From f98fa53d7f6d851b8a1ae804c02780769c98e07c Mon Sep 17 00:00:00 2001
From: Joey Hess <joey@kitenet.net>
Date: Sun, 10 Oct 2010 11:08:40 -0400
Subject: [PATCH] fixed close after locking

---
 LocationLog.hs | 15 +++++++++------
 Utility.hs     |  7 +++++--
 git-annex.hs   |  2 ++
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/LocationLog.hs b/LocationLog.hs
index c921a20052..1523901df7 100644
--- a/LocationLog.hs
+++ b/LocationLog.hs
@@ -12,6 +12,11 @@
  -
  - A line of the log will look like: "date N reponame"
  - Where N=1 when the repo has the file, and 0 otherwise.
+ -
+ - TOOD: compact logs, by storing only current presence infomation when
+ - writing them.
+ -
+ - TODO: use ByteString
  -}
 
 module LocationLog where
@@ -67,9 +72,8 @@ readLog file = do
 	exists <- doesFileExist file
 	if exists
 		then do
-			h <- openLocked file ReadMode
-			s <- hGetContentsStrict h
-			hClose h
+			s <- withFileLocked file ReadMode $ \h -> 
+				hGetContentsStrict h
 			-- filter out any unparsable lines
 			return $ filter (\l -> (status l) /= Undefined )
 				$ map read $ lines s
@@ -80,9 +84,8 @@ readLog file = do
 writeLog :: String -> LogLine -> IO ()
 writeLog file line = do
 	createDirectoryIfMissing True (parentDir file)
-	h <- openLocked file AppendMode
-	hPutStrLn h $ show line
-	hClose h
+	withFileLocked file AppendMode $ \h ->
+		hPutStrLn h $ show line
 
 {- Generates a new LogLine with the current date. -}
 logNow :: LogStatus -> String -> IO LogLine
diff --git a/Utility.hs b/Utility.hs
index ab9ce04f36..d1eb247d3c 100644
--- a/Utility.hs
+++ b/Utility.hs
@@ -9,12 +9,15 @@ import Data.String.Utils
 
 {- Let's just say that Haskell makes reading/writing a file with
  - file locking excessively difficult. -}
-openLocked file mode = do
+withFileLocked file mode action = do
+	-- TODO: find a way to use bracket here
 	handle <- openFile file mode
 	lockfd <- handleToFd handle -- closes handle
 	waitToSetLock lockfd (lockType mode, AbsoluteSeek, 0, 0)
 	handle' <- fdToHandle lockfd
-	return handle'
+	ret <- action handle'
+	hClose handle'
+	return ret
 		where
 			lockType ReadMode = ReadLock
 			lockType _ = WriteLock
diff --git a/git-annex.hs b/git-annex.hs
index e8032a1325..66b9491bde 100644
--- a/git-annex.hs
+++ b/git-annex.hs
@@ -6,3 +6,5 @@ import GitRepo
 
 main = do
 	gitPrep
+	l <- readLog "demo.log"
+	writeLog "demo2.log" $ l !! 0