-
Notifications
You must be signed in to change notification settings - Fork 346
/
unsafe.go
61 lines (50 loc) · 1.12 KB
/
unsafe.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
package unsafe2
import (
"reflect"
"unsafe"
)
type dummy struct{}
// DummyType represents a stand-in for a recursive type.
var DummyType = reflect.TypeOf(dummy{})
// the following type sizes must match their original definition in Go src/reflect/type.go.
type rtype struct {
_ uintptr
_ uintptr
_ uint32
_ uint32
_ uintptr
_ uintptr
_ uint32
_ uint32
}
type emptyInterface struct {
typ *rtype
_ unsafe.Pointer
}
type structField struct {
_ uintptr
typ *rtype
_ uintptr
}
type structType struct {
rtype
_ uintptr
fields []structField
}
// SetFieldType sets the type of the struct field at the given index, to the given type.
//
// The struct type must have been created at runtime. This is very unsafe.
func SetFieldType(s reflect.Type, idx int, t reflect.Type) {
if s.Kind() != reflect.Struct || idx >= s.NumField() {
return
}
rtyp := unpackType(s)
styp := (*structType)(unsafe.Pointer(rtyp))
f := styp.fields[idx]
f.typ = unpackType(t)
styp.fields[idx] = f
}
func unpackType(t reflect.Type) *rtype {
v := reflect.New(t).Elem().Interface()
return (*emptyInterface)(unsafe.Pointer(&v)).typ
}