----------------------------------------------------------------------------- -- | -- Module : ReadFirst -- Copyright : 2004 Malcolm Wallace -- Licence : LGPL -- -- Maintainer : Malcolm Wallace <Malcolm.Wallace@cs.york.ac.uk> -- Stability : experimental -- Portability : All -- -- Read the first file that matches in a list of search paths. ----------------------------------------------------------------------------- module Language.Preprocessor.Cpphs.ReadFirst ( readFirst ) where import System.IO (hPutStrLn, stderr) import System.Directory (doesFileExist) import Data.List (intersperse) import Control.Monad (when) import Language.Preprocessor.Cpphs.Position (Posn,directory,cleanPath) -- | Attempt to read the given file from any location within the search path. -- The first location found is returned, together with the file content. -- (The directory of the calling file is always searched first, then -- the current directory, finally any specified search path.) readFirst :: String -- ^ filename -> Posn -- ^ inclusion point -> [String] -- ^ search path -> Bool -- ^ report warnings? -> IO ( FilePath , String ) -- ^ discovered filepath, and file contents readFirst name demand path warn = try (cons dd (".":path)) where dd = directory demand cons x xs = if null x then xs else x:xs try [] = do when warn $ hPutStrLn stderr ("Warning: Can't find file \""++name ++"\" in directories\n\t" ++concat (intersperse "\n\t" (cons dd (".":path))) ++"\n Asked for by: "++show demand) return ("missing file: "++name,"") try (p:ps) = do let file = cleanPath p++'/':cleanPath name ok <- doesFileExist file if not ok then try ps else do content <- readFile file return (file,content)