(MFC) 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.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkXml.h>
#include <CkFileAccess.h>
#include <CkRest.h>
#include <CkAuthAws.h>
#include <CkStringBuilder.h>
#include <CkStream.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // 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.

    CkXml xmlInit;
    bool success = xmlInit.LoadXmlFile("s3_multipart_uploads/initiate.xml");
    if (success != true) {
        strOut.append("Did not find the initiate.xml XML file.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    const char *uploadId = xmlInit.getChildContent("UploadId");
    strOut.append("UploadId = ");
    strOut.append(uploadId);
    strOut.append("\r\n");

    // 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
    const char *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.
    int 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.
    CkFileAccess fac;
    fac.OpenForRead(fileToUploadPath);

    // How many parts will there be if each part is 5242880 bytes?
    int numParts = fac.GetNumBlocks(partSize);
    strOut.append("numParts = ");
    strOut.appendInt(numParts);
    strOut.append("\r\n");
    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..
    const char *partsListFile = "s3_multipart_uploads/partsList.xml";
    CkXml partsListXml;
    if (fac.FileExists(partsListFile) == true) {
        partsListXml.LoadXmlFile(partsListFile);
    }

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

    // --------------------------------------
    // Before entering the loop to upload parts,
    // setup the REST object with AWS authentication,
    // and make the initial connection.
    CkRest rest;

    // Connect to the Amazon AWS REST server.
    bool bTls = true;
    int port = 443;
    bool 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.
    CkAuthAws authAws;
    authAws.put_AccessKey("AWS_ACCESS_KEY");
    authAws.put_SecretKey("AWS_SECRET_KEY");
    authAws.put_ServiceName("s3");
    success = rest.SetAuthAws(authAws);

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

    int partNumber = 1;
    CkStringBuilder sbPartNumber;

    while ((partNumber <= numParts)) {
        strOut.append("---- ");
        strOut.appendInt(partNumber);
        strOut.append(" ----");
        strOut.append("\r\n");

        // 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);

        bool bPartAlreadyUploaded = false;

        // If there are no children, then the XML is empty and no parts have yet been uploaded.
        int numUploadedParts = partsListXml.get_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.
            CkXml *xRec0 = partsListXml.GetChild(0);
            CkXml *foundRec = xRec0->FindNextRecord("PartNumber",sbPartNumber.getAsString());
            if (xRec0->get_LastMethodSuccess() == true) {
                bPartAlreadyUploaded = true;
                strOut.append("Part ");
                strOut.appendInt(partNumber);
                strOut.append(" was previously uploaded.");
                strOut.append("\r\n");
                strOut.append(foundRec->getXml());
                strOut.append("\r\n");
                delete foundRec;
            }

            delete xRec0;
        }

        // 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) {
            strOut.append("Uploading part ");
            strOut.appendInt(partNumber);
            strOut.append(" ...");
            strOut.append("\r\n");

            // Setup the stream source for the large file to be uploaded..
            CkStream fileStream;
            fileStream.put_SourceFile(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.put_SourceFilePartSize(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.put_SourceFilePart(partNumber - 1);

            // Because the SourceFilePart and SourceFilePartSize properties are set, the stream will 
            // will provide just that part of the file.  
            const char *responseStr = rest.fullRequestStream("PUT","/somethingBig.zip",fileStream);
            if (rest.get_LastMethodSuccess() != true) {
                strOut.append(rest.lastErrorText());
                strOut.append("\r\n");
                SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
                return;
            }

            if (rest.get_ResponseStatusCode() != 200) {
                // Examine the request/response to see what happened.
                strOut.append("response status code = ");
                strOut.appendInt(rest.get_ResponseStatusCode());
                strOut.append("\r\n");
                strOut.append("response status text = ");
                strOut.append(rest.responseStatusText());
                strOut.append("\r\n");
                strOut.append("response header: ");
                strOut.append(rest.responseHeader());
                strOut.append("\r\n");
                strOut.append("response body: ");
                strOut.append(responseStr);
                strOut.append("\r\n");
                strOut.append("---");
                strOut.append("\r\n");
                strOut.append("LastRequestStartLine: ");
                strOut.append(rest.lastRequestStartLine());
                strOut.append("\r\n");
                strOut.append("LastRequestHeader: ");
                strOut.append(rest.lastRequestHeader());
                strOut.append("\r\n");
                SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
                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.
            const char *etag = rest.responseHdrByName("ETag");
            // It should be present, but just in case there was no ETag header...
            if (rest.get_LastMethodSuccess() != true) {
                strOut.append("No ETag response header found!");
                strOut.append("\r\n");
                strOut.append("response header: ");
                strOut.append(rest.responseHeader());
                strOut.append("\r\n");
                SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
                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>
            CkXml *xPart = partsListXml.NewChild("Part","");
            xPart->NewChildInt2("PartNumber",partNumber);
            xPart->NewChild2("ETag",etag);
            delete xPart;

            success = partsListXml.SaveXml(partsListFile);
            if (success != true) {
                strOut.append(partsListXml.lastErrorText());
                strOut.append("\r\n");
                SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
                return;
            }

            strOut.append("-- Part ");
            strOut.appendInt(partNumber);
            strOut.append(" uploaded. ---------------------");
            strOut.append("\r\n");
        }

        partNumber = partNumber + 1;
    }

    strOut.append("Finished.  All parts uploaded.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }