From cec2b6f55a805c010d2acc81abf4cbc41b712130 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Wed, 12 Mar 2025 16:56:15 +0100 Subject: refs/iterator: separate lifecycle from iteration The ref and reflog iterators have their lifecycle attached to iteration: once the iterator reaches its end, it is automatically released and the caller doesn't have to care about that anymore. When the iterator should be released before it has been exhausted, callers must explicitly abort the iterator via `ref_iterator_abort()`. This lifecycle is somewhat unusual in the Git codebase and creates two problems: - Callsites need to be very careful about when exactly they call `ref_iterator_abort()`, as calling the function is only valid when the iterator itself still is. This leads to somewhat awkward calling patterns in some situations. - It is impossible to reuse iterators and re-seek them to a different prefix. This feature isn't supported by any iterator implementation except for the reftable iterators anyway, but if it was implemented it would allow us to optimize cases where we need to search for specific references repeatedly by reusing internal state. Detangle the lifecycle from iteration so that we don't deallocate the iterator anymore once it is exhausted. Instead, callers are now expected to always call a newly introduce `ref_iterator_free()` function that deallocates the iterator and its internal state. Note that the `dir_iterator` is somewhat special because it does not implement the `ref_iterator` interface, but is only used to implement other iterators. Consequently, we have to provide `dir_iterator_free()` instead of `dir_iterator_release()` as the allocated structure itself is managed by the `dir_iterator` interfaces, as well, and not freed by `ref_iterator_free()` like in all the other cases. While at it, drop the return value of `ref_iterator_abort()`, which wasn't really required by any of the iterator implementations anyway. Furthermore, stop calling `base_ref_iterator_free()` in any of the backends, but instead call it in `ref_iterator_free()`. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- refs/ref-cache.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) (limited to 'refs/ref-cache.c') diff --git a/refs/ref-cache.c b/refs/ref-cache.c index 02f09e4df8..6457e02c1e 100644 --- a/refs/ref-cache.c +++ b/refs/ref-cache.c @@ -409,7 +409,7 @@ static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator) if (++level->index == level->dir->nr) { /* This level is exhausted; pop up a level */ if (--iter->levels_nr == 0) - return ref_iterator_abort(ref_iterator); + return ITER_DONE; continue; } @@ -452,21 +452,18 @@ static int cache_ref_iterator_peel(struct ref_iterator *ref_iterator, return peel_object(iter->repo, ref_iterator->oid, peeled) ? -1 : 0; } -static int cache_ref_iterator_abort(struct ref_iterator *ref_iterator) +static void cache_ref_iterator_release(struct ref_iterator *ref_iterator) { struct cache_ref_iterator *iter = (struct cache_ref_iterator *)ref_iterator; - free((char *)iter->prefix); free(iter->levels); - base_ref_iterator_free(ref_iterator); - return ITER_DONE; } static struct ref_iterator_vtable cache_ref_iterator_vtable = { .advance = cache_ref_iterator_advance, .peel = cache_ref_iterator_peel, - .abort = cache_ref_iterator_abort + .release = cache_ref_iterator_release, }; struct ref_iterator *cache_ref_iterator_begin(struct ref_cache *cache, -- cgit v1.3 From 84e656919cb7237f1b11a948974d0591d9d3434f Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Wed, 12 Mar 2025 16:56:19 +0100 Subject: refs/iterator: implement seeking for ref-cache iterators Implement seeking of ref-cache iterators. This is done by splitting most of the logic to seek iterators out of `cache_ref_iterator_begin()` and putting it into `cache_ref_iterator_seek()` so that we can reuse the logic. Note that we cannot use the optimization anymore where we return an empty ref iterator when there aren't any references, as otherwise it wouldn't be possible to reseek the iterator to a different prefix that may exist. This shouldn't be much of a performance concern though as we now start to bail out early in case `advance()` sees that there are no more directories to be searched. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- refs/ref-cache.c | 79 ++++++++++++++++++++++++++++++++++++-------------------- 1 file changed, 51 insertions(+), 28 deletions(-) (limited to 'refs/ref-cache.c') diff --git a/refs/ref-cache.c b/refs/ref-cache.c index 6457e02c1e..c1f1bab1d5 100644 --- a/refs/ref-cache.c +++ b/refs/ref-cache.c @@ -362,9 +362,7 @@ struct cache_ref_iterator { struct ref_iterator base; /* - * The number of levels currently on the stack. This is always - * at least 1, because when it becomes zero the iteration is - * ended and this struct is freed. + * The number of levels currently on the stack. */ size_t levels_nr; @@ -376,7 +374,7 @@ struct cache_ref_iterator { * The prefix is matched textually, without regard for path * component boundaries. */ - const char *prefix; + char *prefix; /* * A stack of levels. levels[0] is the uppermost level that is @@ -389,6 +387,9 @@ struct cache_ref_iterator { struct cache_ref_iterator_level *levels; struct repository *repo; + struct ref_cache *cache; + + int prime_dir; }; static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator) @@ -396,6 +397,9 @@ static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator) struct cache_ref_iterator *iter = (struct cache_ref_iterator *)ref_iterator; + if (!iter->levels_nr) + return ITER_DONE; + while (1) { struct cache_ref_iterator_level *level = &iter->levels[iter->levels_nr - 1]; @@ -444,6 +448,41 @@ static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator) } } +static int cache_ref_iterator_seek(struct ref_iterator *ref_iterator, + const char *prefix) +{ + struct cache_ref_iterator *iter = + (struct cache_ref_iterator *)ref_iterator; + struct cache_ref_iterator_level *level; + struct ref_dir *dir; + + dir = get_ref_dir(iter->cache->root); + if (prefix && *prefix) + dir = find_containing_dir(dir, prefix); + if (!dir) { + iter->levels_nr = 0; + return 0; + } + + if (iter->prime_dir) + prime_ref_dir(dir, prefix); + iter->levels_nr = 1; + level = &iter->levels[0]; + level->index = -1; + level->dir = dir; + + if (prefix && *prefix) { + free(iter->prefix); + iter->prefix = xstrdup(prefix); + level->prefix_state = PREFIX_WITHIN_DIR; + } else { + FREE_AND_NULL(iter->prefix); + level->prefix_state = PREFIX_CONTAINS_DIR; + } + + return 0; +} + static int cache_ref_iterator_peel(struct ref_iterator *ref_iterator, struct object_id *peeled) { @@ -456,12 +495,13 @@ static void cache_ref_iterator_release(struct ref_iterator *ref_iterator) { struct cache_ref_iterator *iter = (struct cache_ref_iterator *)ref_iterator; - free((char *)iter->prefix); + free(iter->prefix); free(iter->levels); } static struct ref_iterator_vtable cache_ref_iterator_vtable = { .advance = cache_ref_iterator_advance, + .seek = cache_ref_iterator_seek, .peel = cache_ref_iterator_peel, .release = cache_ref_iterator_release, }; @@ -471,39 +511,22 @@ struct ref_iterator *cache_ref_iterator_begin(struct ref_cache *cache, struct repository *repo, int prime_dir) { - struct ref_dir *dir; struct cache_ref_iterator *iter; struct ref_iterator *ref_iterator; - struct cache_ref_iterator_level *level; - - dir = get_ref_dir(cache->root); - if (prefix && *prefix) - dir = find_containing_dir(dir, prefix); - if (!dir) - /* There's nothing to iterate over. */ - return empty_ref_iterator_begin(); - - if (prime_dir) - prime_ref_dir(dir, prefix); CALLOC_ARRAY(iter, 1); ref_iterator = &iter->base; base_ref_iterator_init(ref_iterator, &cache_ref_iterator_vtable); ALLOC_GROW(iter->levels, 10, iter->levels_alloc); - iter->levels_nr = 1; - level = &iter->levels[0]; - level->index = -1; - level->dir = dir; + iter->repo = repo; + iter->cache = cache; + iter->prime_dir = prime_dir; - if (prefix && *prefix) { - iter->prefix = xstrdup(prefix); - level->prefix_state = PREFIX_WITHIN_DIR; - } else { - level->prefix_state = PREFIX_CONTAINS_DIR; + if (cache_ref_iterator_seek(&iter->base, prefix) < 0) { + ref_iterator_free(&iter->base); + return NULL; } - iter->repo = repo; - return ref_iterator; } -- cgit v1.3