agent: add compression api

src/Simplex/Messaging/Compression.hs

@@ -7,6 +7,7 @@ module Simplex.Messaging.Compression
     compressionLevel,
     compress1,
     decompress1,
+    limitDecompress1,
     decompressedSize,
   ) where
 
@@ -48,12 +49,20 @@ decompressedSize = \case
   Passthrough bs -> Just $ B.length bs
   Compressed (Large bs) -> Z1.decompressedSize bs
 
-decompress1 :: Int -> Compressed -> Either String ByteString
-decompress1 limit = \case
+decompress1 :: Compressed -> Either String ByteString
+decompress1 = \case
+  Passthrough bs -> Right bs
+  Compressed (Large bs) -> decompress_ bs
+
+limitDecompress1 :: Int -> Compressed -> Either String ByteString
+limitDecompress1 limit = \case
   Passthrough bs -> Right bs
   Compressed (Large bs) -> case Z1.decompressedSize bs of
-    Just sz | sz <= limit -> case Z1.decompress bs of
-      Z1.Error e -> Left e
-      Z1.Skip -> Right mempty
-      Z1.Decompress bs' -> Right bs'
+    Just sz | sz <= limit -> decompress_ bs
     _ -> Left $ "compressed size not specified or exceeds " <> show limit
+
+decompress_ :: ByteString -> Either String ByteString
+decompress_ bs = case Z1.decompress bs of
+  Z1.Error e -> Left e
+  Z1.Skip -> Right mempty
+  Z1.Decompress bs' -> Right bs'