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Diffstat (limited to 'src')
| -rw-r--r-- | src/Text/Pandoc/Process.hs | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/src/Text/Pandoc/Process.hs b/src/Text/Pandoc/Process.hs new file mode 100644 index 000000000..112c5b974 --- /dev/null +++ b/src/Text/Pandoc/Process.hs @@ -0,0 +1,105 @@ +{- +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) + |