modifyCacheEntries :: ImageCache
                   -> (LBM.Map B.ByteString CacheEntry -> LBM.Map B.ByteString CacheEntry)
                   -> IO ()
modifyCacheEntries ic f = atomically . modifyTVar' (icCacheEntries ic) $! f
modifyCacheEntries :: ImageCache
                   -> (LBM.Map B.ByteString CacheEntry -> LBM.Map B.ByteString CacheEntry)
                   -> IO ()
modifyCacheEntries ic f = atomically . modifyTVar' (icCacheEntries ic) $! f
modifyCacheEntries ic f = atomically . modifyTVar' (icCacheEntries ic) $! f