X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Debug%2FTrace.hs;h=c287a4dc5ac7418481d39833eaf2af43afa9ee4c;hb=a34fb5505b42a5f019d1fdf0dd586a5239400346;hp=993a72e412a338913c5f476ffe4fadeb0fdae52f;hpb=2c19d1a0efd17ab30b773ec3fd88f212af8317b6;p=ghc-base.git

diff --git a/Debug/Trace.hs b/Debug/Trace.hs
index 993a72e..c287a4d 100644
--- a/Debug/Trace.hs
+++ b/Debug/Trace.hs
@@ -1,41 +1,96 @@
 -----------------------------------------------------------------------------
--- 
+-- |
 -- Module      :  Debug.Trace
 -- Copyright   :  (c) The University of Glasgow 2001
--- License     :  BSD-style (see the file libraries/core/LICENSE)
+-- License     :  BSD-style (see the file libraries/base/LICENSE)
 -- 
 -- Maintainer  :  libraries@haskell.org
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- $Id: Trace.hs,v 1.2 2002/04/24 16:01:51 simonmar Exp $
---
--- The trace function.
+-- The 'trace' function.
 --
 -----------------------------------------------------------------------------
 
 module Debug.Trace (
-	trace -- :: String -> a -> a
+	-- * Tracing
+	
+	-- ** Tracers
+	-- | The tracer is a function that monitors the trace messages.
+	fileTracer,       -- :: Handle -> String -> IO ()
+#ifdef mingw32_HOST_OS
+	winDebugTracer,   -- :: String -> IO ()
+#endif
+	addTracer,        -- :: String -> (String -> IO ()) -> IO ()
+	removeTracer,     -- :: String -> IO ()
+	
+	-- ** Messages
+	putTraceMsg,      -- :: String -> IO ()
+	trace             -- :: String -> a -> a
   ) where
 
 import Prelude
+import Data.IORef
 import System.IO.Unsafe
 import System.IO
 
-#ifdef __GLASGOW_HASKELL__
-import GHC.IOBase
-import GHC.Handle
+#ifdef mingw32_HOST_OS
+import Foreign.C.String
 #endif
 
-#ifdef __GLASGOW_HASKELL__
+{-# NOINLINE tracers #-}
+tracers :: IORef [(String, String -> IO ())]
+tracers = unsafePerformIO (newIORef [("defaultTracer", fileTracer stderr)])
+
+-- | A tracer function that outputs the message to a file
+fileTracer :: Handle     -- ^ file handle
+           -> String     -- ^ trace message
+           -> IO ()
+fileTracer handle msg = do
+   hPutStr handle msg
+   hPutChar handle '\n'
+
+#ifdef mingw32_HOST_OS
+-- | A tracer function that outputs the message to the debuger (Windows only)
+winDebugTracer :: String  -- ^ trace message
+               -> IO ()
+winDebugTracer msg = do
+   withCString (msg++"\n") outputDebugString
+
+foreign import ccall unsafe "OutputDebugStringA"
+  outputDebugString :: CString -> IO ()
+#endif
+
+-- | Registering a new tracer
+addTracer :: String             -- ^ the tracer name
+          -> (String -> IO ())  -- ^ tracer
+          -> IO ()
+addTracer name tracer = do
+	ts <- readIORef tracers
+	writeIORef tracers ((name,tracer):filter (\(n,l) -> n /= name) ts)
+
+-- | Removing the tracer with the given name
+removeTracer :: String -> IO ()
+removeTracer name = do
+	ts <- readIORef tracers
+	writeIORef tracers (filter (\(n,l) -> n /= name) ts)
+
+-- | 'putTraceMsg' function outputs the trace message from IO monad.
+putTraceMsg :: String -> IO ()
+putTraceMsg msg = do
+	ts <- readIORef tracers
+	mapM_ (\(n,l) -> l msg) ts
+
 {-# NOINLINE trace #-}
+{-|
+When called, 'trace' outputs the string in its first argument using the
+installed tracers, before returning the second argument as its result.
+The 'trace' function is not referentially transparent, and should only
+be used for debugging, or for monitoring execution. Some
+implementations of 'trace' may decorate the string that\'s output to
+indicate that you\'re tracing.
+-}
 trace :: String -> a -> a
 trace string expr = unsafePerformIO $ do
-    hPutStr stderr string
-    hPutChar stderr '\n'
-    fd <- withHandle_ "trace" stderr $ (return.haFD)
-    postTraceHook fd
+    putTraceMsg string
     return expr
-
-foreign import ccall "PostTraceHook" postTraceHook :: Int -> IO ()
-#endif