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