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.md file.
4
5// +build !purego
6
7package cmp
8
9import (
10	"reflect"
11	"unsafe"
12)
13
14const supportExporters = true
15
16// retrieveUnexportedField uses unsafe to forcibly retrieve any field from
17// a struct such that the value has read-write permissions.
18//
19// The parent struct, v, must be addressable, while f must be a StructField
20// describing the field to retrieve. If addr is false,
21// then the returned value will be shallowed copied to be non-addressable.
22func retrieveUnexportedField(v reflect.Value, f reflect.StructField, addr bool) reflect.Value {
23	ve := reflect.NewAt(f.Type, unsafe.Pointer(uintptr(unsafe.Pointer(v.UnsafeAddr()))+f.Offset)).Elem()
24	if !addr {
25		// A field is addressable if and only if the struct is addressable.
26		// If the original parent value was not addressable, shallow copy the
27		// value to make it non-addressable to avoid leaking an implementation
28		// detail of how forcibly exporting a field works.
29		if ve.Kind() == reflect.Interface && ve.IsNil() {
30			return reflect.Zero(f.Type)
31		}
32		return reflect.ValueOf(ve.Interface()).Convert(f.Type)
33	}
34	return ve
35}
36