1 files changed, 15 insertions, 1 deletions

diff --git a/src/Data/PacketQueue.hs b/src/Data/PacketQueue.hs
index 57845ae5..f1be1375 100644
--- a/src/Data/PacketQueue.hs
+++ b/src/Data/PacketQueue.hs
@@ -10,6 +10,7 @@ module Data.PacketQueue
     , new
     , newOverwrite
     , dequeue
+    , getMissing
     , dequeueOrGetMissing
     , markButNotDequeue
     , enqueue
@@ -99,14 +100,27 @@ observeOutOfBand PacketQueue { seqno, qsize, buffend } numberOfNextLosslessPacke
 
 -- | If seqno < buffend then return expected packet numbers for all
 --   the Nothings in the array between them.
+--   Otherwise, return empty list.
+getMissing :: PacketQueue a -> STM [Word32]
+getMissing PacketQueue { pktq, seqno, qsize, buffend } = do
+    seqno0 <- readTVar seqno
+    buffend0 <- readTVar buffend
+    -- note relying on fact that [ b .. a ] is null when a < b
+    maybes <- mapM (readArray pktq) (take (fromIntegral qsize) $ map (`mod` qsize) [ seqno0 .. buffend0 ])
+    let nums = map fst . filter (isNothing . snd) $ zip [buffend0 ..]  maybes
+    return nums
+
+-- | If seqno < buffend then return expected packet numbers for all
+--   the Nothings in the array between them.
 --   Otherwise, behave as 'dequeue' would.
+--   TODO: Do we need this function? Delete it if not.
 dequeueOrGetMissing :: PacketQueue a -> STM (Either [Word32] a)
 dequeueOrGetMissing PacketQueue { pktq, seqno, qsize, buffend } = do
     seqno0 <- readTVar seqno
     buffend0 <- readTVar buffend
     if seqno0 < buffend0
       then do
-        maybes <- mapM (readArray pktq) (take (fromIntegral qsize) $ map (`mod` qsize) [ buffend0 .. seqno0 ])
+        maybes <- mapM (readArray pktq) (take (fromIntegral qsize) $ map (`mod` qsize) [ seqno0 .. buffend0 ])
         let nums = map fst . filter (isNothing . snd) $ zip [buffend0 ..]  maybes
         return (Left nums)
       else do