[project @ 2002-08-30 13:00:31 by simonpj]

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

diff --git a/System/Environment.hs b/System/Environment.hs
index 20b709f..99b25bb 100644 (file)
--- a/System/Environment.hs
+++ b/System/Environment.hs
@@ -14,27 +14,39 @@
 
 module System.Environment
     ( 
-    , getArgs      -- :: IO [String]
-    , getProgName   -- :: IO String
-    , getEnv        -- :: String -> IO String
+      getArgs,      -- :: IO [String]
+      getProgName,   -- :: IO String
+      getEnv,        -- :: String -> IO String
+#ifndef __HUGS__
+      withArgs,
+      withProgName,
+#endif
   ) where
 
 import Prelude
+import System.IO       ( bracket )
 
+#ifndef __HUGS__
 import Foreign
 import Foreign.C
 import Control.Monad
+#endif
 
 #ifdef __GLASGOW_HASKELL__
 import GHC.IOBase
 #endif
 
+#ifdef __HUGS__
+import Hugs.System
+#endif
+
 -- ---------------------------------------------------------------------------
 -- getArgs, getProgName, getEnv
 
 -- Computation `getArgs' returns a list of the program's command
 -- line arguments (not including the program name).
 
+#ifndef __HUGS__
 getArgs :: IO [String]
 getArgs = 
   alloca $ \ p_argc ->  
@@ -48,9 +60,16 @@ getArgs =
 foreign import ccall unsafe "getProgArgv"
   getProgArgv :: Ptr CInt -> Ptr (Ptr CString) -> IO ()
 
--- Computation `getProgName' returns the name of the program
--- as it was invoked.
+{-|
+Computation 'getProgName' returns the name of the program as it was
+invoked.
 
+However, this is hard-to-impossible to implement on some non-Unix
+OSes, so instead, for maximum portability, we just return the leafname
+of the program as invoked. Even then there are some differences
+between platforms: on Windows, for example, a program invoked as foo
+is probably really @FOO.EXE@, and that is what 'getProgName' will return.
+-}
 getProgName :: IO String
 getProgName = 
   alloca $ \ p_argc ->
@@ -97,3 +116,44 @@ getEnv name =
 
 foreign import ccall unsafe "getenv"
    c_getenv :: CString -> IO (Ptr CChar)
+
+{-|
+@withArgs args act@ - while executing action @act@, have 'System.getArgs'
+return @args@.
+-}
+withArgs xs act = do
+   p <- System.Environment.getProgName
+   withArgv (p:xs) act
+
+{-|
+@withProgName name act@ - while executing action @act@, have 'System.getProgName'return @name@.
+-}
+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 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  /* __HUGS__ */