Method NewReader

db/data/reader.go:22–47

NewReader returns a Reader for this data object. If the object has a seek index and if the provided span skips part of the object, the seek index will be used to limit the reading window of the returned reader.

(ctx context.Context, engine storage.Engine, path *storage.URI, ranges []seekindex.Range)

// and if the provided span skips part of the object, the seek index will be used to
// limit the reading window of the returned reader.
func (o *Object) NewReader(ctx context.Context, engine storage.Engine, path *storage.URI, ranges []seekindex.Range) (*Reader, error) {
	objectPath := o.SequenceURI(path)
	reader, err := engine.Get(ctx, objectPath)
	if err != nil {
		return nil, fmt.Errorf("%s: %w", objectPath, err)
	}
	var r io.Reader
	var readBytes int64
	if len(ranges) == 0 {
		r = reader
		readBytes = o.Size
	} else {
		readers := make([]io.Reader, 0, len(ranges))
		for _, rg := range ranges {
			readers = append(readers, io.NewSectionReader(reader, rg.Offset, rg.Length))
			readBytes += rg.Length
		}
		r = io.MultiReader(readers...)
	}
	return &Reader{
		Reader:     r,
		Closer:     reader,
		TotalBytes: o.Size,
		ReadBytes:  readBytes,
	}, nil
}