Swift

S3 Resume Download

See more Amazon S3 (new) Examples

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.

Swift

func chilkatTest() {
    var success: Bool = false

    // 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
    success = rest.connect(hostname: "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(authProvider: 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(path: 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(value: "bytes=")
        sbRange.appendInt(value: sz)
        sbRange.append(value: "-")
        rest.addHeader(name: "Range", value: sbRange.getAsString())
        print("Added Range: \(sbRange.getAsString()!)")
    }

    // Send the request to download the remainder of the file.
    success = rest.sendReqNoBody(httpVerb: "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(stream: 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!)")
        }

    }


}