alias.go

     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
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