Re: [PATCH 09/13] object-file: read objects via the loose object source

> When reading an object via `loose_object_info()` or `map_loose_object()`
> we hand in the whole repository. We then iterate through each of the
> object sources to figure out whether that source has the object in
> question.
>

> This logic is reversing responsibility though: a specific backend should
> only care about one specific source, where the object sources themselves
> are then managed by the object database.
>
> Refactor the code accordingly by passing an object source to both of
> these functions instead. The different sources are then handled by
> either `do_oid_object_info_extended()`, which sits on the object
> database level, and by `open_istream_loose()`. The latter function
> arguably is still at the wrong level, but this will be cleaned up at a
> later point in time.

>
> Signed-off-by: Patrick Steinhardt <ps@pks.im>
> ---
>  object-file.c | 68 ++++++++++++++++++++++-------------------------------------
>  object-file.h | 15 +++++++------
>  odb.c         |  9 ++++++--
>  streaming.c   | 11 +++++++++-
>  4 files changed, 50 insertions(+), 53 deletions(-)
>
> diff --git a/object-file.c b/object-file.c
> index 14daa2bdd90..d9724e3105f 100644
> --- a/object-file.c
> +++ b/object-file.c
> @@ -167,25 +167,22 @@ int stream_object_signature(struct repository *r, const struct object_id *oid)
>  }
>
>  /*
> - * Find "oid" as a loose object in the local repository or in an alternate.
> + * Find "oid" as a loose object in given source.
>   * Returns 0 on success, negative on failure.
>   *
>   * The "path" out-parameter will give the path of the object we found (if any).
>   * Note that it may point to static storage and is only valid until another
>   * call to stat_loose_object().
>   */
> -static int stat_loose_object(struct repository *r, const struct object_id *oid,
> +static int stat_loose_object(struct odb_loose_source *source,
> +			     const struct object_id *oid,
>  			     struct stat *st, const char **path)
>  {
> -	struct odb_source *source;
>  	static struct strbuf buf = STRBUF_INIT;
>
> -	odb_prepare_alternates(r->objects);
> -	for (source = r->objects->sources; source; source = source->next) {
> -		*path = odb_loose_path(source, &buf, oid);
> -		if (!lstat(*path, st))
> -			return 0;
> -	}
> +	*path = odb_loose_path(source->source, &buf, oid);
> +	if (!lstat(*path, st))
> +		return 0;
>
>  	return -1;
>  }
> @@ -194,39 +191,24 @@ static int stat_loose_object(struct repository *r, const struct object_id *oid,
>   * Like stat_loose_object(), but actually open the object and return the
>   * descriptor. See the caveats on the "path" parameter above.
>   */
> -static int open_loose_object(struct repository *r,
> +static int open_loose_object(struct odb_loose_source *source,
>  			     const struct object_id *oid, const char **path)
>  {
> -	int fd;
> -	struct odb_source *source;
> -	int most_interesting_errno = ENOENT;
>  	static struct strbuf buf = STRBUF_INIT;
> +	int fd;
>
> -	odb_prepare_alternates(r->objects);
> -	for (source = r->objects->sources; source; source = source->next) {
> -		*path = odb_loose_path(source, &buf, oid);
> -		fd = git_open(*path);
> -		if (fd >= 0)
> -			return fd;
> +	*path = odb_loose_path(source->source, &buf, oid);
> +	fd = git_open(*path);
> +	if (fd >= 0)
> +		return fd;
>
> -		if (most_interesting_errno == ENOENT)
> -			most_interesting_errno = errno;
> -	}
> -	errno = most_interesting_errno;
>  	return -1;
>  }
>
> -static int quick_has_loose(struct repository *r,
> +static int quick_has_loose(struct odb_loose_source *source,
>  			   const struct object_id *oid)
>  {
> -	struct odb_source *source;
> -
> -	odb_prepare_alternates(r->objects);
> -	for (source = r->objects->sources; source; source = source->next) {
> -		if (oidtree_contains(odb_loose_source_cache(source, oid), oid))
> -			return 1;
> -	}
> -	return 0;
> +	return !!oidtree_contains(odb_loose_source_cache(source->source, oid), oid);
>  }
>

> diff --git a/odb.c b/odb.c
> index 96059456f20..5dc1e2c7eb0 100644
> --- a/odb.c
> +++ b/odb.c
> @@ -697,13 +697,18 @@ static int do_oid_object_info_extended(struct object_database *odb,
>  		return 0;
>  	}
>
> +	odb_prepare_alternates(odb);
> +
>  	while (1) {
> +		struct odb_source *source;
> +
>  		if (find_pack_entry(odb->repo, real, &e))
>  			break;
>
>  		/* Most likely it's a loose object. */
> -		if (!loose_object_info(odb->repo, real, oi, flags))
> -			return 0;
> +		for (source = odb->sources; source; source = source->next)
> +			if (!odb_loose_source_read_object_info(source, real, oi, flags))
> +				return 0;
>

>  		/* Not a loose object; someone else may have just packed it. */
>  		if (!(flags & OBJECT_INFO_QUICK)) {
> diff --git a/streaming.c b/streaming.c
> index 4b13827668e..8e554abd084 100644
> --- a/streaming.c
> +++ b/streaming.c
> @@ -230,12 +230,21 @@ static int open_istream_loose(struct git_istream *st, struct repository *r,
>  			      enum object_type *type)
>  {
>  	struct object_info oi = OBJECT_INFO_INIT;
> +	struct odb_source *source;
> +
>  	oi.sizep = &st->size;
>  	oi.typep = type;
>
> -	st->u.loose.mapped = map_loose_object(r, oid, &st->u.loose.mapsize);
> +	odb_prepare_alternates(r->objects);
> +	for (source = r->objects->sources; source; source = source->next) {
> +		st->u.loose.mapped = odb_loose_source_map_object(source, oid,
> +								 &st->u.loose.mapsize);
> +		if (st->u.loose.mapped)
> +			break;
> +	}
>  	if (!st->u.loose.mapped)
>  		return -1;
> +
>  	switch (unpack_loose_header(&st->z, st->u.loose.mapped,
>  				    st->u.loose.mapsize, st->u.loose.hdr,
>  				    sizeof(st->u.loose.hdr))) {
>
> --
> 2.51.1.930.gacf6e81ea2.dirty