Compressed inventory parser and DarcsRev TH utils

src/Data/Attoparsec/ByteString/Local.hs

@@ -15,15 +15,17 @@
 
 module Data.Attoparsec.ByteString.Local
     ( parseFileIncremental
+    , parseCompressedFileIncremental
     )
 where
 
 import Prelude
 
+import Codec.Compression.Zlib.Internal
 import Data.Attoparsec.ByteString
 import System.IO
 
-import qualified Data.ByteString as B (hGet)
+import qualified Data.ByteString as B (null, hGet)
 import qualified Data.ByteString.Lazy.Internal as BLI (defaultChunkSize)
 
 parseFileIncremental :: FilePath -> Parser a -> IO (Either String a)
@@ -36,3 +38,36 @@ parseFileIncremental file parser =
         firstChunk <- getChunk
         let firstResult = parse parser firstChunk
         go firstResult
+
+parseCompressedFileIncremental
+    :: Format
+    -> DecompressParams
+    -> FilePath
+    -> Parser a
+    -> IO (Either String a)
+parseCompressedFileIncremental format params file parser =
+    withBinaryFile file ReadMode $ \ h -> do
+        let getChunk = B.hGet h BLI.defaultChunkSize
+
+            pGo _ (Fail _remainder _contexts msg) = return $ Left msg
+            pGo f (Partial cont)                  = f cont
+            pGo _ (Done _remainder value)         = return $ Right value
+
+            dGo pCont (DecompressInputRequired dCont) =
+                getChunk >>= dCont >>= dGo pCont
+            dGo pCont (DecompressOutputAvailable output next) =
+                pGo (\ c -> next >>= dGo c) (pCont output)
+            dGo pCont (DecompressStreamEnd remainder) =
+                if B.null remainder
+                    then
+                        pGo
+                            ( const $
+                              return $
+                              Left "Parser wants input but there's none"
+                            )
+                            (pCont remainder)
+                    else return $ Left "Decompression ended with remainder"
+            dGo pCont (DecompressStreamError err) =
+                return $ Left $ show err
+
+        dGo (parse parser) (decompressIO format params)