Subject: Re: [PATCH v3 3/5] refs: teach for_each_ref a flag to avoid recursion

From: Junio C Hamano <[email-masked]>
Date: Thu, 09 Jan 2014 09:51:24 -0800

Jeff King <[email-masked]> writes:

> On Tue, Jan 07, 2014 at 06:58:50PM -0500, Jeff King wrote:
>
>> +			if (flags & DO_FOR_EACH_NO_RECURSE) {
>> +				struct ref_dir *subdir = get_ref_dir(entry);
>> +				sort_ref_dir(subdir);
>> +				retval = do_for_each_entry_in_dir(subdir, 0,
>
> Obviously this is totally wrong and inverts the point of the flag. And
> causes something like half of the test suite to fail.
>
> Michael was nice enough to point it out to me off-list, but well, I have
> to face the brown paper bag at some point. :) In my defense, it was a
> last minute refactor before going to dinner. That is what I get for
> rushing out the series.

And perhaps a bad naming that calls for double-negation in the
normal cases, which might have been less likely to happen it the new
flag were called "onelevel only" or something, perhaps?

> Here's a fixed version of patch 3/5.
>
> -- >8 --
> Subject: refs: teach for_each_ref a flag to avoid recursion
>
> The normal for_each_ref traversal descends into
> subdirectories, returning each ref it finds. However, in
> some cases we may want to just iterate over the top-level of
> a certain part of the tree.
>
> The introduction of the "flags" option is a little
> mysterious. We already have a "flags" option that gets stuck
> in a callback struct and ends up interpreted in do_one_ref.
> But the traversal itself does not currently have any flags,
> and it needs to know about this new flag.
>
> We _could_ introduce this as a completely separate flag
> parameter. But instead, we simply put both flag types into a
> single namespace, and make it available at both sites. This
> is simple, and given that we do not have a proliferation of
> flags (we have had exactly one until now), it is probably
> sufficient.
>
> Signed-off-by: Jeff King <[email-masked]>
> ---
>  refs.c | 61 ++++++++++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 38 insertions(+), 23 deletions(-)
>
> diff --git a/refs.c b/refs.c
> index 3926136..b70b018 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -589,6 +589,8 @@ static void sort_ref_dir(struct ref_dir *dir)
>  
>  /* Include broken references in a do_for_each_ref*() iteration: */
>  #define DO_FOR_EACH_INCLUDE_BROKEN 0x01
> +/* Do not recurse into subdirs, just iterate at a single level. */
> +#define DO_FOR_EACH_NO_RECURSE     0x02
>  
>  /*
>   * Return true iff the reference described by entry can be resolved to
> @@ -661,7 +663,8 @@ static int do_one_ref(struct ref_entry *entry, void *cb_data)
>   * called for all references, including broken ones.
>   */
>  static int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
> -				    each_ref_entry_fn fn, void *cb_data)
> +				    each_ref_entry_fn fn, void *cb_data,
> +				    int flags)
>  {
>  	int i;
>  	assert(dir->sorted == dir->nr);
> @@ -669,9 +672,13 @@ static int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
>  		struct ref_entry *entry = dir->entries[i];
>  		int retval;
>  		if (entry->flag & REF_DIR) {
> -			struct ref_dir *subdir = get_ref_dir(entry);
> -			sort_ref_dir(subdir);
> -			retval = do_for_each_entry_in_dir(subdir, 0, fn, cb_data);
> +			if (!(flags & DO_FOR_EACH_NO_RECURSE)) {
> +				struct ref_dir *subdir = get_ref_dir(entry);
> +				sort_ref_dir(subdir);
> +				retval = do_for_each_entry_in_dir(subdir, 0,
> +								  fn, cb_data,
> +								  flags);
> +			}
>  		} else {
>  			retval = fn(entry, cb_data);
>  		}
> @@ -691,7 +698,8 @@ static int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
>   */
>  static int do_for_each_entry_in_dirs(struct ref_dir *dir1,
>  				     struct ref_dir *dir2,
> -				     each_ref_entry_fn fn, void *cb_data)
> +				     each_ref_entry_fn fn, void *cb_data,
> +				     int flags)
>  {
>  	int retval;
>  	int i1 = 0, i2 = 0;
> @@ -702,10 +710,12 @@ static int do_for_each_entry_in_dirs(struct ref_dir *dir1,
>  		struct ref_entry *e1, *e2;
>  		int cmp;
>  		if (i1 == dir1->nr) {
> -			return do_for_each_entry_in_dir(dir2, i2, fn, cb_data);
> +			return do_for_each_entry_in_dir(dir2, i2, fn, cb_data,
> +							flags);
>  		}
>  		if (i2 == dir2->nr) {
> -			return do_for_each_entry_in_dir(dir1, i1, fn, cb_data);
> +			return do_for_each_entry_in_dir(dir1, i1, fn, cb_data,
> +							flags);
>  		}
>  		e1 = dir1->entries[i1];
>  		e2 = dir2->entries[i2];
> @@ -713,12 +723,15 @@ static int do_for_each_entry_in_dirs(struct ref_dir *dir1,
>  		if (cmp == 0) {
>  			if ((e1->flag & REF_DIR) && (e2->flag & REF_DIR)) {
>  				/* Both are directories; descend them in parallel. */
> -				struct ref_dir *subdir1 = get_ref_dir(e1);
> -				struct ref_dir *subdir2 = get_ref_dir(e2);
> -				sort_ref_dir(subdir1);
> -				sort_ref_dir(subdir2);
> -				retval = do_for_each_entry_in_dirs(
> -						subdir1, subdir2, fn, cb_data);
> +				if (!(flags & DO_FOR_EACH_NO_RECURSE)) {
> +					struct ref_dir *subdir1 = get_ref_dir(e1);
> +					struct ref_dir *subdir2 = get_ref_dir(e2);
> +					sort_ref_dir(subdir1);
> +					sort_ref_dir(subdir2);
> +					retval = do_for_each_entry_in_dirs(
> +							subdir1, subdir2,
> +							fn, cb_data, flags);
> +				}
>  				i1++;
>  				i2++;
>  			} else if (!(e1->flag & REF_DIR) && !(e2->flag & REF_DIR)) {
> @@ -743,7 +756,7 @@ static int do_for_each_entry_in_dirs(struct ref_dir *dir1,
>  				struct ref_dir *subdir = get_ref_dir(e);
>  				sort_ref_dir(subdir);
>  				retval = do_for_each_entry_in_dir(
> -						subdir, 0, fn, cb_data);
> +						subdir, 0, fn, cb_data, flags);
>  			} else {
>  				retval = fn(e, cb_data);
>  			}
> @@ -817,7 +830,7 @@ static int is_refname_available(const char *refname, const char *oldrefname,
>  	data.conflicting_refname = NULL;
>  
>  	sort_ref_dir(dir);
> -	if (do_for_each_entry_in_dir(dir, 0, name_conflict_fn, &data)) {
> +	if (do_for_each_entry_in_dir(dir, 0, name_conflict_fn, &data, 0)) {
>  		error("'%s' exists; cannot create '%s'",
>  		      data.conflicting_refname, refname);
>  		return 0;
> @@ -1651,7 +1664,8 @@ void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
>   * 0.
>   */
>  static int do_for_each_entry(struct ref_cache *refs, const char *base,
> -			     each_ref_entry_fn fn, void *cb_data)
> +			     each_ref_entry_fn fn, void *cb_data,
> +			     int flags)
>  {
>  	struct packed_ref_cache *packed_ref_cache;
>  	struct ref_dir *loose_dir;
> @@ -1684,15 +1698,15 @@ static int do_for_each_entry(struct ref_cache *refs, const char *base,
>  		sort_ref_dir(packed_dir);
>  		sort_ref_dir(loose_dir);
>  		retval = do_for_each_entry_in_dirs(
> -				packed_dir, loose_dir, fn, cb_data);
> +				packed_dir, loose_dir, fn, cb_data, flags);
>  	} else if (packed_dir) {
>  		sort_ref_dir(packed_dir);
>  		retval = do_for_each_entry_in_dir(
> -				packed_dir, 0, fn, cb_data);
> +				packed_dir, 0, fn, cb_data, flags);
>  	} else if (loose_dir) {
>  		sort_ref_dir(loose_dir);
>  		retval = do_for_each_entry_in_dir(
> -				loose_dir, 0, fn, cb_data);
> +				loose_dir, 0, fn, cb_data, flags);
>  	}
>  
>  	release_packed_ref_cache(packed_ref_cache);
> @@ -1718,7 +1732,7 @@ static int do_for_each_ref(struct ref_cache *refs, const char *base,
>  	data.fn = fn;
>  	data.cb_data = cb_data;
>  
> -	return do_for_each_entry(refs, base, do_one_ref, &data);
> +	return do_for_each_entry(refs, base, do_one_ref, &data, flags);
>  }
>  
>  static int do_head_ref(const char *submodule, each_ref_fn fn, void *cb_data)
> @@ -2200,7 +2214,7 @@ int commit_packed_refs(void)
>  
>  	do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
>  				 0, write_packed_entry_fn,
> -				 &packed_ref_cache->lock->fd);
> +				 &packed_ref_cache->lock->fd, 0);
>  	if (commit_lock_file(packed_ref_cache->lock))
>  		error = -1;
>  	packed_ref_cache->lock = NULL;
> @@ -2345,7 +2359,7 @@ int pack_refs(unsigned int flags)
>  	cbdata.packed_refs = get_packed_refs(&ref_cache);
>  
>  	do_for_each_entry_in_dir(get_loose_refs(&ref_cache), 0,
> -				 pack_if_possible_fn, &cbdata);
> +				 pack_if_possible_fn, &cbdata, 0);
>  
>  	if (commit_packed_refs())
>  		die_errno("unable to overwrite old ref-pack file");
> @@ -2447,7 +2461,8 @@ static int repack_without_refs(const char **refnames, int n)
>  	}
>  
>  	/* Remove any other accumulated cruft */
> -	do_for_each_entry_in_dir(packed, 0, curate_packed_ref_fn, &refs_to_delete);
> +	do_for_each_entry_in_dir(packed, 0, curate_packed_ref_fn,
> +				 &refs_to_delete, 0);
>  	for_each_string_list_item(ref_to_delete, &refs_to_delete) {
>  		if (remove_entry(packed, ref_to_delete->string) == -1)
>  			die("internal error");