Byte marshalling

src/Research.hs

@@ -7,6 +7,7 @@ import Data.List                 (intercalate)
 import Data.Map                  ()
 import Data.Text                 (Text, replace)
 import Data.Text.Encoding        (decodeUtf8, encodeUtf8)
+import Data.Word                 (Word8)
 import System.Console.CmdArgs    (Data, Typeable)
 
 import qualified Data.ByteString as BS
@@ -109,6 +110,61 @@ deserializeNode bs =
 
     _ -> errorWithoutStackTrace "invalid merkle node payload"
 
+-- ---------------------------------------------------------------------------
+-- ByteString / bytestream marshalling via existing Tree Calculus conventions
+-- ---------------------------------------------------------------------------
+
+-- | Encode a single byte (Word8) as a Tree Calculus number (0..255).
+ofByte :: Word8 -> T
+ofByte = ofNumber . fromIntegral
+
+-- | Decode a Tree Calculus number as a single byte (Word8).
+--   Rejects values outside the range 0..255.
+toByte :: T -> Either String Word8
+toByte t = case toNumber t of
+  Left err -> Left err
+  Right n
+    | n >= 0 && n <= 255 -> Right (fromIntegral n)
+    | otherwise -> Left ("Byte value out of range: " ++ show n)
+
+-- | Encode a ByteString as a Tree Calculus list of Byte trees.
+ofBytes :: BS.ByteString -> T
+ofBytes = ofList . map ofByte . BS.unpack
+
+-- | Decode a Tree Calculus list of Byte trees as a ByteString.
+--   Rejects non-list trees and elements that are not valid byte values (0..255).
+toBytes :: T -> Either String BS.ByteString
+toBytes t = case toList t of
+  Left err -> Left err
+  Right bs -> BS.pack <$> mapM toByte bs
+
+-- | Convert a canonical Arborix node payload (ByteString) to a Tree
+--   representation (a list of Byte trees).
+nodePayloadToTreeBytes :: BS.ByteString -> T
+nodePayloadToTreeBytes = ofBytes
+
+-- | Convert a Tree representation of a node payload back to ByteString.
+treeBytesToNodePayload :: T -> Either String BS.ByteString
+treeBytesToNodePayload = toBytes
+
+-- | Convert a MerkleHash (hex-encoded) to a Tree of its 32 raw bytes.
+hashToTreeBytes :: MerkleHash -> Either String T
+hashToTreeBytes h = case decode (encodeUtf8 h) of
+  Left _  -> Left "Invalid hex MerkleHash"
+  Right raw
+    | BS.length raw == 32 -> Right (ofBytes raw)
+    | otherwise -> Left "Hash raw bytes must be 32 bytes"
+
+-- | Convert a Tree of 32 Byte trees back to a MerkleHash (hex string).
+treeBytesToHash :: T -> Either String MerkleHash
+treeBytesToHash t = case toList t of
+  Left err -> Left err
+  Right bytes
+    | length bytes == 32 -> do
+        raw <- BS.pack <$> mapM toByte bytes
+        Right $ decodeUtf8 (encode raw)
+    | otherwise -> Left "Expected exactly 32 byte elements for hash"
+
 -- | Build a Merkle DAG from a Tree Calculus term.
 buildMerkle :: T -> Node
 buildMerkle Leaf = NLeaf