This patch avoids a loop over the ID set. This loops removes
object from the set which have reused deltas. Instead, we can
skip such items in another loop which happens further below.

My goal is simply to have less looping over the object set, even
though this doesn't make a measurable difference in performance.

Patch applies on top of the compressed-delta reuse diff.

ok?
 
diff 19b445e416490300e818e4a7b91f10bde1fb3832 fe8175d3d5b2cce6073a5a6f382e6076aeac824f
blob - fb1e3545cc2cf36d2fb0c5ebec569c5b2302472d
blob + ca90c2008f13c7d8d23491fdf83419879cbc986d
--- lib/pack_create.c
+++ lib/pack_create.c
@@ -1870,23 +1870,14 @@ remove_unused_object(struct got_object_id *id, void *d
 }
 
 static const struct got_error *
-remove_reused_object(struct got_object_id *id, void *data, void *arg)
-{
-	struct got_object_idset *idset = arg;
-	struct got_pack_meta *m = data;
-
-	if (m->have_reused_delta)
-		got_object_idset_remove(NULL, idset, id);
-
-	return NULL;
-}
-
-static const struct got_error *
 add_meta_idset_cb(struct got_object_id *id, void *data, void *arg)
 {
 	struct got_pack_meta *m = data;
 	struct got_pack_metavec *v = arg;
 
+	if (m->have_reused_delta)
+		return NULL;
+
 	return add_meta(m, v);
 }
 
@@ -1905,6 +1896,7 @@ got_pack_create(uint8_t *packsha1, FILE *packfile,
 	struct got_ratelimit rl;
 	struct got_pack_metavec deltify, reuse;
 	int ncolored = 0, nfound = 0, ntrees = 0;
+	size_t ndeltify;
 
 	memset(&deltify, 0, sizeof(deltify));
 	memset(&reuse, 0, sizeof(reuse));
@@ -1956,12 +1948,6 @@ got_pack_create(uint8_t *packsha1, FILE *packfile,
 	    cancel_cb, cancel_arg);
 	if (err)
 		goto done;
-	if (reuse.nmeta > 0) {
-		err = got_object_idset_for_each(idset,
-		    remove_reused_object, idset);
-		if (err)
-			goto done;
-	}
 
 	delta_cache = fdopen(delta_cache_fd, "a+");
 	if (delta_cache == NULL) {
@@ -1975,23 +1961,27 @@ got_pack_create(uint8_t *packsha1, FILE *packfile,
 		goto done;
 	}
 
-	deltify.meta = calloc(got_object_idset_num_elements(idset),
-	    sizeof(struct got_pack_meta *));
-	if (deltify.meta == NULL) {
-		err = got_error_from_errno("calloc");
-		goto done;
-	}
-	deltify.metasz = got_object_idset_num_elements(idset);
+	ndeltify = got_object_idset_num_elements(idset) - reuse.nmeta;
+	if (ndeltify > 0) {
+		deltify.meta = calloc(ndeltify, sizeof(struct got_pack_meta *));
+		if (deltify.meta == NULL) {
+			err = got_error_from_errno("calloc");
+			goto done;
+		}
+		deltify.metasz = ndeltify;
 
-	err = got_object_idset_for_each(idset, add_meta_idset_cb, &deltify);
-	if (err)
-		goto done;
-	if (deltify.nmeta > 0) {
-		err = pick_deltas(deltify.meta, deltify.nmeta, ncolored,
-		    nfound, ntrees, nours, reuse.nmeta, delta_cache, repo,
-		    progress_cb, progress_arg, &rl, cancel_cb, cancel_arg);
+		err = got_object_idset_for_each(idset, add_meta_idset_cb,
+		    &deltify);
 		if (err)
 			goto done;
+		if (deltify.nmeta > 0) {
+			err = pick_deltas(deltify.meta, deltify.nmeta,
+			    ncolored, nfound, ntrees, nours, reuse.nmeta,
+			    delta_cache, repo, progress_cb, progress_arg, &rl,
+			    cancel_cb, cancel_arg);
+			if (err)
+				goto done;
+		}
 	}
 
 	if (fflush(delta_cache) == EOF) {