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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftCrypto open source project
//
// Copyright (c) 2019-2020 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
//
//===----------------------------------------------------------------------===//
#if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
@_exported import CryptoKit
#else
#if !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
typealias DigestImpl = CoreCryptoDigestImpl
#else
typealias DigestImpl = OpenSSLDigestImpl
#endif
import Foundation
/// A type that performs cryptographically secure hashing.
///
/// The ``HashFunction`` protocol describes an interface for computing a
/// fixed-length digest from an arbitrarily large collection of bytes. Because
/// the digest is small, you can quickly compare the digests to detect a
/// difference in two corresponding data sets. Alternatively, transmit or store
/// data with its digest to detect changes introduced after initially
/// calculating the digest.
///
/// Use one of the protocol’s adopters, like ``SHA256``, ``SHA384``, or
/// ``SHA512``, to output a digest whose value varies significantly over even
/// small differences in the input data.
///
/// Checking a digest doesn’t guard against changes made by a malicious user who
/// also changes the digest to match. To handle this, compute a message
/// authentication code (MAC) like ``HMAC`` instead. MACs rely on hashing, but
/// incorporate a secret cryptographic key into the digest computation. Only a
/// user that has the key can generate a valid MAC.
public protocol HashFunction {
/// The number of bytes that represents the hash function’s internal state.
static var blockByteCount: Int { get }
#if !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
/// The type of the digest returned by the hash function.
associatedtype Digest: CryptoKit.Digest
#else
associatedtype Digest: Crypto.Digest
#endif
/// Creates a hash function.
///
/// Initialize a new hash function by calling this method if you want to
/// hash the data iteratively, such as when you don’t have a buffer large
/// enough to hold all the data at once. Provide data blocks to the hash
/// function using the ``update(data:)`` or ``update(bufferPointer:)``
/// method. After providing all the data, call ``finalize()`` to get the
/// digest.
///
/// If your data fits into a single buffer, you can use the ``hash(data:)``
/// method instead to compute the digest in a single call.
init()
/// Incrementally updates the hash function with the contents of the buffer.
///
/// Call this method one or more times to provide data to the hash function
/// in blocks. After providing the last block of data, call the
/// ``finalize()`` method to get the computed digest. Don’t call the update
/// method again after finalizing the hash function.
///
/// - Note: Typically, it’s safer to use an instance of
/// <doc://com.apple.documentation/documentation/foundation/data>, or some
/// other type that conforms to the
/// <doc://com.apple.documentation/documentation/foundation/dataprotocol>,
/// to hold your data. When possible, use the ``HashFunction/update(data:)``
/// method instead.
///
/// - Parameters:
/// - bufferPointer: A pointer to the next block of data for the ongoing
/// digest calculation.
mutating func update(bufferPointer: UnsafeRawBufferPointer)
/// Finalizes the hash function and returns the computed digest.
///
/// Call this method after you provide the hash function with all the data
/// to hash using one or more calls to the ``update(data:)`` or
/// ``update(bufferPointer:)`` method. After finalizing the hash function,
/// discard it. To compute a new digest, create a new hash function with a
/// call to the ``init()`` method.
///
/// - Returns: The computed digest of the data.
func finalize() -> Digest
}
extension HashFunction {
/// Computes a digest of the buffer.
///
/// - Parameters:
/// - bufferPointer: The buffer to be hashed.
/// - Returns: The computed digest.
@inlinable
static func hash(bufferPointer: UnsafeRawBufferPointer) -> Digest {
var hasher = Self()
hasher.update(bufferPointer: bufferPointer)
return hasher.finalize()
}
/// Computes the SHA1 digest of the bytes in the given data instance and
/// returns the computed digest.
///
/// Use this method if all your data fits into a single data instance. If
/// the data you want to hash is too large, initialize a hash function and
/// use the ``update(data:)`` and ``finalize()`` methods to compute the
/// digest in blocks.
///
/// - Parameters:
/// - data: The data whose digest the hash function should compute. This can
/// be any type that conforms to
/// <doc://com.apple.documentation/documentation/foundation/dataprotocol>,
/// like <doc://com.apple.documentation/documentation/foundation/data> or an
/// array of <doc://com.apple.documentation/documentation/swift/uint8>
/// instances.
///
/// - Returns: The computed digest of the data.
@inlinable
public static func hash<D: DataProtocol>(data: D) -> Self.Digest {
var hasher = Self()
hasher.update(data: data)
return hasher.finalize()
}
/// Incrementally updates the hash function with the given data.
///
/// Call this method one or more times to provide data to the hash function
/// in blocks. After providing the last block of data, call the
/// ``finalize()`` method to get the computed digest. Don’t call the update
/// method again after finalizing the hash function.
///
/// - Parameters:
/// - data: The next block of data for the ongoing digest calculation. You
/// can provide this as any type that conforms to
/// <doc://com.apple.documentation/documentation/foundation/dataprotocol>,
/// like <doc://com.apple.documentation/documentation/foundation/data> or an
/// array of <doc://com.apple.documentation/documentation/swift/uint8>
/// instances.
@inlinable
public mutating func update<D: DataProtocol>(data: D) {
data.regions.forEach { (regionData) in
regionData.withUnsafeBytes({ (dataPtr) in
self.update(bufferPointer: dataPtr)
})
}
}
}
#endif // Linux or !SwiftPM
|
