v/vlib/crypto/internal/subtle/aliasing.v

// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.

// Package subtle implements functions that are often useful in cryptographic
// code but require careful thought to use correctly.

module subtle

// NOTE: require unsafe in future

// any_overlap reports whether x and y share memory at any (not necessarily
// corresponding) index. The memory beyond the slice length is ignored.
pub fn any_overlap(x, y []byte) bool {
	// NOTE: Remember to come back to this (joe-c)
	return x.len > 0 && y.len > 0 &&
		// &x.data[0] <= &y.data[y.len-1] &&
		// &y.data[0] <= &x.data[x.len-1]
		unsafe { &x[0] <= &y[y.len-1] &&
		&y[0] <= &x[x.len-1] }
}

// inexact_overlap reports whether x and y share memory at any non-corresponding
// index. The memory beyond the slice length is ignored. Note that x and y can
// have different lengths and still not have any inexact overlap.
//
// inexact_overlap can be used to implement the requirements of the crypto/cipher
// AEAD, Block, BlockMode and Stream interfaces.
pub fn inexact_overlap(x, y []byte) bool {
	if x.len == 0 || y.len == 0 || unsafe { &x[0] == &y[0] } {
		return false
	}
	return any_overlap(x, y)
}