func (f field) IsValid() bool {
	return f != ^field(0)
}
IsValid reports whether the field identifier is valid.
package proto
import (
	"reflect"
	"unsafe"
)
type structPointer unsafe.Pointer
func toStructPointer(v reflect.Value) structPointer {
	return structPointer(unsafe.Pointer(v.Pointer()))
}
func structPointer_IsNil(p structPointer) bool {
	return p == nil
}
func structPointer_Interface(p structPointer, t reflect.Type) interface{} {
	return reflect.NewAt(t, unsafe.Pointer(p)).Interface()
}
type field uintptr
func toField(f *reflect.StructField) field {
	return field(f.Offset)
}
const invalidField = ^field(0)