(Go) S3 Upload the Parts for a Multipart Upload

This example uploads a large file in parts. The multipart upload needs to have been first initiated prior to uploading the parts.

See http://docs.aws.amazon.com/AmazonS3/latest/API/mpUploadUploadPart.html for more information about uploading parts.

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    // In the 1st step for uploading a large file, the multipart upload was initiated
    // as shown here: Initiate Multipart Upload

    // Other S3 Multipart Upload Examples:
    // Complete Multipart Upload
    // Abort Multipart Upload
    // List Parts

    // When we initiated the multipart upload, we saved the XML response to a file.  This
    // XML response contains the UploadId.  We'll begin by loading that XML and getting
    // the Upload ID.

    xmlInit := chilkat.NewXml()
    success := xmlInit.LoadXmlFile("s3_multipart_uploads/initiate.xml")
    if success != true {
        fmt.Println("Did not find the initiate.xml XML file.")
        xmlInit.DisposeXml()
        return
    }

    uploadId := xmlInit.GetChildContent("UploadId")
    fmt.Println("UploadId = ", *uploadId)

    // When uploading parts, we need to keep an XML record of each part number
    // and its corresponding ETag, which is received in the response for each part.
    // There can be up to 10000 parts, numbered 1 to 10000.  
    // After all parts have been uploaded, the final step will be to complete
    // the multipart upload (see Complete Multipart Upload)

    // In this example, the large file we want to upload is somethingBig.zip
    fileToUploadPath := "s3_multipart_uploads/somethingBig.zip"

    // The minimum allowed part size is 5MB (5242880 bytes).  The last part can be smaller because
    // it will contain the remainder of the file.  (This minimum is enforced by the AWS service.)
    // We'll use the minimum allowed part size for this example.
    partSize := 5242880

    // Let's use Chilkat's FileAccess API to examine the file to be uploaded.  We'll get the size
    // of the file and find out how many parts will be needed, including the final "partial" part.
    fac := chilkat.NewFileAccess()
    fac.OpenForRead(fileToUploadPath)

    // How many parts will there be if each part is 5242880 bytes?
    numParts := fac.GetNumBlocks(partSize)
    fmt.Println("numParts = ", numParts)
    fac.FileClose()

    // Imagine that we may be running this for the 1st time, or maybe we already
    // attempted to upload parts, and something failed. Maybe there was a network problem
    // the resulted in not all parts getting uploaded.  We'll write this code so that if run again,
    // it will upload whatever parts haven't yet been uploaded.

    // We'll keep a partsList.xml file to record the parts that have already been successfully
    // uploaded.  If this file does not yet exist, we'll create it..
    partsListFile := "s3_multipart_uploads/partsList.xml"
    partsListXml := chilkat.NewXml()
    if fac.FileExists(partsListFile) == true {
        partsListXml.LoadXmlFile(partsListFile)
    }

    // Make sure the top-level tag is "CompleteMultipartUpload"
    partsListXml.SetTag("CompleteMultipartUpload")

    // --------------------------------------
    // Before entering the loop to upload parts,
    // setup the REST object with AWS authentication,
    // and make the initial connection.
    rest := chilkat.NewRest()

    // Connect to the Amazon AWS REST server.
    bTls := true
    port := 443
    bAutoReconnect := true
    success = rest.Connect("s3.amazonaws.com",port,bTls,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.
    authAws := chilkat.NewAuthAws()
    authAws.SetAccessKey("AWS_ACCESS_KEY")
    authAws.SetSecretKey("AWS_SECRET_KEY")
    authAws.SetServiceName("s3")
    success = rest.SetAuthAws(authAws)

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat100".
    rest.SetHost("chilkat100.s3.amazonaws.com")
    // --------------------------------------

    partNumber := 1
    sbPartNumber := chilkat.NewStringBuilder()

    for (partNumber <= numParts) {
        fmt.Println("---- ", partNumber, " ----")

        // This cumbersome way of converting an integer to a string is because
        // Chilkat examples are written in a script that is converted to many programming languages.
        // At this time, the translator does not have integer-to-string code generation capability..
        sbPartNumber.Clear()
        sbPartNumber.AppendInt(partNumber)

        bPartAlreadyUploaded := false

        // If there are no children, then the XML is empty and no parts have yet been uploaded.
        numUploadedParts := partsListXml.NumChildren()
        if numUploadedParts > 0 {
            // If some parts have been uploaded, check to see if this particular part was already upload.
            // If so, then it can be skipped.

            // Position ourselves at the 1st record.
            xRec0 := partsListXml.GetChild(0)
            foundRec := xRec0.FindNextRecord("PartNumber",*sbPartNumber.GetAsString())
            if xRec0.LastMethodSuccess() == true {
                bPartAlreadyUploaded = true
                fmt.Println("Part ", partNumber, " was previously uploaded.")
                fmt.Println(*foundRec.GetXml())
                foundRec.DisposeXml()
            }

            xRec0.DisposeXml()
        }

        // If this part was not already uploaded, we need to upload.
        // Also update the partsListXml and save as each part is successfully uploaded.
        if bPartAlreadyUploaded == false {
            fmt.Println("Uploading part ", partNumber, " ...")

            // Setup the stream source for the large file to be uploaded..
            fileStream := chilkat.NewStream()
            fileStream.SetSourceFile(fileToUploadPath)
            // The Chilkat Stream API has features to make uploading a parts
            // of a file easy.  Indicate the part size by setting the SourceFilePartSize
            // property.
            fileStream.SetSourceFilePartSize(partSize)

            // Our HTTP start line to upload a part will look like this:
            // PUT /ObjectName?partNumber=PartNumber&uploadId=UploadId HTTP/1.1

            // Set the query params.  We'll need partNumber and uploadId.
            // Make sure the query params from previous iterations are clear.
            rest.ClearAllQueryParams()
            rest.AddQueryParam("partNumber",*sbPartNumber.GetAsString())
            rest.AddQueryParam("uploadId",*uploadId)

            // Upload this particular file part.
            // Tell the fileStream which part is being uploaded.
            // Our partNumber is 1-based (the 1st part is at index 1), but the fileStream's SourceFilePart
            // property is 0-based.  Therefore we use partNumber-1.
            fileStream.SetSourceFilePart(partNumber - 1)

            // Because the SourceFilePart and SourceFilePartSize properties are set, the stream will 
            // will provide just that part of the file.  
            responseStr := rest.FullRequestStream("PUT","/somethingBig.zip",fileStream)
            if rest.LastMethodSuccess() != true {
                fmt.Println(rest.LastErrorText())
                xmlInit.DisposeXml()
                fac.DisposeFileAccess()
                partsListXml.DisposeXml()
                rest.DisposeRest()
                authAws.DisposeAuthAws()
                sbPartNumber.DisposeStringBuilder()
                fileStream.DisposeStream()
                return
            }

            if rest.ResponseStatusCode() != 200 {
                // Examine the request/response to see what happened.
                fmt.Println("response status code = ", rest.ResponseStatusCode())
                fmt.Println("response status text = ", rest.ResponseStatusText())
                fmt.Println("response header: ", rest.ResponseHeader())
                fmt.Println("response body: ", *responseStr)
                fmt.Println("---")
                fmt.Println("LastRequestStartLine: ", rest.LastRequestStartLine())
                fmt.Println("LastRequestHeader: ", rest.LastRequestHeader())
                xmlInit.DisposeXml()
                fac.DisposeFileAccess()
                partsListXml.DisposeXml()
                rest.DisposeRest()
                authAws.DisposeAuthAws()
                sbPartNumber.DisposeStringBuilder()
                fileStream.DisposeStream()
                return
            }

            // OK, this part was uploaded..
            // The response will have a 0-length body.  The only information we need is the 
            // ETag response header field.
            etag := rest.ResponseHdrByName("ETag")
            // It should be present, but just in case there was no ETag header...
            if rest.LastMethodSuccess() != true {
                fmt.Println("No ETag response header found!")
                fmt.Println("response header: ", rest.ResponseHeader())
                xmlInit.DisposeXml()
                fac.DisposeFileAccess()
                partsListXml.DisposeXml()
                rest.DisposeRest()
                authAws.DisposeAuthAws()
                sbPartNumber.DisposeStringBuilder()
                fileStream.DisposeStream()
                return
            }

            // We need to add record to the partsListXml.
            // The record will look like this:
            // &lt;Part>
            //   &lt;PartNumber>PartNumber&lt;/PartNumber>
            //   &lt;ETag>ETag&lt;/ETag>
            // &lt;/Part>
            xPart := partsListXml.NewChild("Part","")
            xPart.NewChildInt2("PartNumber",partNumber)
            xPart.NewChild2("ETag",*etag)
            xPart.DisposeXml()

            success = partsListXml.SaveXml(partsListFile)
            if success != true {
                fmt.Println(partsListXml.LastErrorText())
                xmlInit.DisposeXml()
                fac.DisposeFileAccess()
                partsListXml.DisposeXml()
                rest.DisposeRest()
                authAws.DisposeAuthAws()
                sbPartNumber.DisposeStringBuilder()
                fileStream.DisposeStream()
                return
            }

            fmt.Println("-- Part ", partNumber, " uploaded. ---------------------")
        }

        partNumber = partNumber + 1
    }

    fmt.Println("Finished.  All parts uploaded.")

    xmlInit.DisposeXml()
    fac.DisposeFileAccess()
    partsListXml.DisposeXml()
    rest.DisposeRest()
    authAws.DisposeAuthAws()
    sbPartNumber.DisposeStringBuilder()
    fileStream.DisposeStream()