Add Glob module, update docs.

--HG--
extra : convert_revision : e114cb9154838d7f74c72671db22dbddb97e3a58

System/FilePath/Glob.hs

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+-- |
+-- Module:      System.FilePath.Glob
+-- Copyright:   Bryan O'Sullivan
+-- License:     LGPL
+-- Maintainer:  Bryan O'Sullivan <bos@serpentine.com>
+-- Stability:   unstable
+-- Portability: everywhere
+
+module System.FilePath.Glob (
+      namesMatching
+    ) where
+
+import Control.Exception (handle)
+import Control.Monad (forM)
+import System.FilePath.GlobPattern ((~~))
+import System.Directory (doesDirectoryExist, doesFileExist,
+                         getCurrentDirectory, getDirectoryContents)
+import System.FilePath (dropTrailingPathSeparator, splitFileName, (</>))
+import System.IO.Unsafe (unsafeInterleaveIO)
+
+-- | Return a list of names matching a glob pattern.  The list is
+-- generated lazily.
+namesMatching :: String -> IO [FilePath]
+namesMatching pat
+  | not (isPattern pat) = do
+    exists <- doesNameExist pat
+    return (if exists then [pat] else [])
+  | otherwise = do
+    case splitFileName pat of
+      ("", baseName) -> do
+          curDir <- getCurrentDirectory
+          listMatches curDir baseName
+      (dirName, baseName) -> do
+          dirs <- if isPattern dirName
+                  then namesMatching (dropTrailingPathSeparator dirName)
+                  else return [dirName]
+          let listDir = if isPattern baseName
+                        then listMatches
+                        else listPlain
+          pathNames <- forM dirs $ \dir -> do
+                           baseNames <- listDir dir baseName
+                           return (map (dir </>) baseNames)
+          return (concat pathNames)
+  where isPattern = any (`elem` "[*?")
+
+listMatches :: FilePath -> String -> IO [String]
+listMatches dirName pat = do
+    dirName' <- if null dirName
+                then getCurrentDirectory
+                else return dirName
+    names <- unsafeInterleaveIO (handle (const (return [])) $
+                                        getDirectoryContents dirName')
+    let names' = if isHidden pat
+                 then filter isHidden names
+                 else filter (not . isHidden) names
+    return (filter (~~ pat) names')
+  where isHidden ('.':_) = True
+        isHidden _ = False
+
+listPlain :: FilePath -> String -> IO [String]
+listPlain dirName baseName = do
+    exists <- if null baseName
+              then doesDirectoryExist dirName
+              else doesNameExist (dirName </> baseName)
+    return (if exists then [baseName] else [])
+
+doesNameExist :: FilePath -> IO Bool
+doesNameExist name = do
+    fileExists <- doesFileExist name
+    if fileExists
+      then return True
+      else doesDirectoryExist name