From: Ramakrishnan Muthukrishnan <ram@rkrishnan.org>
Date: Tue, 3 Feb 2015 23:56:12 +0000 (+0530)
Subject: parser for strings
X-Git-Url: https://git.rkrishnan.org/pf/content/en/using.html?a=commitdiff_plain;h=fba9b0fbfe561e37ff6ca205e4b9315b9e207c25;p=functorrent.git

parser for strings
---

diff --git a/src/Bencode.hs b/src/Bencode.hs
new file mode 100644
index 0000000..951f4f1
--- /dev/null
+++ b/src/Bencode.hs
@@ -0,0 +1,38 @@
+module Bencode where
+
+-- import qualified Data.ByteString.Lazy as BL
+import qualified Data.ByteString.Char8 as BC
+import qualified Data.Map as M
+import qualified Text.Parsec.ByteString as ParsecBS
+import Text.ParserCombinators.Parsec
+import Control.Applicative ((<*))
+import Data.Functor
+
+
+
+data BVal =
+    Bint Integer
+  | Bstr BC.ByteString
+  | Blist [BVal]
+  | Bdict (M.Map BVal BVal)
+  deriving (Ord, Eq)
+
+-- | parse strings
+--
+-- >>> parse bencStr "Bstr" (BC.pack "4:spam")
+-- Right "spam"
+-- >>> parse bencStr "Bstr" (BC.pack "0:")
+-- Right ""
+-- >>> parse bencStr "Bstr" (BC.pack "0:hello")
+-- Right ""
+bencStr :: ParsecBS.Parser BC.ByteString
+bencStr = do _ <- spaces
+             ds <- many1 digit <* char ':'
+             s <- count (read ds) anyChar
+             return (BC.pack s)
+
+bencParser :: ParsecBS.Parser BVal
+bencParser = Bstr <$> bencStr
+
+decode :: BC.ByteString -> Either ParseError BVal
+decode = parse bencParser "BVal"