    {-# LANGUAGE BangPatterns #-}
    {-# LANGUAGE CPP #-}
    {-# LANGUAGE FlexibleInstances #-}
    {-# LANGUAGE MagicHash #-}
    {-# LANGUAGE MultiParamTypeClasses #-}
    {-# LANGUAGE UnboxedTuples #-}
    {-# OPTIONS_GHC -optc-DNON_POSIX_SOURCE #-}
    --
    --  (c) The University of Glasgow 2002-2006
    --

    -- | ByteCodeLink: Bytecode assembler and linker
    module ByteCodeLink (
            ClosureEnv, emptyClosureEnv, extendClosureEnv,
            linkBCO, lookupStaticPtr, lookupName
           ,lookupIE
      ) where

    #include "HsVersions.h"

    import ByteCodeItbls
    import ByteCodeAsm
    import ObjLink

    import DynFlags
    import BasicTypes
    import Name
    import NameEnv
    import PrimOp
    import Module
    import FastString
    import Panic
    import Outputable
    import Util

    -- Standard libraries

    import Data.Array.Base

    import Control.Monad
    import Control.Monad.ST ( stToIO )

    import GHC.Arr          ( Array(..), STArray(..) )
    import GHC.IO           ( IO(..) )
    import GHC.Exts
    import GHC.Ptr          ( castPtr )

    {-
      Linking interpretables into something we can run
    -}

    type ClosureEnv = NameEnv (Name, HValue)

    emptyClosureEnv :: ClosureEnv
    emptyClosureEnv = emptyNameEnv

    extendClosureEnv :: ClosureEnv -> [(Name,HValue)] -> ClosureEnv
    extendClosureEnv cl_env pairs
      = extendNameEnvList cl_env [ (n, (n,v)) | (n,v) <- pairs]

    {-
      Linking interpretables into something we can run
    -}

    {-
    data BCO# = BCO# ByteArray#             -- instrs   :: Array Word16#
                     ByteArray#             -- literals :: Array Word32#
                     PtrArray#              -- ptrs     :: Array HValue
                     ByteArray#             -- itbls    :: Array Addr#
    -}

    linkBCO :: DynFlags -> ItblEnv -> ClosureEnv -> UnlinkedBCO -> IO HValue
    linkBCO dflags ie ce ul_bco
       = do BCO bco# <- linkBCO' dflags ie ce ul_bco
            -- SDM: Why do we need mkApUpd0 here?  I *think* it's because
            -- otherwise top-level interpreted CAFs don't get updated
            -- after evaluation.   A top-level BCO will evaluate itself and
            -- return its value when entered, but it won't update itself.
            -- Wrapping the BCO in an AP_UPD thunk will take care of the
            -- update for us.
            --
            -- Update: the above is true, but now we also have extra invariants:
            --   (a) An AP thunk *must* point directly to a BCO
            --   (b) A zero-arity BCO *must* be wrapped in an AP thunk
            --   (c) An AP is always fully saturated, so we *can't* wrap
            --       non-zero arity BCOs in an AP thunk.
            --
            if (unlinkedBCOArity ul_bco > 0)
               then return (HValue (unsafeCoerce# bco#))
               else case mkApUpd0# bco# of { (# final_bco #) -> return (HValue final_bco) }

    linkBCO' :: DynFlags -> ItblEnv -> ClosureEnv -> UnlinkedBCO -> IO BCO
    linkBCO' dflags ie ce (UnlinkedBCO _ arity insns_barr bitmap literalsSS ptrsSS)
       -- Raises an IO exception on failure
       = do let literals = ssElts literalsSS
                ptrs     = ssElts ptrsSS

            linked_literals <- mapM (lookupLiteral dflags ie) literals

            let n_literals = sizeSS literalsSS
                n_ptrs     = sizeSS ptrsSS

            ptrs_arr <- mkPtrsArray dflags ie ce n_ptrs ptrs

            let
                !ptrs_parr = case ptrs_arr of Array _lo _hi _n parr -> parr

                litRange
                 | n_literals > 0     = (0, fromIntegral n_literals - 1)
                 | otherwise          = (1, 0)
                literals_arr :: UArray Word Word
                literals_arr = listArray litRange linked_literals
                !literals_barr = case literals_arr of UArray _lo _hi _n barr -> barr

                !(I# arity#)  = arity

            newBCO insns_barr literals_barr ptrs_parr arity# bitmap

    -- we recursively link any sub-BCOs while making the ptrs array
    mkPtrsArray :: DynFlags -> ItblEnv -> ClosureEnv -> Word -> [BCOPtr] -> IO (Array Word HValue)
    mkPtrsArray dflags ie ce n_ptrs ptrs = do
      let ptrRange = if n_ptrs > 0 then (0, n_ptrs-1) else (1, 0)
      marr <- newArray_ ptrRange
      let
        fill (BCOPtrName n)     i = do
            ptr <- lookupName ce n
            unsafeWrite marr i ptr
        fill (BCOPtrPrimOp op)  i = do
            ptr <- lookupPrimOp op
            unsafeWrite marr i ptr
        fill (BCOPtrBCO ul_bco) i = do
            BCO bco# <- linkBCO' dflags ie ce ul_bco
            writeArrayBCO marr i bco#
        fill (BCOPtrBreakInfo brkInfo) i =
            unsafeWrite marr i (HValue (unsafeCoerce# brkInfo))
        fill (BCOPtrArray brkArray) i =
            unsafeWrite marr i (HValue (unsafeCoerce# brkArray))
      zipWithM_ fill ptrs [0..]
      unsafeFreeze marr

    newtype IOArray i e = IOArray (STArray RealWorld i e)

    instance MArray IOArray e IO where
        getBounds (IOArray marr) = stToIO $ getBounds marr
        getNumElements (IOArray marr) = stToIO $ getNumElements marr
        newArray lu init = stToIO $ do
            marr <- newArray lu init; return (IOArray marr)
        newArray_ lu = stToIO $ do
            marr <- newArray_ lu; return (IOArray marr)
        unsafeRead (IOArray marr) i = stToIO (unsafeRead marr i)
        unsafeWrite (IOArray marr) i e = stToIO (unsafeWrite marr i e)

    -- XXX HACK: we should really have a new writeArray# primop that takes a BCO#.
    writeArrayBCO :: IOArray Word a -> Int -> BCO# -> IO ()
    writeArrayBCO (IOArray (STArray _ _ _ marr#)) (I# i#) bco# = IO $ \s# ->
      case (unsafeCoerce# writeArray#) marr# i# bco# s# of { s# ->
      (# s#, () #) }

    {-
    writeArrayMBA :: IOArray Int a -> Int -> MutableByteArray# a -> IO ()
    writeArrayMBA (IOArray (STArray _ _ marr#)) (I# i#) mba# = IO $ \s# ->
      case (unsafeCoerce# writeArray#) marr# i# bco# s# of { s# ->
      (# s#, () #) }
    -}

    data BCO = BCO BCO#

    newBCO :: ByteArray# -> ByteArray# -> Array# a -> Int# -> ByteArray# -> IO BCO
    newBCO instrs lits ptrs arity bitmap
       = IO $ \s -> case newBCO# instrs lits ptrs arity bitmap s of
                      (# s1, bco #) -> (# s1, BCO bco #)

    lookupLiteral :: DynFlags -> ItblEnv -> BCONPtr -> IO Word
    lookupLiteral _      _  (BCONPtrWord lit) = return lit
    lookupLiteral _      _  (BCONPtrLbl  sym) = do Ptr a# <- lookupStaticPtr sym
                                                   return (W# (int2Word# (addr2Int# a#)))
    lookupLiteral dflags ie (BCONPtrItbl nm)  = do Ptr a# <- lookupIE dflags ie nm
                                                   return (W# (int2Word# (addr2Int# a#)))

    lookupStaticPtr :: FastString -> IO (Ptr ())
    lookupStaticPtr addr_of_label_string
       = do let label_to_find = unpackFS addr_of_label_string
            m <- lookupSymbol label_to_find
            case m of
               Just ptr -> return ptr
               Nothing  -> linkFail "ByteCodeLink: can't find label"
                                    label_to_find

    lookupPrimOp :: PrimOp -> IO HValue
    lookupPrimOp primop
       = do let sym_to_find = primopToCLabel primop "closure"
            m <- lookupSymbol sym_to_find
            case m of
               Just (Ptr addr) -> case addrToAny# addr of
                                     (# a #) -> return (HValue a)
               Nothing -> linkFail "ByteCodeLink.lookupCE(primop)" sym_to_find

    lookupName :: ClosureEnv -> Name -> IO HValue
    lookupName ce nm
       = case lookupNameEnv ce nm of
            Just (_,aa) -> return aa
            Nothing
               -> ASSERT2(isExternalName nm, ppr nm)
                  do let sym_to_find = nameToCLabel nm "closure"
                     m <- lookupSymbol sym_to_find
                     case m of
                        Just (Ptr addr) -> case addrToAny# addr of
                                              (# a #) -> return (HValue a)
                        Nothing         -> linkFail "ByteCodeLink.lookupCE" sym_to_find

    lookupIE :: DynFlags -> ItblEnv -> Name -> IO (Ptr a)
    lookupIE dflags ie con_nm
       = case lookupNameEnv ie con_nm of
            Just (_, a) -> return (castPtr (itblCode dflags a))
            Nothing
               -> do -- try looking up in the object files.
                     let sym_to_find1 = nameToCLabel con_nm "con_info"
                     m <- lookupSymbol sym_to_find1
                     case m of
                        Just addr -> return addr
                        Nothing
                           -> do -- perhaps a nullary constructor?
                                 let sym_to_find2 = nameToCLabel con_nm "static_info"
                                 n <- lookupSymbol sym_to_find2
                                 case n of
                                    Just addr -> return addr
                                    Nothing   -> linkFail "ByteCodeLink.lookupIE"
                                                    (sym_to_find1 ++ " or " ++ sym_to_find2)

    linkFail :: String -> String -> IO a
    linkFail who what
       = throwGhcExceptionIO (ProgramError $
            unlines [ "",who
                    , "During interactive linking, GHCi couldn't find the following symbol:"
                    , ' ' : ' ' : what
                    , "This may be due to you not asking GHCi to load extra object files,"
                    , "archives or DLLs needed by your current session.  Restart GHCi, specifying"
                    , "the missing library using the -L/path/to/object/dir and -lmissinglibname"
                    , "flags, or simply by naming the relevant files on the GHCi command line."
                    , "Alternatively, this link failure might indicate a bug in GHCi."
                    , "If you suspect the latter, please send a bug report to:"
                    , "  glasgow-haskell-bugs@haskell.org"
                    ])

    nameToCLabel :: Name -> String -> String
    nameToCLabel n suffix = label where
        encodeZ = zString . zEncodeFS
        (Module pkgKey modName) = ASSERT( isExternalName n ) nameModule n
        packagePart = encodeZ (packageKeyFS pkgKey)
        modulePart  = encodeZ (moduleNameFS modName)
        occPart     = encodeZ (occNameFS (nameOccName n))

        label = concat
            [ if pkgKey == mainPackageKey then "" else packagePart ++ "_"
            , modulePart
            , '_':occPart
            , '_':suffix
            ]

    primopToCLabel :: PrimOp -> String -> String
    primopToCLabel primop suffix = concat
        [ "ghczmprim_GHCziPrimopWrappers_"
        , zString (zEncodeFS (occNameFS (primOpOcc primop)))
        , '_':suffix
        ]