(Swift 3,4,5...) AES Encrypt and Decrypt a File

Swift 3,4,5... demonstrates how to AES encrypt a file of any size, and then decrypt.

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let crypt = CkoCrypt2()!

    crypt.cryptAlgorithm = "aes"

    // CipherMode may be "ecb" or "cbc"
    crypt.cipherMode = "cbc"

    // KeyLength may be 128, 192, 256
    crypt.keyLength = 256

    // The padding scheme determines the contents of the bytes
    // that are added to pad the result to a multiple of the
    // encryption algorithm's block size.  AES has a block
    // size of 16 bytes, so encrypted output is always
    // a multiple of 16.
    crypt.paddingScheme = 0

    // An initialization vector is required if using CBC mode.
    // ECB mode does not use an IV.
    // The length of the IV is equal to the algorithm's block size.
    // It is NOT equal to the length of the key.
    var ivHex: String? = "000102030405060708090A0B0C0D0E0F"
    crypt.setEncodedIV(ivHex, encoding: "hex")

    // The secret key must equal the size of the key.  For
    // 256-bit encryption, the binary secret key is 32 bytes.
    // For 128-bit encryption, the binary secret key is 16 bytes.
    var keyHex: String? = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
    crypt.setEncodedKey(keyHex, encoding: "hex")

    // Encrypt a file, producing the .aes as output.
    // The input file is unchanged, the output .aes contains the encrypted
    // contents of the input file.

    // Note: The .aes output file has no file format.  It is simply a stream
    // of bytes that resembles random binary data.
    var inFile: String? = "/Users/chilkat/testData/pdf/sample.pdf"
    var outFile: String? = "/Users/chilkat/testData/p7m/sample.pdf.aes"
    var success: Bool = crypt.ckEncryptFile(inFile, destFile: outFile)
    if success != true {
        print("\(crypt.lastErrorText!)")
        return
    }

    // For demonstration purposes, a different instance of the object will be used
    // for decryption.
    let decrypt = CkoCrypt2()!

    // All settings must match to be able to decrypt:
    decrypt.cryptAlgorithm = "aes"
    decrypt.cipherMode = "cbc"
    decrypt.keyLength = 256
    decrypt.paddingScheme = 0
    decrypt.setEncodedIV(ivHex, encoding: "hex")
    decrypt.setEncodedKey(keyHex, encoding: "hex")

    // Decrypt the .aes
    inFile = "/Users/chilkat/testData/p7m/sample.pdf.aes"
    outFile = "/Users/chilkat/testData/pdf/recovered.pdf"
    success = decrypt.ckDecryptFile(inFile, destFile: outFile)
    if success == false {
        print("\(decrypt.lastErrorText!)")
        return
    }

    print("Success!")

}