object-file: adapt `stream_object_signature()` to take a stream

The function `stream_object_signature()` is responsible for verifying
whether the given object ID matches the actual hash of the object's
contents. In contrast to `check_object_signature()` it does so in a
streaming fashion so that we don't have to load the full object into
memory.

In a subsequent commit we'll want to adapt one of its callsites to pass
a preconstructed stream. Prepare for this by accepting a stream as input
that the caller needs to assemble.

While at it, improve the error reporting in `parse_object_with_flags()`
to tell apart the two failure modes.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 7 deletions

diff --git a/object-file.c b/object-file.c
index e7e4c3348f..a59b7abaaf 100644
--- a/object-file.c
+++ b/object-file.c
@@ -129,18 +129,15 @@ int check_object_signature(struct repository *r, const struct object_id *oid,
 	return !oideq(oid, &real_oid) ? -1 : 0;
 }
 
-int stream_object_signature(struct repository *r, const struct object_id *oid)
+int stream_object_signature(struct repository *r,
+			    struct odb_read_stream *st,
+			    const struct object_id *oid)
 {
 	struct object_id real_oid;
-	struct odb_read_stream *st;
 	struct git_hash_ctx c;
 	char hdr[MAX_HEADER_LEN];
 	int hdrlen;
 
-	st = odb_read_stream_open(r->objects, oid, NULL);
-	if (!st)
-		return -1;
-
 	/* Generate the header */
 	hdrlen = format_object_header(hdr, sizeof(hdr), st->type, st->size);
 
@@ -160,7 +157,6 @@ int stream_object_signature(struct repository *r, const struct object_id *oid)
 		git_hash_update(&c, buf, readlen);
 	}
 	git_hash_final_oid(&real_oid, &c);
-	odb_read_stream_close(st);
 	return !oideq(oid, &real_oid) ? -1 : 0;
 }