| // Copyright 2018 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // +build appengine |
| |
| // Package subtle implements functions that are often useful in cryptographic |
| // code but require careful thought to use correctly. |
| package subtle // import "golang.org/x/crypto/internal/subtle" |
| |
| // This is the Google App Engine standard variant based on reflect |
| // because the unsafe package and cgo are disallowed. |
| |
| import "reflect" |
| |
| // AnyOverlap reports whether x and y share memory at any (not necessarily |
| // corresponding) index. The memory beyond the slice length is ignored. |
| func AnyOverlap(x, y []byte) bool { |
| return len(x) > 0 && len(y) > 0 && |
| reflect.ValueOf(&x[0]).Pointer() <= reflect.ValueOf(&y[len(y)-1]).Pointer() && |
| reflect.ValueOf(&y[0]).Pointer() <= reflect.ValueOf(&x[len(x)-1]).Pointer() |
| } |
| |
| // InexactOverlap reports whether x and y share memory at any non-corresponding |
| // index. The memory beyond the slice length is ignored. Note that x and y can |
| // have different lengths and still not have any inexact overlap. |
| // |
| // InexactOverlap can be used to implement the requirements of the crypto/cipher |
| // AEAD, Block, BlockMode and Stream interfaces. |
| func InexactOverlap(x, y []byte) bool { |
| if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] { |
| return false |
| } |
| return AnyOverlap(x, y) |
| } |