Start to opentracker's memory requirements

* peer lists for v4 and v6 are now lazily allocated and, more importantly, will be freed once there are no more peers
* The downloaded count is now per torrent and not per peer list anymore, moving in what was alignment loss, anyway
* The (now) per torrent downloaded and the per peer list peer and seed count shrunk from size_t to uint32_t
* A helper guards accesses to the peer and seed count to prevent null pointer dereferences
* The base time also shrank from time_t to uint32_t, minutes since the epoch currently fits in 25 bits

1 files changed, 48 insertions, 29 deletions

diff --git a/src/ot_clean.c b/src/ot_clean.c
index eaf069a..77cb4ba 100644
--- a/src/ot_clean.c
+++ b/src/ot_clean.c
@@ -49,26 +49,17 @@ static ssize_t clean_single_bucket(ot_peer *peers, size_t peer_count, size_t pee
   return (peers - insert_point) / peer_size;
 }
 
-int clean_single_peer_list(ot_peerlist *peer_list, size_t peer_size) {
-  ot_vector *peer_vector = &peer_list->peers;
-  ot_time    timedout    = time_since_minutes(peer_list->base);
-  size_t     num_buckets = 1, removed_seeders = 0;
+/* Age one family's peers by timedout minutes. Frees the list and clears the
+   slot once its last peer is gone, so an absent family costs nothing. */
+static void clean_peer_list_family(ot_peerlist **slot, size_t peer_size, ot_time timedout) {
+  ot_peerlist *peer_list = *slot;
+  ot_vector   *peer_vector;
+  size_t       num_buckets = 1, removed_seeders = 0;
 
-  /* No need to clean empty torrent */
-  if (!timedout)
-    return 0;
-
-  /* Torrent has idled out */
-  if (timedout > OT_TORRENT_TIMEOUT)
-    return 1;
-
-  /* Nothing to be cleaned here? Test if torrent is worth keeping */
-  if (timedout > OT_PEER_TIMEOUT) {
-    if (!peer_list->peer_count)
-      return peer_list->down_count ? 0 : 1;
-    timedout = OT_PEER_TIMEOUT;
-  }
+  if (!peer_list)
+    return;
 
+  peer_vector = &peer_list->peers;
   if (OT_PEERLIST_HASBUCKETS(peer_list)) {
     num_buckets = peer_vector->size;
     peer_vector = (ot_vector *)peer_vector->data;
@@ -87,25 +78,53 @@ int clean_single_peer_list(ot_peerlist *peer_list, size_t peer_size) {
 
   peer_list->seed_count -= removed_seeders;
 
-  /* See if we need to convert a torrent from simple vector to bucket list */
+  if (!peer_list->peer_count) {
+    free_peerlist(peer_list);
+    *slot = NULL;
+    return;
+  }
+
+  /* See if we need to convert the list from simple vector to bucket list */
   if ((peer_list->peer_count > OT_PEER_BUCKET_MINCOUNT) || OT_PEERLIST_HASBUCKETS(peer_list))
     vector_redistribute_buckets(peer_list, peer_size);
-
-  if (peer_list->peer_count)
-    peer_list->base = time_now_minutes();
-  else {
-    /* When we got here, the last time that torrent
-     has been touched is OT_PEER_TIMEOUT Minutes before */
-    peer_list->base = time_now_minutes() - OT_PEER_TIMEOUT;
-  }
-  return 0;
 }
 
 /* Clean a single torrent
    return 1 if torrent timed out
 */
 int clean_single_torrent(ot_torrent *torrent) {
-  return clean_single_peer_list(torrent->peer_list6, OT_PEER_SIZE6) * clean_single_peer_list(torrent->peer_list4, OT_PEER_SIZE4);
+  ot_time timedout = time_since_minutes(torrent->base);
+
+  /* Touched since the last sweep: nothing to do */
+  if (!timedout)
+    return 0;
+
+  /* Torrent has idled out */
+  if (timedout > OT_TORRENT_TIMEOUT)
+    return 1;
+
+  /* Already empty and nothing arrived before the peer timeout: keep it only
+     while a down count is worth remembering */
+  if (timedout > OT_PEER_TIMEOUT && !torrent->peer_list6 && !torrent->peer_list4)
+    return torrent->down_count ? 0 : 1;
+
+  /* Peers past the peer timeout are gone regardless, which caps how far the
+     lists are aged in this pass */
+  if (timedout > OT_PEER_TIMEOUT)
+    timedout = OT_PEER_TIMEOUT;
+
+  clean_peer_list_family(&torrent->peer_list6, OT_PEER_SIZE6, timedout);
+  clean_peer_list_family(&torrent->peer_list4, OT_PEER_SIZE4, timedout);
+
+  if (torrent->peer_list6 || torrent->peer_list4)
+    torrent->base = time_now_minutes(); /* still carrying peers */
+  else {
+    /* Fell empty: hold base a peer timeout back so a later idle sweep makes
+       the keep-or-drop decision above */
+    ot_time now   = time_now_minutes();
+    torrent->base = now > OT_PEER_TIMEOUT ? (uint32_t)(now - OT_PEER_TIMEOUT) : 0;
+  }
+  return 0;
 }
 
 /* Written to once, by clean_deinit, and never read: the byte stays in and