Distribution/Utils/Generic.hs

    {-# LANGUAGE CPP #-}
    {-# LANGUAGE ScopedTypeVariables #-}
    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE RankNTypes #-}
    {-# LANGUAGE DeriveGeneric #-}
    {-# LANGUAGE BangPatterns #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Utils
    -- Copyright   :  Isaac Jones, Simon Marlow 2003-2004
    -- License     :  BSD3
    --                portions Copyright (c) 2007, Galois Inc.
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- A large and somewhat miscellaneous collection of utility functions used
    -- throughout the rest of the Cabal lib and in other tools that use the Cabal
    -- lib like @cabal-install@. It has a very simple set of logging actions. It
    -- has low level functions for running programs, a bunch of wrappers for
    -- various directory and file functions that do extra logging.

    module Distribution.Utils.Generic (
            -- * reading and writing files safely
            withFileContents,
            writeFileAtomic,

            -- * Unicode
            fromUTF8,
            fromUTF8BS,
            fromUTF8LBS,
            toUTF8,
            readUTF8File,
            withUTF8FileContents,
            writeUTF8File,
            normaliseLineEndings,

            -- * BOM
            startsWithBOM,
            fileHasBOM,
            ignoreBOM,

            -- * generic utils
            dropWhileEndLE,
            takeWhileEndLE,
            equating,
            comparing,
            isInfixOf,
            intercalate,
            lowercase,
            listUnion,
            listUnionRight,
            ordNub,
            ordNubBy,
            ordNubRight,
            safeTail,
            unintersperse,
            wrapText,
            wrapLine,

            -- * FilePath stuff
            isAbsoluteOnAnyPlatform,
            isRelativeOnAnyPlatform,
      ) where

    import Prelude ()
    import Distribution.Compat.Prelude

    import Distribution.Utils.String

    import Data.Bits
        ( Bits((.|.), (.&.), shiftL, shiftR) )
    import Data.List
        ( isInfixOf )
    import Data.Ord
        ( comparing )
    import qualified Data.ByteString.Lazy as BS
    import qualified Data.Set as Set

    import qualified Data.ByteString as SBS

    import System.Directory
        ( removeFile )
    import System.FilePath
        ( (<.>), splitFileName )
    import System.Directory
        ( renameFile )
    import System.IO
        ( openFile, openBinaryFile, openBinaryTempFileWithDefaultPermissions
        , IOMode(ReadMode), hGetContents, hClose )
    import qualified Control.Exception as Exception

    -- -----------------------------------------------------------------------------
    -- Helper functions

    -- | Wraps text to the default line width. Existing newlines are preserved.
    wrapText :: String -> String
    wrapText = unlines
             . map (intercalate "\n"
                  . map unwords
                  . wrapLine 79
                  . words)
             . lines

    -- | Wraps a list of words to a list of lines of words of a particular width.
    wrapLine :: Int -> [String] -> [[String]]
    wrapLine width = wrap 0 []
      where wrap :: Int -> [String] -> [String] -> [[String]]
            wrap 0   []   (w:ws)
              | length w + 1 > width
              = wrap (length w) [w] ws
            wrap col line (w:ws)
              | col + length w + 1 > width
              = reverse line : wrap 0 [] (w:ws)
            wrap col line (w:ws)
              = let col' = col + length w + 1
                 in wrap col' (w:line) ws
            wrap _ []   [] = []
            wrap _ line [] = [reverse line]

    -----------------------------------
    -- Safely reading and writing files

    -- | Gets the contents of a file, but guarantee that it gets closed.
    --
    -- The file is read lazily but if it is not fully consumed by the action then
    -- the remaining input is truncated and the file is closed.
    --
    withFileContents :: FilePath -> (String -> NoCallStackIO a) -> NoCallStackIO a
    withFileContents name action =
      Exception.bracket (openFile name ReadMode) hClose
                        (\hnd -> hGetContents hnd >>= action)

    -- | Writes a file atomically.
    --
    -- The file is either written successfully or an IO exception is raised and
    -- the original file is left unchanged.
    --
    -- On windows it is not possible to delete a file that is open by a process.
    -- This case will give an IO exception but the atomic property is not affected.
    --
    writeFileAtomic :: FilePath -> BS.ByteString -> NoCallStackIO ()
    writeFileAtomic targetPath content = do
      let (targetDir, targetFile) = splitFileName targetPath
      Exception.bracketOnError
        (openBinaryTempFileWithDefaultPermissions targetDir $ targetFile <.> "tmp")
        (\(tmpPath, handle) -> hClose handle >> removeFile tmpPath)
        (\(tmpPath, handle) -> do
            BS.hPut handle content
            hClose handle
            renameFile tmpPath targetPath)

    -- ------------------------------------------------------------
    -- * Unicode stuff
    -- ------------------------------------------------------------

    -- This is a modification of the UTF8 code from gtk2hs and the
    -- utf8-string package.

    fromUTF8 :: String -> String
    fromUTF8 []     = []
    fromUTF8 (c:cs)
      | c <= '\x7F' = c : fromUTF8 cs
      | c <= '\xBF' = replacementChar : fromUTF8 cs
      | c <= '\xDF' = twoBytes c cs
      | c <= '\xEF' = moreBytes 3 0x800     cs (ord c .&. 0xF)
      | c <= '\xF7' = moreBytes 4 0x10000   cs (ord c .&. 0x7)
      | c <= '\xFB' = moreBytes 5 0x200000  cs (ord c .&. 0x3)
      | c <= '\xFD' = moreBytes 6 0x4000000 cs (ord c .&. 0x1)
      | otherwise   = replacementChar : fromUTF8 cs
      where
        twoBytes c0 (c1:cs')
          | ord c1 .&. 0xC0 == 0x80
          = let d = ((ord c0 .&. 0x1F) `shiftL` 6)
                 .|. (ord c1 .&. 0x3F)
             in if d >= 0x80
                   then  chr d           : fromUTF8 cs'
                   else  replacementChar : fromUTF8 cs'
        twoBytes _ cs' = replacementChar : fromUTF8 cs'

        moreBytes :: Int -> Int -> [Char] -> Int -> [Char]
        moreBytes 1 overlong cs' acc
          | overlong <= acc && acc <= 0x10FFFF
         && (acc < 0xD800 || 0xDFFF < acc)
         && (acc < 0xFFFE || 0xFFFF < acc)
          = chr acc : fromUTF8 cs'

          | otherwise
          = replacementChar : fromUTF8 cs'

        moreBytes byteCount overlong (cn:cs') acc
          | ord cn .&. 0xC0 == 0x80
          = moreBytes (byteCount-1) overlong cs'
              ((acc `shiftL` 6) .|. ord cn .&. 0x3F)

        moreBytes _ _ cs' _
          = replacementChar : fromUTF8 cs'

        replacementChar = '\xfffd'

    fromUTF8BS :: SBS.ByteString -> String
    fromUTF8BS = decodeStringUtf8 . SBS.unpack

    fromUTF8LBS :: BS.ByteString -> String
    fromUTF8LBS = decodeStringUtf8 . BS.unpack

    toUTF8 :: String -> String
    toUTF8 []        = []
    toUTF8 (c:cs)
      | c <= '\x07F' = c
                     : toUTF8 cs
      | c <= '\x7FF' = chr (0xC0 .|. (w `shiftR` 6))
                     : chr (0x80 .|. (w .&. 0x3F))
                     : toUTF8 cs
      | c <= '\xFFFF'= chr (0xE0 .|.  (w `shiftR` 12))
                     : chr (0x80 .|. ((w `shiftR` 6)  .&. 0x3F))
                     : chr (0x80 .|.  (w .&. 0x3F))
                     : toUTF8 cs
      | otherwise    = chr (0xf0 .|.  (w `shiftR` 18))
                     : chr (0x80 .|. ((w `shiftR` 12)  .&. 0x3F))
                     : chr (0x80 .|. ((w `shiftR` 6)  .&. 0x3F))
                     : chr (0x80 .|.  (w .&. 0x3F))
                     : toUTF8 cs
      where w = ord c

    -- | Whether BOM is at the beginning of the input
    startsWithBOM :: String -> Bool
    startsWithBOM ('\xFEFF':_) = True
    startsWithBOM _            = False

    -- | Check whether a file has Unicode byte order mark (BOM).
    fileHasBOM :: FilePath -> NoCallStackIO Bool
    fileHasBOM f = fmap (startsWithBOM . fromUTF8)
                 . hGetContents =<< openBinaryFile f ReadMode

    -- | Ignore a Unicode byte order mark (BOM) at the beginning of the input
    --
    ignoreBOM :: String -> String
    ignoreBOM ('\xFEFF':string) = string
    ignoreBOM string            = string

    -- | Reads a UTF8 encoded text file as a Unicode String
    --
    -- Reads lazily using ordinary 'readFile'.
    --
    readUTF8File :: FilePath -> NoCallStackIO String
    readUTF8File f = fmap (ignoreBOM . fromUTF8)
                   . hGetContents =<< openBinaryFile f ReadMode

    -- | Reads a UTF8 encoded text file as a Unicode String
    --
    -- Same behaviour as 'withFileContents'.
    --
    withUTF8FileContents :: FilePath -> (String -> IO a) -> IO a
    withUTF8FileContents name action =
      Exception.bracket
        (openBinaryFile name ReadMode)
        hClose
        (\hnd -> hGetContents hnd >>= action . ignoreBOM . fromUTF8)

    -- | Writes a Unicode String as a UTF8 encoded text file.
    --
    -- Uses 'writeFileAtomic', so provides the same guarantees.
    --
    writeUTF8File :: FilePath -> String -> NoCallStackIO ()
    writeUTF8File path = writeFileAtomic path . BS.pack . encodeStringUtf8

    -- | Fix different systems silly line ending conventions
    normaliseLineEndings :: String -> String
    normaliseLineEndings [] = []
    normaliseLineEndings ('\r':'\n':s) = '\n' : normaliseLineEndings s -- windows
    normaliseLineEndings ('\r':s)      = '\n' : normaliseLineEndings s -- old OS X
    normaliseLineEndings (  c :s)      =   c  : normaliseLineEndings s

    -- ------------------------------------------------------------
    -- * Common utils
    -- ------------------------------------------------------------

    -- | @dropWhileEndLE p@ is equivalent to @reverse . dropWhile p . reverse@, but
    -- quite a bit faster. The difference between "Data.List.dropWhileEnd" and this
    -- version is that the one in "Data.List" is strict in elements, but spine-lazy,
    -- while this one is spine-strict but lazy in elements. That's what @LE@ stands
    -- for - "lazy in elements".
    --
    -- Example:
    --
    -- @
    -- > tail $ Data.List.dropWhileEnd (<3) [undefined, 5, 4, 3, 2, 1]
    -- *** Exception: Prelude.undefined
    -- > tail $ dropWhileEndLE (<3) [undefined, 5, 4, 3, 2, 1]
    -- [5,4,3]
    -- > take 3 $ Data.List.dropWhileEnd (<3) [5, 4, 3, 2, 1, undefined]
    -- [5,4,3]
    -- > take 3 $ dropWhileEndLE (<3) [5, 4, 3, 2, 1, undefined]
    -- *** Exception: Prelude.undefined
    -- @
    dropWhileEndLE :: (a -> Bool) -> [a] -> [a]
    dropWhileEndLE p = foldr (\x r -> if null r && p x then [] else x:r) []

    -- | @takeWhileEndLE p@ is equivalent to @reverse . takeWhile p . reverse@, but
    -- is usually faster (as well as being easier to read).
    takeWhileEndLE :: (a -> Bool) -> [a] -> [a]
    takeWhileEndLE p = fst . foldr go ([], False)
      where
        go x (rest, done)
          | not done && p x = (x:rest, False)
          | otherwise = (rest, True)

    -- | Like 'Data.List.nub', but has @O(n log n)@ complexity instead of
    -- @O(n^2)@. Code for 'ordNub' and 'listUnion' taken from Niklas Hambüchen's
    -- <http://github.com/nh2/haskell-ordnub ordnub> package.
    ordNub :: Ord a => [a] -> [a]
    ordNub = ordNubBy id

    -- | Like 'ordNub' and 'Data.List.nubBy'. Selects a key for each element and
    -- takes the nub based on that key.
    ordNubBy :: Ord b => (a -> b) -> [a] -> [a]
    ordNubBy f l = go Set.empty l
      where
        go !_ [] = []
        go !s (x:xs)
          | y `Set.member` s = go s xs
          | otherwise        = let !s' = Set.insert y s
                                in x : go s' xs
          where
            y = f x

    -- | Like "Data.List.union", but has @O(n log n)@ complexity instead of
    -- @O(n^2)@.
    listUnion :: (Ord a) => [a] -> [a] -> [a]
    listUnion a b = a ++ ordNub (filter (`Set.notMember` aSet) b)
      where
        aSet = Set.fromList a

    -- | A right-biased version of 'ordNub'.
    --
    -- Example:
    --
    -- @
    -- > ordNub [1,2,1]
    -- [1,2]
    -- > ordNubRight [1,2,1]
    -- [2,1]
    -- @
    ordNubRight :: (Ord a) => [a] -> [a]
    ordNubRight = fst . foldr go ([], Set.empty)
      where
        go x p@(l, s) = if x `Set.member` s then p
                                            else (x:l, Set.insert x s)

    -- | A right-biased version of 'listUnion'.
    --
    -- Example:
    --
    -- @
    -- > listUnion [1,2,3,4,3] [2,1,1]
    -- [1,2,3,4,3]
    -- > listUnionRight [1,2,3,4,3] [2,1,1]
    -- [4,3,2,1,1]
    -- @
    listUnionRight :: (Ord a) => [a] -> [a] -> [a]
    listUnionRight a b = ordNubRight (filter (`Set.notMember` bSet) a) ++ b
      where
        bSet = Set.fromList b

    -- | A total variant of 'tail'.
    safeTail :: [a] -> [a]
    safeTail []     = []
    safeTail (_:xs) = xs

    equating :: Eq a => (b -> a) -> b -> b -> Bool
    equating p x y = p x == p y

    lowercase :: String -> String
    lowercase = map toLower

    unintersperse :: Char -> String -> [String]
    unintersperse mark = unfoldr unintersperse1 where
      unintersperse1 str
        | null str = Nothing
        | otherwise =
            let (this, rest) = break (== mark) str in
            Just (this, safeTail rest)

    -- ------------------------------------------------------------
    -- * FilePath stuff
    -- ------------------------------------------------------------

    -- | 'isAbsoluteOnAnyPlatform' and 'isRelativeOnAnyPlatform' are like
    -- 'System.FilePath.isAbsolute' and 'System.FilePath.isRelative' but have
    -- platform independent heuristics.
    -- The System.FilePath exists in two versions, Windows and Posix. The two
    -- versions don't agree on what is a relative path and we don't know if we're
    -- given Windows or Posix paths.
    -- This results in false positives when running on Posix and inspecting
    -- Windows paths, like the hackage server does.
    -- System.FilePath.Posix.isAbsolute \"C:\\hello\" == False
    -- System.FilePath.Windows.isAbsolute \"/hello\" == False
    -- This means that we would treat paths that start with \"/\" to be absolute.
    -- On Posix they are indeed absolute, while on Windows they are not.
    --
    -- The portable versions should be used when we might deal with paths that
    -- are from another OS than the host OS. For example, the Hackage Server
    -- deals with both Windows and Posix paths while performing the
    -- PackageDescription checks. In contrast, when we run 'cabal configure' we
    -- do expect the paths to be correct for our OS and we should not have to use
    -- the platform independent heuristics.
    isAbsoluteOnAnyPlatform :: FilePath -> Bool
    -- C:\\directory
    isAbsoluteOnAnyPlatform (drive:':':'\\':_) = isAlpha drive
    -- UNC
    isAbsoluteOnAnyPlatform ('\\':'\\':_) = True
    -- Posix root
    isAbsoluteOnAnyPlatform ('/':_) = True
    isAbsoluteOnAnyPlatform _ = False

    -- | @isRelativeOnAnyPlatform = not . 'isAbsoluteOnAnyPlatform'@
    isRelativeOnAnyPlatform :: FilePath -> Bool
    isRelativeOnAnyPlatform = not . isAbsoluteOnAnyPlatform