never executed always true always false

    1 module Reanimate.Morph.Cache
    2   ( cachePointCorrespondence -- :: Int -> PointCorrespondence -> PointCorrespondence
    3   ) where
    4 
    5 import           Control.Exception
    6 import qualified Data.ByteString        as B
    7 import           Data.Hashable
    8 import           Data.Serialize
    9 import           Reanimate.Cache        (encodeInt)
   10 import           Reanimate.Misc         (renameOrCopyFile)
   11 import           Reanimate.Morph.Common
   12 import           System.Directory
   13 import           System.FilePath
   14 import           System.IO
   15 import           System.IO.Temp
   16 import           System.IO.Unsafe
   17 
   18 -- type PointCorrespondence = Polygon → Polygon → (Polygon, Polygon)
   19 cachePointCorrespondence :: Int -> PointCorrespondence -> PointCorrespondence
   20 cachePointCorrespondence ident fn src dst = unsafePerformIO $ do
   21     root <- getXdgDirectory XdgCache "reanimate"
   22     createDirectoryIfMissing True root
   23     let path = root </> template
   24     hit <- doesFileExist path
   25     if hit
   26       then do
   27         inp <- B.readFile path
   28         case decode inp of
   29           Left{} -> do
   30             removeFile path
   31             gen path
   32           Right out -> return out
   33       else gen path
   34   where
   35     gen path = do
   36       correspondence <- evaluate (fn src dst)
   37       withSystemTempFile template $ \tmp h -> do
   38         hClose h
   39         B.writeFile tmp (encode correspondence)
   40         renameOrCopyFile tmp path
   41       return correspondence
   42     template = encodeInt key <.> "morph"
   43     key = hashWithSalt ident (src,dst)