38 lines
1,020 B
Haskell
38 lines
1,020 B
Haskell
{- Opening files
|
|
-
|
|
- Copyright 2024 Joey Hess <id@joeyh.name>
|
|
-
|
|
- License: BSD-2-clause
|
|
-}
|
|
|
|
{-# LANGUAGE CPP #-}
|
|
|
|
module Utility.OpenFile where
|
|
|
|
#ifndef mingw32_HOST_OS
|
|
|
|
import System.IO
|
|
import System.Posix.IO
|
|
import GHC.IO.FD
|
|
import GHC.IO.Handle.FD
|
|
import GHC.IO.Device
|
|
|
|
import Utility.OpenFd
|
|
import Utility.RawFilePath
|
|
import Utility.FileSystemEncoding
|
|
|
|
{- Usually, opening a Handle to a file that another thread also has open
|
|
- for write is prevented, which avoids a lot of concurrency bugs especially
|
|
- with lazy IO.
|
|
-
|
|
- However, sometimes one thread is writing and another thread really wants
|
|
- to read from the same file. This bypasses the usual locking, by claiming
|
|
- that an opened FD is a Stream.
|
|
-}
|
|
openFileBeingWritten :: RawFilePath -> IO Handle
|
|
openFileBeingWritten f = do
|
|
fd <- openFdWithMode f ReadOnly Nothing defaultFileFlags
|
|
(fd', fdtype) <- mkFD (fromIntegral fd) ReadMode (Just (Stream, 0, 0)) False False
|
|
mkHandleFromFD fd' fdtype (fromRawFilePath f) ReadMode False Nothing
|
|
|
|
#endif
|