Cannot invoke initializer for type UnsafeMutablePointer<UInt8>

Question

I'm trying to convert my string into SHA256 hash, but I get the next error:

Cannot invoke initializer for type 'UnsafeMutablePointer<UInt8>' with an argument list of type '(UnsafeMutableRawPointer)'

That's my function:

func SHA256(data: String) -> Data {
    var hash = NSMutableData(length: Int(CC_SHA256_DIGEST_LENGTH))!

    if let newData: Data = data.data(using: .utf8) {
        let bytes = newData.withUnsafeBytes {(bytes: UnsafePointer<CChar>) -> Void in
            CC_SHA256(bytes, CC_LONG(newData.length), UnsafeMutablePointer<UInt8>(hash.mutableBytes))
        }
    }

    return hash as Data
}

so, for this part

UnsafeMutablePointer<UInt8>(hash.mutableBytes)

I get this error:

Cannot invoke initializer for type 'UnsafeMutablePointer<UInt8>' with an argument list of type '(UnsafeMutableRawPointer)'

How can I fix that and what I do wrong?

Answer 1

You'd better use Data also for the result hash .

In Swift 3, withUnsafePointer(_:) and withUnsafeMutablePointer(:_) are generic types and Swift can infer the Pointee types correctly when used with "well-formed" closures, which means you have no need to convert Pointee types manually.

func withUnsafeBytes((UnsafePointer) -> ResultType)

func withUnsafeMutableBytes((UnsafeMutablePointer) -> ResultType)

func SHA256(data: String) -> Data {
    var hash = Data(count: Int(CC_SHA256_DIGEST_LENGTH))

    if let newData: Data = data.data(using: .utf8) {
        _ = hash.withUnsafeMutableBytes {mutableBytes in
            newData.withUnsafeBytes {bytes in
                CC_SHA256(bytes, CC_LONG(newData.count), mutableBytes)
            }
        }
    }

    return hash
}

In Swift 3, the initializers of UnsafePointer and UnsafeMutablePointer , which was used to convert Pointee types till Swift 2, are removed. But in many cases, you can work without type conversions of pointers.