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|
{-# OPTIONS -fallow-overlapping-instances #-}
{- arch-tag: Python file-like objects
Copyright (C) 2005 John Goerzen <jgoerzen@complete.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-}
{- |
Module : Python.Objects.File
Copyright : Copyright (C) 2005 John Goerzen
License : GNU GPL, version 2 or above
Maintainer : John Goerzen,
Maintainer : jgoerzen\@complete.org
Stability : provisional
Portability: portable
Python file-like objects
Written by John Goerzen, jgoerzen\@complete.org
This module provides a Haskell interface to work with Python file-like objects.
The Haskell interface is a "System.IO.HVIO" interface, which is similar
in concept to the Python file-like object system.
You can create such objects by using 'openPyFile' from this module, or
'MissingPy.FileArchive.GZip.openGz' or 'MissingPy.FileArchive.BZip2.openBz2'.
Functions that you can use to operate on these objects are defined at
"System.IO.HVIO".
-}
module Python.Objects.File (-- * PyFile Objects
PyFile,
mkPyFile,
fromPyFile,
openPyFile,
pyfwrap,
openModeConv
)
where
import Python.Types
import Python.Utils
import Python.Objects
import Python.Interpreter
import System.IO
import System.IO.Error
import System.IO.Unsafe
import Python.Exceptions
import System.IO.HVIO
import Foreign.C.Types
{- | The basic type for a Python file or file-like object.
'PyFile's are a member of System.IO.HVIO and can be used as any other
Haskell HVFS object such as a Handle.
'PyFile' objects cannot reliably detect EOF when asked by 'vIsEOF', but
can detect it and raise the appropriate IOError when it is reached.
Also, 'PyFile' objects cannot determine if they are readable, writable,
or seekable in advance.
-}
newtype PyFile = PyFile PyObject
{- | Takes a 'PyObject' representing a Python file or file-like object
and makes it into a 'PyFile'. -}
mkPyFile :: PyObject -> PyFile
mkPyFile o = PyFile o
{- | Extracts the 'PyObject' representing this 'PyFile'. -}
fromPyFile :: PyFile -> PyObject
fromPyFile (PyFile o) = o
{- | Convert a Haskell open mode to a Python mode string -}
openModeConv ReadMode = "r"
openModeConv WriteMode = "w"
openModeConv AppendMode = "a"
openModeConv ReadWriteMode = "w+"
{- | Open a file on disk and return a 'PyFile'. -}
openPyFile :: FilePath -> IOMode -> IO PyFile
openPyFile fp mode =
do parms1 <- toPyObject [fp]
parms2 <- toPyObject [openModeConv mode]
obj <- callByName "open" [parms1, parms2] []
return $ mkPyFile obj
------------------------------------------------------------
-- HVIO
------------------------------------------------------------
instance Show PyFile where
show _ = "<Python File Object>"
{- | Wrap an operation, raising exceptions in the IO monad as appropriate. -}
pyfwrap :: PyFile -> (PyObject -> IO a) -> IO a
pyfwrap (PyFile pyobj) func = catchPy (func pyobj) exc2ioerror
raiseEOF :: PyFile -> IO a
raiseEOF h = vThrow h eofErrorType
instance HVIO PyFile where
vClose pyf = pyfwrap pyf (\pyo -> runMethodHs pyo "close" noParms noKwParms)
vIsClosed pyf = pyfwrap pyf (\pyo ->
do h <- hasattr pyo "closed"
if h then
do v <- (getattr pyo "closed" >>= fromPyObject)::IO CInt
if v == 0
then return False
else return True
else return False -- Don't know; fake it.
)
vGetContents pyf = do vTestOpen pyf
vTestEOF pyf
pyfwrap pyf (\pyo ->
let loop = unsafeInterleaveIO $
do block <- callMethodHs pyo "read"
[4096::CLong] noKwParms
case block of
[] -> do vClose pyf
return []
x -> do next <- loop
return $ x : next
in do c <- loop
return $ concat c
)
-- Have to fake it. We have no EOF indication.
vIsEOF pyf = return False
vShow pyf = pyfwrap pyf showPyObject
vGetChar pyf = do vTestOpen pyf
pyfwrap pyf (\pyo ->
do c <- callMethodHs pyo "read" [1::CInt] noKwParms
case c of
[] -> raiseEOF pyf
[x] -> return x
)
vGetLine pyf = do vTestOpen pyf
pyfwrap pyf (\pyo ->
do line <- callMethodHs pyo "readline" noParms noKwParms
case reverse line of
[] -> raiseEOF pyf
'\n':xs -> return $ reverse xs
x -> return line
)
vPutChar pyf c = vPutStr pyf [c]
{- Python strings are non-lazy, so process these in chunks. -}
vPutStr pyf [] = vTestOpen pyf >> return ()
vPutStr pyf s = let (this, next) = (splitAt 4096 s)::(String, String)
in do vTestOpen pyf
pyfwrap pyf (\pyo ->
runMethodHs pyo "write" [this] noKwParms)
vPutStr pyf next
vFlush pyf = pyfwrap pyf (\pyo ->
do vTestOpen pyf
h <- hasattr pyo "flush"
if h then runMethodHs pyo "flush" noParms noKwParms
else return ()
)
{- Some file-like objects don't take an offset. Sigh. -}
vSeek pyf sm offset =
let seekint = case sm of
AbsoluteSeek -> 0::CLong
RelativeSeek -> 1
SeekFromEnd -> 2
in do vTestOpen pyf
pyfwrap pyf (\pyo ->
case sm of
AbsoluteSeek -> runMethodHs pyo "seek"
[(fromIntegral offset)::CLong]
noKwParms
_ -> runMethodHs pyo "seek" [(fromIntegral offset),
seekint] noKwParms
)
vTell pyf = pyfwrap pyf (\pyo ->
vTestOpen pyf >> callMethodHs pyo "tell" noParms noKwParms)
vIsSeekable _ = return True -- fake it
vIsWritable _ = return True -- fake it
vIsReadable _ = return True -- fake it
|
