MD5 and SH1 Digest

// remembers to import in Bridging-Header.h :
// #import <CommonCrypto/CommonDigest.h>

extension String {

    public func sha1() -> Data? {

        guard let messageData = self.data(using:.utf8) else {
            return nil
        }

        var digestData = Data(count: Int(CC_SHA1_DIGEST_LENGTH))

        _ = digestData.withUnsafeMutableBytes {digestBytes in
            messageData.withUnsafeBytes {messageBytes in
                CC_SHA1(messageBytes, CC_LONG(messageData.count), digestBytes)
            }
        }

        return digestData
    }

    public func md5() -> Data? {

        guard let messageData = self.data(using:.utf8) else {
            return nil
        }

        var digestData = Data(count: Int(CC_MD5_DIGEST_LENGTH))

        _ = digestData.withUnsafeMutableBytes {digestBytes in
            messageData.withUnsafeBytes {messageBytes in
                CC_MD5(messageBytes, CC_LONG(messageData.count), digestBytes)
            }
        }

        return digestData
    }
}