[PATCH 3/8] http: refactor subsystem to use `packfile_list`s

[Patrick Steinhardt <ps@pks.im>]

The dumb HTTP protocol directly fetches packfiles from the remote server
and temporarily stores them in a list of packfiles. Those packfiles are
not yet added to the repository's packfile store until we finalize the
whole fetch.

Refactor the code to instead use a `struct packfile_list` to store those
packs. This prepares us for a subsequent change where the `->next`
pointer of `struct packed_git` will go away.

Note that this refactoring creates some temporary duplication of code,
as we now have both `packfile_list_find_oid()` and `find_oid_pack()`.
The latter function will be removed in a subsequent commit though.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 http-push.c   |  6 +++---
 http-walker.c | 26 +++++++++-----------------
 http.c        | 21 ++++++++-------------
 http.h        |  5 +++--
 packfile.c    |  9 +++++++++
 packfile.h    |  8 ++++++++
 6 files changed, 40 insertions(+), 35 deletions(-)

diff --git a/http-push.c b/http-push.c
index a1c01e3b9b9..d86ce771198 100644
--- a/http-push.c
+++ b/http-push.c
@@ -104,7 +104,7 @@ struct repo {
 	int has_info_refs;
 	int can_update_info_refs;
 	int has_info_packs;
-	struct packed_git *packs;
+	struct packfile_list packs;
 	struct remote_lock *locks;
 };
 
@@ -311,7 +311,7 @@ static void start_fetch_packed(struct transfer_request *request)
 	struct transfer_request *check_request = request_queue_head;
 	struct http_pack_request *preq;
 
-	target = find_oid_pack(&request->obj->oid, repo->packs);
+	target = packfile_list_find_oid(repo->packs.head, &request->obj->oid);
 	if (!target) {
 		fprintf(stderr, "Unable to fetch %s, will not be able to update server info refs\n", oid_to_hex(&request->obj->oid));
 		repo->can_update_info_refs = 0;
@@ -683,7 +683,7 @@ static int add_send_request(struct object *obj, struct remote_lock *lock)
 		get_remote_object_list(obj->oid.hash[0]);
 	if (obj->flags & (REMOTE | PUSHING))
 		return 0;
-	target = find_oid_pack(&obj->oid, repo->packs);
+	target = packfile_list_find_oid(repo->packs.head, &obj->oid);
 	if (target) {
 		obj->flags |= REMOTE;
 		return 0;
diff --git a/http-walker.c b/http-walker.c
index 0f7ae46d7f1..e886e648664 100644
--- a/http-walker.c
+++ b/http-walker.c
@@ -15,7 +15,7 @@
 struct alt_base {
 	char *base;
 	int got_indices;
-	struct packed_git *packs;
+	struct packfile_list packs;
 	struct alt_base *next;
 };
 
@@ -324,11 +324,8 @@ static void process_alternates_response(void *callback_data)
 				} else if (is_alternate_allowed(target.buf)) {
 					warning("adding alternate object store: %s",
 						target.buf);
-					newalt = xmalloc(sizeof(*newalt));
-					newalt->next = NULL;
+					CALLOC_ARRAY(newalt, 1);
 					newalt->base = strbuf_detach(&target, NULL);
-					newalt->got_indices = 0;
-					newalt->packs = NULL;
 
 					while (tail->next != NULL)
 						tail = tail->next;
@@ -435,7 +432,7 @@ static int http_fetch_pack(struct walker *walker, struct alt_base *repo,
 
 	if (fetch_indices(walker, repo))
 		return -1;
-	target = find_oid_pack(oid, repo->packs);
+	target = packfile_list_find_oid(repo->packs.head, oid);
 	if (!target)
 		return -1;
 	close_pack_index(target);
@@ -584,17 +581,15 @@ static void cleanup(struct walker *walker)
 	if (data) {
 		alt = data->alt;
 		while (alt) {
-			struct packed_git *pack;
+			struct packfile_list_entry *e;
 
 			alt_next = alt->next;
 
-			pack = alt->packs;
-			while (pack) {
-				struct packed_git *pack_next = pack->next;
-				close_pack(pack);
-				free(pack);
-				pack = pack_next;
+			for (e = alt->packs.head; e; e = e->next) {
+				close_pack(e->pack);
+				free(e->pack);
 			}
+			packfile_list_clear(&alt->packs);
 
 			free(alt->base);
 			free(alt);
@@ -612,14 +607,11 @@ struct walker *get_http_walker(const char *url)
 	struct walker_data *data = xmalloc(sizeof(struct walker_data));
 	struct walker *walker = xmalloc(sizeof(struct walker));
 
-	data->alt = xmalloc(sizeof(*data->alt));
+	CALLOC_ARRAY(data->alt, 1);
 	data->alt->base = xstrdup(url);
 	for (s = data->alt->base + strlen(data->alt->base) - 1; *s == '/'; --s)
 		*s = 0;
 
-	data->alt->got_indices = 0;
-	data->alt->packs = NULL;
-	data->alt->next = NULL;
 	data->got_alternates = -1;
 
 	walker->corrupt_object_found = 0;
diff --git a/http.c b/http.c
index 17130823f00..41f850db16d 100644
--- a/http.c
+++ b/http.c
@@ -2413,8 +2413,9 @@ static char *fetch_pack_index(unsigned char *hash, const char *base_url)
 	return tmp;
 }
 
-static int fetch_and_setup_pack_index(struct packed_git **packs_head,
-	unsigned char *sha1, const char *base_url)
+static int fetch_and_setup_pack_index(struct packfile_list *packs,
+				      unsigned char *sha1,
+				      const char *base_url)
 {
 	struct packed_git *new_pack, *p;
 	char *tmp_idx = NULL;
@@ -2448,12 +2449,11 @@ static int fetch_and_setup_pack_index(struct packed_git **packs_head,
 	if (ret)
 		return -1;
 
-	new_pack->next = *packs_head;
-	*packs_head = new_pack;
+	packfile_list_prepend(packs, new_pack);
 	return 0;
 }
 
-int http_get_info_packs(const char *base_url, struct packed_git **packs_head)
+int http_get_info_packs(const char *base_url, struct packfile_list *packs)
 {
 	struct http_get_options options = {0};
 	int ret = 0;
@@ -2477,7 +2477,7 @@ int http_get_info_packs(const char *base_url, struct packed_git **packs_head)
 		    !parse_oid_hex(data, &oid, &data) &&
 		    skip_prefix(data, ".pack", &data) &&
 		    (*data == '\n' || *data == '\0')) {
-			fetch_and_setup_pack_index(packs_head, oid.hash, base_url);
+			fetch_and_setup_pack_index(packs, oid.hash, base_url);
 		} else {
 			data = strchrnul(data, '\n');
 		}
@@ -2541,14 +2541,9 @@ int finish_http_pack_request(struct http_pack_request *preq)
 }
 
 void http_install_packfile(struct packed_git *p,
-			   struct packed_git **list_to_remove_from)
+			   struct packfile_list *list_to_remove_from)
 {
-	struct packed_git **lst = list_to_remove_from;
-
-	while (*lst != p)
-		lst = &((*lst)->next);
-	*lst = (*lst)->next;
-
+	packfile_list_remove(list_to_remove_from, p);
 	packfile_store_add_pack(the_repository->objects->packfiles, p);
 }
 
diff --git a/http.h b/http.h
index 553e16205ce..f9d45934047 100644
--- a/http.h
+++ b/http.h
@@ -2,6 +2,7 @@
 #define HTTP_H
 
 struct packed_git;
+struct packfile_list;
 
 #include "git-zlib.h"
 
@@ -190,7 +191,7 @@ struct curl_slist *http_append_auth_header(const struct credential *c,
 
 /* Helpers for fetching packs */
 int http_get_info_packs(const char *base_url,
-			struct packed_git **packs_head);
+			struct packfile_list *packs);
 
 /* Helper for getting Accept-Language header */
 const char *http_get_accept_language_header(void);
@@ -226,7 +227,7 @@ void release_http_pack_request(struct http_pack_request *preq);
  * from http_get_info_packs() and have chosen a specific pack to fetch.
  */
 void http_install_packfile(struct packed_git *p,
-			   struct packed_git **list_to_remove_from);
+			   struct packfile_list *list_to_remove_from);
 
 /* Helpers for fetching object */
 struct http_object_request {
diff --git a/packfile.c b/packfile.c
index 4d2d3b674f3..6aa2ca8ac9e 100644
--- a/packfile.c
+++ b/packfile.c
@@ -121,6 +121,15 @@ void packfile_list_append(struct packfile_list *list, struct packed_git *pack)
 	}
 }
 
+struct packed_git *packfile_list_find_oid(struct packfile_list_entry *packs,
+					  const struct object_id *oid)
+{
+	for (; packs; packs = packs->next)
+		if (find_pack_entry_one(oid, packs->pack))
+			return packs->pack;
+	return NULL;
+}
+
 void pack_report(struct repository *repo)
 {
 	fprintf(stderr,
diff --git a/packfile.h b/packfile.h
index 39ed1073e4a..a53336d722a 100644
--- a/packfile.h
+++ b/packfile.h
@@ -65,6 +65,14 @@ void packfile_list_remove(struct packfile_list *list, struct packed_git *pack);
 void packfile_list_prepend(struct packfile_list *list, struct packed_git *pack);
 void packfile_list_append(struct packfile_list *list, struct packed_git *pack);
 
+/*
+ * Find the pack within the "packs" list whose index contains the object
+ * "oid". For general object lookups, you probably don't want this; use
+ * find_pack_entry() instead.
+ */
+struct packed_git *packfile_list_find_oid(struct packfile_list_entry *packs,
+					  const struct object_id *oid);
+
 /*
  * A store that manages packfiles for a given object database.
  */

-- 
2.51.2.997.g839fc31de9.dirty