(Swift 2) S3 Resume Download

Suppose an S3 download of a very large file failed for some reason and you have a partial file on disk. Rather than restart the entire download, you wish to download the remaining portion. This example demonstrates how to finish a previously failed download.

Note: This example requires Chilkat v9.5.0.83 or above.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

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

    let rest = CkoRest()

    // Connect to the Amazon AWS REST server.
    var bTls: Bool = true
    var port: Int = 443
    var bAutoReconnect: Bool = true
    var success: Bool = rest.Connect("s3.amazonaws.com", port: port, tls: bTls, autoReconnect: bAutoReconnect)

    // ---------------------------------------------------------------------------
    // Important: For buckets created in regions outside us-east-1,
    // there are three important changes that need to be made.
    // See Working with S3 Buckets in Non-us-east-1 Regions for the details.
    // ---------------------------------------------------------------------------

    // Provide AWS credentials for the REST call.
    let authAws = CkoAuthAws()
    authAws.AccessKey = "AWS_ACCESS_KEY"
    authAws.SecretKey = "AWS_SECRET_KEY"
    authAws.ServiceName = "s3"
    success = rest.SetAuthAws(authAws)

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat100".
    rest.Host = "chilkat100.s3.amazonaws.com"

    // We want to continue downloading a file.
    // The relative local filepath of our previously partially downoaded file is: qa_output/hamlet.xml
    // Let's find out how many bytes are already downloaded.
    let fac = CkoFileAccess()
    var localFilepath: String? = "qa_output/hamlet.xml"
    // Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
    // the size of the file as a string, then convert to an integer value.
    var sz: Int = fac.FileSize(localFilepath).intValue
    if sz > 0 {
        print("sz = \(sz)")

        // If the sz equals 42375 bytes, then we want to add a Range header that looks like this:
        // Range: bytes=42375-
        let sbRange = CkoStringBuilder()
        sbRange.Append("bytes=")
        sbRange.AppendInt(sz)
        sbRange.Append("-")
        rest.AddHeader("Range", value: sbRange.GetAsString())
        print("Added Range: \(sbRange.GetAsString())")
    }

    // Send the request to download the remainder of the file.
    success = rest.SendReqNoBody("GET", uriPath: "/hamlet.xml")
    if success != true {
        print("\(rest.LastErrorText)")
        return
    }

    // Read the response header.
    var responseStatusCode: Int = rest.ReadResponseHeader().intValue
    if responseStatusCode < 0 {
        print("\(rest.LastErrorText)")
        return
    }

    print("Response status code = \(responseStatusCode)")

    // We expect a 200 or 206 response status if the file data is coming.
    // Otherwise, we'll get a string response body with an error message(or no response body).
    if (responseStatusCode == 200) || (responseStatusCode == 206) {

        let bodyStream = CkoStream()

        // The stream's sink will be a file.
        // We will append to the file..
        bodyStream.SinkFile = localFilepath

        // Indicate that we wish to append to the output file.
        // The SinkFileAppend property was added in Chilkat v9.50.83
        bodyStream.SinkFileAppend = true

        // Read the response body to the stream.  Given that we've
        // set the stream's sink to a file, it will stream directly
        // to the file.
        success = rest.ReadRespBodyStream(bodyStream, autoSetStreamCharset: true)
        if success != true {
            print("\(rest.LastErrorText)")
            return
        }

        print("Successfully downloaded the file.")

    }
    else {
        var errResponse: String? = rest.ReadRespBodyString()
        if rest.LastMethodSuccess != true {
            print("\(rest.LastErrorText)")
        }
        else {
            print("\(errResponse!)")
        }

    }


}