[3/4] object-file: refactor replace object lookup

Commit Message

Jonathan Tan Nov. 30, 2022, 8:30 p.m. UTC

Move the replace object lookup (specifically, the ability for the caller
to know the result of the lookup) from read_object_file_extended()
to one of the functions that it indirectly calls,
do_oid_object_info_extended(), because a subsequent patch will need that
ability from the latter.

Signed-off-by: Jonathan Tan <[e-mail]>
---
 object-file.c  | 28 +++++++++++++++++++++-------
 object-store.h |  1 +
 2 files changed, 22 insertions(+), 7 deletions(-)

Comments

Jeff King Nov. 30, 2022, 8:54 p.m. UTC | #1

On Wed, Nov 30, 2022 at 12:30:48PM -0800, Jonathan Tan wrote:

> diff --git a/object-store.h b/object-store.h
> index 88c879c61e..9684562eb2 100644
> --- a/object-store.h
> +++ b/object-store.h
> @@ -406,6 +406,7 @@ struct object_info {
>  	struct object_id *delta_base_oid;
>  	struct strbuf *type_name;
>  	void **contentp;
> +	const struct object_id **real_oidp;

OK. The double-pointer here is a bit funky as an interface. It may point
back to the "oid" we fed the function, or it may point to long-term
storage owned by the replace mechanism. A more straightforward one would
be to store a single-pointer to caller-owned storage, and copy to that
(like we do for delta_base_oid, for example).

But doing it this way avoids extra oid copies in the normal,
non-replaced case, and matches how the current callers view things. So
while it's a little convoluted, I think it makes sense to do it as you
did.

-Peff

Patch

diff --git a/object-file.c b/object-file.c
index 37468bc256..fd394f1ace 100644
--- a/object-file.c
+++ b/object-file.c
@@ -1546,6 +1546,11 @@  static int do_oid_object_info_extended(struct repository *r,
 
 	if (flags & OBJECT_INFO_LOOKUP_REPLACE)
 		real = lookup_replace_object(r, oid);
+	if (oi && oi->real_oidp) {
+		if (!(flags & OBJECT_INFO_LOOKUP_REPLACE))
+			BUG("specifying real_oidp does not make sense without OBJECT_INFO_LOOKUP_REPLACE");
+		*oi->real_oidp = real;
+	}
 
 	if (is_null_oid(real))
 		return -1;
@@ -1659,17 +1664,27 @@  int oid_object_info(struct repository *r,
 	return type;
 }
 
+/*
+ * If real_oid is not NULL, check if oid has a replace object and store the
+ * object that we end up using there.
+ */
 static void *read_object(struct repository *r,
 			 const struct object_id *oid, enum object_type *type,
-			 unsigned long *size)
+			 unsigned long *size, const struct object_id **real_oid)
 {
 	struct object_info oi = OBJECT_INFO_INIT;
 	void *content;
+	unsigned int flags = 0;
 	oi.typep = type;
 	oi.sizep = size;
 	oi.contentp = &content;
 
-	if (oid_object_info_extended(r, oid, &oi, 0) < 0)
+	if (real_oid) {
+		flags |= OBJECT_INFO_LOOKUP_REPLACE;
+		oi.real_oidp = real_oid;
+	}
+
+	if (oid_object_info_extended(r, oid, &oi, flags) < 0)
 		return NULL;
 	return content;
 }
@@ -1705,14 +1720,13 @@  void *read_object_file_extended(struct repository *r,
 				int lookup_replace)
 {
 	void *data;
-	const struct object_id *repl = lookup_replace ?
-		lookup_replace_object(r, oid) : oid;
+	const struct object_id *real_oid;
 
 	errno = 0;
-	data = read_object(r, repl, type, size);
+	data = read_object(r, oid, type, size, &real_oid);
 	if (data)
 		return data;
-	die_if_corrupt(r, oid, repl);
+	die_if_corrupt(r, oid, real_oid);
 
 	return NULL;
 }
@@ -2283,7 +2297,7 @@  int force_object_loose(const struct object_id *oid, time_t mtime)
 
 	if (has_loose_object(oid))
 		return 0;
-	buf = read_object(the_repository, oid, &type, &len);
+	buf = read_object(the_repository, oid, &type, &len, NULL);
 	if (!buf)
 		return error(_("cannot read object for %s"), oid_to_hex(oid));
 	hdrlen = format_object_header(hdr, sizeof(hdr), type, len);
diff --git a/object-store.h b/object-store.h
index 88c879c61e..9684562eb2 100644
--- a/object-store.h
+++ b/object-store.h
@@ -406,6 +406,7 @@  struct object_info {
 	struct object_id *delta_base_oid;
 	struct strbuf *type_name;
 	void **contentp;
+	const struct object_id **real_oidp;
 
 	/* Response */
 	enum {