Create sha256 hash from different formats like Data, String, SecCertificate.

SSLPinning.swift

func sha256(_ certificate: SecCertificate) -> String? {
        let certData = SecCertificateCopyData(certificate) as Data
        let certStr = certData.base64EncodedString()
        return sha256(certStr)
    }
    func sha256(_ data: Data) -> Data? {
        guard let dataBuffer = NSMutableData(length: Int(CC_SHA256_DIGEST_LENGTH)) else { return nil }
        CC_SHA256((data as NSData).bytes, CC_LONG(data.count), dataBuffer.mutableBytes.assumingMemoryBound(to: UInt8.self))
        return dataBuffer as Data
    }
    func sha256(_ str: String) -> String? {
        guard let data = str.data(using: String.Encoding.utf8), let shaData = sha256(data)
            else { return nil }
        return shaData.base64EncodedString()
    }