1// Copyright 2017, 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
 5package cmp
 6
 7import (
 8	"reflect"
 9	"unsafe"
10)
11
12// retrieveUnexportedField uses unsafe to forcibly retrieve any field from
13// a struct such that the value has read-write permissions.
14//
15// The parent struct, v, must be addressable, while f must be a StructField
16// describing the field to retrieve. If addr is false,
17// then the returned value will be shallowed copied to be non-addressable.
18func retrieveUnexportedField(v reflect.Value, f reflect.StructField, addr bool) reflect.Value {
19	ve := reflect.NewAt(f.Type, unsafe.Pointer(uintptr(unsafe.Pointer(v.UnsafeAddr()))+f.Offset)).Elem()
20	if !addr {
21		// A field is addressable if and only if the struct is addressable.
22		// If the original parent value was not addressable, shallow copy the
23		// value to make it non-addressable to avoid leaking an implementation
24		// detail of how forcibly exporting a field works.
25		if ve.Kind() == reflect.Interface && ve.IsNil() {
26			return reflect.Zero(f.Type)
27		}
28		return reflect.ValueOf(ve.Interface()).Convert(f.Type)
29	}
30	return ve
31}