github.com/primecitizens/pcz/std@v0.2.1/core/mem/alias.go (about)

     1  // SPDX-License-Identifier: Apache-2.0
     2  // Copyright 2023 The Prime Citizens
     3  //
     4  // Copyright 2018 The Go Authors. All rights reserved.
     5  // Use of this source code is governed by a BSD-style
     6  // license that can be found in the LICENSE file.
     7  
     8  package mem
     9  
    10  // alias implements memory alaising tests.
    11  // This code also exists as golang.org/x/crypto/internal/alias.
    12  
    13  import (
    14  	"unsafe"
    15  )
    16  
    17  // AnyOverlap reports whether x and y share memory at any (not necessarily
    18  // corresponding) index. The memory beyond the slice length is ignored.
    19  func AnyOverlap(x, y []byte) bool {
    20  	return len(x) > 0 && len(y) > 0 &&
    21  		uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) &&
    22  		uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1]))
    23  }
    24  
    25  // InexactOverlap reports whether x and y share memory at any non-corresponding
    26  // index. The memory beyond the slice length is ignored. Note that x and y can
    27  // have different lengths and still not have any inexact overlap.
    28  //
    29  // InexactOverlap can be used to implement the requirements of the crypto/cipher
    30  // AEAD, Block, BlockMode and Stream interfaces.
    31  func InexactOverlap(x, y []byte) bool {
    32  	if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
    33  		return false
    34  	}
    35  	return AnyOverlap(x, y)
    36  }