How to use crc32 from zlib in swift (Xcode 9)

Question

I'm new to swift/xcode and am trying to use the crc32 function that, as mentioned here, is provided in zlib from libz.dylib .

I've modified the code so that I am now trying:

let message1 = "some message".first?.value!.data(using: String.Encoding.utf8, allowLossyConversion: false) let crc = crc32(CLong(0), UnsafePointer<Bytef>(strcat!.bytes), UInt(message1!.length))

however I am encountering the error: use of unresolved identifier 'crc32'.

Could anyone help me to figure out what step I might be missing in trying to use the crc32 function?

Thanks!