Added more helper functions, some of Index function implementations

Data/Git/Helpers.hs

@@ -18,4 +18,11 @@ ptrFunc f m = alloca $ \ptrptr -> do
   result <- f ptrptr
   ptr <- peek ptrptr
   free ptrptr
-  result `errorOr` m ptr
+  result `errorOr` m ptr
+
+stateMod :: Integral a1 => (Ptr a -> IO a1) -> ForeignPtr a -> IO ()
+stateMod f p = withForeignPtr p $ \p' -> do
+  result <- f p'
+  result `errorOr` return ()
+
+stateMod' = flip withForeignPtr

Data/Git/Index.hs

@@ -3,7 +3,7 @@ module Data.Git.Index (
   IndexEntry,
   open,
   clear,
-  free,
+ -- free,
   read,
   write,
   find,
@@ -27,24 +27,44 @@ import Data.Git.Types
 import Bindings.Libgit2.Index
 import Control.Exception
 import System.FilePath
+import Foreign.Marshal
+import Foreign.C.String
+import Foreign.Ptr
+import Foreign.ForeignPtr
+{-| Create a new bare Git index object as a memory representation
+of the Git index file in 'index_path', without a repository
+to back it.
+
+Since there is no ODB or working directory behind this index,
+any Index methods which rely on these (e.g. index_add) will
+fail with a BareIndex error.
+
+If you need to access the index of an actual repository,
+use the Data.Git.Repository.index wrapper.
+-}
 
 open :: FilePath -> IO Index
-open = undefined
+open fp = withCString fp $ \fp' -> ptrFunc (\pp -> c'git_index_open pp fp') toIndex
 
 clear :: Index -> IO ()
-clear = undefined
-free :: Index -> IO ()
-free = undefined
+clear = stateMod' c'git_index_clear . ixPrim
+-- free :: Index -> IO ()
+-- free = undefined
 read :: Index -> IO ()
-read = undefined
+read = stateMod c'git_index_read . ixPrim
+
 write :: Index -> IO ()
-write = undefined
+write = stateMod c'git_index_write . ixPrim
+
 find :: Index -> FilePath -> IO Bool
 find = undefined
+
 unique :: Index -> IO ()
-unique = undefined
+unique = stateMod' c'git_index_uniq . ixPrim
+
 add :: Index -> FilePath -> Int -> IO ()
 add = undefined
+
 addIndexEntry :: Index -> IndexEntry -> IO ()
 addIndexEntry = undefined
 append :: Index -> FilePath -> Int -> IO ()