Dart

S3 Upload the Parts for a Multipart Upload

See more Amazon S3 (new) Examples

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.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.

  final xmlInit = CkXml();
  try {
    xmlInit.loadXmlFile('s3_multipart_uploads/initiate.xml');
  } on ChilkatException {
    print('Did not find the initiate.xml XML file.');
    return;
  }

  final uploadId = xmlInit.getChildContent('UploadId');
  print('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
  final 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.
  final 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.
  final fac = CkFileAccess();
  fac.openForRead(fileToUploadPath);

  // How many parts will there be if each part is 5242880 bytes?
  final numParts = fac.getNumBlocks(partSize);
  print('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..
  final partsListFile = 's3_multipart_uploads/partsList.xml';
  final partsListXml = CkXml();
  if (fac.fileExists(partsListFile)) {
    partsListXml.loadXmlFile(partsListFile);
  }

  // Make sure the top-level tag is "CompleteMultipartUpload"
  partsListXml.tag = 'CompleteMultipartUpload';

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

  // Connect to the Amazon AWS REST server.
  final bTls = true;
  final port = 443;
  final bAutoReconnect = true;
  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.
  final authAws = CkAuthAws();
  authAws.accessKey = 'AWS_ACCESS_KEY';
  authAws.secretKey = 'AWS_SECRET_KEY';
  authAws.serviceName = 's3';
  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';
  // --------------------------------------

  var partNumber = 1;
  final sbPartNumber = CkStringBuilder();

  while (partNumber <= numParts) {
    print('---- $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);

    var bPartAlreadyUploaded = false;

    // If there are no children, then the XML is empty and no parts have yet been uploaded.
    final 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.
      final xRec0 = partsListXml.getChild(0);
      try {
        final foundRec = xRec0.findNextRecord('PartNumber', sbPartNumber.getAsString());
        bPartAlreadyUploaded = true;
        print('Part $partNumber was previously uploaded.');
        print(foundRec.getXml());
      } on ChilkatException {
        // xRec0.findNextRecord() failed; continue anyway.
      }
    }

    // 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) {
      print('Uploading part $partNumber ...');

      // Setup the stream source for the large file to be uploaded..
      final fileStream = CkStream();
      fileStream.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.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.sourceFilePart = partNumber - 1;

      // Because the SourceFilePart and SourceFilePartSize properties are set, the stream will 
      // will provide just that part of the file.  
      final String responseStr;
      try {
        responseStr = rest.fullRequestStream('PUT', '/somethingBig.zip', fileStream);
      } on ChilkatException catch (e) {
        print(e.lastErrorText);
        return;
      }

      if (rest.responseStatusCode != 200) {
        // Examine the request/response to see what happened.
        print('response status code = ${rest.responseStatusCode}');
        print('response status text = ${rest.responseStatusText}');
        print('response header: ${rest.responseHeader}');
        print('response body: $responseStr');
        print('---');
        print('LastRequestStartLine: ${rest.lastRequestStartLine}');
        print('LastRequestHeader: ${rest.lastRequestHeader}');
        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.
      // It should be present, but just in case there was no ETag header...
      final String etag;
      try {
        etag = rest.responseHdrByName('ETag');
      } on ChilkatException {
        print('No ETag response header found!');
        print('response header: ${rest.responseHeader}');
        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>
      final xPart = partsListXml.newChild('Part', '');
      xPart.newChildInt2('PartNumber', partNumber);
      xPart.newChild2('ETag', etag);

      try {
        partsListXml.saveXml(partsListFile);
      } on ChilkatException catch (e) {
        print(e.lastErrorText);
        return;
      }

      print('-- Part $partNumber uploaded. ---------------------');
    }

    partNumber++;
  }

  print('Finished.  All parts uploaded.');
}