added function abstractName from the API

src/runtime/haskell/PGF2/FFI.hsc

@@ -2,11 +2,15 @@
 
 module PGF2.FFI where
 
+import Data.Word
+import Foreign ( alloca, peek, poke, peekByteOff )
 import Foreign.C
 import Foreign.Ptr
 import Foreign.ForeignPtr
 import qualified Data.Map as Map
 
+#include <pgf.h>
+
 -- | An abstract data type representing multilingual grammar
 -- in Portable Grammar Format.
 data PGF = PGF {a_pgf :: ForeignPtr PgfPGF, langs :: Map.Map String Concr}
@@ -16,12 +20,34 @@ data Concr = Concr {c_pgf :: ForeignPtr PgfPGF, concr :: Ptr PgfConcr}
 -- libpgf API
 
 data PgfExn
+data PgfText
 data PgfPGF
 data PgfConcr
 
+foreign import ccall unsafe "pgf_utf8_decode"
+  pgf_utf8_decode :: Ptr CString -> IO Word32
+
 foreign import ccall "pgf.h pgf_read"
   pgf_read :: CString -> Ptr PgfExn -> IO (Ptr PgfPGF)
 
 foreign import ccall "&pgf_free"
   pgf_free_fptr :: FinalizerPtr PgfPGF
 
+foreign import ccall "pgf/pgf.h pgf_abstract_name"
+  pgf_abstract_name :: Ptr PgfPGF -> IO (Ptr PgfText)
+
+peekText :: Ptr PgfText -> IO String
+peekText ptr =
+  alloca $ \pptr -> do
+    size <- ((#peek PgfText, size) ptr) :: IO CSize
+    let c_text = castPtr ptr `plusPtr` (#offset PgfText, text)
+    poke pptr c_text
+    decode pptr (c_text `plusPtr` fromIntegral size)
+  where
+    decode pptr end = do
+      ptr <- peek pptr
+      if ptr >= end
+        then return []
+        else do x <- pgf_utf8_decode pptr
+                cs <- decode pptr end
+                return (((toEnum . fromEnum) x) : cs)