alias.mx raw

   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  // Package alias implements memory aliasing tests.
   6  // This code also exists as golang.org/x/crypto/internal/alias.
   7  package alias
   8  
   9  import "unsafe"
  10  
  11  // AnyOverlap reports whether x and y share memory at any (not necessarily
  12  // corresponding) index. The memory beyond the slice length is ignored.
  13  func AnyOverlap(x, y []byte) bool {
  14  	return len(x) > 0 && len(y) > 0 &&
  15  		uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) &&
  16  		uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1]))
  17  }
  18  
  19  // InexactOverlap reports whether x and y share memory at any non-corresponding
  20  // index. The memory beyond the slice length is ignored. Note that x and y can
  21  // have different lengths and still not have any inexact overlap.
  22  //
  23  // InexactOverlap can be used to implement the requirements of the crypto/cipher
  24  // AEAD, Block, BlockMode and Stream interfaces.
  25  func InexactOverlap(x, y []byte) bool {
  26  	if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
  27  		return false
  28  	}
  29  	return AnyOverlap(x, y)
  30  }
  31