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