// that satisfies the match function and a boolean indicating if
// the field was found.
//
// FieldByNameFunc considers the fields in the struct itself
// and then the fields in any embedded structs, in breadth first order,
// stopping at the shallowest nesting depth containing one or more
// fields satisfying the match function. If multiple fields at that depth
// satisfy the match function, they cancel each other
// and FieldByNameFunc returns no match.
// This behavior mirrors Go's handling of name lookup in
// structs containing embedded fields.
//
// If the returned field is promoted from an embedded struct,
// then Offset in the returned StructField is the offset in
// the embedded struct.
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
// OverflowComplex reports whether the complex128 x cannot be represented by type t.
// It panics if t's Kind is not Complex64 or Complex128.
OverflowComplex(x complex128) bool
// OverflowFloat reports whether the float64 x cannot be represented by type t.
// It panics if t's Kind is not Float32 or Float64.
OverflowFloat(x float64) bool
// OverflowInt reports whether the int64 x cannot be represented by type t.
// It panics if t's Kind is not Int, Int8, Int16, Int32, or Int64.
OverflowInt(x int64) bool
// OverflowUint reports whether the uint64 x cannot be represented by type t.
// It panics if t's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
OverflowUint(x uint64) bool
// CanSeq reports whether a [Value] with this type can be iterated over using [Value.Seq].
CanSeq() bool
// CanSeq2 reports whether a [Value] with this type can be iterated over using [Value.Seq2].
CanSeq2() bool
common() *abi.Type
uncommon() *uncommonType
}
// BUG(rsc): FieldByName and related functions consider struct field names to be equal
// if the names are equal, even if they are unexported names originating
// in different packages. The practical effect of this is that the result of
// t.FieldByName("x") is not well defined if the struct type t contains
// multiple fields named x (embedded from different packages).
// FieldByName may return one of the fields named x or may report that there are none.
// See https://golang.org/issue/4876 for more details.
/*
* These data structures are known to the compiler (../cmd/compile/internal/reflectdata/reflect.go).
* A few are known to ../runtime/type.go to convey to debuggers.
* They are also known to ../runtime/type.go.
*/
// 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
Pointer
Slice
String
Struct
UnsafePointer
)
// Ptr is the old name for the [Pointer] kind.
const Ptr = Pointer
// uncommonType is present only for defined types or types with methods
// (if T is a defined type, the uncommonTypes for T and *T have methods).
// Using a pointer to this struct reduces the overall size required
// to describe a non-defined type with no methods.
type uncommonType = abi.UncommonType
// Embed this type to get common/uncommon
type common struct {
abi.Type
}
// rtype is the common implementation of most values.
// It is embedded in other struct types.
type rtype struct {
t abi.Type
}
func (t *rtype) common() *abi.Type {
return &t.t
}
func (t *rtype) uncommon() *abi.UncommonType {
return t.t.Uncommon()
}
type aNameOff = abi.NameOff
type aTypeOff = abi.TypeOff
type aTextOff = abi.TextOff
// ChanDir represents a channel type's direction.
type ChanDir int
const (
RecvDir ChanDir = 1 << iota // <-chan
SendDir // chan<-
BothDir = RecvDir | SendDir // chan
)
// arrayType represents a fixed array type.
type arrayType = abi.ArrayType
// chanType represents a channel type.
type chanType = abi.ChanType
// funcType represents a function type.
//
// A *rtype for each in and out parameter is stored in an array that
// directly follows the funcType (and possibly its uncommonType). So
// a function type with one method, one input, and one output is:
//
// struct {
// funcType
// uncommonType
// [2]*rtype // [0] is in, [1] is out
// }
type funcType = abi.FuncType
// interfaceType represents an interface type.
type interfaceType struct {
abi.InterfaceType // can embed directly because not a public type.
}
func (t *interfaceType) nameOff(off aNameOff) abi.Name {
return toRType(&t.Type).nameOff(off)
}
func nameOffFor(t *abi.Type, off aNameOff) abi.Name {
return toRType(t).nameOff(off)
}
func typeOffFor(t *abi.Type, off aTypeOff) *abi.Type {
return toRType(t).typeOff(off)
}
func (t *interfaceType) typeOff(off aTypeOff) *abi.Type {
return toRType(&t.Type).typeOff(off)
}
func (t *interfaceType) common() *abi.Type {
return &t.Type
}
func (t *interfaceType) uncommon() *abi.UncommonType {
return t.Uncommon()
}
// mapType represents a map type.
type mapType struct {
abi.MapType
}
// ptrType represents a pointer type.
type ptrType struct {
abi.PtrType
}
// sliceType represents a slice type.
type sliceType struct {
abi.SliceType
}
// Struct field
type structField = abi.StructField
// structType represents a struct type.
type structType struct {
abi.StructType
}
func pkgPath(n abi.Name) string {
if n.Bytes == nil || *n.DataChecked(0, "name flag field")&(1<<2) == 0 {
return ""
}
i, l := n.ReadVarint(1)
off := 1 + i + l
if n.HasTag() {
i2, l2 := n.ReadVarint(off)
off += i2 + l2
}
var nameOff int32
// Note that this field may not be aligned in memory,
// so we cannot use a direct int32 assignment here.
copy((*[4]byte)(unsafe.Pointer(&nameOff))[:], (*[4]byte)(unsafe.Pointer(n.DataChecked(off, "name offset field")))[:])
pkgPathName := abi.Name{Bytes: (*byte)(resolveTypeOff(unsafe.Pointer(n.Bytes), nameOff))}
return pkgPathName.Name()
}
func newName(n, tag string, exported, embedded bool) abi.Name {
return abi.NewName(n, tag, exported, embedded)
}
/*
* 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 {
// Name is the method name.
Name string
// PkgPath is the package path that qualifies a lower case (unexported)
// method name. It is empty for upper case (exported) method names.
// The combination of PkgPath and Name uniquely identifies a method
// in a method set.
// See https://golang.org/ref/spec#Uniqueness_of_identifiers
PkgPath string
Type Type // method type
Func Value // func with receiver as first argument
Index int // index for Type.Method
}
// IsExported reports whether the method is exported.
func (m Method) IsExported() bool {
return m.PkgPath == ""
}
// String returns the name of k.
func (k Kind) String() string {
if uint(k) < uint(len(kindNames)) {
return kindNames[uint(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",
Pointer: "ptr",
Slice: "slice",
String: "string",
Struct: "struct",
UnsafePointer: "unsafe.Pointer",
}
// resolveNameOff resolves a name offset from a base pointer.
// The (*rtype).nameOff method is a convenience wrapper for this function.
// Implemented in the runtime package.
//
//go:noescape
func resolveNameOff(ptrInModule unsafe.Pointer, off int32) unsafe.Pointer
// resolveTypeOff resolves an *rtype offset from a base type.
// The (*rtype).typeOff method is a convenience wrapper for this function.
// Implemented in the runtime package.
//
//go:noescape
func resolveTypeOff(rtype unsafe.Pointer, off int32) unsafe.Pointer
// resolveTextOff resolves a function pointer offset from a base type.
// The (*rtype).textOff method is a convenience wrapper for this function.
// Implemented in the runtime package.
//
//go:noescape
func resolveTextOff(rtype unsafe.Pointer, off int32) unsafe.Pointer
// addReflectOff adds a pointer to the reflection lookup map in the runtime.
// It returns a new ID that can be used as a typeOff or textOff, and will
// be resolved correctly. Implemented in the runtime package.
//
//go:noescape
func addReflectOff(ptr unsafe.Pointer) int32
// resolveReflectName adds a name to the reflection lookup map in the runtime.
// It returns a new nameOff that can be used to refer to the pointer.
func resolveReflectName(n abi.Name) aNameOff {
return aNameOff(addReflectOff(unsafe.Pointer(n.Bytes)))
}
// resolveReflectType adds a *rtype to the reflection lookup map in the runtime.
// It returns a new typeOff that can be used to refer to the pointer.
func resolveReflectType(t *abi.Type) aTypeOff {
return aTypeOff(addReflectOff(unsafe.Pointer(t)))
}
// resolveReflectText adds a function pointer to the reflection lookup map in
// the runtime. It returns a new textOff that can be used to refer to the
// pointer.
func resolveReflectText(ptr unsafe.Pointer) aTextOff {
return aTextOff(addReflectOff(ptr))
}
func (t *rtype) nameOff(off aNameOff) abi.Name {
return abi.Name{Bytes: (*byte)(resolveNameOff(unsafe.Pointer(t), int32(off)))}
}
func (t *rtype) typeOff(off aTypeOff) *abi.Type {
return (*abi.Type)(resolveTypeOff(unsafe.Pointer(t), int32(off)))
}
func (t *rtype) textOff(off aTextOff) unsafe.Pointer {
return resolveTextOff(unsafe.Pointer(t), int32(off))
}
func textOffFor(t *abi.Type, off aTextOff) unsafe.Pointer {
return toRType(t).textOff(off)
}
func (t *rtype) String() string {
s := t.nameOff(t.t.Str).Name()
if t.t.TFlag&abi.TFlagExtraStar != 0 {
return s[1:]
}
return s
}
func (t *rtype) Size() uintptr { return t.t.Size() }
func (t *rtype) 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.t.Size_) * 8
}
func (t *rtype) Align() int { return t.t.Align() }
func (t *rtype) FieldAlign() int { return t.t.FieldAlign() }
func (t *rtype) Kind() Kind { return Kind(t.t.Kind()) }
func (t *rtype) exportedMethods() []abi.Method {
ut := t.uncommon()
if ut == nil {
return nil
}
return ut.ExportedMethods()
}
func (t *rtype) NumMethod() int {
if t.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(t))
return tt.NumMethod()
}
return len(t.exportedMethods())
}
func (t *rtype) Method(i int) (m Method) {
if t.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(t))
return tt.Method(i)
}
methods := t.exportedMethods()
if i < 0 || i >= len(methods) {
panic("reflect: Method index out of range")
}
p := methods[i]
pname := t.nameOff(p.Name)
m.Name = pname.Name()
fl := flag(Func)
mtyp := t.typeOff(p.Mtyp)
ft := (*funcType)(unsafe.Pointer(mtyp))
in := make([]Type, 0, 1+ft.NumIn())
in = append(in, t)
for _, arg := range ft.InSlice() {
in = append(in, toRType(arg))
}
out := make([]Type, 0, ft.NumOut())
for _, ret := range ft.OutSlice() {
out = append(out, toRType(ret))
}
mt := FuncOf(in, out, ft.IsVariadic())
m.Type = mt
tfn := t.textOff(p.Tfn)
fn := unsafe.Pointer(&tfn)
m.Func = Value{&mt.(*rtype).t, fn, fl}
m.Index = i
return m
}
func (t *rtype) MethodByName(name string) (m Method, ok bool) {
if t.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(t))
return tt.MethodByName(name)
}
ut := t.uncommon()
if ut == nil {
return Method{}, false
}
methods := ut.ExportedMethods()
// We are looking for the first index i where the string becomes >= s.
// This is a copy of sort.Search, with f(h) replaced by (t.nameOff(methods[h].name).name() >= name).
i, j := 0, len(methods)
for i < j {
h := int(uint(i+j) >> 1) // avoid overflow when computing h
// i ≤ h < j
if !(t.nameOff(methods[h].Name).Name() >= name) {
i = h + 1 // preserves f(i-1) == false
} else {
j = h // preserves f(j) == true
}
}
// i == j, f(i-1) == false, and f(j) (= f(i)) == true => answer is i.
if i < len(methods) && name == t.nameOff(methods[i].Name).Name() {
return t.Method(i), true
}
return Method{}, false
}
func (t *rtype) PkgPath() string {
if t.t.TFlag&abi.TFlagNamed == 0 {
return ""
}
ut := t.uncommon()
if ut == nil {
return ""
}
return t.nameOff(ut.PkgPath).Name()
}
func pkgPathFor(t *abi.Type) string {
return toRType(t).PkgPath()
}
func (t *rtype) Name() string {
if !t.t.HasName() {
return ""
}
s := t.String()
i := len(s) - 1
sqBrackets := 0
for i >= 0 && (s[i] != '.' || sqBrackets != 0) {
switch s[i] {
case ']':
sqBrackets++
case '[':
sqBrackets--
}
i--
}
return s[i+1:]
}
func nameFor(t *abi.Type) string {
return toRType(t).Name()
}
func (t *rtype) ChanDir() ChanDir {
if t.Kind() != Chan {
panic("reflect: ChanDir of non-chan type " + t.String())
}
tt := (*abi.ChanType)(unsafe.Pointer(t))
return ChanDir(tt.Dir)
}
func toRType(t *abi.Type) *rtype {
return (*rtype)(unsafe.Pointer(t))
}
func elem(t *abi.Type) *abi.Type {
et := t.Elem()
if et != nil {
return et
}
panic("reflect: Elem of invalid type " + stringFor(t))
}
func (t *rtype) Elem() Type {
return toType(elem(t.common()))
}
func (t *rtype) Field(i int) StructField {
if t.Kind() != Struct {
panic("reflect: Field of non-struct type " + t.String())
}
tt := (*structType)(unsafe.Pointer(t))
return tt.Field(i)
}
func (t *rtype) FieldByIndex(index []int) StructField {
if t.Kind() != Struct {
panic("reflect: FieldByIndex of non-struct type " + t.String())
}
tt := (*structType)(unsafe.Pointer(t))
return tt.FieldByIndex(index)
}
func (t *rtype) FieldByName(name string) (StructField, bool) {
if t.Kind() != Struct {
panic("reflect: FieldByName of non-struct type " + t.String())
}
tt := (*structType)(unsafe.Pointer(t))
return tt.FieldByName(name)
}
func (t *rtype) FieldByNameFunc(match func(string) bool) (StructField, bool) {
if t.Kind() != Struct {
panic("reflect: FieldByNameFunc of non-struct type " + t.String())
}
tt := (*structType)(unsafe.Pointer(t))
return tt.FieldByNameFunc(match)
}
func (t *rtype) Key() Type {
if t.Kind() != Map {
panic("reflect: Key of non-map type " + t.String())
}
tt := (*mapType)(unsafe.Pointer(t))
return toType(tt.Key)
}
func (t *rtype) Len() int {
if t.Kind() != Array {
panic("reflect: Len of non-array type " + t.String())
}
tt := (*arrayType)(unsafe.Pointer(t))
return int(tt.Len)
}
func (t *rtype) NumField() int {
if t.Kind() != Struct {
panic("reflect: NumField of non-struct type " + t.String())
}
tt := (*structType)(unsafe.Pointer(t))
return len(tt.Fields)
}
func (t *rtype) In(i int) Type {
if t.Kind() != Func {
panic("reflect: In of non-func type " + t.String())
}
tt := (*abi.FuncType)(unsafe.Pointer(t))
return toType(tt.InSlice()[i])
}
func (t *rtype) NumIn() int {
if t.Kind() != Func {
panic("reflect: NumIn of non-func type " + t.String())
}
tt := (*abi.FuncType)(unsafe.Pointer(t))
return tt.NumIn()
}
func (t *rtype) NumOut() int {
if t.Kind() != Func {
panic("reflect: NumOut of non-func type " + t.String())
}
tt := (*abi.FuncType)(unsafe.Pointer(t))
return tt.NumOut()
}
func (t *rtype) Out(i int) Type {
if t.Kind() != Func {
panic("reflect: Out of non-func type " + t.String())
}
tt := (*abi.FuncType)(unsafe.Pointer(t))
return toType(tt.OutSlice()[i])
}
func (t *rtype) IsVariadic() bool {
if t.Kind() != Func {
panic("reflect: IsVariadic of non-func type " + t.String())
}
tt := (*abi.FuncType)(unsafe.Pointer(t))
return tt.IsVariadic()
}
func (t *rtype) OverflowComplex(x complex128) bool {
k := t.Kind()
switch k {
case Complex64:
return overflowFloat32(real(x)) || overflowFloat32(imag(x))
case Complex128:
return false
}
panic("reflect: OverflowComplex of non-complex type " + t.String())
}
func (t *rtype) OverflowFloat(x float64) bool {
k := t.Kind()
switch k {
case Float32:
return overflowFloat32(x)
case Float64:
return false
}
panic("reflect: OverflowFloat of non-float type " + t.String())
}
func (t *rtype) OverflowInt(x int64) bool {
k := t.Kind()
switch k {
case Int, Int8, Int16, Int32, Int64:
bitSize := t.Size() * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic("reflect: OverflowInt of non-int type " + t.String())
}
func (t *rtype) OverflowUint(x uint64) bool {
k := t.Kind()
switch k {
case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64:
bitSize := t.Size() * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic("reflect: OverflowUint of non-uint type " + t.String())
}
func (t *rtype) CanSeq() bool {
switch t.Kind() {
case Int8, Int16, Int32, Int64, Int, Uint8, Uint16, Uint32, Uint64, Uint, Uintptr, Array, Slice, Chan, String, Map:
return true
case Func:
return canRangeFunc(&t.t)
case Pointer:
return t.Elem().Kind() == Array
}
return false
}
func canRangeFunc(t *abi.Type) bool {
if t.Kind() != abi.Func {
return false
}
f := t.FuncType()
if f.InCount != 1 || f.OutCount != 0 {
return false
}
y := f.In(0)
if y.Kind() != abi.Func {
return false
}
yield := y.FuncType()
return yield.InCount == 1 && yield.OutCount == 1 && yield.Out(0).Kind() == abi.Bool
}
func (t *rtype) CanSeq2() bool {
switch t.Kind() {
case Array, Slice, String, Map:
return true
case Func:
return canRangeFunc2(&t.t)
case Pointer:
return t.Elem().Kind() == Array
}
return false
}
func canRangeFunc2(t *abi.Type) bool {
if t.Kind() != abi.Func {
return false
}
f := t.FuncType()
if f.InCount != 1 || f.OutCount != 0 {
return false
}
y := f.In(0)
if y.Kind() != abi.Func {
return false
}
yield := y.FuncType()
return yield.InCount == 2 && yield.OutCount == 1 && yield.Out(0).Kind() == abi.Bool
}
// add returns p+x.
//
// The whySafe string is ignored, so that the function still inlines
// as efficiently as p+x, but all call sites should use the string to
// record why the addition is safe, which is to say why the addition
// does not cause x to advance to the very end of p's allocation
// and therefore point incorrectly at the next block in memory.
//
// add should be an internal detail (and is trivially copyable),
// but widely used packages access it using linkname.
// Notable members of the hall of shame include:
// - github.com/vmware/govmomi
//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname add
func add(p unsafe.Pointer, x uintptr, whySafe string) unsafe.Pointer {
return unsafe.Pointer(uintptr(p) + x)
}
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]
pname := t.nameOff(p.Name)
m.Name = pname.Name()
if !pname.IsExported() {
m.PkgPath = pkgPath(pname)
if m.PkgPath == "" {
m.PkgPath = t.PkgPath.Name()
}
}
m.Type = toType(t.typeOff(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 *abi.Imethod
for i := range t.Methods {
p = &t.Methods[i]
if t.nameOff(p.Name).Name() == name {
return t.Method(i), true
}
}
return
}
// A StructField describes a single field in a struct.
type StructField struct {
// Name is the field name.
Name string
// PkgPath is the package path that qualifies a lower case (unexported)
// field name. It is empty for upper case (exported) field names.
// See https://golang.org/ref/spec#Uniqueness_of_identifiers
PkgPath string
Type Type // field type
Tag StructTag // field tag string
Offset uintptr // offset within struct, in bytes
Index []int // index sequence for Type.FieldByIndex
Anonymous bool // is an embedded field
}
// IsExported reports whether the field is exported.
func (f StructField) IsExported() bool {
return f.PkgPath == ""
}
// 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. To determine whether a tag is
// explicitly set to the empty string, use [StructTag.Lookup].
func (tag StructTag) Get(key string) string {
v, _ := tag.Lookup(key)
return v
}
// Lookup returns the value associated with key in the tag string.
// If the key is present in the tag the value (which may be empty)
// is returned. Otherwise the returned value will be the empty string.
// The ok return value reports whether the value was explicitly set in
// the tag string. If the tag does not have the conventional format,
// the value returned by Lookup is unspecified.
func (tag StructTag) Lookup(key string) (value string, ok bool) {
// When modifying this code, also update the validateStructTag code
// in cmd/vet/structtag.go.
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, a quote or a control character is a syntax error.
// Strictly speaking, control chars include the range [0x7f, 0x9f], not just
// [0x00, 0x1f], but in practice, we ignore the multi-byte control characters
// as it is simpler to inspect the tag's bytes than the tag's runes.
i = 0
for i < len(tag) && tag[i] > ' ' && tag[i] != ':' && tag[i] != '"' && tag[i] != 0x7f {
i++
}
if i == 0 || 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, err := strconv.Unquote(qvalue)
if err != nil {
break
}
return value, true
}
}
return "", false
}
// Field returns the i'th struct field.
func (t *structType) Field(i int) (f StructField) {
if i < 0 || i >= len(t.Fields) {
panic("reflect: Field index out of bounds")
}
p := &t.Fields[i]
f.Type = toType(p.Typ)
f.Name = p.Name.Name()
f.Anonymous = p.Embedded()
if !p.Name.IsExported() {
f.PkgPath = t.PkgPath.Name()
}
if tag := p.Name.Tag(); tag != "" {
f.Tag = StructTag(tag)
}
f.Offset = p.Offset
// NOTE(rsc): This is the only allocation in the interface
// presented by a reflect.Type. It would be nice to avoid,
// at least in the common cases, but we need to make sure
// that misbehaving clients of reflect cannot affect other
// uses of reflect. One possibility is CL 5371098, but we
// postponed that ugliness until there is a demonstrated
// need for the performance. This is issue 2320.
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 = toType(&t.Type)
for i, x := range index {
if i > 0 {
ft := f.Type
if ft.Kind() == Pointer && ft.Elem().Kind() == Struct {
ft = ft.Elem()
}
f.Type = ft
}
f = f.Type.Field(x)
}
return
}
// A fieldScan represents an item on the fieldByNameFunc scan work list.
type fieldScan struct {
typ *structType
index []int
}
// 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) (result StructField, ok bool) {
// This uses the same condition that the Go language does: there must be a unique instance
// of the match at a given depth level. If there are multiple instances of a match at the
// same depth, they annihilate each other and inhibit any possible match at a lower level.
// The algorithm is breadth first search, one depth level at a time.
// The current and next slices are work queues:
// current lists the fields to visit on this depth level,
// and next lists the fields on the next lower level.
current := []fieldScan{}
next := []fieldScan{{typ: t}}
// nextCount records the number of times an embedded type has been
// encountered and considered for queueing in the 'next' slice.
// We only queue the first one, but we increment the count on each.
// If a struct type T can be reached more than once at a given depth level,
// then it annihilates itself and need not be considered at all when we
// process that next depth level.
var nextCount map[*structType]int
// visited records the structs that have been considered already.
// Embedded pointer fields can create cycles in the graph of
// reachable embedded types; visited avoids following those cycles.
// It also avoids duplicated effort: if we didn't find the field in an
// embedded type T at level 2, we won't find it in one at level 4 either.
visited := map[*structType]bool{}
for len(next) > 0 {
current, next = next, current[:0]
count := nextCount
nextCount = nil
// Process all the fields at this depth, now listed in 'current'.
// The loop queues embedded fields found in 'next', for processing during the next
// iteration. The multiplicity of the 'current' field counts is recorded
// in 'count'; the multiplicity of the 'next' field counts is recorded in 'nextCount'.
for _, scan := range current {
t := scan.typ
if visited[t] {
// We've looked through this type before, at a higher level.
// That higher level would shadow the lower level we're now at,
// so this one can't be useful to us. Ignore it.
continue
}
visited[t] = true
for i := range t.Fields {
f := &t.Fields[i]
// Find name and (for embedded field) type for field f.
fname := f.Name.Name()
var ntyp *abi.Type
if f.Embedded() {
// Embedded field of type T or *T.
ntyp = f.Typ
if ntyp.Kind() == abi.Pointer {
ntyp = ntyp.Elem()
}
}
// Does it match?
if match(fname) {
// Potential match
if count[t] > 1 || ok {
// Name appeared multiple times at this level: annihilate.
return StructField{}, false
}
result = t.Field(i)
result.Index = nil
result.Index = append(result.Index, scan.index...)
result.Index = append(result.Index, i)
ok = true
continue
}
// Queue embedded struct fields for processing with next level,
// but only if we haven't seen a match yet at this level and only
// if the embedded types haven't already been queued.
if ok || ntyp == nil || ntyp.Kind() != abi.Struct {
continue
}
styp := (*structType)(unsafe.Pointer(ntyp))
if nextCount[styp] > 0 {
nextCount[styp] = 2 // exact multiple doesn't matter
continue
}
if nextCount == nil {
nextCount = map[*structType]int{}
}
nextCount[styp] = 1
if count[t] > 1 {
nextCount[styp] = 2 // exact multiple doesn't matter
}
var index []int
index = append(index, scan.index...)
index = append(index, i)
next = append(next, fieldScan{styp, index})
}
}
if ok {
break
}
}
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) {
// Quick check for top-level name, or struct without embedded fields.
hasEmbeds := false
if name != "" {
for i := range t.Fields {
tf := &t.Fields[i]
if tf.Name.Name() == name {
return t.Field(i), true
}
if tf.Embedded() {
hasEmbeds = true
}
}
}
if !hasEmbeds {
return
}
return t.FieldByNameFunc(func(s string) bool { return s == name })
}
// TypeOf returns the reflection [Type] that represents the dynamic type of i.
// If i is a nil interface value, TypeOf returns nil.
func TypeOf(i any) Type {
return toType(abi.TypeOf(i))
}
// rtypeOf directly extracts the *rtype of the provided value.
func rtypeOf(i any) *abi.Type {
return abi.TypeOf(i)
}
// ptrMap is the cache for PointerTo.
var ptrMap sync.Map // map[*rtype]*ptrType
// PtrTo returns the pointer type with element t.
// For example, if t represents type Foo, PtrTo(t) represents *Foo.
//
// PtrTo is the old spelling of [PointerTo].
// The two functions behave identically.
//
// Deprecated: Superseded by [PointerTo].
func PtrTo(t Type) Type { return PointerTo(t) }
// PointerTo returns the pointer type with element t.
// For example, if t represents type Foo, PointerTo(t) represents *Foo.
func PointerTo(t Type) Type {
return toRType(t.(*rtype).ptrTo())
}
func (t *rtype) ptrTo() *abi.Type {
at := &t.t
if at.PtrToThis != 0 {
return t.typeOff(at.PtrToThis)
}
// Check the cache.
if pi, ok := ptrMap.Load(t); ok {
return &pi.(*ptrType).Type
}
// Look in known types.
s := "*" + t.String()
for _, tt := range typesByString(s) {
p := (*ptrType)(unsafe.Pointer(tt))
if p.Elem != &t.t {
continue
}
pi, _ := ptrMap.LoadOrStore(t, p)
return &pi.(*ptrType).Type
}
// Create a new ptrType starting with the description
// of an *unsafe.Pointer.
var iptr any = (*unsafe.Pointer)(nil)
prototype := *(**ptrType)(unsafe.Pointer(&iptr))
pp := *prototype
pp.Str = resolveReflectName(newName(s, "", false, false))
pp.PtrToThis = 0
// 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 "*".
pp.Hash = fnv1(t.t.Hash, '*')
pp.Elem = at
pi, _ := ptrMap.LoadOrStore(t, &pp)
return &pi.(*ptrType).Type
}
func ptrTo(t *abi.Type) *abi.Type {
return toRType(t).ptrTo()
}
// fnv1 incorporates the list of bytes into the hash x using the FNV-1 hash function.
func fnv1(x uint32, list ...byte) uint32 {
for _, b := range list {
x = x*16777619 ^ uint32(b)
}
return x
}
func (t *rtype) 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.common(), t.common())
}
func (t *rtype) AssignableTo(u Type) bool {
if u == nil {
panic("reflect: nil type passed to Type.AssignableTo")
}
uu := u.common()
return directlyAssignable(uu, t.common()) || implements(uu, t.common())
}
func (t *rtype) ConvertibleTo(u Type) bool {
if u == nil {
panic("reflect: nil type passed to Type.ConvertibleTo")
}
return convertOp(u.common(), t.common()) != nil
}
func (t *rtype) Comparable() bool {
return t.t.Equal != nil
}
// implements reports whether the type V implements the interface type T.
func implements(T, V *abi.Type) bool {
if T.Kind() != abi.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.go.
if V.Kind() == abi.Interface {
v := (*interfaceType)(unsafe.Pointer(V))
i := 0
for j := 0; j < len(v.Methods); j++ {
tm := &t.Methods[i]
tmName := t.nameOff(tm.Name)
vm := &v.Methods[j]
vmName := nameOffFor(V, vm.Name)
if vmName.Name() == tmName.Name() && typeOffFor(V, vm.Typ) == t.typeOff(tm.Typ) {
if !tmName.IsExported() {
tmPkgPath := pkgPath(tmName)
if tmPkgPath == "" {
tmPkgPath = t.PkgPath.Name()
}
vmPkgPath := pkgPath(vmName)
if vmPkgPath == "" {
vmPkgPath = v.PkgPath.Name()
}
if tmPkgPath != vmPkgPath {
continue
}
}
if i++; i >= len(t.Methods) {
return true
}
}
}
return false
}
v := V.Uncommon()
if v == nil {
return false
}
i := 0
vmethods := v.Methods()
for j := 0; j < int(v.Mcount); j++ {
tm := &t.Methods[i]
tmName := t.nameOff(tm.Name)
vm := vmethods[j]
vmName := nameOffFor(V, vm.Name)
if vmName.Name() == tmName.Name() && typeOffFor(V, vm.Mtyp) == t.typeOff(tm.Typ) {
if !tmName.IsExported() {
tmPkgPath := pkgPath(tmName)
if tmPkgPath == "" {
tmPkgPath = t.PkgPath.Name()
}
vmPkgPath := pkgPath(vmName)
if vmPkgPath == "" {
vmPkgPath = nameOffFor(V, v.PkgPath).Name()
}
if tmPkgPath != vmPkgPath {
continue
}
}
if i++; i >= len(t.Methods) {
return true
}
}
}
return false
}
// specialChannelAssignability reports whether a value x of channel type V
// can be directly assigned (using memmove) to another channel type T.
// https://golang.org/doc/go_spec.html#Assignability
// T and V must be both of Chan kind.
func specialChannelAssignability(T, V *abi.Type) bool {
// Special case:
// x is a bidirectional channel value, T is a channel type,
// x's type V and T have identical element types,
// and at least one of V or T is not a defined type.
return V.ChanDir() == abi.BothDir && (nameFor(T) == "" || nameFor(V) == "") && haveIdenticalType(T.Elem(), V.Elem(), true)
}
// directlyAssignable reports whether a value x of type V can be directly
// assigned (using memmove) to a value of type T.
// https://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 *abi.Type) bool {
// x's type V is identical to T?
if T == V {
return true
}
// Otherwise at least one of T and V must not be defined
// and they must have the same kind.
if T.HasName() && V.HasName() || T.Kind() != V.Kind() {
return false
}
if T.Kind() == abi.Chan && specialChannelAssignability(T, V) {
return true
}
// x's type T and V must have identical underlying types.
return haveIdenticalUnderlyingType(T, V, true)
}
func haveIdenticalType(T, V *abi.Type, cmpTags bool) bool {
if cmpTags {
return T == V
}
if nameFor(T) != nameFor(V) || T.Kind() != V.Kind() || pkgPathFor(T) != pkgPathFor(V) {
return false
}
return haveIdenticalUnderlyingType(T, V, false)
}
func haveIdenticalUnderlyingType(T, V *abi.Type, cmpTags bool) bool {
if T == V {
return true
}
kind := Kind(T.Kind())
if kind != Kind(V.Kind()) {
return false
}
// Non-composite types of equal kind have same underlying type
// (the predefined instance of the type).
if Bool <= kind && kind <= Complex128 || kind == String || kind == UnsafePointer {
return true
}
// Composite types.
switch kind {
case Array:
return T.Len() == V.Len() && haveIdenticalType(T.Elem(), V.Elem(), cmpTags)
case Chan:
return V.ChanDir() == T.ChanDir() && haveIdenticalType(T.Elem(), V.Elem(), cmpTags)
case Func:
t := (*funcType)(unsafe.Pointer(T))
v := (*funcType)(unsafe.Pointer(V))
if t.OutCount != v.OutCount || t.InCount != v.InCount {
return false
}
for i := 0; i < t.NumIn(); i++ {
if !haveIdenticalType(t.In(i), v.In(i), cmpTags) {
return false
}
}
for i := 0; i < t.NumOut(); i++ {
if !haveIdenticalType(t.Out(i), v.Out(i), cmpTags) {
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 haveIdenticalType(T.Key(), V.Key(), cmpTags) && haveIdenticalType(T.Elem(), V.Elem(), cmpTags)
case Pointer, Slice:
return haveIdenticalType(T.Elem(), V.Elem(), cmpTags)
case Struct:
t := (*structType)(unsafe.Pointer(T))
v := (*structType)(unsafe.Pointer(V))
if len(t.Fields) != len(v.Fields) {
return false
}
if t.PkgPath.Name() != v.PkgPath.Name() {
return false
}
for i := range t.Fields {
tf := &t.Fields[i]
vf := &v.Fields[i]
if tf.Name.Name() != vf.Name.Name() {
return false
}
if !haveIdenticalType(tf.Typ, vf.Typ, cmpTags) {
return false
}
if cmpTags && tf.Name.Tag() != vf.Name.Tag() {
return false
}
if tf.Offset != vf.Offset {
return false
}
if tf.Embedded() != vf.Embedded() {
return false
}
}
return true
}
return false
}
// typelinks is implemented in package runtime.
// It returns a slice of the sections in each module,
// and a slice of *rtype offsets in each module.
//
// The types in each module are sorted by string. That is, the first
// two linked types of the first module are:
//
// d0 := sections[0]
// t1 := (*rtype)(add(d0, offset[0][0]))
// t2 := (*rtype)(add(d0, offset[0][1]))
//
// and
//
// t1.String() < t2.String()
//
// Note that strings are not unique identifiers for types:
// there can be more than one with a given string.
// Only types we might want to look up are included:
// pointers, channels, maps, slices, and arrays.
func typelinks() (sections []unsafe.Pointer, offset [][]int32)
// rtypeOff should be an internal detail,
// but widely used packages access it using linkname.
// Notable members of the hall of shame include:
// - github.com/goccy/go-json
//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname rtypeOff
func rtypeOff(section unsafe.Pointer, off int32) *abi.Type {
return (*abi.Type)(add(section, uintptr(off), "sizeof(rtype) > 0"))
}
// typesByString returns the subslice of typelinks() whose elements have
// the given string representation.
// It may be empty (no known types with that string) or may have
// multiple elements (multiple types with that string).
//
// typesByString should be an internal detail,
// but widely used packages access it using linkname.
// Notable members of the hall of shame include:
// - github.com/aristanetworks/goarista
//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname typesByString
func typesByString(s string) []*abi.Type {
sections, offset := typelinks()
var ret []*abi.Type
for offsI, offs := range offset {
section := sections[offsI]
// We are looking for the first index i where the string becomes >= s.
// This is a copy of sort.Search, with f(h) replaced by (*typ[h].String() >= s).
i, j := 0, len(offs)
for i < j {
h := int(uint(i+j) >> 1) // avoid overflow when computing h
// i ≤ h < j
if !(stringFor(rtypeOff(section, offs[h])) >= s) {
i = h + 1 // preserves f(i-1) == false
} else {
j = h // preserves f(j) == true
}
}
// i == j, f(i-1) == false, and f(j) (= f(i)) == true => answer is i.
// Having found the first, linear scan forward to find the last.
// We could do a second binary search, but the caller is going
// to do a linear scan anyway.
for j := i; j < len(offs); j++ {
typ := rtypeOff(section, offs[j])
if stringFor(typ) != s {
break
}
ret = append(ret, typ)
}
}
return ret
}
// The lookupCache caches ArrayOf, ChanOf, MapOf and SliceOf lookups.
var lookupCache sync.Map // map[cacheKey]*rtype
// A cacheKey is the key for use in the lookupCache.
// Four values describe any of the types we are looking for:
// type kind, one or two subtypes, and an extra integer.
type cacheKey struct {
kind Kind
t1 *abi.Type
t2 *abi.Type
extra uintptr
}
// The funcLookupCache caches FuncOf lookups.
// FuncOf does not share the common lookupCache since cacheKey is not
// sufficient to represent functions unambiguously.
var funcLookupCache struct {
sync.Mutex // Guards stores (but not loads) on m.
// m is a map[uint32][]*rtype keyed by the hash calculated in FuncOf.
// Elements of m are append-only and thus safe for concurrent reading.
m sync.Map
}
// ChanOf returns the channel type with the given direction and element type.
// For example, if t represents int, ChanOf(RecvDir, t) represents <-chan int.
//
// The gc runtime imposes a limit of 64 kB on channel element types.
// If t's size is equal to or exceeds this limit, ChanOf panics.
func ChanOf(dir ChanDir, t Type) Type {
typ := t.common()
// Look in cache.
ckey := cacheKey{Chan, typ, nil, uintptr(dir)}
if ch, ok := lookupCache.Load(ckey); ok {
return ch.(*rtype)
}
// This restriction is imposed by the gc compiler and the runtime.
if typ.Size_ >= 1<<16 {
panic("reflect.ChanOf: element size too large")
}
// Look in known types.
var s string
switch dir {
default:
panic("reflect.ChanOf: invalid dir")
case SendDir:
s = "chan<- " + stringFor(typ)
case RecvDir:
s = "<-chan " + stringFor(typ)
case BothDir:
typeStr := stringFor(typ)
if typeStr[0] == '<' {
// typ is recv chan, need parentheses as "<-" associates with leftmost
// chan possible, see:
// * https://golang.org/ref/spec#Channel_types
// * https://github.com/golang/go/issues/39897
s = "chan (" + typeStr + ")"
} else {
s = "chan " + typeStr
}
}
for _, tt := range typesByString(s) {
ch := (*chanType)(unsafe.Pointer(tt))
if ch.Elem == typ && ch.Dir == abi.ChanDir(dir) {
ti, _ := lookupCache.LoadOrStore(ckey, toRType(tt))
return ti.(Type)
}
}
// Make a channel type.
var ichan any = (chan unsafe.Pointer)(nil)
prototype := *(**chanType)(unsafe.Pointer(&ichan))
ch := *prototype
ch.TFlag = abi.TFlagRegularMemory
ch.Dir = abi.ChanDir(dir)
ch.Str = resolveReflectName(newName(s, "", false, false))
ch.Hash = fnv1(typ.Hash, 'c', byte(dir))
ch.Elem = typ
ti, _ := lookupCache.LoadOrStore(ckey, toRType(&ch.Type))
return ti.(Type)
}
// MapOf returns the map type with the given key and element types.
// For example, if k represents int and e represents string,
// MapOf(k, e) represents map[int]string.
//
// If the key type is not a valid map key type (that is, if it does
// not implement Go's == operator), MapOf panics.
func MapOf(key, elem Type) Type {
ktyp := key.common()
etyp := elem.common()
if ktyp.Equal == nil {
panic("reflect.MapOf: invalid key type " + stringFor(ktyp))
}
// Look in cache.
ckey := cacheKey{Map, ktyp, etyp, 0}
if mt, ok := lookupCache.Load(ckey); ok {
return mt.(Type)
}
// Look in known types.
s := "map[" + stringFor(ktyp) + "]" + stringFor(etyp)
for _, tt := range typesByString(s) {
mt := (*mapType)(unsafe.Pointer(tt))
if mt.Key == ktyp && mt.Elem == etyp {
ti, _ := lookupCache.LoadOrStore(ckey, toRType(tt))
return ti.(Type)
}
}
// Make a map type.
// Note: flag values must match those used in the TMAP case
// in ../cmd/compile/internal/reflectdata/reflect.go:writeType.
var imap any = (map[unsafe.Pointer]unsafe.Pointer)(nil)
mt := **(**mapType)(unsafe.Pointer(&imap))
mt.Str = resolveReflectName(newName(s, "", false, false))
mt.TFlag = 0
mt.Hash = fnv1(etyp.Hash, 'm', byte(ktyp.Hash>>24), byte(ktyp.Hash>>16), byte(ktyp.Hash>>8), byte(ktyp.Hash))
mt.Key = ktyp
mt.Elem = etyp
mt.Bucket = bucketOf(ktyp, etyp)
mt.Hasher = func(p unsafe.Pointer, seed uintptr) uintptr {
return typehash(ktyp, p, seed)
}
mt.Flags = 0
if ktyp.Size_ > abi.MapMaxKeyBytes {
mt.KeySize = uint8(goarch.PtrSize)
mt.Flags |= 1 // indirect key
} else {
mt.KeySize = uint8(ktyp.Size_)
}
if etyp.Size_ > abi.MapMaxElemBytes {
mt.ValueSize = uint8(goarch.PtrSize)
mt.Flags |= 2 // indirect value
} else {
mt.MapType.ValueSize = uint8(etyp.Size_)
}
mt.MapType.BucketSize = uint16(mt.Bucket.Size_)
if isReflexive(ktyp) {
mt.Flags |= 4
}
if needKeyUpdate(ktyp) {
mt.Flags |= 8
}
if hashMightPanic(ktyp) {
mt.Flags |= 16
}
mt.PtrToThis = 0
ti, _ := lookupCache.LoadOrStore(ckey, toRType(&mt.Type))
return ti.(Type)
}
var funcTypes []Type
var funcTypesMutex sync.Mutex
func initFuncTypes(n int) Type {
funcTypesMutex.Lock()
defer funcTypesMutex.Unlock()
if n >= len(funcTypes) {
newFuncTypes := make([]Type, n+1)
copy(newFuncTypes, funcTypes)
funcTypes = newFuncTypes
}
if funcTypes[n] != nil {
return funcTypes[n]
}
funcTypes[n] = StructOf([]StructField{
{
Name: "FuncType",
Type: TypeOf(funcType{}),
},
{
Name: "Args",
Type: ArrayOf(n, TypeOf(&rtype{})),
},
})
return funcTypes[n]
}
// FuncOf returns the function type with the given argument and result types.
// For example if k represents int and e represents string,
// FuncOf([]Type{k}, []Type{e}, false) represents func(int) string.
//
// The variadic argument controls whether the function is variadic. FuncOf
// panics if the in[len(in)-1] does not represent a slice and variadic is
// true.
func FuncOf(in, out []Type, variadic bool) Type {
if variadic && (len(in) == 0 || in[len(in)-1].Kind() != Slice) {
panic("reflect.FuncOf: last arg of variadic func must be slice")
}
// Make a func type.
var ifunc any = (func())(nil)
prototype := *(**funcType)(unsafe.Pointer(&ifunc))
n := len(in) + len(out)
if n > 128 {
panic("reflect.FuncOf: too many arguments")
}
o := New(initFuncTypes(n)).Elem()
ft := (*funcType)(unsafe.Pointer(o.Field(0).Addr().Pointer()))
args := unsafe.Slice((**rtype)(unsafe.Pointer(o.Field(1).Addr().Pointer())), n)[0:0:n]
*ft = *prototype
// Build a hash and minimally populate ft.
var hash uint32
for _, in := range in {
t := in.(*rtype)
args = append(args, t)
hash = fnv1(hash, byte(t.t.Hash>>24), byte(t.t.Hash>>16), byte(t.t.Hash>>8), byte(t.t.Hash))
}
if variadic {
hash = fnv1(hash, 'v')
}
hash = fnv1(hash, '.')
for _, out := range out {
t := out.(*rtype)
args = append(args, t)
hash = fnv1(hash, byte(t.t.Hash>>24), byte(t.t.Hash>>16), byte(t.t.Hash>>8), byte(t.t.Hash))
}
ft.TFlag = 0
ft.Hash = hash
ft.InCount = uint16(len(in))
ft.OutCount = uint16(len(out))
if variadic {
ft.OutCount |= 1 << 15
}
// Look in cache.
if ts, ok := funcLookupCache.m.Load(hash); ok {
for _, t := range ts.([]*abi.Type) {
if haveIdenticalUnderlyingType(&ft.Type, t, true) {
return toRType(t)
}
}
}
// Not in cache, lock and retry.
funcLookupCache.Lock()
defer funcLookupCache.Unlock()
if ts, ok := funcLookupCache.m.Load(hash); ok {
for _, t := range ts.([]*abi.Type) {
if haveIdenticalUnderlyingType(&ft.Type, t, true) {
return toRType(t)
}
}
}
addToCache := func(tt *abi.Type) Type {
var rts []*abi.Type
if rti, ok := funcLookupCache.m.Load(hash); ok {
rts = rti.([]*abi.Type)
}
funcLookupCache.m.Store(hash, append(rts, tt))
return toType(tt)
}
// Look in known types for the same string representation.
str := funcStr(ft)
for _, tt := range typesByString(str) {
if haveIdenticalUnderlyingType(&ft.Type, tt, true) {
return addToCache(tt)
}
}
// Populate the remaining fields of ft and store in cache.
ft.Str = resolveReflectName(newName(str, "", false, false))
ft.PtrToThis = 0
return addToCache(&ft.Type)
}
func stringFor(t *abi.Type) string {
return toRType(t).String()
}
// funcStr builds a string representation of a funcType.
func funcStr(ft *funcType) string {
repr := make([]byte, 0, 64)
repr = append(repr, "func("...)
for i, t := range ft.InSlice() {
if i > 0 {
repr = append(repr, ", "...)
}
if ft.IsVariadic() && i == int(ft.InCount)-1 {
repr = append(repr, "..."...)
repr = append(repr, stringFor((*sliceType)(unsafe.Pointer(t)).Elem)...)
} else {
repr = append(repr, stringFor(t)...)
}
}
repr = append(repr, ')')
out := ft.OutSlice()
if len(out) == 1 {
repr = append(repr, ' ')
} else if len(out) > 1 {
repr = append(repr, " ("...)
}
for i, t := range out {
if i > 0 {
repr = append(repr, ", "...)
}
repr = append(repr, stringFor(t)...)
}
if len(out) > 1 {
repr = append(repr, ')')
}
return string(repr)
}
// isReflexive reports whether the == operation on the type is reflexive.
// That is, x == x for all values x of type t.
func isReflexive(t *abi.Type) bool {
switch Kind(t.Kind()) {
case Bool, Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr, Chan, Pointer, String, UnsafePointer:
return true
case Float32, Float64, Complex64, Complex128, Interface:
return false
case Array:
tt := (*arrayType)(unsafe.Pointer(t))
return isReflexive(tt.Elem)
case Struct:
tt := (*structType)(unsafe.Pointer(t))
for _, f := range tt.Fields {
if !isReflexive(f.Typ) {
return false
}
}
return true
default:
// Func, Map, Slice, Invalid
panic("isReflexive called on non-key type " + stringFor(t))
}
}
// needKeyUpdate reports whether map overwrites require the key to be copied.
func needKeyUpdate(t *abi.Type) bool {
switch Kind(t.Kind()) {
case Bool, Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr, Chan, Pointer, UnsafePointer:
return false
case Float32, Float64, Complex64, Complex128, Interface, String:
// Float keys can be updated from +0 to -0.
// String keys can be updated to use a smaller backing store.
// Interfaces might have floats or strings in them.
return true
case Array:
tt := (*arrayType)(unsafe.Pointer(t))
return needKeyUpdate(tt.Elem)
case Struct:
tt := (*structType)(unsafe.Pointer(t))
for _, f := range tt.Fields {
if needKeyUpdate(f.Typ) {
return true
}
}
return false
default:
// Func, Map, Slice, Invalid
panic("needKeyUpdate called on non-key type " + stringFor(t))
}
}
// hashMightPanic reports whether the hash of a map key of type t might panic.
func hashMightPanic(t *abi.Type) bool {
switch Kind(t.Kind()) {
case Interface:
return true
case Array:
tt := (*arrayType)(unsafe.Pointer(t))
return hashMightPanic(tt.Elem)
case Struct:
tt := (*structType)(unsafe.Pointer(t))
for _, f := range tt.Fields {
if hashMightPanic(f.Typ) {
return true
}
}
return false
default:
return false
}
}
func bucketOf(ktyp, etyp *abi.Type) *abi.Type {
if ktyp.Size_ > abi.MapMaxKeyBytes {
ktyp = ptrTo(ktyp)
}
if etyp.Size_ > abi.MapMaxElemBytes {
etyp = ptrTo(etyp)
}
// Prepare GC data if any.
// A bucket is at most bucketSize*(1+maxKeySize+maxValSize)+ptrSize bytes,
// or 2064 bytes, or 258 pointer-size words, or 33 bytes of pointer bitmap.
// Note that since the key and value are known to be <= 128 bytes,
// they're guaranteed to have bitmaps instead of GC programs.
var gcdata *byte
var ptrdata uintptr
size := abi.MapBucketCount*(1+ktyp.Size_+etyp.Size_) + goarch.PtrSize
if size&uintptr(ktyp.Align_-1) != 0 || size&uintptr(etyp.Align_-1) != 0 {
panic("reflect: bad size computation in MapOf")
}
if ktyp.Pointers() || etyp.Pointers() {
nptr := (abi.MapBucketCount*(1+ktyp.Size_+etyp.Size_) + goarch.PtrSize) / goarch.PtrSize
n := (nptr + 7) / 8
// Runtime needs pointer masks to be a multiple of uintptr in size.
n = (n + goarch.PtrSize - 1) &^ (goarch.PtrSize - 1)
mask := make([]byte, n)
base := uintptr(abi.MapBucketCount / goarch.PtrSize)
if ktyp.Pointers() {
emitGCMask(mask, base, ktyp, abi.MapBucketCount)
}
base += abi.MapBucketCount * ktyp.Size_ / goarch.PtrSize
if etyp.Pointers() {
emitGCMask(mask, base, etyp, abi.MapBucketCount)
}
base += abi.MapBucketCount * etyp.Size_ / goarch.PtrSize
word := base
mask[word/8] |= 1 << (word % 8)
gcdata = &mask[0]
ptrdata = (word + 1) * goarch.PtrSize
// overflow word must be last
if ptrdata != size {
panic("reflect: bad layout computation in MapOf")
}
}
b := &abi.Type{
Align_: goarch.PtrSize,
Size_: size,
Kind_: abi.Struct,
PtrBytes: ptrdata,
GCData: gcdata,
}
s := "bucket(" + stringFor(ktyp) + "," + stringFor(etyp) + ")"
b.Str = resolveReflectName(newName(s, "", false, false))
return b
}
func (t *rtype) gcSlice(begin, end uintptr) []byte {
return (*[1 << 30]byte)(unsafe.Pointer(t.t.GCData))[begin:end:end]
}
// emitGCMask writes the GC mask for [n]typ into out, starting at bit
// offset base.
func emitGCMask(out []byte, base uintptr, typ *abi.Type, n uintptr) {
if typ.Kind_&abi.KindGCProg != 0 {
panic("reflect: unexpected GC program")
}
ptrs := typ.PtrBytes / goarch.PtrSize
words := typ.Size_ / goarch.PtrSize
mask := typ.GcSlice(0, (ptrs+7)/8)
for j := uintptr(0); j < ptrs; j++ {
if (mask[j/8]>>(j%8))&1 != 0 {
for i := uintptr(0); i < n; i++ {
k := base + i*words + j
out[k/8] |= 1 << (k % 8)
}
}
}
}
// appendGCProg appends the GC program for the first ptrdata bytes of
// typ to dst and returns the extended slice.
func appendGCProg(dst []byte, typ *abi.Type) []byte {
if typ.Kind_&abi.KindGCProg != 0 {
// Element has GC program; emit one element.
n := uintptr(*(*uint32)(unsafe.Pointer(typ.GCData)))
prog := typ.GcSlice(4, 4+n-1)
return append(dst, prog...)
}
// Element is small with pointer mask; use as literal bits.
ptrs := typ.PtrBytes / goarch.PtrSize
mask := typ.GcSlice(0, (ptrs+7)/8)
// Emit 120-bit chunks of full bytes (max is 127 but we avoid using partial bytes).
for ; ptrs > 120; ptrs -= 120 {
dst = append(dst, 120)
dst = append(dst, mask[:15]...)
mask = mask[15:]
}
dst = append(dst, byte(ptrs))
dst = append(dst, mask...)
return dst
}
// SliceOf returns the slice type with element type t.
// For example, if t represents int, SliceOf(t) represents []int.
func SliceOf(t Type) Type {
typ := t.common()
// Look in cache.
ckey := cacheKey{Slice, typ, nil, 0}
if slice, ok := lookupCache.Load(ckey); ok {
return slice.(Type)
}
// Look in known types.
s := "[]" + stringFor(typ)
for _, tt := range typesByString(s) {
slice := (*sliceType)(unsafe.Pointer(tt))
if slice.Elem == typ {
ti, _ := lookupCache.LoadOrStore(ckey, toRType(tt))
return ti.(Type)
}
}
// Make a slice type.
var islice any = ([]unsafe.Pointer)(nil)
prototype := *(**sliceType)(unsafe.Pointer(&islice))
slice := *prototype
slice.TFlag = 0
slice.Str = resolveReflectName(newName(s, "", false, false))
slice.Hash = fnv1(typ.Hash, '[')
slice.Elem = typ
slice.PtrToThis = 0
ti, _ := lookupCache.LoadOrStore(ckey, toRType(&slice.Type))
return ti.(Type)
}
// The structLookupCache caches StructOf lookups.
// StructOf does not share the common lookupCache since we need to pin
// the memory associated with *structTypeFixedN.
var structLookupCache struct {
sync.Mutex // Guards stores (but not loads) on m.
// m is a map[uint32][]Type keyed by the hash calculated in StructOf.
// Elements in m are append-only and thus safe for concurrent reading.
m sync.Map
}
type structTypeUncommon struct {
structType
u uncommonType
}
// isLetter reports whether a given 'rune' is classified as a Letter.
func isLetter(ch rune) bool {
return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch >= utf8.RuneSelf && unicode.IsLetter(ch)
}
// isValidFieldName checks if a string is a valid (struct) field name or not.
//
// According to the language spec, a field name should be an identifier.
//
// identifier = letter { letter | unicode_digit } .
// letter = unicode_letter | "_" .
func isValidFieldName(fieldName string) bool {
for i, c := range fieldName {
if i == 0 && !isLetter(c) {
return false
}
if !(isLetter(c) || unicode.IsDigit(c)) {
return false
}
}
return len(fieldName) > 0
}
// This must match cmd/compile/internal/compare.IsRegularMemory
func isRegularMemory(t Type) bool {
switch t.Kind() {
case Array:
elem := t.Elem()
if isRegularMemory(elem) {
return true
}
return elem.Comparable() && t.Len() == 0
case Int8, Int16, Int32, Int64, Int, Uint8, Uint16, Uint32, Uint64, Uint, Uintptr, Chan, Pointer, Bool, UnsafePointer:
return true
case Struct:
num := t.NumField()
switch num {
case 0:
return true
case 1:
field := t.Field(0)
if field.Name == "_" {
return false
}
return isRegularMemory(field.Type)
default:
for i := range num {
field := t.Field(i)
if field.Name == "_" || !isRegularMemory(field.Type) || isPaddedField(t, i) {
return false
}
}
return true
}
}
return false
}
// isPaddedField reports whether the i'th field of struct type t is followed
// by padding.
func isPaddedField(t Type, i int) bool {
field := t.Field(i)
if i+1 < t.NumField() {
return field.Offset+field.Type.Size() != t.Field(i+1).Offset
}
return field.Offset+field.Type.Size() != t.Size()
}
// StructOf returns the struct type containing fields.
// The Offset and Index fields are ignored and computed as they would be
// by the compiler.
//
// StructOf currently does not support promoted methods of embedded fields
// and panics if passed unexported StructFields.
func StructOf(fields []StructField) Type {
var (
hash = fnv1(0, []byte("struct {")...)
size uintptr
typalign uint8
comparable = true
methods []abi.Method
fs = make([]structField, len(fields))
repr = make([]byte, 0, 64)
fset = map[string]struct{}{} // fields' names
hasGCProg = false // records whether a struct-field type has a GCProg
)
lastzero := uintptr(0)
repr = append(repr, "struct {"...)
pkgpath := ""
for i, field := range fields {
if field.Name == "" {
panic("reflect.StructOf: field " + strconv.Itoa(i) + " has no name")
}
if !isValidFieldName(field.Name) {
panic("reflect.StructOf: field " + strconv.Itoa(i) + " has invalid name")
}
if field.Type == nil {
panic("reflect.StructOf: field " + strconv.Itoa(i) + " has no type")
}
f, fpkgpath := runtimeStructField(field)
ft := f.Typ
if ft.Kind_&abi.KindGCProg != 0 {
hasGCProg = true
}
if fpkgpath != "" {
if pkgpath == "" {
pkgpath = fpkgpath
} else if pkgpath != fpkgpath {
panic("reflect.Struct: fields with different PkgPath " + pkgpath + " and " + fpkgpath)
}
}
// Update string and hash
name := f.Name.Name()
hash = fnv1(hash, []byte(name)...)
if !f.Embedded() {
repr = append(repr, (" " + name)...)
} else {
// Embedded field
if f.Typ.Kind() == abi.Pointer {
// Embedded ** and *interface{} are illegal
elem := ft.Elem()
if k := elem.Kind(); k == abi.Pointer || k == abi.Interface {
panic("reflect.StructOf: illegal embedded field type " + stringFor(ft))
}
}
switch Kind(f.Typ.Kind()) {
case Interface:
ift := (*interfaceType)(unsafe.Pointer(ft))
for _, m := range ift.Methods {
if pkgPath(ift.nameOff(m.Name)) != "" {
// TODO(sbinet). Issue 15924.
panic("reflect: embedded interface with unexported method(s) not implemented")
}
fnStub := resolveReflectText(unsafe.Pointer(abi.FuncPCABIInternal(embeddedIfaceMethStub)))
methods = append(methods, abi.Method{
Name: resolveReflectName(ift.nameOff(m.Name)),
Mtyp: resolveReflectType(ift.typeOff(m.Typ)),
Ifn: fnStub,
Tfn: fnStub,
})
}
case Pointer:
ptr := (*ptrType)(unsafe.Pointer(ft))
if unt := ptr.Uncommon(); unt != nil {
if i > 0 && unt.Mcount > 0 {
// Issue 15924.
panic("reflect: embedded type with methods not implemented if type is not first field")
}
if len(fields) > 1 {
panic("reflect: embedded type with methods not implemented if there is more than one field")
}
for _, m := range unt.Methods() {
mname := nameOffFor(ft, m.Name)
if pkgPath(mname) != "" {
// TODO(sbinet).
// Issue 15924.
panic("reflect: embedded interface with unexported method(s) not implemented")
}
methods = append(methods, abi.Method{
Name: resolveReflectName(mname),
Mtyp: resolveReflectType(typeOffFor(ft, m.Mtyp)),
Ifn: resolveReflectText(textOffFor(ft, m.Ifn)),
Tfn: resolveReflectText(textOffFor(ft, m.Tfn)),
})
}
}
if unt := ptr.Elem.Uncommon(); unt != nil {
for _, m := range unt.Methods() {
mname := nameOffFor(ft, m.Name)
if pkgPath(mname) != "" {
// TODO(sbinet)
// Issue 15924.
panic("reflect: embedded interface with unexported method(s) not implemented")
}
methods = append(methods, abi.Method{
Name: resolveReflectName(mname),
Mtyp: resolveReflectType(typeOffFor(ptr.Elem, m.Mtyp)),
Ifn: resolveReflectText(textOffFor(ptr.Elem, m.Ifn)),
Tfn: resolveReflectText(textOffFor(ptr.Elem, m.Tfn)),
})
}
}
default:
if unt := ft.Uncommon(); unt != nil {
if i > 0 && unt.Mcount > 0 {
// Issue 15924.
panic("reflect: embedded type with methods not implemented if type is not first field")
}
if len(fields) > 1 && ft.Kind_&abi.KindDirectIface != 0 {
panic("reflect: embedded type with methods not implemented for non-pointer type")
}
for _, m := range unt.Methods() {
mname := nameOffFor(ft, m.Name)
if pkgPath(mname) != "" {
// TODO(sbinet)
// Issue 15924.
panic("reflect: embedded interface with unexported method(s) not implemented")
}
methods = append(methods, abi.Method{
Name: resolveReflectName(mname),
Mtyp: resolveReflectType(typeOffFor(ft, m.Mtyp)),
Ifn: resolveReflectText(textOffFor(ft, m.Ifn)),
Tfn: resolveReflectText(textOffFor(ft, m.Tfn)),
})
}
}
}
}
if _, dup := fset[name]; dup && name != "_" {
panic("reflect.StructOf: duplicate field " + name)
}
fset[name] = struct{}{}
hash = fnv1(hash, byte(ft.Hash>>24), byte(ft.Hash>>16), byte(ft.Hash>>8), byte(ft.Hash))
repr = append(repr, (" " + stringFor(ft))...)
if f.Name.HasTag() {
hash = fnv1(hash, []byte(f.Name.Tag())...)
repr = append(repr, (" " + strconv.Quote(f.Name.Tag()))...)
}
if i < len(fields)-1 {
repr = append(repr, ';')
}
comparable = comparable && (ft.Equal != nil)
offset := align(size, uintptr(ft.Align_))
if offset < size {
panic("reflect.StructOf: struct size would exceed virtual address space")
}
if ft.Align_ > typalign {
typalign = ft.Align_
}
size = offset + ft.Size_
if size < offset {
panic("reflect.StructOf: struct size would exceed virtual address space")
}
f.Offset = offset
if ft.Size_ == 0 {
lastzero = size
}
fs[i] = f
}
if size > 0 && lastzero == size {
// This is a non-zero sized struct that ends in a
// zero-sized field. We add an extra byte of padding,
// to ensure that taking the address of the final
// zero-sized field can't manufacture a pointer to the
// next object in the heap. See issue 9401.
size++
if size == 0 {
panic("reflect.StructOf: struct size would exceed virtual address space")
}
}
var typ *structType
var ut *uncommonType
if len(methods) == 0 {
t := new(structTypeUncommon)
typ = &t.structType
ut = &t.u
} else {
// A *rtype representing a struct is followed directly in memory by an
// array of method objects representing the methods attached to the
// struct. To get the same layout for a run time generated type, we
// need an array directly following the uncommonType memory.
// A similar strategy is used for funcTypeFixed4, ...funcTypeFixedN.
tt := New(StructOf([]StructField{
{Name: "S", Type: TypeOf(structType{})},
{Name: "U", Type: TypeOf(uncommonType{})},
{Name: "M", Type: ArrayOf(len(methods), TypeOf(methods[0]))},
}))
typ = (*structType)(tt.Elem().Field(0).Addr().UnsafePointer())
ut = (*uncommonType)(tt.Elem().Field(1).Addr().UnsafePointer())
copy(tt.Elem().Field(2).Slice(0, len(methods)).Interface().([]abi.Method), methods)
}
// TODO(sbinet): Once we allow embedding multiple types,
// methods will need to be sorted like the compiler does.
// TODO(sbinet): Once we allow non-exported methods, we will
// need to compute xcount as the number of exported methods.
ut.Mcount = uint16(len(methods))
ut.Xcount = ut.Mcount
ut.Moff = uint32(unsafe.Sizeof(uncommonType{}))
if len(fs) > 0 {
repr = append(repr, ' ')
}
repr = append(repr, '}')
hash = fnv1(hash, '}')
str := string(repr)
// Round the size up to be a multiple of the alignment.
s := align(size, uintptr(typalign))
if s < size {
panic("reflect.StructOf: struct size would exceed virtual address space")
}
size = s
// Make the struct type.
var istruct any = struct{}{}
prototype := *(**structType)(unsafe.Pointer(&istruct))
*typ = *prototype
typ.Fields = fs
if pkgpath != "" {
typ.PkgPath = newName(pkgpath, "", false, false)
}
// Look in cache.
if ts, ok := structLookupCache.m.Load(hash); ok {
for _, st := range ts.([]Type) {
t := st.common()
if haveIdenticalUnderlyingType(&typ.Type, t, true) {
return toType(t)
}
}
}
// Not in cache, lock and retry.
structLookupCache.Lock()
defer structLookupCache.Unlock()
if ts, ok := structLookupCache.m.Load(hash); ok {
for _, st := range ts.([]Type) {
t := st.common()
if haveIdenticalUnderlyingType(&typ.Type, t, true) {
return toType(t)
}
}
}
addToCache := func(t Type) Type {
var ts []Type
if ti, ok := structLookupCache.m.Load(hash); ok {
ts = ti.([]Type)
}
structLookupCache.m.Store(hash, append(ts, t))
return t
}
// Look in known types.
for _, t := range typesByString(str) {
if haveIdenticalUnderlyingType(&typ.Type, t, true) {
// even if 't' wasn't a structType with methods, we should be ok
// as the 'u uncommonType' field won't be accessed except when
// tflag&abi.TFlagUncommon is set.
return addToCache(toType(t))
}
}
typ.Str = resolveReflectName(newName(str, "", false, false))
if isRegularMemory(toType(&typ.Type)) {
typ.TFlag = abi.TFlagRegularMemory
} else {
typ.TFlag = 0
}
typ.Hash = hash
typ.Size_ = size
typ.PtrBytes = typeptrdata(&typ.Type)
typ.Align_ = typalign
typ.FieldAlign_ = typalign
typ.PtrToThis = 0
if len(methods) > 0 {
typ.TFlag |= abi.TFlagUncommon
}
if hasGCProg {
lastPtrField := 0
for i, ft := range fs {
if ft.Typ.Pointers() {
lastPtrField = i
}
}
prog := []byte{0, 0, 0, 0} // will be length of prog
var off uintptr
for i, ft := range fs {
if i > lastPtrField {
// gcprog should not include anything for any field after
// the last field that contains pointer data
break
}
if !ft.Typ.Pointers() {
// Ignore pointerless fields.
continue
}
// Pad to start of this field with zeros.
if ft.Offset > off {
n := (ft.Offset - off) / goarch.PtrSize
prog = append(prog, 0x01, 0x00) // emit a 0 bit
if n > 1 {
prog = append(prog, 0x81) // repeat previous bit
prog = appendVarint(prog, n-1) // n-1 times
}
off = ft.Offset
}
prog = appendGCProg(prog, ft.Typ)
off += ft.Typ.PtrBytes
}
prog = append(prog, 0)
*(*uint32)(unsafe.Pointer(&prog[0])) = uint32(len(prog) - 4)
typ.Kind_ |= abi.KindGCProg
typ.GCData = &prog[0]
} else {
typ.Kind_ &^= abi.KindGCProg
bv := new(bitVector)
addTypeBits(bv, 0, &typ.Type)
if len(bv.data) > 0 {
typ.GCData = &bv.data[0]
}
}
typ.Equal = nil
if comparable {
typ.Equal = func(p, q unsafe.Pointer) bool {
for _, ft := range typ.Fields {
pi := add(p, ft.Offset, "&x.field safe")
qi := add(q, ft.Offset, "&x.field safe")
if !ft.Typ.Equal(pi, qi) {
return false
}
}
return true
}
}
switch {
case len(fs) == 1 && !fs[0].Typ.IfaceIndir():
// structs of 1 direct iface type can be direct
typ.Kind_ |= abi.KindDirectIface
default:
typ.Kind_ &^= abi.KindDirectIface
}
return addToCache(toType(&typ.Type))
}
func embeddedIfaceMethStub() {
panic("reflect: StructOf does not support methods of embedded interfaces")
}
// runtimeStructField takes a StructField value passed to StructOf and
// returns both the corresponding internal representation, of type
// structField, and the pkgpath value to use for this field.
func runtimeStructField(field StructField) (structField, string) {
if field.Anonymous && field.PkgPath != "" {
panic("reflect.StructOf: field \"" + field.Name + "\" is anonymous but has PkgPath set")
}
if field.IsExported() {
// Best-effort check for misuse.
// Since this field will be treated as exported, not much harm done if Unicode lowercase slips through.
c := field.Name[0]
if 'a' <= c && c <= 'z' || c == '_' {
panic("reflect.StructOf: field \"" + field.Name + "\" is unexported but missing PkgPath")
}
}
resolveReflectType(field.Type.common()) // install in runtime
f := structField{
Name: newName(field.Name, string(field.Tag), field.IsExported(), field.Anonymous),
Typ: field.Type.common(),
Offset: 0,
}
return f, field.PkgPath
}
// typeptrdata returns the length in bytes of the prefix of t
// containing pointer data. Anything after this offset is scalar data.
// keep in sync with ../cmd/compile/internal/reflectdata/reflect.go
func typeptrdata(t *abi.Type) uintptr {
switch t.Kind() {
case abi.Struct:
st := (*structType)(unsafe.Pointer(t))
// find the last field that has pointers.
field := -1
for i := range st.Fields {
ft := st.Fields[i].Typ
if ft.Pointers() {
field = i
}
}
if field == -1 {
return 0
}
f := st.Fields[field]
return f.Offset + f.Typ.PtrBytes
default:
panic("reflect.typeptrdata: unexpected type, " + stringFor(t))
}
}
// ArrayOf returns the array type with the given length and element type.
// For example, if t represents int, ArrayOf(5, t) represents [5]int.
//
// If the resulting type would be larger than the available address space,
// ArrayOf panics.
func ArrayOf(length int, elem Type) Type {
if length < 0 {
panic("reflect: negative length passed to ArrayOf")
}
typ := elem.common()
// Look in cache.
ckey := cacheKey{Array, typ, nil, uintptr(length)}
if array, ok := lookupCache.Load(ckey); ok {
return array.(Type)
}
// Look in known types.
s := "[" + strconv.Itoa(length) + "]" + stringFor(typ)
for _, tt := range typesByString(s) {
array := (*arrayType)(unsafe.Pointer(tt))
if array.Elem == typ {
ti, _ := lookupCache.LoadOrStore(ckey, toRType(tt))
return ti.(Type)
}
}
// Make an array type.
var iarray any = [1]unsafe.Pointer{}
prototype := *(**arrayType)(unsafe.Pointer(&iarray))
array := *prototype
array.TFlag = typ.TFlag & abi.TFlagRegularMemory
array.Str = resolveReflectName(newName(s, "", false, false))
array.Hash = fnv1(typ.Hash, '[')
for n := uint32(length); n > 0; n >>= 8 {
array.Hash = fnv1(array.Hash, byte(n))
}
array.Hash = fnv1(array.Hash, ']')
array.Elem = typ
array.PtrToThis = 0
if typ.Size_ > 0 {
max := ^uintptr(0) / typ.Size_
if uintptr(length) > max {
panic("reflect.ArrayOf: array size would exceed virtual address space")
}
}
array.Size_ = typ.Size_ * uintptr(length)
if length > 0 && typ.Pointers() {
array.PtrBytes = typ.Size_*uintptr(length-1) + typ.PtrBytes
}
array.Align_ = typ.Align_
array.FieldAlign_ = typ.FieldAlign_
array.Len = uintptr(length)
array.Slice = &(SliceOf(elem).(*rtype).t)
switch {
case !typ.Pointers() || array.Size_ == 0:
// No pointers.
array.GCData = nil
array.PtrBytes = 0
case length == 1:
// In memory, 1-element array looks just like the element.
array.Kind_ |= typ.Kind_ & abi.KindGCProg
array.GCData = typ.GCData
array.PtrBytes = typ.PtrBytes
case typ.Kind_&abi.KindGCProg == 0 && array.Size_ <= abi.MaxPtrmaskBytes*8*goarch.PtrSize:
// Element is small with pointer mask; array is still small.
// Create direct pointer mask by turning each 1 bit in elem
// into length 1 bits in larger mask.
n := (array.PtrBytes/goarch.PtrSize + 7) / 8
// Runtime needs pointer masks to be a multiple of uintptr in size.
n = (n + goarch.PtrSize - 1) &^ (goarch.PtrSize - 1)
mask := make([]byte, n)
emitGCMask(mask, 0, typ, array.Len)
array.GCData = &mask[0]
default:
// Create program that emits one element
// and then repeats to make the array.
prog := []byte{0, 0, 0, 0} // will be length of prog
prog = appendGCProg(prog, typ)
// Pad from ptrdata to size.
elemPtrs := typ.PtrBytes / goarch.PtrSize
elemWords := typ.Size_ / goarch.PtrSize
if elemPtrs < elemWords {
// Emit literal 0 bit, then repeat as needed.
prog = append(prog, 0x01, 0x00)
if elemPtrs+1 < elemWords {
prog = append(prog, 0x81)
prog = appendVarint(prog, elemWords-elemPtrs-1)
}
}
// Repeat length-1 times.
if elemWords < 0x80 {
prog = append(prog, byte(elemWords|0x80))
} else {
prog = append(prog, 0x80)
prog = appendVarint(prog, elemWords)
}
prog = appendVarint(prog, uintptr(length)-1)
prog = append(prog, 0)
*(*uint32)(unsafe.Pointer(&prog[0])) = uint32(len(prog) - 4)
array.Kind_ |= abi.KindGCProg
array.GCData = &prog[0]
array.PtrBytes = array.Size_ // overestimate but ok; must match program
}
etyp := typ
esize := etyp.Size()
array.Equal = nil
if eequal := etyp.Equal; eequal != nil {
array.Equal = func(p, q unsafe.Pointer) bool {
for i := 0; i < length; i++ {
pi := arrayAt(p, i, esize, "i < length")
qi := arrayAt(q, i, esize, "i < length")
if !eequal(pi, qi) {
return false
}
}
return true
}
}
switch {
case length == 1 && !typ.IfaceIndir():
// array of 1 direct iface type can be direct
array.Kind_ |= abi.KindDirectIface
default:
array.Kind_ &^= abi.KindDirectIface
}
ti, _ := lookupCache.LoadOrStore(ckey, toRType(&array.Type))
return ti.(Type)
}
func appendVarint(x []byte, v uintptr) []byte {
for ; v >= 0x80; v >>= 7 {
x = append(x, byte(v|0x80))
}
x = append(x, byte(v))
return x
}
// toType converts from a *rtype to a Type that can be returned
// to the client of package reflect. In gc, the only concern is that
// a nil *rtype must be replaced by a nil Type, but in gccgo this
// function takes care of ensuring that multiple *rtype for the same
// type are coalesced into a single Type.
//
// toType should be an internal detail,
// but widely used packages access it using linkname.
// Notable members of the hall of shame include:
// - github.com/goccy/go-json
//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname toType
func toType(t *abi.Type) Type {
if t == nil {
return nil
}
return toRType(t)
}
type layoutKey struct {
ftyp *funcType // function signature
rcvr *abi.Type // receiver type, or nil if none
}
type layoutType struct {
t *abi.Type
framePool *sync.Pool
abid abiDesc
}
var layoutCache sync.Map // map[layoutKey]layoutType
// funcLayout computes a struct type representing the layout of the
// stack-assigned function arguments and return values for the function
// type t.
// If rcvr != nil, rcvr specifies the type of the receiver.
// The returned type exists only for GC, so we only fill out GC relevant info.
// Currently, that's just size and the GC program. We also fill in
// the name for possible debugging use.
func funcLayout(t *funcType, rcvr *abi.Type) (frametype *abi.Type, framePool *sync.Pool, abid abiDesc) {
if t.Kind() != abi.Func {
panic("reflect: funcLayout of non-func type " + stringFor(&t.Type))
}
if rcvr != nil && rcvr.Kind() == abi.Interface {
panic("reflect: funcLayout with interface receiver " + stringFor(rcvr))
}
k := layoutKey{t, rcvr}
if lti, ok := layoutCache.Load(k); ok {
lt := lti.(layoutType)
return lt.t, lt.framePool, lt.abid
}
// Compute the ABI layout.
abid = newAbiDesc(t, rcvr)
// build dummy rtype holding gc program
x := &abi.Type{
Align_: goarch.PtrSize,
// Don't add spill space here; it's only necessary in
// reflectcall's frame, not in the allocated frame.
// TODO(mknyszek): Remove this comment when register
// spill space in the frame is no longer required.
Size_: align(abid.retOffset+abid.ret.stackBytes, goarch.PtrSize),
PtrBytes: uintptr(abid.stackPtrs.n) * goarch.PtrSize,
}
if abid.stackPtrs.n > 0 {
x.GCData = &abid.stackPtrs.data[0]
}
var s string
if rcvr != nil {
s = "methodargs(" + stringFor(rcvr) + ")(" + stringFor(&t.Type) + ")"
} else {
s = "funcargs(" + stringFor(&t.Type) + ")"
}
x.Str = resolveReflectName(newName(s, "", false, false))
// cache result for future callers
framePool = &sync.Pool{New: func() any {
return unsafe_New(x)
}}
lti, _ := layoutCache.LoadOrStore(k, layoutType{
t: x,
framePool: framePool,
abid: abid,
})
lt := lti.(layoutType)
return lt.t, lt.framePool, lt.abid
}
// Note: this type must agree with runtime.bitvector.
type bitVector struct {
n uint32 // number of bits
data []byte
}
// append a bit to the bitmap.
func (bv *bitVector) append(bit uint8) {
if bv.n%(8*goarch.PtrSize) == 0 {
// Runtime needs pointer masks to be a multiple of uintptr in size.
// Since reflect passes bv.data directly to the runtime as a pointer mask,
// we append a full uintptr of zeros at a time.
for i := 0; i < goarch.PtrSize; i++ {
bv.data = append(bv.data, 0)
}
}
bv.data[bv.n/8] |= bit << (bv.n % 8)
bv.n++
}
func addTypeBits(bv *bitVector, offset uintptr, t *abi.Type) {
if !t.Pointers() {
return
}
switch Kind(t.Kind_ & abi.KindMask) {
case Chan, Func, Map, Pointer, Slice, String, UnsafePointer:
// 1 pointer at start of representation
for bv.n < uint32(offset/goarch.PtrSize) {
bv.append(0)
}
bv.append(1)
case Interface:
// 2 pointers
for bv.n < uint32(offset/goarch.PtrSize) {
bv.append(0)
}
bv.append(1)
bv.append(1)
case Array:
// repeat inner type
tt := (*arrayType)(unsafe.Pointer(t))
for i := 0; i < int(tt.Len); i++ {
addTypeBits(bv, offset+uintptr(i)*tt.Elem.Size_, tt.Elem)
}
case Struct:
// apply fields
tt := (*structType)(unsafe.Pointer(t))
for i := range tt.Fields {
f := &tt.Fields[i]
addTypeBits(bv, offset+f.Offset, f.Typ)
}
}
}
// TypeFor returns the [Type] that represents the type argument T.
func TypeFor[T any]() Type {
var v T
if t := TypeOf(v); t != nil {
return t // optimize for T being a non-interface kind
}
return TypeOf((*T)(nil)).Elem() // only for an interface kind
}