[project @ 2003-08-30 22:55:42 by ross]

[ghc-base.git] / System / Environment.hs

diff --git a/System/Environment.hs b/System/Environment.hs
index 4e9efb6..a0761d5 100644 (file)
--- a/System/Environment.hs
+++ b/System/Environment.hs
@@ -14,34 +14,47 @@
 
 module System.Environment
     ( 
-      getArgs      -- :: IO [String]
-    , getProgName   -- :: IO String
-    , getEnv        -- :: String -> IO String
+      getArgs,      -- :: IO [String]
+      getProgName,   -- :: IO String
+      getEnv,        -- :: String -> IO String
+#ifdef __GLASGOW_HASKELL__
+      withArgs,
+      withProgName,
+#endif
   ) where
 
 import Prelude
+#ifndef __NHC__
+import Control.Exception       ( bracket )
+#endif
 
-#ifndef __HUGS__
+#ifdef __GLASGOW_HASKELL__
 import Foreign
 import Foreign.C
 import Control.Monad
-#endif
-
-#ifdef __GLASGOW_HASKELL__
 import GHC.IOBase
+#include "config.h"
 #endif
 
 #ifdef __HUGS__
 import Hugs.System
 #endif
 
+#ifdef __NHC__
+import System
+  ( getArgs
+  , getProgName
+  , getEnv
+  )
+#endif
+
 -- ---------------------------------------------------------------------------
 -- getArgs, getProgName, getEnv
 
--- Computation `getArgs' returns a list of the program's command
+-- | Computation 'getArgs' returns a list of the program's command
 -- line arguments (not including the program name).
 
-#ifndef __HUGS__
+#ifdef __GLASGOW_HASKELL__
 getArgs :: IO [String]
 getArgs = 
   alloca $ \ p_argc ->  
@@ -94,11 +107,13 @@ unpackProgName argv = do
    isPathSeparator _    = False
 
 
--- Computation `getEnv var' returns the value
--- of the environment variable {\em var}.  
-
--- This computation may fail with
---    NoSuchThing: The environment variable does not exist.
+-- | Computation 'getEnv' @var@ returns the value
+-- of the environment variable @var@.  
+--
+-- This computation may fail with:
+--
+--  * 'System.IO.Error.isDoesNotExistError' if the environment variable
+--    does not exist.
 
 getEnv :: String -> IO String
 getEnv name =
@@ -111,4 +126,48 @@ getEnv name =
 
 foreign import ccall unsafe "getenv"
    c_getenv :: CString -> IO (Ptr CChar)
-#endif  /* __HUGS__ */
+
+{-|
+@withArgs args act@ - while executing action @act@, have 'System.getArgs'
+return @args@ (GHC only).
+-}
+withArgs :: [String] -> IO a -> IO a
+withArgs xs act = do
+   p <- System.Environment.getProgName
+   withArgv (p:xs) act
+
+{-|
+@withProgName name act@ - while executing action @act@,
+have 'System.getProgName' return @name@ (GHC only).
+-}
+withProgName :: String -> IO a -> IO a
+withProgName nm act = do
+   xs <- System.Environment.getArgs
+   withArgv (nm:xs) act
+
+-- Worker routine which marshals and replaces an argv vector for
+-- the duration of an action.
+
+withArgv :: [String] -> IO a -> IO a
+withArgv new_args act = do
+  pName <- System.Environment.getProgName
+  existing_args <- System.Environment.getArgs
+  bracket (setArgs new_args) 
+         (\argv -> do setArgs (pName:existing_args); freeArgv argv)
+         (const act)
+
+freeArgv :: Ptr CString -> IO ()
+freeArgv argv = do
+  size <- lengthArray0 nullPtr argv
+  sequence_ [peek (argv `advancePtr` i) >>= free | i <- [size, size-1 .. 0]]
+  free argv
+
+setArgs :: [String] -> IO (Ptr CString)
+setArgs argv = do
+  vs <- mapM newCString argv >>= newArray0 nullPtr
+  setArgsPrim (length argv) vs
+  return vs
+
+foreign import ccall unsafe "setProgArgv" 
+  setArgsPrim  :: Int -> Ptr CString -> IO ()
+#endif  /* __GLASGOW_HASKELL__ */