func()

in sharedlibraries/storage/storage.go [361:422]
58 lines of code
14 McCabe index (conditional complexity)

func (rw *ReadWriter) Download(ctx context.Context) (int64, error) {
	if rw.BucketHandle == nil {
		return 0, errors.New("no bucket defined")
	}

	if rw.EncryptionKey != "" || rw.KMSKey != "" {
		log.CtxLogger(ctx).Infow("Decryption enabled for download", "bucket", rw.BucketName, "object", rw.ObjectName)
	}
	object := rw.BucketHandle.Object(rw.ObjectName)
	var decodedKey []byte
	if rw.EncryptionKey != "" {
		var err error
		decodedKey, err = base64.StdEncoding.DecodeString(rw.EncryptionKey)
		if err != nil {
			return 0, err
		}
		object = object.Key(decodedKey)
	}

	var reader io.ReadCloser
	var err error
	if rw.ParallelDownloadWorkers > 1 {
		reader, err = rw.NewParallelReader(ctx, decodedKey)
	} else {
		object = object.Retryer(rw.retryOptions("Failed to download data from Google Cloud Storage, retrying.")...)
		reader, err = object.NewReader(ctx)
	}
	if err != nil {
		return 0, err
	}
	defer reader.Close()
	rw.Reader = reader

	rw = rw.defaultArgs()
	log.CtxLogger(ctx).Infow("Download starting", "bucket", rw.BucketName, "object", rw.ObjectName, "totalBytes", rw.TotalBytes)
	var bytesWritten int64
	attrs, err := object.Attrs(ctx)
	if err != nil {
		return 0, err
	}
	if attrs.ContentType == compressedContentType {
		log.CtxLogger(ctx).Infow("Compressed file detected, decompressing during download", "bucket", rw.BucketName, "object", rw.ObjectName)
		gzipReader, err := gzip.NewReader(rw)
		if err != nil {
			return 0, err
		}
		if bytesWritten, err = rw.Copier(rw.Writer, gzipReader); err != nil {
			return 0, err
		}
		if err := gzipReader.Close(); err != nil {
			return 0, err
		}
	} else {
		if bytesWritten, err = rw.Copier(rw.Writer, rw); err != nil {
			return 0, err
		}
	}

	avgTransferSpeedMBps := float64(rw.bytesTransferred) / rw.totalTransferTime.Seconds() / 1024 / 1024
	log.CtxLogger(ctx).Infow("Download success", "bucket", rw.BucketName, "object", rw.ObjectName, "bytesWritten", bytesWritten, "bytesTransferred", rw.bytesTransferred, "totalBytes", rw.TotalBytes, "percentComplete", 100, "avgTransferSpeedMBps", fmt.Sprintf("%g", math.Round(avgTransferSpeedMBps)))
	return bytesWritten, nil
}