| 32 | } |
| 33 | |
| 34 | func (m *MultiBlockIterator[T]) Next(ctx context.Context) (common.ID, T, error) { |
| 35 | if m.done(ctx) { |
| 36 | return nil, nil, io.EOF |
| 37 | } |
| 38 | |
| 39 | var ( |
| 40 | lowestID common.ID |
| 41 | lowestBookmarks []*bookmark[T] |
| 42 | ) |
| 43 | |
| 44 | // find lowest ID of the new object |
| 45 | for _, b := range m.bookmarks { |
| 46 | id, err := b.peekID(ctx) |
| 47 | if err != nil && !errors.Is(err, io.EOF) { |
| 48 | return nil, nil, err |
| 49 | } |
| 50 | if id == nil { |
| 51 | continue |
| 52 | } |
| 53 | |
| 54 | comparison := bytes.Compare(id, lowestID) |
| 55 | |
| 56 | if comparison == 0 { |
| 57 | lowestBookmarks = append(lowestBookmarks, b) |
| 58 | } else if len(lowestID) == 0 || comparison == -1 { |
| 59 | lowestID = id |
| 60 | |
| 61 | // reset and reuse |
| 62 | lowestBookmarks = lowestBookmarks[:0] |
| 63 | lowestBookmarks = append(lowestBookmarks, b) |
| 64 | } |
| 65 | } |
| 66 | |
| 67 | // now get the lowest objects from our bookmarks |
| 68 | lowestObjects := make([]T, 0, len(lowestBookmarks)) |
| 69 | for _, b := range lowestBookmarks { |
| 70 | _, obj, err := b.current(ctx) |
| 71 | if err != nil && !errors.Is(err, io.EOF) { |
| 72 | return nil, nil, err |
| 73 | } |
| 74 | if obj == nil { |
| 75 | // this should never happen. id was non-nil above |
| 76 | return nil, nil, errors.New("unexpected nil object from lowest bookmark") |
| 77 | } |
| 78 | lowestObjects = append(lowestObjects, obj) |
| 79 | } |
| 80 | |
| 81 | lowestObject, err := m.combine(lowestObjects) |
| 82 | if err != nil { |
| 83 | return nil, nil, fmt.Errorf("combining: %w", err) |
| 84 | } |
| 85 | |
| 86 | for _, b := range lowestBookmarks { |
| 87 | b.clear() |
| 88 | } |
| 89 | |
| 90 | return lowestID, lowestObject, nil |
| 91 | } |