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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftCrypto open source project
//
// Copyright (c) 2019 Apple Inc. and the SwiftCrypto project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.md for the list of SwiftCrypto project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
extension UnsafeMutableRawBufferPointer {
@inlinable
func initializeWithRandomBytes(count: Int) {
guard count > 0 else {
return
}
precondition(count <= self.count)
var rng = SystemRandomNumberGenerator()
// We store bytes 64-bits at a time until we can't anymore.
var targetPtr = self
while targetPtr.count > 8 {
targetPtr.storeBytes(of: rng.next(), as: UInt64.self)
targetPtr = UnsafeMutableRawBufferPointer(rebasing: targetPtr[8...])
}
// Now we're down to having to store things an integer at a time. We do this by shifting and
// masking.
var remainingWord: UInt64 = rng.next()
while targetPtr.count > 0 {
targetPtr.storeBytes(of: UInt8(remainingWord & 0xFF), as: UInt8.self)
remainingWord >>= 8
targetPtr = UnsafeMutableRawBufferPointer(rebasing: targetPtr[1...])
}
}
}
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