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 5 package cmp 6 7 import ( 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. 18 func 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 } 32