Method GetObject

storage/gcs/reader.go:20–80

GetObject retrieves an object from Azure cloud

(
	ctx context.Context,
	reqHeader http.Header,
	bucket, key, query string,
)

// GetObject retrieves an object from Azure cloud
func (s *Storage) GetObject(
	ctx context.Context,
	reqHeader http.Header,
	bucket, key, query string,
) (*storage.ObjectReader, error) {
	// If either bucket or object key is empty, return 404
	if len(bucket) == 0 || len(key) == 0 {
		return storage.NewObjectNotFound(
			"invalid GCS Storage URL: bucket name or object key are empty",
		), nil
	}

	// Check if access to the bucket is allowed
	if !common.IsBucketAllowed(bucket, s.config.AllowedBuckets, s.config.DeniedBuckets) {
		return nil, fmt.Errorf("access to the GCS bucket %s is denied", bucket)
	}

	var (
		reader *gcs.Reader
		size   int64
	)

	bkt := s.client.Bucket(bucket)
	obj := bkt.Object(key)

	if g, err := strconv.ParseInt(query, 10, 64); err == nil && g > 0 {
		obj = obj.Generation(g)
	}

	header := make(http.Header)

	// Try respond with partial: if that was a partial request,
	// we either return error or Object
	if r, err := s.tryRespondWithPartial(ctx, obj, reqHeader, header); r != nil || err != nil {
		return r, err
	}

	var err error
	reader, err = obj.NewReader(ctx)
	if err != nil {
		return handleError(err)
	}

	// Generate artificial ETag from CRC32 and LastModified
	var etag [12]byte
	binary.LittleEndian.PutUint32(etag[:4], reader.Attrs.CRC32C)
	binary.LittleEndian.PutUint64(etag[4:], uint64(reader.Attrs.LastModified.UnixNano()))

	header.Set(httpheaders.Etag, hex.EncodeToString(etag[:]))
	header.Set(httpheaders.LastModified, reader.Attrs.LastModified.Format(http.TimeFormat))

	if common.IsNotModified(reqHeader, header) {
		reader.Close()
		return storage.NewObjectNotModified(header), nil
	}

	size = reader.Attrs.Size
	setHeadersFromReader(header, reader, size)