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// Copyright 2017, The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package cmp
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import (
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	"reflect"
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	"unsafe"
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)
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// retrieveUnexportedField uses unsafe to forcibly retrieve any field from
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// a struct such that the value has read-write permissions.
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//
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// The parent struct, v, must be addressable, while f must be a StructField
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// describing the field to retrieve. If addr is false,
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// then the returned value will be shallowed copied to be non-addressable.
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func retrieveUnexportedField(v reflect.Value, f reflect.StructField, addr bool) reflect.Value {
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	ve := reflect.NewAt(f.Type, unsafe.Pointer(uintptr(unsafe.Pointer(v.UnsafeAddr()))+f.Offset)).Elem()
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	if !addr {
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		// A field is addressable if and only if the struct is addressable.
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		// If the original parent value was not addressable, shallow copy the
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		// value to make it non-addressable to avoid leaking an implementation
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		// detail of how forcibly exporting a field works.
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		if ve.Kind() == reflect.Interface && ve.IsNil() {
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			return reflect.Zero(f.Type)
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		}
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		return reflect.ValueOf(ve.Interface()).Convert(f.Type)
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	}
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	return ve
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}
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