Diğer cevaplar, büyük miktarda veriden (örneğin, büyük dosyalar) özetleri hesaplamak için performans problemlerine sahip olacaktır. Tüm verileri hafızaya aynı anda yüklemek istemeyeceksiniz. Update / finalize kullanarak aşağıdaki yaklaşımı düşünün:
final class SHA256Digest {
enum InputStreamError: Error {
case createFailed(URL)
case readFailed
}
private lazy var context: CC_SHA256_CTX = {
var shaContext = CC_SHA256_CTX()
CC_SHA256_Init(&shaContext)
return shaContext
}()
private var result: Data? = nil
init() {
}
func update(url: URL) throws {
guard let inputStream = InputStream(url: url) else {
throw InputStreamError.createFailed(url)
}
return try update(inputStream: inputStream)
}
func update(inputStream: InputStream) throws {
guard result == nil else {
return
}
inputStream.open()
defer {
inputStream.close()
}
let bufferSize = 4096
let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)
defer {
buffer.deallocate()
}
while true {
let bytesRead = inputStream.read(buffer, maxLength: bufferSize)
if bytesRead < 0 {
throw (inputStream.streamError ?? InputStreamError.readFailed)
} else if bytesRead == 0 {
break
}
self.update(bytes: buffer, length: bytesRead)
}
}
func update(data: Data) {
guard result == nil else {
return
}
data.withUnsafeBytes {
self.update(bytes: $0, length: data.count)
}
}
func update(bytes: UnsafeRawPointer, length: Int) {
guard result == nil else {
return
}
_ = CC_SHA256_Update(&self.context, bytes, CC_LONG(length))
}
func finalize() -> Data {
if let calculatedResult = result {
return calculatedResult
}
var resultBuffer = [UInt8](repeating: 0, count: Int(CC_SHA256_DIGEST_LENGTH))
CC_SHA256_Final(&resultBuffer, &self.context)
let theResult = Data(bytes: resultBuffer)
result = theResult
return theResult
}
}
extension Data {
private static let hexCharacterLookupTable: [Character] = [
"0",
"1",
"2",
"3",
"4",
"5",
"6",
"7",
"8",
"9",
"a",
"b",
"c",
"d",
"e",
"f"
]
var hexString: String {
return self.reduce(into: String(), { (result, byte) in
let c1: Character = Data.hexCharacterLookupTable[Int(byte >> 4)]
let c2: Character = Data.hexCharacterLookupTable[Int(byte & 0x0F)]
result.append(c1)
result.append(c2)
})
}
}
Aşağıdaki gibi kullanabilirsiniz:
let digest = SHA256Digest()
try digest.update(url: fileURL)
let result = digest.finalize().hexString
print(result)