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--------------------------------------------------------------------------------
-- | A Compiler that supports unix filters.
module Hakyll.Core.UnixFilter
( unixFilter
, unixFilterLBS
) where
--------------------------------------------------------------------------------
import Control.Concurrent (forkIO)
import Data.ByteString.Lazy (ByteString)
import qualified Data.ByteString.Lazy as LB
import System.IO (Handle, hClose, hGetContents, hPutStr,
hSetEncoding, localeEncoding)
import System.Process
--------------------------------------------------------------------------------
import Hakyll.Core.Compiler
--------------------------------------------------------------------------------
-- | Use a unix filter as compiler. For example, we could use the 'rev' program
-- as a compiler.
--
-- > rev :: Compiler String
-- > rev = getResourceString >>= withItemBody (unixFilter "rev" [])
--
-- A more realistic example: one can use this to call, for example, the sass
-- compiler on CSS files. More information about sass can be found here:
--
-- <http://sass-lang.com/>
--
-- The code is fairly straightforward, given that we use @.scss@ for sass:
--
-- > match "style.scss" $ do
-- > route $ setExtension "css"
-- > compile $ getResourceString >>=
-- > withItemBody (unixFilter "sass" ["-s", "--scss"]) >>=
-- > return . fmap compressCss
unixFilter :: String -- ^ Program name
-> [String] -- ^ Program args
-> String -- ^ Program input
-> Compiler String -- ^ Program output
unixFilter = unixFilterWith writer reader
where
writer handle input = do
hSetEncoding handle localeEncoding
hPutStr handle input
reader handle = do
hSetEncoding handle localeEncoding
hGetContents handle
--------------------------------------------------------------------------------
-- | Variant of 'unixFilter' that should be used for binary files
--
-- > match "music.wav" $ do
-- > route $ setExtension "ogg"
-- > compile $ getResourceLBS >>= withItemBody (unixFilterLBS "oggenc" ["-"])
unixFilterLBS :: String -- ^ Program name
-> [String] -- ^ Program args
-> ByteString -- ^ Program input
-> Compiler ByteString -- ^ Program output
unixFilterLBS = unixFilterWith LB.hPutStr LB.hGetContents
--------------------------------------------------------------------------------
-- | Overloaded compiler
unixFilterWith :: (Handle -> i -> IO ()) -- ^ Writer
-> (Handle -> IO o) -- ^ Reader
-> String -- ^ Program name
-> [String] -- ^ Program args
-> i -- ^ Program input
-> Compiler o -- ^ Program output
unixFilterWith writer reader programName args input = do
debugCompiler ("Executing external program " ++ programName)
unsafeCompiler $ unixFilterIO writer reader programName args input
--------------------------------------------------------------------------------
-- | Internally used function
unixFilterIO :: (Handle -> i -> IO ())
-> (Handle -> IO o)
-> String
-> [String]
-> i
-> IO o
unixFilterIO writer reader programName args input = do
let process = (proc programName args)
{ std_in = CreatePipe
, std_out = CreatePipe
, close_fds = True
}
(Just stdinWriteHandle, Just stdoutReadHandle, _, _) <-
createProcess process
-- Write the input to the child pipe
_ <- forkIO $ do
writer stdinWriteHandle input
hClose stdinWriteHandle
-- Receive the output from the child
reader stdoutReadHandle
|