uploadID := r.Form.Get(xhttp.UploadID)
	partIDString := r.Form.Get(xhttp.PartNumber)

	partID, err := strconv.Atoi(partIDString)
	if err != nil || partID <= 0 {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidPart), r.URL)
		return
	}

	// check partID with maximum part ID for multipart objects
	if isMaxPartID(partID) {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidMaxParts), r.URL)
		return
	}

	}

	// Read escaped copy source path to check for parameters.
	cpSrcPath := r.Header.Get(xhttp.AmzCopySource)
	var vid string
	if u, err := url.Parse(cpSrcPath); err == nil {
		vid = strings.TrimSpace(u.Query().Get(xhttp.VersionID))
		// Note that url.Parse does the unescaping
		cpSrcPath = u.Path
	}

	srcBucket, srcObject := path2BucketObject(cpSrcPath)