{-# LINE 1 "libraries/base/System/CPUTime.hsc" #-}
{-# LANGUAGE Trustworthy #-}
{-# LINE 2 "libraries/base/System/CPUTime.hsc" #-}
{-# LANGUAGE CPP, NondecreasingIndentation, ForeignFunctionInterface, CApiFFI #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  System.CPUTime
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)
-- 
-- Maintainer  :  libraries@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- The standard CPUTime library.
--
-----------------------------------------------------------------------------


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module System.CPUTime 
        (
         getCPUTime,       -- :: IO Integer
         cpuTimePrecision  -- :: Integer
        ) where

import Prelude

import Data.Ratio


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import Foreign.Safe
import Foreign.C
import System.IO.Unsafe (unsafePerformIO)

-- For _SC_CLK_TCK

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-- For struct rusage

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-- For FILETIME etc. on Windows

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-- for CLK_TCK

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-- for struct tms

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#ifdef mingw32_HOST_OS
# if defined(i386_HOST_ARCH)
#  define WINDOWS_CCONV stdcall
# elif defined(x86_64_HOST_ARCH)
#  define WINDOWS_CCONV ccall
# else
#  error Unknown mingw32 arch
# endif
#else
#endif


{-# LINE 85 "libraries/base/System/CPUTime.hsc" #-}
realToInteger :: Real a => a -> Integer
realToInteger ct = round (realToFrac ct :: Double)
  -- CTime, CClock, CUShort etc are in Real but not Fractional, 
  -- so we must convert to Double before we can round it

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{-# LINE 92 "libraries/base/System/CPUTime.hsc" #-}
-- -----------------------------------------------------------------------------
-- |Computation 'getCPUTime' returns the number of picoseconds CPU time
-- used by the current program.  The precision of this result is
-- implementation-dependent.

getCPUTime :: IO Integer
getCPUTime = do


{-# LINE 101 "libraries/base/System/CPUTime.hsc" #-}
-- getrusage() is right royal pain to deal with when targetting multiple
-- versions of Solaris, since some versions supply it in libc (2.3 and 2.5),
-- while 2.4 has got it in libucb (I wouldn't be too surprised if it was back
-- again in libucb in 2.6..)
--
-- Avoid the problem by resorting to times() instead.
--

{-# LINE 125 "libraries/base/System/CPUTime.hsc" #-}
    allocaBytes (32) $ \ p_tms -> do
{-# LINE 126 "libraries/base/System/CPUTime.hsc" #-}
    _ <- times p_tms
    u_ticks  <- ((\hsc_ptr -> peekByteOff hsc_ptr 0)) p_tms :: IO CClock
{-# LINE 128 "libraries/base/System/CPUTime.hsc" #-}
    s_ticks  <- ((\hsc_ptr -> peekByteOff hsc_ptr 8)) p_tms :: IO CClock
{-# LINE 129 "libraries/base/System/CPUTime.hsc" #-}
    return (( (realToInteger u_ticks + realToInteger s_ticks) * 1000000000000) 
                        `div` fromIntegral clockTicks)

type CTms = ()
foreign import ccall unsafe times :: Ptr CTms -> IO CClock

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-- |The 'cpuTimePrecision' constant is the smallest measurable difference
-- in CPU time that the implementation can record, and is given as an
-- integral number of picoseconds.


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cpuTimePrecision :: Integer
cpuTimePrecision = round ((1000000000000::Integer) % fromIntegral (clockTicks))

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{-# LINE 186 "libraries/base/System/CPUTime.hsc" #-}
clockTicks :: Int
clockTicks =
    unsafePerformIO (sysconf (3) >>= return . fromIntegral)
{-# LINE 189 "libraries/base/System/CPUTime.hsc" #-}
foreign import ccall unsafe sysconf :: CInt -> IO CLong

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