extern access modifiers don't work

问题

I'm trying to hide my P/Invoke functions, like this one:

[<DllImport("kernel32.dll", SetLastError=true)>]
extern bool private CreateTimerQueueTimer(IntPtr& phNewTimer, nativeint TimerQueue, WaitOrTimerDelegate Callback, nativeint Parameter, uint32 DueTime, uint32 Period, ExecuteFlags Flags)

Strangely, though, the private gets ignored -- which is really annoying, because I want to hide all the unwieldy structs and enums associated with these functions.

I guess I could put everything in a private module, so it's not too big of a deal, but am I missing something?

回答1:

This will do the job.

module a =
    [<AbstractClass>]
    type private NativeMethods() =
        [<DllImport("kernel32.dll", EntryPoint="CreateTimerQueueTimer",
                    SetLastError=true)>]
        static extern bool sCreateTimerQueueTimer( (* whatever *) )
        static member CreateTimerQueueTimer = sCreateTimerQueueTimer

    let usedInside = NativeMethods.CreateTimerQueueTimer

module b =
    open a
    // the next line fails to compile
    let usedOutside = NativeMethods.CreateTimerQueueTimer( (* whatever *) )

Notes:

private class can be accessed only from the enclosing module, this is what you need, so just wrap the methods in a NativeMethods class;
You cannot set your extern method private since it wouldn't be accessible from the rest of module a;
extern member of a class is always private, so there's another method with same signature;
Finally, use EntryPoint to resolve naming.

来源：https://stackoverflow.com/questions/11216552/extern-access-modifiers-dont-work

标签

pinvoke

access-modifiers