Expose ringMask for buffer bounds usage with ffi.

1 files changed, 7 insertions, 2 deletions

diff --git a/RingBuffer.hs b/RingBuffer.hs
index 64b0624..dd8a7f7 100644
--- a/RingBuffer.hs
+++ b/RingBuffer.hs
@@ -37,8 +37,8 @@ newRing sz newBuffer = do
     syncRing r
     return r
 
-syncRing :: RingBuffer u -> IO ()
-syncRing r = do
+ringMask :: RingBuffer u -> IO (Int32 -> [(Int32,Int32)])
+ringMask r = do
     size <- fromIntegral <$> readIORef (rSize r)
     back <- fromIntegral <$> readIORef (rBack r)
     let mask 0   = []
@@ -47,6 +47,11 @@ syncRing r = do
             | otherwise = case cnt + back - size of
                 front | front > cnt -> [(front - cnt,size)]
                       | otherwise   -> [(0,back), (front,cnt - front)]
+    return mask
+
+syncRing :: RingBuffer u -> IO ()
+syncRing r = do
+    mask <- ringMask r
     syncBuffer (rBuffer r) mask
 
 clearRing :: RingBuffer u -> IO ()