internal/unsafe: fix vet warnings about SliceHeader use

Signed-off-by: Elias Naur <mail@eliasnaur.com>

internal/unsafe/unsafe.go

@@ -12,11 +12,12 @@ func BytesView(s interface{}) []byte {
 	v := reflect.ValueOf(s)
 	first := v.Index(0)
 	sz := int(first.Type().Size())
-	return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
-		Data: uintptr(unsafe.Pointer((*reflect.SliceHeader)(unsafe.Pointer(first.UnsafeAddr())))),
-		Len:  v.Len() * sz,
-		Cap:  v.Cap() * sz,
-	}))
+	var res []byte
+	h := (*reflect.SliceHeader)(unsafe.Pointer(&res))
+	h.Data = first.UnsafeAddr()
+	h.Cap = v.Cap() * sz
+	h.Len = v.Len() * sz
+	return res
 }
 
 // SliceOf returns a slice from a (native) pointer.
@@ -24,12 +25,11 @@ func SliceOf(s uintptr) []byte {
 	if s == 0 {
 		return nil
 	}
-	sh := reflect.SliceHeader{
-		Data: s,
-		Len:  1 << 30,
-		Cap:  1 << 30,
-	}
-	return *(*[]byte)(unsafe.Pointer(&sh))
+	var res []byte
+	h := (*reflect.SliceHeader)(unsafe.Pointer(&res))
+	h.Data = s
+	h.Cap = 1 << 30
+	return res
 }
 
 // GoString convert a NUL-terminated C string