1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
-----------------------------------------------------------------------------
--- Library for IO operations like reading and writing files
--- that are not already contained in the prelude.
---
--- @author Michael Hanus, Bernd Brassel
--- @version March 2021
-----------------------------------------------------------------------------

module System.IO
  ( Handle, IOMode(..), SeekMode(..), stdin, stdout, stderr
  , openFile, hClose, hFlush, hIsEOF, isEOF
  , hSeek, hWaitForInput, hWaitForInputs, hReady
  , hGetChar, hGetLine, hGetContents, getContents
  , hPutChar, hPutStr, hPutStrLn, hPrint
  , hIsReadable, hIsWritable, hIsTerminalDevice
  ) where

import Data.Either

--- The abstract type of a handle for a stream.
external data Handle -- internally defined

instance Eq Handle where
  h1 == h2 = (handle_eq $# h2) $# h1

handle_eq :: Handle -> Handle -> Bool
handle_eq external

--- The modes for opening a file.
data IOMode = ReadMode | WriteMode | AppendMode

--- The modes for positioning with `hSeek` in a file.
data SeekMode = AbsoluteSeek | RelativeSeek | SeekFromEnd


--- Standard input stream.
stdin :: Handle
stdin external

--- Standard output stream.
stdout :: Handle
stdout external

--- Standard error stream.
stderr :: Handle
stderr external

--- Opens a file in specified mode and returns a handle to it.
openFile :: String -> IOMode -> IO Handle
openFile filename mode = (prim_openFile $## filename) $# mode

prim_openFile :: String -> IOMode -> IO Handle
prim_openFile external

--- Closes a file handle and flushes the buffer in case of output file.
hClose :: Handle -> IO ()
hClose h = prim_hClose $# h

prim_hClose :: Handle -> IO ()
prim_hClose external

--- Flushes the buffer associated to handle in case of output file.
hFlush :: Handle -> IO ()
hFlush h = prim_hFlush $# h

prim_hFlush :: Handle -> IO ()
prim_hFlush external

--- Is handle at end of file?
hIsEOF :: Handle -> IO Bool
hIsEOF h = prim_hIsEOF $# h

prim_hIsEOF :: Handle -> IO Bool
prim_hIsEOF external

--- Is standard input at end of file?
isEOF :: IO Bool
isEOF = hIsEOF stdin


--- Set the position of a handle to a seekable stream (e.g., a file).
--- If the second argument is `AbsoluteSeek`,
--- `SeekFromEnd`, or `RelativeSeek`,
--- the position is set relative to the beginning of the file,
--- to the end of the file, or to the current position, respectively.
hSeek :: Handle -> SeekMode -> Int -> IO ()
hSeek h sm pos = ((prim_hSeek $# h) $# sm) $# pos

prim_hSeek :: Handle -> SeekMode -> Int -> IO ()
prim_hSeek external


--- Waits until input is available on the given handle.
--- If no input is available within t milliseconds, it returns False,
--- otherwise it returns True.
--- @param handle - a handle for an input stream
--- @param timeout - milliseconds to wait for input (< 0 : no time out)
hWaitForInput :: Handle -> Int -> IO Bool
hWaitForInput handle timeout = (prim_hWaitForInput $# handle)  $## timeout

prim_hWaitForInput :: Handle -> Int -> IO Bool
prim_hWaitForInput external

--- Waits until input is available on some of the given handles.
--- If no input is available within t milliseconds, it returns -1,
--- otherwise it returns the index of the corresponding handle with the available
--- data.
--- @param handles - a list of handles for input streams
--- @param timeout - milliseconds to wait for input (< 0 : no time out)
--- @return -1 if no input is available within the time out, otherwise i
---         if (handles!!i) has data available
hWaitForInputs :: [Handle] -> Int -> IO Int
hWaitForInputs handles timeout = (prim_hWaitForInputs $## handles) $## timeout

prim_hWaitForInputs :: [Handle] -> Int -> IO Int
prim_hWaitForInputs external


--- Checks whether an input is available on a given handle.
hReady :: Handle -> IO Bool
hReady h = hWaitForInput h 0


--- Reads a character from an input handle and returns it.
--- Throws an error if the end of file has been reached.
hGetChar    :: Handle -> IO Char
hGetChar h = prim_hGetChar $# h

prim_hGetChar :: Handle -> IO Char
prim_hGetChar external

--- Reads a line from an input handle and returns it.
--- Throws an error if the end of file has been reached while reading
--- the *first* character. If the end of file is reached later in the line,
--- it ist treated as a line terminator and the (partial) line is returned.
hGetLine  :: Handle -> IO String
hGetLine h = do c  <- hGetChar h
                if c == '\n'
                   then return []
                   else do eof <- hIsEOF h
                           if eof then return [c]
                                  else do cs <- hGetLine h
                                          return (c:cs)


--- Reads the complete contents from an input handle and closes the input handle
--- before returning the contents.
hGetContents  :: Handle -> IO String
hGetContents h = do
  eof <- hIsEOF h
  if eof then hClose h >> return ""
         else do c <- hGetChar h
                 cs <- hGetContents h
                 return (c:cs)

--- Reads the complete contents from the standard input stream until EOF.
getContents  :: IO String
getContents = hGetContents stdin

--- Puts a character to an output handle.
hPutChar    :: Handle -> Char -> IO ()
hPutChar h c = (prim_hPutChar $# h)  $## c

prim_hPutChar :: Handle -> Char -> IO ()
prim_hPutChar external

--- Puts a string to an output handle.
hPutStr :: Handle -> String -> IO ()
hPutStr _ []     = return ()
hPutStr h (c:cs) = hPutChar h c >> hPutStr h cs

--- Puts a string with a newline to an output handle.
hPutStrLn :: Handle -> String -> IO ()
hPutStrLn h s = hPutStr h s >> hPutChar h '\n'

--- Converts a term into a string and puts it to an output handle.
hPrint :: Show a => Handle -> a -> IO ()
hPrint h = hPutStrLn h . show


--- Is the handle readable?
hIsReadable :: Handle -> IO Bool
hIsReadable  h = prim_hIsReadable $# h

prim_hIsReadable :: Handle -> IO Bool
prim_hIsReadable external

--- Is the handle writable?
hIsWritable :: Handle -> IO Bool
hIsWritable h = prim_hIsWritable $# h

prim_hIsWritable :: Handle -> IO Bool
prim_hIsWritable external

--- Is the handle connected to a terminal?
hIsTerminalDevice :: Handle -> IO Bool
hIsTerminalDevice h = prim_hIsTerminalDevice $# h

prim_hIsTerminalDevice :: Handle -> IO Bool
prim_hIsTerminalDevice external