private DownloadFileResult downloadFileWithCheckpoint()

in src/main/java/com/aliyun/oss/internal/OSSDownloadOperation.java [399:469]
47 lines of code
11 McCabe index (conditional complexity)

    private DownloadFileResult downloadFileWithCheckpoint(DownloadFileRequest downloadFileRequest) throws Throwable {
        DownloadFileResult downloadFileResult = new DownloadFileResult();
        DownloadCheckPoint downloadCheckPoint = new DownloadCheckPoint();

        // The checkpoint is enabled, downloads the parts download results from
        // checkpoint file.
        if (downloadFileRequest.isEnableCheckpoint()) {
            // read the last download result. If checkpoint file dosx not exist,
            // or the file is updated/corrupted,
            // re-download again.
            try {
                downloadCheckPoint.load(downloadFileRequest.getCheckpointFile());
            } catch (Exception e) {
                remove(downloadFileRequest.getCheckpointFile());
            }

            // The download checkpoint is corrupted, download again.
            if (!downloadCheckPoint.isValid(objectOperation, downloadFileRequest)) {
                prepare(downloadCheckPoint, downloadFileRequest);
                remove(downloadFileRequest.getCheckpointFile());
            }
        } else {
            // The checkpoint is not enabled, download the file again.
            prepare(downloadCheckPoint, downloadFileRequest);
        }

        // Progress listen starts tracking the progress.
        ProgressListener listener = downloadFileRequest.getProgressListener();
        ProgressPublisher.publishProgress(listener, ProgressEventType.TRANSFER_STARTED_EVENT);

        // Concurrently download parts.
        DownloadResult downloadResult = download(downloadCheckPoint, downloadFileRequest);
        Long serverCRC = null;
        for (PartResult partResult : downloadResult.getPartResults()) {
            if (partResult.getServerCRC() != null) {
                serverCRC = partResult.getServerCRC();
            }
            if (partResult.isFailed()) {
                ProgressPublisher.publishProgress(listener, ProgressEventType.TRANSFER_PART_FAILED_EVENT);
                throw partResult.getException();
            }
        }

        // check crc64
        if(objectOperation.getInnerClient().getClientConfiguration().isCrcCheckEnabled() &&
           !hasRangeInRequest(downloadFileRequest)) {
            Long clientCRC = calcObjectCRCFromParts(downloadResult.getPartResults());
            try {
                OSSUtils.checkChecksum(clientCRC, serverCRC, downloadResult.getObjectMetadata().getRequestId());
            } catch (Exception e) {
                ProgressPublisher.publishProgress(listener, ProgressEventType.TRANSFER_FAILED_EVENT);
                throw new InconsistentException(clientCRC, serverCRC, downloadResult.getObjectMetadata().getRequestId());
            }
        }


        // Publish the complete status.
        ProgressPublisher.publishProgress(listener, ProgressEventType.TRANSFER_COMPLETED_EVENT);

        // rename the temp file.
        renameTo(downloadFileRequest.getTempDownloadFile(), downloadFileRequest.getDownloadFile());

        // The checkpoint is enabled, delete the checkpoint file after a
        // successful download.
        if (downloadFileRequest.isEnableCheckpoint()) {
            remove(downloadFileRequest.getCheckpointFile());
        }

        downloadFileResult.setObjectMetadata(downloadResult.getObjectMetadata());
        return downloadFileResult;
    }