1 // Copyright 2018 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 //go:build purego 6 7 // Package alias implements memory aliasing tests. 8 package alias 9 10 // This is the Google App Engine standard variant based on reflect 11 // because the unsafe package and cgo are disallowed. 12 13 import "reflect" 14 15 // AnyOverlap reports whether x and y share memory at any (not necessarily 16 // corresponding) index. The memory beyond the slice length is ignored. 17 func AnyOverlap(x, y []byte) bool { 18 return len(x) > 0 && len(y) > 0 && 19 reflect.ValueOf(&x[0]).Pointer() <= reflect.ValueOf(&y[len(y)-1]).Pointer() && 20 reflect.ValueOf(&y[0]).Pointer() <= reflect.ValueOf(&x[len(x)-1]).Pointer() 21 } 22 23 // InexactOverlap reports whether x and y share memory at any non-corresponding 24 // index. The memory beyond the slice length is ignored. Note that x and y can 25 // have different lengths and still not have any inexact overlap. 26 // 27 // InexactOverlap can be used to implement the requirements of the crypto/cipher 28 // AEAD, Block, BlockMode and Stream interfaces. 29 func InexactOverlap(x, y []byte) bool { 30 if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] { 31 return false 32 } 33 return AnyOverlap(x, y) 34 } 35