Re: [boost] 2. It is unavoidable to use threads

From: Aaron W. LaFramboise (aaronrabiddog51_at_[hidden])
Date: 2004-09-13 15:27:12

Carlo Wood wrote:
> On Mon, Sep 13, 2004 at 10:18:00AM -0500, Aaron W. LaFramboise wrote:
> 
>>>But while that might be possible on GNU/Linux, it might be impossible
>>>on windows (for example).  The demand to provide a portable interface
>>>forces us to create (hidden) threads therefore.  If a user decided that
>>>he only needs one thread and the library is not allowed to implement
>>>the requested interface by running two or more threads internally,
>>>then how can I implement an interface that allows one to wait for
>>>events on 100 sockets, a timer, a few named pipes, a fifo and some
>>>large diskfile I/O at the same time?  That is possible on linux,
>>>but I failed to figure out how this can be done on windows :/
>>
>>I am confused.  What feature is missing on Windows?  It is my perception
>>that the Windows API is quite as expressive as anything Linux has.
> 
> No, I am confused.  You do as if it trivial.  But where is the answer to
> my question?  How can I implement an interface that allows one to wait for
> events on 100 sockets, a timer, a few named pipes, a fifo and some
> large diskfile I/O at the same time?

Sorry, I thought it was rhetorical.

-100 sockets: implemented using I/O completion so they trigger with
APC's: no slots used on NT or 9x with winsock 2.0 (but probably requires
a separate thread on win9x with winsock 1.1 or earlier due to going over
the limit (can winsock 1.1 on win9x even handle 100 sockets?) )

-a timer: implemented internals, no handle slots needed.

-a few named pipes: implemented with APC on NT, but 9x doesn't have
named pipes at all.

-a fifo: I'm assuming you mean a normal pipe.  as above, APC on winNT,
uses one handle slot on win9x.

-some large diskfile io: uses APCs, or on Win9x, one handle slot.

Total handles used: None on NT, two on win9x.  That leaves 62 handles left.

The key here is MsgWaitForMultipleObjectsEx().  (Both Msg- and -Ex are
necessary.)  Win95 mysteriously lacks this, so probably
MsgWaitForMultipleObjects() should be used.

> Is your answer WaitForMultipleObjects ?  Then 1) what about the limit
> of 64?  And 2) How can I use that to wait for events on SOCKET's?  The
> only thing I can find for that is WSAWaitForMultipleEvents.  But obviously
> you can call WSAWaitForMultipleEvents *and* WaitForMultipleObjects at
> the same time (without using threads).

1) I do not see how a realitistic use case would ever hit the limit.

2) IO completion routines.

Aaron W. LaFramboise