{-# LINE 1 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE DoAndIfThenElse #-}
{-# LANGUAGE ForeignFunctionInterface #-}
{-# LANGUAGE EmptyDataDecls #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE NoImplicitPrelude #-}

-------------------------------------------------------------------------------

-- |

-- Module      :  GHC.Event.Windows.FFI

-- Copyright   :  (c) Tamar Christina 2019

-- License     :  BSD-style (see the file libraries/base/LICENSE)

--

-- Maintainer  :  libraries@haskell.org

-- Stability   :  stable

-- Portability :  non-portable

--

-- WinIO Windows API Foreign Function imports

--

-------------------------------------------------------------------------------


module GHC.Event.Windows.FFI (
    -- * IOCP

    IOCP(..),
    CompletionKey,
    newIOCP,
    associateHandleWithIOCP,
    getQueuedCompletionStatusEx,
    postQueuedCompletionStatus,
    getOverlappedResult,

    -- * Completion Data

    CompletionData(..),
    CompletionCallback,
    withRequest,

    -- * Overlapped

    OVERLAPPED,
    LPOVERLAPPED,
    OVERLAPPED_ENTRY(..),
    LPOVERLAPPED_ENTRY,
    HASKELL_OVERLAPPED,
    LPHASKELL_OVERLAPPED,
    allocOverlapped,
    zeroOverlapped,
    pokeOffsetOverlapped,
    overlappedIOStatus,
    overlappedIONumBytes,

    -- * Cancel pending I/O

    cancelIoEx,
    cancelIoEx',

    -- * Monotonic time


    -- ** GetTickCount

    getTickCount64,

    -- ** QueryPerformanceCounter

    queryPerformanceCounter,
    queryPerformanceFrequency,

    -- ** Miscellaneous

    throwWinErr,
    setLastError
) where





#include "windows_cconv.h"

import Data.Maybe
import Foreign
import GHC.Base
import GHC.Num ((*))
import GHC.Real (fromIntegral)
import GHC.Show
import GHC.Windows
import qualified GHC.Event.Array as A
import qualified GHC.Windows     as Win32
import GHC.IO.Handle.Internals (debugIO)

------------------------------------------------------------------------

-- IOCP


-- | An I/O completion port.

newtype IOCP = IOCP HANDLE
    deriving (Eq, Ord, Show)

type CompletionKey = ULONG_PTR

-- | This function has two distinct purposes depending on the value of

-- The completion port handle:

--

--  - When the IOCP port is NULL then the function creates a new I/O completion

--    port.  See `newIOCP`.

--

--  - When The port contains a valid handle then the given handle is

--    associated with he given completion port handle.  Once associated it

--    cannot be easily changed.  Associating a Handle with a Completion Port

--    allows the I/O manager's worker threads to handle requests to the given

--    handle.

foreign import WINDOWS_CCONV unsafe "windows.h CreateIoCompletionPort"
    c_CreateIoCompletionPort :: HANDLE -> IOCP -> ULONG_PTR -> DWORD
                             -> IO IOCP

-- | Create a new I/O completion port.

newIOCP :: IO IOCP
newIOCP = failIf (== IOCP nullPtr) "newIOCP" $
          c_CreateIoCompletionPort iNVALID_HANDLE_VALUE (IOCP nullPtr) 0 0

-- | Associate a HANDLE with an I/O completion port.

associateHandleWithIOCP :: IOCP -> HANDLE -> CompletionKey -> IO ()
associateHandleWithIOCP iocp handle completionKey =
    failIf_ (/= iocp) "associateHandleWithIOCP" $
        c_CreateIoCompletionPort handle iocp completionKey 0

foreign import WINDOWS_CCONV safe "windows.h GetOverlappedResult"
    c_GetOverlappedResult :: HANDLE -> LPOVERLAPPED -> Ptr DWORD -> BOOL
                          -> IO BOOL

-- | Get the result of a single overlap operation without the IO manager

getOverlappedResult :: HANDLE -> Ptr OVERLAPPED -> BOOL -> IO (Maybe DWORD)
getOverlappedResult handle lp block
  = alloca $ \bytes ->
        do res <- c_GetOverlappedResult handle lp bytes block
           if res
              then fmap Just $ peek bytes
              else return Nothing

foreign import WINDOWS_CCONV safe "windows.h GetQueuedCompletionStatusEx"
    c_GetQueuedCompletionStatusEx :: IOCP -> LPOVERLAPPED_ENTRY -> Word32
                                  -> Ptr ULONG -> DWORD -> BOOL -> IO BOOL

-- | Note [Completion Ports]

--   ~~~~~~~~~~~~~~~~~~~~~~~

-- When an I/O operation has been queued by an operation

-- (ReadFile/WriteFile/etc) it is placed in a queue that the driver uses when

-- servicing IRQs.  This queue has some important properties:

--

-- 1.) It is not an ordered queue.  Requests may be performed out of order as

--     as the OS's native I/O manager may try to re-order requests such that as

--     few random seeks as possible are needed to complete the pending

--     operations.  As such do not assume a fixed order between something being

--     queued and dequeued.

--

-- 2.) Operations may skip the queue entirely.  In which case they do not end in

--     in this function. (This is an optimization flag we have turned on. See

--     `openFile`.)

--

-- 3.) Across this call the specified OVERLAPPED_ENTRY buffer MUST remain live,

--     and the buffer for an I/O operation cannot be freed or moved until

--     `getOverlappedResult` says it's done.  The reason is the kernel may not

--     have fully released the buffer, or finished writing to it when this

--     operation returns.  Failure to adhere to this will cause your IRQs to be

--     silently dropped and your program will never receive a completion for it.

--     This means that the OVERLAPPED buffer must also remain valid for the

--     duration of the call and as such must be allocated on the unmanaged heap.

--

-- 4.) When a thread calls this method it is associated with the I/O manager's

--     worker threads pool.  You should always use dedicated threads for this

--     since the OS I/O manager will now monitor the threads.  If the thread

--     becomes blocked for whatever reason, the Haskell I/O manager will wake up

--     another threads from it's pool to service the remaining results.

--     A new thread will also be woken up from the pool when the previous thread

--     is busy servicing requests and new requests have finished.  For this

--     reason the Haskell I/O manager multiplexes I/O operations from N haskell

--     threads into 1 completion port, which is serviced by M native threads in

--     an asynchronous method. This allows it to scale efficiently.

getQueuedCompletionStatusEx :: IOCP
                            -> A.Array OVERLAPPED_ENTRY
                            -> DWORD  -- ^ Timeout in milliseconds (or

                                      -- 'GHC.Windows.iNFINITE')

                            -> IO Int
getQueuedCompletionStatusEx iocp arr timeout =
    alloca $ \num_removed_ptr ->do
        A.unsafeLoad arr $ \oes cap -> do
            -- TODO: remove after debugging

            fillBytes oes 0 (cap * (sizeOf (undefined :: OVERLAPPED_ENTRY)))
            debugIO $ "-- call getQueuedCompletionStatusEx "
            -- don't block the call if the rts is not supporting threads.

            -- this would block the entire program.

            let alertable = False -- not rtsSupportsBoundThreads

            ok <- c_GetQueuedCompletionStatusEx iocp oes (fromIntegral cap)
                  num_removed_ptr timeout alertable
            debugIO $ "-- call getQueuedCompletionStatusEx: " ++ show ok
            err <- getLastError
            nc <- (peek num_removed_ptr)
            debugIO $ "-- getQueuedCompletionStatusEx: n=" ++ show nc ++ " ,err=" ++ show err
            if ok then fromIntegral `fmap` peek num_removed_ptr
            else do debugIO $ "failed getQueuedCompletionStatusEx: " ++ show err
                    if err == 258 || alertable then return 0
{-# LINE 196 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
                    else failWith "GetQueuedCompletionStatusEx" err

overlappedIOStatus :: LPOVERLAPPED -> IO NTSTATUS
overlappedIOStatus lpol = do
  status <- (\hsc_ptr -> peekByteOff hsc_ptr 0) lpol
{-# LINE 201 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
  -- TODO: Map NTSTATUS to ErrCode?

  -- See https://github.com/libuv/libuv/blob/b12624c13693c4d29ca84b3556eadc9e9c0936a4/src/win/winsock.c#L153

  return status
{-# INLINE overlappedIOStatus #-}

overlappedIONumBytes :: LPOVERLAPPED -> IO ULONG_PTR
overlappedIONumBytes lpol = do
  bytes <- (\hsc_ptr -> peekByteOff hsc_ptr 8) lpol
{-# LINE 209 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
  return bytes
{-# INLINE overlappedIONumBytes #-}

foreign import WINDOWS_CCONV unsafe "windows.h PostQueuedCompletionStatus"
    c_PostQueuedCompletionStatus :: IOCP -> DWORD -> ULONG_PTR -> LPOVERLAPPED
                                 -> IO BOOL

-- | Manually post a completion to the specified I/O port.  This will wake up

-- a thread waiting `GetQueuedCompletionStatusEx`.

postQueuedCompletionStatus :: IOCP -> DWORD -> CompletionKey -> LPOVERLAPPED
                           -> IO ()
postQueuedCompletionStatus iocp numBytes completionKey lpol =
    failIfFalse_ "PostQueuedCompletionStatus" $
    c_PostQueuedCompletionStatus iocp numBytes completionKey lpol

------------------------------------------------------------------------

-- Completion Data


-- | Called when the completion is delivered.

type CompletionCallback a = ErrCode   -- ^ 0 indicates success

                          -> DWORD     -- ^ Number of bytes transferred

                          -> IO a

-- | Callback type that will be called when an I/O operation completes.

type IOCallback = CompletionCallback ()

-- | Structure that the I/O manager uses to associate callbacks with

-- additional payload such as their OVERLAPPED structure and Win32 handle

-- etc.  *Must* be kept in sync with that in `winio_structs.h` or horrible things

-- happen.

--

-- We keep the handle around for the benefit of ghc-external libraries making

-- use of the manager.

data CompletionData = CompletionData { cdHandle   :: !HANDLE
                                     , cdCallback :: !(StablePtr IOCallback)
                                     }

instance Storable CompletionData where
    sizeOf _    = (16)
{-# LINE 248 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
    alignment _ = 8
{-# LINE 249 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}

    peek ptr = do
      cdCallback <- (\hsc_ptr -> peekByteOff hsc_ptr 8) ptr
{-# LINE 252 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      cdHandle   <- (\hsc_ptr -> peekByteOff hsc_ptr 0) ptr
{-# LINE 253 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      let !cd = CompletionData{..}
      return cd

    poke ptr CompletionData{..} = do
      (\hsc_ptr -> pokeByteOff hsc_ptr 8) ptr cdCallback
{-# LINE 258 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      (\hsc_ptr -> pokeByteOff hsc_ptr 0) ptr cdHandle
{-# LINE 259 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}

------------------------------------------------------------------------

-- Overlapped


-- | Tag type for @LPOVERLAPPED@.

data OVERLAPPED

-- | Tag type for the extended version of @OVERLAPPED@ containing some book

--   keeping information.

data HASKELL_OVERLAPPED

-- | Identifies an I/O operation.  Used as the @LPOVERLAPPED@ parameter

-- for overlapped I/O functions (e.g. @ReadFile@, @WSASend@).

type LPOVERLAPPED = Ptr OVERLAPPED

-- | Pointer to the extended HASKELL_OVERLAPPED function.

type LPHASKELL_OVERLAPPED = Ptr HASKELL_OVERLAPPED

-- | An array of these is passed to GetQueuedCompletionStatusEx as an output

-- argument.

data OVERLAPPED_ENTRY = OVERLAPPED_ENTRY {
      lpCompletionKey            :: ULONG_PTR,
      lpOverlapped               :: LPOVERLAPPED,
      dwNumberOfBytesTransferred :: DWORD
    }

type LPOVERLAPPED_ENTRY = Ptr OVERLAPPED_ENTRY

instance Storable OVERLAPPED_ENTRY where
    sizeOf _    = (32)
{-# LINE 289 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
    alignment _ = 8
{-# LINE 290 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}

    peek ptr = do
      lpCompletionKey <- (\hsc_ptr -> peekByteOff hsc_ptr 0) ptr
{-# LINE 293 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      lpOverlapped    <- (\hsc_ptr -> peekByteOff hsc_ptr 8) ptr
{-# LINE 294 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      dwNumberOfBytesTransferred <-
          (\hsc_ptr -> peekByteOff hsc_ptr 24) ptr
{-# LINE 296 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      let !oe = OVERLAPPED_ENTRY{..}
      return oe

    poke ptr OVERLAPPED_ENTRY{..} = do
      (\hsc_ptr -> pokeByteOff hsc_ptr 0) ptr lpCompletionKey
{-# LINE 301 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      (\hsc_ptr -> pokeByteOff hsc_ptr 8) ptr lpOverlapped
{-# LINE 302 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      (\hsc_ptr -> pokeByteOff hsc_ptr 24)
{-# LINE 303 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
        ptr dwNumberOfBytesTransferred

-- | Allocate a new

-- <http://msdn.microsoft.com/en-us/library/windows/desktop/ms684342%28v=vs.85%29.aspx

-- OVERLAPPED> structure on the unmanaged heap. This also zeros the memory to

-- prevent the values inside the struct to be incorrectly interpreted as data

-- payload.

--

-- We extend the overlapped structure with some extra book keeping information

-- such that we don't have to do a lookup on the Haskell side.

--

-- Future: We can gain some performance here by using a pool instead of calling

--         malloc for each request. A simple block allocator would be very

--         useful here, especially when we implement sockets support.

allocOverlapped :: Word64 -- ^ Offset/OffsetHigh

                -> IO (Ptr HASKELL_OVERLAPPED)
allocOverlapped offset = do
  lpol <- mallocBytes (40)
{-# LINE 321 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
  zeroOverlapped lpol
  pokeOffsetOverlapped (castPtr lpol) offset
  return lpol

-- | Zero-fill an HASKELL_OVERLAPPED structure.

zeroOverlapped :: LPHASKELL_OVERLAPPED -> IO ()
zeroOverlapped lpol = fillBytes lpol 0 (40)
{-# LINE 328 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
{-# INLINE zeroOverlapped #-}

-- | Set the offset field in an OVERLAPPED structure.

pokeOffsetOverlapped :: LPOVERLAPPED -> Word64 -> IO ()
pokeOffsetOverlapped lpol offset = do
  let (offsetHigh, offsetLow) = Win32.ddwordToDwords offset
  (\hsc_ptr -> pokeByteOff hsc_ptr 16) lpol offsetLow
{-# LINE 335 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
  (\hsc_ptr -> pokeByteOff hsc_ptr 20) lpol offsetHigh
{-# LINE 336 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
{-# INLINE pokeOffsetOverlapped #-}

-- | Set the event field in an OVERLAPPED structure.

pokeEventOverlapped :: LPOVERLAPPED -> HANDLE -> IO ()
pokeEventOverlapped lpol event = do
  (\hsc_ptr -> pokeByteOff hsc_ptr 24) lpol event
{-# LINE 342 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
{-# INLINE pokeEventOverlapped #-}

------------------------------------------------------------------------

-- Request management


-- Note [AsyncHandles]

-- ~~~~~~~~~~~~~~~~~~~

-- In `winio` we have designed it to work in asynchronous mode always.

-- According to the MSDN documentation[1][2], when a handle is not opened

-- in asynchronous mode then the operation would simply work but operate

-- synchronously.

--

-- This seems to happen as documented for `File` handles, but `pipes` don't

-- seem to follow this documented behavior and so are a problem.

-- Under `msys2` your standard handles are actually pipes, not console

-- handles or files.  As such running under an msys2 console causes a hang

-- as the pipe read never returns.

--

-- [1] https://docs.microsoft.com/en-us/windows/win32/fileio/synchronous-and-asynchronous-i-o

-- [2] https://docs.microsoft.com/en-us/windows/win32/sync/synchronization-and-overlapped-input-and-output

--

-- As such we need to annotate all NativeHandles with a Boolean to indicate

-- whether it's an asynchronous handle or not.

-- This allows us to manually wait for the completion instead of relying

-- on the I/O system to do the right thing.  As we have been using the

-- buffers in async mode we may not have moved the file pointer on the kernel

-- object, as such we still need to give an `OVERLAPPED` structure, but we

-- instead create an event object that we can wait on.

--

-- As documented in MSDN this even object must be in manual reset mode.  This

-- approach gives us the flexibility, with minimum impact to support both

-- synchronous and asynchronous access.

--

-- Additional approaches explored

--

-- Normally the I/O system is in full control of all Handles it creates, with

-- one big exception: inheritance.

--

-- For any `HANDLE` we inherit we don't know how it's been open.  A different

-- solution I have explored was to try to detect the `HANDLE` mode.

-- But this approach would never work for a few reasons:

--

-- 1. The presence of an asynchronous flag does not indicate that we are able

--    to handle the operation asynchronously.  In particular, just because a

--    `HANDLE` is open in async mode, it may not be associated with our

--    completion port.

-- 2. One can only associate a `HANDLE` to a *single* completion port.  As

--    such, if the handle is opened in async mode but already registered to a

--    completion port then we can't use it asynchronously.

-- 3. You can only associate a completion port once, even if it's the same

--    port.  This means were we to strap a `HANDLE` of it's `NativeHandle`

--    wrapper and then wrap it again, we can't retest as the result would be

--    invalid.  This is an issue because to pass `HANDLE`s we have to pass

--    the native OS Handle not the Haskell one. i.e. remote-iserv.


-- See Note [AsyncHandles]

withRequest :: Bool -> Word64 -> HANDLE -> IOCallback
            -> (Ptr HASKELL_OVERLAPPED -> Ptr CompletionData -> IO a)
            -> IO a
withRequest async offset hdl cb f = do
    -- Create the completion record and store it.

    -- We only need the record when we enqueue a request, however if we

    -- delay creating it then we will run into a race condition where the

    -- driver may have finished servicing the request before we were ready

    -- and so the request won't have the book keeping information to know

    -- what to do.  So because of that we always create the payload,  If we

    -- need it ok, if we don't that's no problem.  This approach prevents

    -- expensive lookups in hash-tables.

    --

    -- Todo: Use a memory pool for this so we don't have to hit malloc every

    --       time.  This would allow us to scale better.

    cb_sptr <- newStablePtr cb
    let cbData :: CompletionData
        cbData = CompletionData hdl cb_sptr
    r <- allocaBytes (40) $ \hs_lpol ->
{-# LINE 417 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
      with cbData $ \cdData -> do
        zeroOverlapped hs_lpol
        let lpol = castPtr hs_lpol
        pokeOffsetOverlapped lpol offset
        -- If doing a synchronous request then register an event object.

        -- This event object MUST be manual reset per MSDN.

        case async of
          True -> f hs_lpol cdData
          False -> do
            event <- failIfNull "withRequest (create)" $
                       c_CreateEvent nullPtr True False nullPtr
            debugIO $ "{{ event " ++ show event ++ " for " ++ show hs_lpol
            pokeEventOverlapped lpol event
            res <- f hs_lpol cdData
            -- Once the request has finished, close the object and free it.

            failIfFalse_ "withRequest (free)" $ c_CloseHandle event
            return res

    freeStablePtr cb_sptr
    return r


-- | Create an event object for use when the HANDLE isn't asynchronous

foreign import WINDOWS_CCONV unsafe "windows.h CreateEventW"
    c_CreateEvent :: Ptr () -> Bool -> Bool -> LPCWSTR -> IO HANDLE

-- | Close a handle object

foreign import WINDOWS_CCONV unsafe "windows.h CloseHandle"
    c_CloseHandle :: HANDLE -> IO Bool

------------------------------------------------------------------------

-- Cancel pending I/O


-- | CancelIo shouldn't block, but cancellation happens infrequently,

-- so we might as well be on the safe side.

foreign import WINDOWS_CCONV unsafe "windows.h CancelIoEx"
    c_CancelIoEx :: HANDLE -> LPOVERLAPPED -> IO BOOL

-- | Cancel all pending overlapped I/O for the given file that was initiated by

-- the current OS thread.  Cancelling is just a request for cancellation and

-- before the OVERLAPPED struct is freed we must make sure that the IRQ has been

-- removed from the queue.  See `getOverlappedResult`.

cancelIoEx :: HANDLE -> LPOVERLAPPED -> IO ()
cancelIoEx h o = failIfFalse_ "CancelIoEx" . c_CancelIoEx h $ o

cancelIoEx' :: HANDLE -> LPOVERLAPPED -> IO Bool
cancelIoEx' = c_CancelIoEx

------------------------------------------------------------------------

-- Monotonic time


foreign import WINDOWS_CCONV "windows.h GetTickCount64"
    c_GetTickCount64 :: IO Word64
{-# LINE 470 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}

-- | Call the @GetTickCount64@ function, which returns a monotonic time in

-- milliseconds.

--

-- Problems:

--

--  * Low resolution (10 to 16 milliseconds).

--

-- <http://msdn.microsoft.com/en-us/library/windows/desktop/ms724408%28v=vs.85%29.aspx>

getTickCount64 :: IO Word64
getTickCount64 = c_GetTickCount64

-- | Call the @QueryPerformanceCounter@ function.

--

-- Problems:

--

--  * Might not be available on some hardware.  Use 'queryPerformanceFrequency'

--    to test for availability before calling this function.

--

--  * On a multiprocessor computer, may produce different results on

--    different processors due to hardware bugs.

--

-- To get a monotonic time in seconds, divide the result of

-- 'queryPerformanceCounter' by that of 'queryPerformanceFrequency'.

--

-- <http://msdn.microsoft.com/en-us/library/windows/desktop/ms644904%28v=vs.85%29.aspx>

queryPerformanceCounter :: IO Int64
queryPerformanceCounter =
    callQP c_QueryPerformanceCounter
    >>= maybe (throwGetLastError "QueryPerformanceCounter") return

-- | Call the @QueryPerformanceFrequency@ function.  Return 'Nothing' if the

-- hardware does not provide a high-resolution performance counter.

--

-- <http://msdn.microsoft.com/en-us/library/windows/desktop/ms644905%28v=vs.85%29.aspx>

queryPerformanceFrequency :: IO (Maybe Int64)
queryPerformanceFrequency = do
    m <- callQP c_QueryPerformanceFrequency
    case m of
        Nothing   -> return Nothing
        Just 0    -> return Nothing -- Shouldn't happen; just a safeguard to

                                    -- avoid a zero denominator.

        Just freq -> return (Just freq)

type QPFunc = Ptr Int64 -> IO BOOL

foreign import WINDOWS_CCONV "Windows.h QueryPerformanceCounter"
    c_QueryPerformanceCounter :: QPFunc

foreign import WINDOWS_CCONV "Windows.h QueryPerformanceFrequency"
    c_QueryPerformanceFrequency :: QPFunc

callQP :: QPFunc -> IO (Maybe Int64)
callQP qpfunc =
    allocaBytes (8) $ \ptr -> do
{-# LINE 525 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
        ok <- qpfunc ptr
        if ok then do
            n <- (\hsc_ptr -> peekByteOff hsc_ptr 0) ptr
{-# LINE 528 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}
            return (Just n)
        else
            return Nothing

------------------------------------------------------------------------

-- Miscellaneous


type ULONG_PTR  = Word64
{-# LINE 536 "libraries\\base\\GHC\\Event\\Windows\\FFI.hsc" #-}

throwWinErr :: String -> ErrCode -> IO a
throwWinErr loc err = do
    c_SetLastError err
    Win32.failWith loc err

setLastError :: ErrCode -> IO ()
setLastError = c_SetLastError

foreign import WINDOWS_CCONV unsafe "windows.h SetLastError"
    c_SetLastError :: ErrCode -> IO ()