export_test.go

Documentation: internal/reflectlite

     1  // Copyright 2019 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.
     4  
     5  package reflectlite
     6  
     7  import (
     8  	"unsafe"
     9  )
    10  
    11  // Field returns the i'th field of the struct v.
    12  // It panics if v's Kind is not Struct or i is out of range.
    13  func Field(v Value, i int) Value {
    14  	if v.kind() != Struct {
    15  		panic(&ValueError{"reflect.Value.Field", v.kind()})
    16  	}
    17  	tt := (*structType)(unsafe.Pointer(v.typ()))
    18  	if uint(i) >= uint(len(tt.Fields)) {
    19  		panic("reflect: Field index out of range")
    20  	}
    21  	field := &tt.Fields[i]
    22  	typ := field.Typ
    23  
    24  	// Inherit permission bits from v, but clear flagEmbedRO.
    25  	fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind())
    26  	// Using an unexported field forces flagRO.
    27  	if !field.Name.IsExported() {
    28  		if field.Embedded() {
    29  			fl |= flagEmbedRO
    30  		} else {
    31  			fl |= flagStickyRO
    32  		}
    33  	}
    34  	// Either flagIndir is set and v.ptr points at struct,
    35  	// or flagIndir is not set and v.ptr is the actual struct data.
    36  	// In the former case, we want v.ptr + offset.
    37  	// In the latter case, we must have field.offset = 0,
    38  	// so v.ptr + field.offset is still the correct address.
    39  	ptr := add(v.ptr, field.Offset, "same as non-reflect &v.field")
    40  	return Value{typ, ptr, fl}
    41  }
    42  
    43  func TField(typ Type, i int) Type {
    44  	t := typ.(rtype)
    45  	if t.Kind() != Struct {
    46  		panic("reflect: Field of non-struct type")
    47  	}
    48  	tt := (*structType)(unsafe.Pointer(t.Type))
    49  
    50  	return StructFieldType(tt, i)
    51  }
    52  
    53  // Field returns the i'th struct field.
    54  func StructFieldType(t *structType, i int) Type {
    55  	if i < 0 || i >= len(t.Fields) {
    56  		panic("reflect: Field index out of bounds")
    57  	}
    58  	p := &t.Fields[i]
    59  	return toType(p.Typ)
    60  }
    61  
    62  // Zero returns a Value representing the zero value for the specified type.
    63  // The result is different from the zero value of the Value struct,
    64  // which represents no value at all.
    65  // For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0.
    66  // The returned value is neither addressable nor settable.
    67  func Zero(typ Type) Value {
    68  	if typ == nil {
    69  		panic("reflect: Zero(nil)")
    70  	}
    71  	t := typ.common()
    72  	fl := flag(t.Kind())
    73  	if t.IfaceIndir() {
    74  		return Value{t, unsafe_New(t), fl | flagIndir}
    75  	}
    76  	return Value{t, nil, fl}
    77  }
    78  
    79  // ToInterface returns v's current value as an interface{}.
    80  // It is equivalent to:
    81  //
    82  //	var i interface{} = (v's underlying value)
    83  //
    84  // It panics if the Value was obtained by accessing
    85  // unexported struct fields.
    86  func ToInterface(v Value) (i any) {
    87  	return valueInterface(v)
    88  }
    89  
    90  type EmbedWithUnexpMeth struct{}
    91  
    92  func (EmbedWithUnexpMeth) f() {}
    93  
    94  type pinUnexpMeth interface {
    95  	f()
    96  }
    97  
    98  var pinUnexpMethI = pinUnexpMeth(EmbedWithUnexpMeth{})
    99  
   100  func FirstMethodNameBytes(t Type) *byte {
   101  	_ = pinUnexpMethI
   102  
   103  	ut := t.uncommon()
   104  	if ut == nil {
   105  		panic("type has no methods")
   106  	}
   107  	m := ut.Methods()[0]
   108  	mname := t.(rtype).nameOff(m.Name)
   109  	if *mname.DataChecked(0, "name flag field")&(1<<2) == 0 {
   110  		panic("method name does not have pkgPath *string")
   111  	}
   112  	return mname.Bytes
   113  }
   114  
   115  type Buffer struct {
   116  	buf []byte
   117  }
   118
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