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{- misc utility functions
-
- Copyright 2010-2011 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# OPTIONS_GHC -fno-warn-tabs #-}
module Utility.Misc where
import System.IO
import Control.Monad
import Foreign
import Data.Char
import Data.List
import System.Exit
import Control.Applicative
import Prelude
{- A version of hgetContents that is not lazy. Ensures file is
- all read before it gets closed. -}
hGetContentsStrict :: Handle -> IO String
hGetContentsStrict = hGetContents >=> \s -> length s `seq` return s
{- A version of readFile that is not lazy. -}
readFileStrict :: FilePath -> IO String
readFileStrict = readFile >=> \s -> length s `seq` return s
{- Like break, but the item matching the condition is not included
- in the second result list.
-
- separate (== ':') "foo:bar" = ("foo", "bar")
- separate (== ':') "foobar" = ("foobar", "")
-}
separate :: (a -> Bool) -> [a] -> ([a], [a])
separate c l = unbreak $ break c l
where
unbreak r@(a, b)
| null b = r
| otherwise = (a, tail b)
{- Breaks out the first line. -}
firstLine :: String -> String
firstLine = takeWhile (/= '\n')
{- Splits a list into segments that are delimited by items matching
- a predicate. (The delimiters are not included in the segments.)
- Segments may be empty. -}
segment :: (a -> Bool) -> [a] -> [[a]]
segment p l = map reverse $ go [] [] l
where
go c r [] = reverse $ c:r
go c r (i:is)
| p i = go [] (c:r) is
| otherwise = go (i:c) r is
prop_segment_regressionTest :: Bool
prop_segment_regressionTest = all id
-- Even an empty list is a segment.
[ segment (== "--") [] == [[]]
-- There are two segements in this list, even though the first is empty.
, segment (== "--") ["--", "foo", "bar"] == [[],["foo","bar"]]
]
{- Includes the delimiters as segments of their own. -}
segmentDelim :: (a -> Bool) -> [a] -> [[a]]
segmentDelim p l = map reverse $ go [] [] l
where
go c r [] = reverse $ c:r
go c r (i:is)
| p i = go [] ([i]:c:r) is
| otherwise = go (i:c) r is
{- Replaces multiple values in a string.
-
- Takes care to skip over just-replaced values, so that they are not
- mangled. For example, massReplace [("foo", "new foo")] does not
- replace the "new foo" with "new new foo".
-}
massReplace :: [(String, String)] -> String -> String
massReplace vs = go [] vs
where
go acc _ [] = concat $ reverse acc
go acc [] (c:cs) = go ([c]:acc) vs cs
go acc ((val, replacement):rest) s
| val `isPrefixOf` s =
go (replacement:acc) vs (drop (length val) s)
| otherwise = go acc rest s
{- Wrapper around hGetBufSome that returns a String.
-
- The null string is returned on eof, otherwise returns whatever
- data is currently available to read from the handle, or waits for
- data to be written to it if none is currently available.
-
- Note on encodings: The normal encoding of the Handle is ignored;
- each byte is converted to a Char. Not unicode clean!
-}
hGetSomeString :: Handle -> Int -> IO String
hGetSomeString h sz = do
fp <- mallocForeignPtrBytes sz
len <- withForeignPtr fp $ \buf -> hGetBufSome h buf sz
map (chr . fromIntegral) <$> withForeignPtr fp (peekbytes len)
where
peekbytes :: Int -> Ptr Word8 -> IO [Word8]
peekbytes len buf = mapM (peekElemOff buf) [0..pred len]
exitBool :: Bool -> IO a
exitBool False = exitFailure
exitBool True = exitSuccess
|
