libtorrent: Optimize chunk selection based on priority (#16)

* libtorrent: Optimize chunk selector

Only search the bitfield for the priority type we're looking for.

* libtorrent: Fix download delegator for priority searches

We need to adjust the download delegator slightly to search the chunk selector by priority type.

libtorrent/src/download/chunk_selector.cc

@@ -88,7 +88,7 @@ ChunkSelector::update_priorities() {
 }
 
 uint32_t
-ChunkSelector::find(PeerChunks* pc, __UNUSED bool highPriority) {
+ChunkSelector::find(PeerChunks* pc, bool highPriority) {
   // This needs to be re-enabled.
   if (m_position == invalid_chunk)
     return invalid_chunk;
@@ -128,24 +128,15 @@ ChunkSelector::find(PeerChunks* pc, __UNUSED bool highPriority) {
 
   queue->clear();
 
-  (search_linear(pc->bitfield(), queue, m_data->high_priority(), m_position, size()) &&
-   search_linear(pc->bitfield(), queue, m_data->high_priority(), 0, m_position));
-
-  if (queue->prepare_pop()) {
-    // Set that the peer has high priority pieces cached.
-
-  } else {
-    // Set that the peer has normal priority pieces cached.
-
-    // Urgh...
-    queue->clear();
-
+  if (highPriority)
+    (search_linear(pc->bitfield(), queue, m_data->high_priority(), m_position, size()) &&
+     search_linear(pc->bitfield(), queue, m_data->high_priority(), 0, m_position));
+  else
     (search_linear(pc->bitfield(), queue, m_data->normal_priority(), m_position, size()) &&
      search_linear(pc->bitfield(), queue, m_data->normal_priority(), 0, m_position));
-
-    if (!queue->prepare_pop())
-      return invalid_chunk;
-  }
+
+  if (!queue->prepare_pop())
+    return invalid_chunk;
 
   uint32_t pos = queue->pop();
 

libtorrent/src/download/delegator.cc

@@ -78,12 +78,15 @@ Delegator::delegate(PeerChunks* peerChunks, uint32_t affinity, uint32_t maxPiece
         delegate_from_blocklist(new_transfers, maxPieces, itr, peerInfo);
     }
     // Create new high priority pieces.
-    delegate_new_chunks(new_transfers, maxPieces, peerChunks, true);
+    delegate_new_chunks(new_transfers, maxPieces, peerChunks, true);	
+    if (new_transfers.size() >= maxPieces)
+      return new_transfers;
+
     // Create new normal priority pieces.
     delegate_new_chunks(new_transfers, maxPieces, peerChunks, false);
+    if (new_transfers.size() >= maxPieces)
+      return new_transfers;
   }
-  if (new_transfers.size() >= maxPieces)
-    return new_transfers;
 
   // Find existing high priority pieces.
   for (BlockList* itr : m_transfers) {