code: function PutPart(fileUpload, part) {
              this.part = part;
  
              this.partNumber = part.partNumber;
              this.start = (this.partNumber - 1) * fileUpload.con.partSize;
              this.end = Math.min(this.partNumber * fileUpload.con.partSize, fileUpload.sizeBytes);
  
              var request = {
                  method: 'PUT',
                  path: '?partNumber=' + this.partNumber + '&uploadId=' + fileUpload.uploadId,
                  step: 'upload #' + this.partNumber,
                  x_amz_headers: fileUpload.xAmzHeadersCommon || fileUpload.xAmzHeadersAtUpload,
                  contentSha256: "UNSIGNED-PAYLOAD",
                  onProgress: this.onProgress.bind(this)
              };
  
              SignedS3AWSRequest.call(this, fileUpload, request);
          }
docs: http://docs.aws.amazon.com/AmazonS3/latest/API/mpUploadUploadPart.html