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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
//
//===----------------------------------------------------------------------===//
import Foundation
/// This function performs a safe comparison between two buffers of bytes. It exists as a temporary shim until we refactor
/// some of the usage sites to pass better data structures to us.
@inlinable
internal func openSSLSafeCompare<LHS: ContiguousBytes, RHS: ContiguousBytes>(_ lhs: LHS, _ rhs: RHS) -> Bool {
lhs.withUnsafeBytes { lhsPtr in
rhs.withUnsafeBytes { rhsPtr in
constantTimeCompare(lhsPtr, rhsPtr)
}
}
}
/// A straightforward constant-time comparison function for any two collections of bytes.
@inlinable
internal func constantTimeCompare<LHS: Collection, RHS: Collection>(_ lhs: LHS, _ rhs: RHS) -> Bool where LHS.Element == UInt8, RHS.Element == UInt8 {
guard lhs.count == rhs.count else {
return false
}
return zip(lhs, rhs).reduce(into: 0) { $0 |= $1.0 ^ $1.1 } == 0
}
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