forked from Imagelibrary/rtems
a6f3cff703
The select function is not particularly efficient when dealing with a
large number of sockets. The application has to build a big set of
bits and pass it in. RTEMS has to look through all those bits and see
what is ready. Then the application has to look through all the bits
again.
On the other hand, when using RTEMS, the select function is needed
exactly when you have a large number of sockets, because that is when
it becomes prohibitive to use a separate thread for each socket.
I think it would make more sense for RTEMS to support callback
functions which could be invoked when there is data available to read
from a socket, or when there is space available to write to a socket.
Accordingly, I implemented them.
This patch adds two new SOL_SOCKET options to setsockopt and
getsockopt: SO_SNDWAKEUP and SO_RCVWAKEUP. They take arguments of
type struct sockwakeup:
struct sockwakeup {
void (*sw_pfn) __P((struct socket *, caddr_t));
caddr_t sw_arg;
};
They are used to add or remove a function which will be called when
something happens for the socket. Getting a callback doesn't imply
that a read or write will succeed, but it does imply that it is worth
trying.
This adds functionality to RTEMS which is somewhat like interrupt
driven socket I/O on Unix.
After the patch to RTEMS, I have appended a patch to
netdemos-19990407/select/test.c to test the new functionality and
demonstrate one way it might be used. To run the new test instead of
the select test, change doSocket to call echoServer2 instead of
echoServer.
#
# $Id$
#
This is the top level of the RTEMS directory structure. The following
is a description of the files and directories in this directory:
Makefile.in
The top-level Make command file used to build the C implementation
of RTEMS. [RTEMS assumes the use of GNU make.]
README
This file.
REQUIRES
A list of the other tools which are assumed to be installed
before RTEMS is built.
SUPPORT
Information on third-party support for RTEMS.
build-tools
This directory contains the source for various utilities
needed to build RTEMS.
make
Make command files "included" from those in the source distribution.
[RTEMS assumes the use of GNU make.]
patches
This directory contains patches for this release of RTEMS.
src
This directory contains the source code for the C
implementation of RTEMS as well as the test suites, sample
applications, Board Support Packages, Device Drivers, and
support libraries.