urbit-hob

commit 7cc5346f3a5d9737af6acbef041b90aa34c81bb4
parent 7cd97c9b8a70f35d756ff15f9c428c206a900c68
Author: Jared Tobin <jared@jtobin.io>
Date:   Fri, 28 Feb 2020 18:35:46 +0400

serialize: handle 0 encoding correctly

'unroll' returned the empty bytestring on an input of 0, leading 'patp
0' to encode ~zod as the empty bytestring.  On the other hand,
'parsePatp "~zod"' would correctly encode ~zod as \NUL.

This led to an equality comparison bug in some circumstances, depending
on how Patp values of ~zod were gotten.

Fixes #3.

Diffstat:
M
lib/Data/Serialize/Extended.hs
 | 
9
++++++---

1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/lib/Data/Serialize/Extended.hs b/lib/Data/Serialize/Extended.hs
@@ -11,9 +11,12 @@ import Numeric.Natural (Natural)
 
 -- | Simple little-endian ByteString encoding for Naturals.
 unroll :: Natural -> BS.ByteString
-unroll = BS.pack . unfoldr step where
-  step 0 = Nothing
-  step i = Just (fromIntegral i, i `shiftR` 8)
+unroll nat = case nat of
+    0 -> BS.singleton 0
+    _ -> BS.pack (unfoldr step nat)
+  where
+    step 0 = Nothing
+    step i = Just (fromIntegral i, i `shiftR` 8)
 
 -- | Simple little-endian ByteString decoding for Naturals.
 roll :: BS.ByteString -> Natural