(Swift 3,4,5...) Parse Multipart Binary Http Response

This example demonstrates how to parse an HTTP response that is multipart and contains a binary file, such as a .zip or .pdf.

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

    var success: Bool
    let http = CkoHttp()!

    let req = CkoHttpRequest()!

    // ...
    // Insert code here to construct some kind of HTTP request.
    // this example is to show how to parse a particular kind of response.
    // ...
    // ...

    // Send the request (whatever it may be in your case) to get the HTTP response object.
    var resp: CkoHttpResponse? = http.synchronousRequest("www.somedomain.com", port: 443, ssl: true, req: req)
    if http.lastMethodSuccess != true {
        print("\(http.lastErrorText!)")
        return
    }

    // Get the response body (which is expected to be binary)
    let respBody = CkoBinData()!
    resp!.getBodyBd(respBody)
    resp = nil

    // For this example, the response body contains something like this:

    // ------=_Part_21302_2029949381.1547401515443
    // Content-Type: application/xop+xml; charset=UTF-8; type="text/xml"
    // Content-Transfer-Encoding: 8bit
    // Content-ID: <rootpart@ws.jboss.org>
    // 
    // <env:Envelope xmlns:env='http://schemas.xmlsoap.org/soap/envelope/'><env:Header></env:Header><env:Body>...</env:Body></env:Envelope>
    // ------=_Part_21302_2029949381.1547401515443
    // Content-Type: application/octet-stream
    // Content-Transfer-Encoding: binary
    // Content-Id: <fileArchivio-7d302908-4d64-43d3-bf4e-79ce806d43b3@ws.jboss.org>
    // 
    // BINARY_CONTENT_HERE...
    // 
    // ------=_Part_21302_2029949381.1547401515443--
    // 

    // Load it into a Chilkat MIME object.
    let mime = CkoMime()!
    success = mime.loadBd(respBody)
    if success != true {
        print("\(mime.lastErrorText!)")
        return
    }

    var numParts: Int = mime.numParts.intValue
    if numParts < 2 {
        print("Expected multipart MIME with at least 2 sub-parts.")
        return
    }

    // Get the 1st sub-part, which is the XML.
    var part0: CkoMime? = mime.getPart(0)
    // Should be OK because we checked NumParts above..
    var xmlStr: String? = part0!.getBodyDecoded()
    print("\(xmlStr!)")
    print("----")
    part0 = nil

    // Save the 2nd part to a file.  (It is a .zip file in our test case..)
    var part1: CkoMime? = mime.getPart(1)
    success = part1!.saveBody("qa_output/attachedZip.zip")

    // Alternatively, we could extract the binary data to a BinData and use elsewhere..
    let zipData = CkoBinData()!
    success = part1!.getBodyBd(zipData)
    success = zipData.writeFile("qa_output/attachedZip_again.zip")
    part1 = nil

    print("OK.")

}