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authorJohn MacFarlane <jgm@berkeley.edu>2013-08-08 15:13:28 -0700
committerJohn MacFarlane <jgm@berkeley.edu>2013-08-08 15:15:12 -0700
commit7d694e15697a4b1cc974b6316a08117afe663a74 (patch)
tree62f62f77c85463934a0cb2b4d38c0406a5c85e56 /src/Text/Pandoc
parentb0143bfad6ebc3b2ae1ced2fb3a9bed989c41000 (diff)
downloadpandoc-7d694e15697a4b1cc974b6316a08117afe663a74.tar.gz
Added Text.Pandoc.Process (pipeProcess).
A souped up version of readProcessWithErrorCode that uses lazy bytestrings and allows setting environment.
Diffstat (limited to 'src/Text/Pandoc')
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diff --git a/src/Text/Pandoc/Process.hs b/src/Text/Pandoc/Process.hs
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+{-
+Copyright (C) 2013 John MacFarlane <jgm@berkeley.edu>
+
+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 : Text.Pandoc.Process
+ Copyright : Copyright (C) 2013 John MacFarlane
+ License : GNU GPL, version 2 or above
+
+ Maintainer : John MacFarlane <jgm@berkeley.edu>
+ Stability : alpha
+ Portability : portable
+
+ByteString variant of 'readProcessWithExitCode'.
+-}
+module Text.Pandoc.Process (pipeProcess)
+where
+import System.Process
+import System.Exit (ExitCode (..))
+import Control.Exception
+import System.IO (hClose, hFlush)
+import Control.Concurrent (putMVar, takeMVar, newEmptyMVar, forkIO)
+import Control.Monad (unless)
+import qualified Data.ByteString.Lazy as BL
+
+{- |
+Version of 'System.Process.readProcessWithExitCode' that uses lazy bytestrings
+instead of strings and allows setting environment variables.
+
+@readProcessWithExitCode@ creates an external process, reads its
+standard output and standard error strictly, waits until the process
+terminates, and then returns the 'ExitCode' of the process,
+the standard output, and the standard error.
+
+If an asynchronous exception is thrown to the thread executing
+@readProcessWithExitCode@. The forked process will be terminated and
+@readProcessWithExitCode@ will wait (block) until the process has been
+terminated.
+-}
+
+pipeProcess
+ :: Maybe [(String, String)] -- ^ environment variables
+ -> FilePath -- ^ Filename of the executable (see 'proc' for details)
+ -> [String] -- ^ any arguments
+ -> BL.ByteString -- ^ standard input
+ -> IO (ExitCode,BL.ByteString,BL.ByteString) -- ^ exitcode, stdout, stderr
+pipeProcess mbenv cmd args input =
+ mask $ \restore -> do
+ (Just inh, Just outh, Just errh, pid) <- createProcess (proc cmd args)
+ { env = mbenv,
+ std_in = CreatePipe,
+ std_out = CreatePipe,
+ std_err = CreatePipe }
+ flip onException
+ (do hClose inh; hClose outh; hClose errh;
+ terminateProcess pid; waitForProcess pid) $ restore $ do
+ -- fork off a thread to start consuming stdout
+ out <- BL.hGetContents outh
+ waitOut <- forkWait $ evaluate $ BL.length out
+
+ -- fork off a thread to start consuming stderr
+ err <- BL.hGetContents errh
+ waitErr <- forkWait $ evaluate $ BL.length err
+
+ -- now write and flush any input
+ let writeInput = do
+ unless (BL.null input) $ do
+ BL.hPutStr inh input
+ hFlush inh
+ hClose inh
+
+ writeInput
+
+ -- wait on the output
+ waitOut
+ waitErr
+
+ hClose outh
+ hClose errh
+
+ -- wait on the process
+ ex <- waitForProcess pid
+
+ return (ex, out, err)
+
+forkWait :: IO a -> IO (IO a)
+forkWait a = do
+ res <- newEmptyMVar
+ _ <- mask $ \restore -> forkIO $ try (restore a) >>= putMVar res
+ return (takeMVar res >>= either (\ex -> throwIO (ex :: SomeException)) return)
+