reorganize and refactor lock code

Added a convenience Utility.LockFile that is not a windows/posix
portability shim, but still manages to cut down on the boilerplate around
locking.

This commit was sponsored by Johan Herland.

1 files changed, 0 insertions, 74 deletions

diff --git a/Utility/WinLock.hs b/Utility/WinLock.hs
deleted file mode 100644
index fc7c8a8a9..000000000
--- a/Utility/WinLock.hs
+++ /dev/null
@@ -1,74 +0,0 @@
-{- Windows lock files
- -
- - Copyright 2014 Joey Hess <joey@kitenet.net>
- -
- - License: BSD-2-clause
- -}
-
-module Utility.WinLock (
-	lockShared,
-	lockExclusive,
-	dropLock,
-	waitToLock,
-	LockHandle
-) where
-
-import System.Win32.Types
-import System.Win32.File
-import Control.Concurrent
-
-{- Locking is exclusive, and prevents the file from being opened for read
- - or write by any other process. So for advisory locking of a file, a
- - different LockFile should be used. -}
-type LockFile = FilePath
-
-type LockHandle = HANDLE
-
-{- Tries to lock a file with a shared lock, which allows other processes to
- - also lock it shared. Fails is the file is exclusively locked. -}
-lockShared :: LockFile -> IO (Maybe LockHandle)
-lockShared = openLock fILE_SHARE_READ
-
-{- Tries to take an exclusive lock on a file. Fails if another process has
- - a shared or exclusive lock. -}
-lockExclusive :: LockFile -> IO (Maybe LockHandle)
-lockExclusive = openLock fILE_SHARE_NONE
-
-{- Windows considers just opening a file enough to lock it. This will
- - create the LockFile if it does not already exist.
- -
- - Will fail if the file is already open with an incompatable ShareMode.
- - Note that this may happen if an unrelated process, such as a virus
- - scanner, even looks at the file. See http://support.microsoft.com/kb/316609
- -
- - Note that createFile busy-waits to try to avoid failing when some other
- - process briefly has a file open. But that would make checking locks
- - much more expensive, so is not done here. Thus, the use of c_CreateFile.
- -
- - Also, passing Nothing for SECURITY_ATTRIBUTES ensures that the lock file
- - is not inheerited by any child process.
- -}
-openLock :: ShareMode -> LockFile -> IO (Maybe LockHandle)
-openLock sharemode f = do
-	h <- withTString f $ \c_f ->
-		c_CreateFile c_f gENERIC_READ sharemode security_attributes
-			oPEN_ALWAYS fILE_ATTRIBUTE_NORMAL (maybePtr Nothing)
-	return $ if h == iNVALID_HANDLE_VALUE
-		then Nothing
-		else Just h
-  where
-	security_attributes = maybePtr Nothing
-
-dropLock :: LockHandle -> IO ()
-dropLock = closeHandle
-
-{- If the initial lock fails, this is a BUSY wait, and does not
- - guarentee FIFO order of waiters. In other news, Windows is a POS. -}
-waitToLock :: IO (Maybe LockHandle) -> IO LockHandle
-waitToLock locker = takelock
-  where
-	takelock = go =<< locker
-	go (Just lck) = return lck
-	go Nothing = do
-		threadDelay (500000) -- half a second
-		takelock