On Thu, Sep 26, 2019 at 10:53:08AM -0700, Emily Shaffer wrote:
> > should probably just see if we're already at the end, which also covers
> > the single-element case. Like:
> >
> > if (!r->next)
> > return; /* we're already at the end */
>
> Hmm, I guess I wasn't familiar enough on the lifetime of a
> promisor_remote - I suppose I was expecting
> promisor_remote_move_to_tail() could be used for a first-time insert,
> too, although it looks like promisor_remote_new() actually does the
> insert for us every time.
Right, having to call move_to_tail at all is itself a special case, for
when partialclone points to a remote which doesn't have its
"remote.*.promisor" config set. I haven't followed the details of this
promisor stuff enough to know what it means, but presumably that's what
the non-multi-promisor case looks like.
> > or possibly:
> >
> > if (promisors_tail == &r->next)
> > return; /* we're already at the end */
>
> With the above concern I initially feel a little more comfortable with
> this, although now that I'm thinking through the case when 'r' isn't
> already in the list, I think it would replace the entire list by taking
> the 'else' branch, having a nulled r->next, and therefore replacing the
> head pointer 'promisors' with itself.
Yeah, I agree things get weird there.
> > I also can't help but think this would all be a lot simpler using the
> > implementation in list.h. Then we don't have to pass this weird
> > "previous" pointer around (because it's a doubly-linked list). And
> > functions like this one could go away in favor of list_move(). But
> > that's obviously a bigger change.
>
> Agreed. I joked to my team that this was the first time I've needed to
> understand linked list manipulation outside of an interview setting,
> ever ;)
I was curious how this would look, so I sketched it out. One of the
annoying things about list.h is that there's a little extra boilerplate
when iterating, since you have to cast back to the original type with
list_entry() (in the kernel they use typeof() to avoid this, but it's
not portable enough for us).
The result _is_ shorter by lines. I don't know if it's worth the churn.
---
promisor-remote.c | 75 ++++++++++++++++++++++++-------------------------------
promisor-remote.h | 4 ++-
2 files changed, 35 insertions(+), 44 deletions(-)
diff --git a/promisor-remote.c b/promisor-remote.c
index 9bc296cdde..a158ac44e0 100644
--- a/promisor-remote.c
+++ b/promisor-remote.c
@@ -50,8 +50,7 @@ static int fetch_objects(const char *remote_name,
return fetch_refs(remote_name, ref);
}
-static struct promisor_remote *promisors;
-static struct promisor_remote **promisors_tail = &promisors;
+static LIST_HEAD(promisors);
static struct promisor_remote *promisor_remote_new(const char *remote_name)
{
@@ -64,40 +63,24 @@ static struct promisor_remote *promisor_remote_new(const char *remote_name)
}
FLEX_ALLOC_STR(r, name, remote_name);
-
- *promisors_tail = r;
- promisors_tail = &r->next;
-
+ list_add_tail(&r->list, &promisors);
return r;
}
-static struct promisor_remote *promisor_remote_lookup(const char *remote_name,
- struct promisor_remote **previous)
+static struct promisor_remote *promisor_remote_lookup(const char *remote_name)
{
- struct promisor_remote *r, *p;
+ struct list_head *pos;
- for (p = NULL, r = promisors; r; p = r, r = r->next)
- if (!strcmp(r->name, remote_name)) {
- if (previous)
- *previous = p;
+ list_for_each(pos, &promisors) {
+ struct promisor_remote *r =
+ list_entry(pos, struct promisor_remote, list);
+ if (!strcmp(r->name, remote_name))
return r;
- }
+ }
return NULL;
}
-static void promisor_remote_move_to_tail(struct promisor_remote *r,
- struct promisor_remote *previous)
-{
- if (previous)
- previous->next = r->next;
- else
- promisors = r->next ? r->next : r;
- r->next = NULL;
- *promisors_tail = r;
- promisors_tail = &r->next;
-}
-
static int promisor_remote_config(const char *var, const char *value, void *data)
{
const char *name;
@@ -119,7 +102,7 @@ static int promisor_remote_config(const char *var, const char *value, void *data
remote_name = xmemdupz(name, namelen);
- if (!promisor_remote_lookup(remote_name, NULL))
+ if (!promisor_remote_lookup(remote_name))
promisor_remote_new(remote_name);
free(remote_name);
@@ -129,7 +112,7 @@ static int promisor_remote_config(const char *var, const char *value, void *data
struct promisor_remote *r;
char *remote_name = xmemdupz(name, namelen);
- r = promisor_remote_lookup(remote_name, NULL);
+ r = promisor_remote_lookup(remote_name);
if (!r)
r = promisor_remote_new(remote_name);
@@ -155,26 +138,27 @@ static void promisor_remote_init(void)
git_config(promisor_remote_config, NULL);
if (repository_format_partial_clone) {
- struct promisor_remote *o, *previous;
+ struct promisor_remote *o;
- o = promisor_remote_lookup(repository_format_partial_clone,
- &previous);
- if (o)
- promisor_remote_move_to_tail(o, previous);
- else
+ o = promisor_remote_lookup(repository_format_partial_clone);
+ if (o) {
+ list_del(&o->list);
+ list_add_tail(&o->list, &promisors);
+ } else
promisor_remote_new(repository_format_partial_clone);
}
}
static void promisor_remote_clear(void)
{
- while (promisors) {
- struct promisor_remote *r = promisors;
- promisors = promisors->next;
+ struct list_head *pos, *tmp;
+
+ list_for_each_safe(pos, tmp, &promisors) {
+ struct promisor_remote *r =
+ list_entry(pos, struct promisor_remote, list);
+ list_del(pos);
free(r);
}
-
- promisors_tail = &promisors;
}
void promisor_remote_reinit(void)
@@ -189,9 +173,11 @@ struct promisor_remote *promisor_remote_find(const char *remote_name)
promisor_remote_init();
if (!remote_name)
- return promisors;
+ return list_empty(&promisors) ?
+ NULL :
+ list_first_entry(&promisors, struct promisor_remote, list);
- return promisor_remote_lookup(remote_name, NULL);
+ return promisor_remote_lookup(remote_name);
}
int has_promisor_remote(void)
@@ -235,15 +221,18 @@ int promisor_remote_get_direct(struct repository *repo,
const struct object_id *oids,
int oid_nr)
{
- struct promisor_remote *r;
+ struct list_head *pos;
struct object_id *remaining_oids = (struct object_id *)oids;
int remaining_nr = oid_nr;
int to_free = 0;
int res = -1;
promisor_remote_init();
- for (r = promisors; r; r = r->next) {
+ list_for_each(pos, &promisors) {
+ struct promisor_remote *r =
+ list_entry(pos, struct promisor_remote, list);
+
if (fetch_objects(r->name, remaining_oids, remaining_nr) < 0) {
if (remaining_nr == 1)
continue;
diff --git a/promisor-remote.h b/promisor-remote.h
index 8200dfc940..e3ddc329ba 100644
--- a/promisor-remote.h
+++ b/promisor-remote.h
@@ -1,6 +1,8 @@
#ifndef PROMISOR_REMOTE_H
#define PROMISOR_REMOTE_H
+#include "list.h"
+
struct object_id;
/*
@@ -10,7 +12,7 @@ struct object_id;
* from extensions.partialclone or core.partialclonefilter.
*/
struct promisor_remote {
- struct promisor_remote *next;
+ struct list_head list;
const char *partial_clone_filter;
const char name[FLEX_ARRAY];
};
