MPI encode/decode QuickCheck

1 files changed, 4 insertions, 2 deletions

diff --git a/Data/OpenPGP.hs b/Data/OpenPGP.hs
index bf7cdf5..63d4dc1 100644
--- a/Data/OpenPGP.hs
+++ b/Data/OpenPGP.hs
@@ -56,6 +56,7 @@ module Data.OpenPGP (
 
 import Numeric
 import Control.Monad
+import Control.Exception (assert)
 import Data.Bits
 import Data.Word
 import Data.Char
@@ -632,10 +633,11 @@ instance BINARY_CLASS MPI where
                         + 1 :: Word16)
                 putSomeByteString bytes
                 where
-                bytes = B.reverse $ B.unfoldr (\x ->
+                bytes = if B.null bytes' then B.singleton 0 else bytes'
+                bytes' = B.reverse $ B.unfoldr (\x ->
                                 if x == 0 then Nothing else
                                         Just (fromIntegral x, x `shiftR` 8)
-                        ) i
+                        ) (assert (i>=0) i)
         get = do
                 length <- fmap fromIntegral (get :: Get Word16)
                 bytes <- getSomeByteString ((length + 7) `div` 8)