89 lines
2.4 KiB
Haskell
89 lines
2.4 KiB
Haskell
{- git-annex utility functions
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-}
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module Utility (
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withFileLocked,
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hGetContentsStrict,
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parentDir,
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relPathCwdToDir,
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relPathDirToDir,
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) where
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import System.IO
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import System.Posix.IO
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import Data.String.Utils
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import System.Path
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import System.FilePath
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import System.Directory
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{- Let's just say that Haskell makes reading/writing a file with
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- file locking excessively difficult. -}
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withFileLocked file mode action = do
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-- TODO: find a way to use bracket here
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handle <- openFile file mode
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lockfd <- handleToFd handle -- closes handle
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waitToSetLock lockfd (lockType mode, AbsoluteSeek, 0, 0)
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handle' <- fdToHandle lockfd
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ret <- action handle'
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hClose handle'
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return ret
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where
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lockType ReadMode = ReadLock
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lockType _ = WriteLock
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{- A version of hgetContents that is not lazy. Ensures file is
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- all read before it gets closed. -}
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hGetContentsStrict h = hGetContents h >>= \s -> length s `seq` return s
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{- Returns the parent directory of a path. Parent of / is "" -}
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parentDir :: String -> String
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parentDir dir =
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if length dirs > 0
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then slash ++ (join s $ take ((length dirs) - 1) dirs)
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else ""
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where
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dirs = filter (\x -> length x > 0) $
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split s dir
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slash = if (not $ isAbsolute dir) then "" else s
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s = [pathSeparator]
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{- Constructs a relative path from the CWD to a directory.
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-
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- For example, assuming CWD is /tmp/foo/bar:
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- relPathCwdToDir "/tmp/foo" == "../"
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- relPathCwdToDir "/tmp/foo/bar" == ""
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- relPathCwdToDir "/tmp/foo/bar" == ""
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-}
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relPathCwdToDir :: FilePath -> IO FilePath
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relPathCwdToDir dir = do
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cwd <- getCurrentDirectory
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let absdir = abs cwd dir
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return $ relPathDirToDir cwd absdir
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where
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-- absolute, normalized form of the directory
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abs cwd dir =
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case (absNormPath cwd dir) of
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Just d -> d
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Nothing -> error $ "unable to normalize " ++ dir
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{- Constructs a relative path from one directory to another.
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-
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- Both directories must be absolute, and normalized (eg with absNormpath).
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-
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- The path will end with "/", unless it is empty.
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-}
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relPathDirToDir :: FilePath -> FilePath -> FilePath
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relPathDirToDir from to =
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if (0 < length path)
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then addTrailingPathSeparator path
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else ""
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where
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s = [pathSeparator]
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pfrom = split s from
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pto = split s to
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common = map fst $ filter same $ zip pfrom pto
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same (c,d) = c == d
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uncommon = drop numcommon pto
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dotdots = take ((length pfrom) - numcommon) $ repeat ".."
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numcommon = length $ common
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path = join s $ dotdots ++ uncommon
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