pemParser

1 files changed, 34 insertions, 0 deletions

diff --git a/PEM.hs b/PEM.hs
new file mode 100644
index 0000000..e6c8259
--- /dev/null
+++ b/PEM.hs
@@ -0,0 +1,34 @@
+{-# LANGUAGE OverloadedStrings #-}
+module PEM where
+
+import Data.Maybe
+import Data.Monoid
+import qualified Data.ByteString.Lazy as LW
+import qualified Data.ByteString.Lazy.Char8 as L
+import Control.Monad
+import Control.Applicative
+import qualified Codec.Binary.Base64 as Base64
+import ScanningParser
+
+data PEMBlob = PEMBlob { pemType :: L.ByteString
+                       , pemBlob :: L.ByteString
+                       }
+
+pemParser mtyp = ScanningParser (maybe fndany fndtyp mtyp) pbdy
+ where
+    hdr typ = "-----BEGIN " <> typ <> "-----"
+    fndtyp typ bs = if bs==hdr typ then Just typ else Nothing
+    fndany bs = do
+        guard $ "-----BEGIN " `L.isPrefixOf` bs
+        let x0 = L.drop 11 bs
+        guard $ "-----" `LW.isSuffixOf` x0
+        let typ = L.take (L.length x0 - 5) x0
+        return typ
+
+    pbdy typ xs = (mblob, rs)
+     where
+        (ys,rs) = span (/="-----END " <> typ <> "-----") xs
+        mblob = PEMBlob typ <$> LW.pack <$> Base64.decode (L.unpack dta)
+        dta = case ys of
+                _:dta_lines -> L.concat dta_lines
+                []          -> ""