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|
\begin{code}
{-# LANGUAGE Unsafe #-}
{-# LANGUAGE NoImplicitPrelude, MagicHash, UnboxedTuples #-}
{-# OPTIONS_HADDOCK hide #-}
-----------------------------------------------------------------------------
-- |
-- Module : GHC.Pack
-- Copyright : (c) The University of Glasgow 1997-2002
-- License : see libraries/base/LICENSE
--
-- Maintainer : cvs-ghc@haskell.org
-- Stability : internal
-- Portability : non-portable (GHC Extensions)
--
-- This module provides a small set of low-level functions for packing
-- and unpacking a chunk of bytes. Used by code emitted by the compiler
-- plus the prelude libraries.
--
-- The programmer level view of packed strings is provided by a GHC
-- system library PackedString.
--
-----------------------------------------------------------------------------
module GHC.Pack
(
-- (**) - emitted by compiler.
packCString#,
unpackCString,
unpackCString#,
unpackNBytes#,
unpackFoldrCString#, -- (**)
unpackAppendCString#, -- (**)
)
where
import GHC.Base
import GHC.List ( length )
import GHC.ST
import GHC.Ptr
data ByteArray ix = ByteArray ix ix ByteArray#
data MutableByteArray s ix = MutableByteArray ix ix (MutableByteArray# s)
unpackCString :: Ptr a -> [Char]
unpackCString a@(Ptr addr)
| a == nullPtr = []
| otherwise = unpackCString# addr
packCString# :: [Char] -> ByteArray#
packCString# str = case (packString str) of { ByteArray _ _ bytes -> bytes }
packString :: [Char] -> ByteArray Int
packString str = runST (packStringST str)
packStringST :: [Char] -> ST s (ByteArray Int)
packStringST str =
let len = length str in
packNBytesST len str
packNBytesST :: Int -> [Char] -> ST s (ByteArray Int)
packNBytesST (I# length#) str =
{-
allocate an array that will hold the string
(not forgetting the NUL byte at the end)
-}
new_ps_array (length# +# 1#) >>= \ ch_array ->
-- fill in packed string from "str"
fill_in ch_array 0# str >>
-- freeze the puppy:
freeze_ps_array ch_array length#
where
fill_in :: MutableByteArray s Int -> Int# -> [Char] -> ST s ()
fill_in arr_in# idx [] =
write_ps_array arr_in# idx (chr# 0#) >>
return ()
fill_in arr_in# idx (C# c : cs) =
write_ps_array arr_in# idx c >>
fill_in arr_in# (idx +# 1#) cs
-- (Very :-) ``Specialised'' versions of some CharArray things...
new_ps_array :: Int# -> ST s (MutableByteArray s Int)
write_ps_array :: MutableByteArray s Int -> Int# -> Char# -> ST s ()
freeze_ps_array :: MutableByteArray s Int -> Int# -> ST s (ByteArray Int)
new_ps_array size = ST $ \ s ->
case (newByteArray# size s) of { (# s2#, barr# #) ->
(# s2#, MutableByteArray bot bot barr# #) }
where
bot = error "new_ps_array"
write_ps_array (MutableByteArray _ _ barr#) n ch = ST $ \ s# ->
case writeCharArray# barr# n ch s# of { s2# ->
(# s2#, () #) }
-- same as unsafeFreezeByteArray
freeze_ps_array (MutableByteArray _ _ arr#) len# = ST $ \ s# ->
case unsafeFreezeByteArray# arr# s# of { (# s2#, frozen# #) ->
(# s2#, ByteArray 0 (I# len#) frozen# #) }
\end{code}
|
