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{- misc utility functions
-
- Copyright 2010-2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Utility.Misc where
import System.IO
import Control.Monad
import Foreign
import Data.Char
import Control.Applicative
{- 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 character 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.) -}
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
{- Given two orderings, returns the second if the first is EQ and returns
- the first otherwise.
-
- Example use:
-
- compare lname1 lname2 `thenOrd` compare fname1 fname2
-}
thenOrd :: Ordering -> Ordering -> Ordering
thenOrd EQ x = x
thenOrd x _ = x
{-# INLINE thenOrd #-}
{- 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]
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