2 {-# OPTIONS_GHC -fno-implicit-prelude #-}
3 -----------------------------------------------------------------------------
6 -- Copyright : (c) The University of Glasgow 1997-2002
7 -- License : see libraries/base/LICENSE
9 -- Maintainer : cvs-ghc@haskell.org
10 -- Stability : internal
11 -- Portability : non-portable (GHC Extensions)
13 -- This module provides a small set of low-level functions for packing
14 -- and unpacking a chunk of bytes. Used by code emitted by the compiler
15 -- plus the prelude libraries.
17 -- The programmer level view of packed strings is provided by a GHC
18 -- system library PackedString.
20 -----------------------------------------------------------------------------
25 -- (**) - emitted by compiler.
27 packCString#, -- :: [Char] -> ByteArray# (**)
29 unpackCString#, -- :: Addr# -> [Char] (**)
30 unpackNBytes#, -- :: Addr# -> Int# -> [Char] (**)
31 unpackFoldrCString#, -- (**)
32 unpackAppendCString#, -- (**)
37 import {-# SOURCE #-} GHC.Err ( error )
38 import GHC.List ( length )
43 data ByteArray ix = ByteArray ix ix ByteArray#
44 data MutableByteArray s ix = MutableByteArray ix ix (MutableByteArray# s)
46 unpackCString :: Ptr a -> [Char]
47 unpackCString a@(Ptr addr)
49 | otherwise = unpackCString# addr
51 packCString# :: [Char] -> ByteArray#
52 packCString# str = case (packString str) of { ByteArray _ _ bytes -> bytes }
54 packString :: [Char] -> ByteArray Int
55 packString str = runST (packStringST str)
57 packStringST :: [Char] -> ST s (ByteArray Int)
59 let len = length str in
62 packNBytesST :: Int -> [Char] -> ST s (ByteArray Int)
63 packNBytesST (I# length#) str =
65 allocate an array that will hold the string
66 (not forgetting the NUL byte at the end)
68 new_ps_array (length# +# 1#) >>= \ ch_array ->
69 -- fill in packed string from "str"
70 fill_in ch_array 0# str >>
72 freeze_ps_array ch_array length#
74 fill_in :: MutableByteArray s Int -> Int# -> [Char] -> ST s ()
75 fill_in arr_in# idx [] =
76 write_ps_array arr_in# idx (chr# 0#) >>
79 fill_in arr_in# idx (C# c : cs) =
80 write_ps_array arr_in# idx c >>
81 fill_in arr_in# (idx +# 1#) cs
83 -- (Very :-) ``Specialised'' versions of some CharArray things...
85 new_ps_array :: Int# -> ST s (MutableByteArray s Int)
86 write_ps_array :: MutableByteArray s Int -> Int# -> Char# -> ST s ()
87 freeze_ps_array :: MutableByteArray s Int -> Int# -> ST s (ByteArray Int)
89 new_ps_array size = ST $ \ s ->
90 case (newByteArray# size s) of { (# s2#, barr# #) ->
91 (# s2#, MutableByteArray bot bot barr# #) }
93 bot = error "new_ps_array"
95 write_ps_array (MutableByteArray _ _ barr#) n ch = ST $ \ s# ->
96 case writeCharArray# barr# n ch s# of { s2# ->
99 -- same as unsafeFreezeByteArray
100 freeze_ps_array (MutableByteArray _ _ arr#) len# = ST $ \ s# ->
101 case unsafeFreezeByteArray# arr# s# of { (# s2#, frozen# #) ->
102 (# s2#, ByteArray 0 (I# len#) frozen# #) }