Adding an option to the gf compiler to add an index to pgf files

This is gonna be used by the android library to skip unused part of a
pgf file

src/compiler/GF/Index.hs

@@ -0,0 +1,36 @@
+{--
+This module provide a function for indexing a pgf. 
+
+It reads the pgf and add a global flag, called "index", containing a string 
+with concrete names and size in bytes separated by a column.
+ex : "DisambPhrasebookEng:18778 PhrasebookBul:49971 PhrasebookCat:32738..."
+--}
+module GF.Index (addIndex) where
+
+import PGF
+import PGF.Data
+import PGF.Binary
+import Data.Binary
+import Data.ByteString.Lazy (readFile,length)
+import qualified Data.Map as Map
+import Data.Map (toAscList)
+import Data.List (intercalate)
+import qualified Data.ByteString.Lazy as BS
+
+addIndex  :: PGF -> PGF
+addIndex pgf = pgf {gflags = flags}  
+  where flags = Map.insert (mkCId "index") (LStr $ showIndex index) (gflags pgf)
+        index = getIndex pgf
+
+
+showIndex :: [(String,Int)] -> String
+showIndex = intercalate " " . map f
+  where f (name,size) = name ++ ":" ++ show size
+
+getsize :: Binary a => a -> Int
+getsize x = let bs = encode x in fromIntegral $ Data.ByteString.Lazy.length bs
+
+getIndex :: PGF -> [(String,Int)]
+getIndex pgf = cncindex
+  where cncindex = map f $ Data.Map.toAscList $ concretes pgf
+        f (cncname,cnc) = (show cncname, getsize cnc)