refs/iterator: implement seeking for reftable iterators

Implement seeking of reftable iterators. As the low-level reftable iterators already support seeking this change is straight-forward. Two notes though: - We do not support seeking on reflog iterators. It is unclear what seeking would even look like in this context, as you typically would want to seek to a specific entry in the reflog for a specific ref. There is currently no use case for this, but if one arises in the future, we can still implement seeking at that later point. - We start to check whether `reftable_stack_init_ref_iterator()` is successful. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Patrick Steinhardt committed Mar 12, 2025 at 16:56 UTC 53de20c931faabdb6fa9a30d949266b2a7471497
1 file changed +30 -5
refs/reftable-backend.c
+30 -5
@@ -547,7 +547,7 @@ struct reftable_ref_iterator {
547 struct reftable_ref_record ref;
548 struct object_id oid;
549
550 - const char *prefix;
550 + char *prefix;
551 size_t prefix_len;
552 char **exclude_patterns;
553 size_t exclude_patterns_index;
@@ -718,6 +718,20 @@ static int reftable_ref_iterator_advance(struct ref_iterator *ref_iterator)
718 return ITER_OK;
719 }
720
721 +static int reftable_ref_iterator_seek(struct ref_iterator *ref_iterator,
722 + const char *prefix)
723 +{
724 + struct reftable_ref_iterator *iter =
725 + (struct reftable_ref_iterator *)ref_iterator;
726 +
727 + free(iter->prefix);
728 + iter->prefix = xstrdup_or_null(prefix);
729 + iter->prefix_len = prefix ? strlen(prefix) : 0;
730 + iter->err = reftable_iterator_seek_ref(&iter->iter, prefix);
731 +
732 + return iter->err;
733 +}
734 +
735 static int reftable_ref_iterator_peel(struct ref_iterator *ref_iterator,
736 struct object_id *peeled)
737 {
@@ -744,10 +758,12 @@ static void reftable_ref_iterator_release(struct ref_iterator *ref_iterator)
758 free(iter->exclude_patterns[i]);
759 free(iter->exclude_patterns);
760 }
761 + free(iter->prefix);
762 }
763
764 static struct ref_iterator_vtable reftable_ref_iterator_vtable = {
765 .advance = reftable_ref_iterator_advance,
766 + .seek = reftable_ref_iterator_seek,
767 .peel = reftable_ref_iterator_peel,
768 .release = reftable_ref_iterator_release,
769 };
@@ -806,8 +822,6 @@ static struct reftable_ref_iterator *ref_iterator_for_stack(struct reftable_ref_
822
823 iter = xcalloc(1, sizeof(*iter));
824 base_ref_iterator_init(&iter->base, &reftable_ref_iterator_vtable);
809 - iter->prefix = prefix;
810 - iter->prefix_len = prefix ? strlen(prefix) : 0;
825 iter->base.oid = &iter->oid;
826 iter->flags = flags;
827 iter->refs = refs;
@@ -821,8 +835,11 @@ static struct reftable_ref_iterator *ref_iterator_for_stack(struct reftable_ref_
835 if (ret)
836 goto done;
837
824 - reftable_stack_init_ref_iterator(stack, &iter->iter);
825 - ret = reftable_iterator_seek_ref(&iter->iter, prefix);
838 + ret = reftable_stack_init_ref_iterator(stack, &iter->iter);
839 + if (ret)
840 + goto done;
841 +
842 + ret = reftable_ref_iterator_seek(&iter->base, prefix);
843 if (ret)
844 goto done;
845
@@ -2018,6 +2035,13 @@ static int reftable_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2035 return ITER_OK;
2036 }
2037
2038 +static int reftable_reflog_iterator_seek(struct ref_iterator *ref_iterator UNUSED,
2039 + const char *prefix UNUSED)
2040 +{
2041 + BUG("reftable reflog iterator cannot be seeked");
2042 + return -1;
2043 +}
2044 +
2045 static int reftable_reflog_iterator_peel(struct ref_iterator *ref_iterator UNUSED,
2046 struct object_id *peeled UNUSED)
2047 {
@@ -2036,6 +2060,7 @@ static void reftable_reflog_iterator_release(struct ref_iterator *ref_iterator)
2060
2061 static struct ref_iterator_vtable reftable_reflog_iterator_vtable = {
2062 .advance = reftable_reflog_iterator_advance,
2063 + .seek = reftable_reflog_iterator_seek,
2064 .peel = reftable_reflog_iterator_peel,
2065 .release = reftable_reflog_iterator_release,
2066 };