Initial project import

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

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+// Copyright (c) 2019-2024 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 []u8, y []u8) 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 []u8, y []u8) bool {
+	if x.len == 0 || y.len == 0 || unsafe { &x[0] == &y[0] } {
+		return false
+	}
+	return any_overlap(x, y)
+}