Select Event Loop Sample in C
The Select Event Loop sample demonstrates how to add HTTP server functionality to your C application and use a POSIX select event loop to wait for I/O events. AppWeb offers several methods to wait for events. See the Programming Paradigms document for further information.
The sample is a single-threaded main program that listens on port 8888 for HTTP requests.
See also the equivalent C++ selectEventLoop sample.
selectEventLoop.conf
selectEventLoop.c
This configuration file loads the embedded JavaScript module and the embedded server pages and embedded gateway interface, and static content handlers. It is configured to run single-threaded. It assumes that the sample is being run from the C/selectEventLoop directory. Modify these module paths to suit your installation.
You should modify the DocumentRoot and Listen directives to suit your application's needs.
The sample is a single-threaded main program that listens on port 8888 for HTTP requests.
See also the equivalent C++ selectEventLoop sample.
Files
selectEventLoop.confselectEventLoop.c
Configuration File
selectEventLoop.conf
DocumentRoot "."
Listen 8888
ThreadLimit 0
LoadModule ejs ../../../lib/libejsModule
LoadModule egi ../../../lib/libegiHandler
LoadModule esp ../../../lib/libespHandler
LoadModule static ../../../lib/libcopyHandler
AddHandler egiHandler .egi
AddHandler espHandler .esp
AddHandler copyHandler
This configuration file loads the embedded JavaScript module and the embedded server pages and embedded gateway interface, and static content handlers. It is configured to run single-threaded. It assumes that the sample is being run from the C/selectEventLoop directory. Modify these module paths to suit your installation.
You should modify the DocumentRoot and Listen directives to suit your application's needs.
Source Code
selectEventLoop.c
/*
* Copyright (c) Mbedthis Software LLC, 2003-2004. All Rights Reserved.
*/
/*!
* @file selectEventLoop.c
* @brief Embed the AppWeb server in a simple single-threaded C
* application that uses a select event loop.
*/
/******************************* Includes *****************************/
#include "appWeb/appWeb.h"
#if MPR_FEATURE_C_API
/************************** Forward Declarations **********************/
static void eventLoop();
/********************************* Code *******************************/
int main(int argc, char** argv)
{
MaHttp *http; /* For the http service inside our app */
MaServer *server; /* For a HTTP server */
/*
* Initialize the run-time and give our app a name
* "selectEventLoop"
*/
mprCreateMpr("selectEventLoop");
/*
* Do the following two statements only if you want debug trace
*/
mprAddLogFileListener();
mprSetLogSpec("stdout:4");
/*
* Start run-time services. Zero means single-threaded.
*/
mprStartMpr(0);
/*
* Create the HTTP and server objects. Give the server a name
* "default" and define "." as the default serverRoot, ie. the
* directory with the server configuration files.
*/
http = maCreateHttp();
server = maCreateServer(http, "default", ".");
/*
* Configure the server based on the directives in
* selectEventLoop.conf.
*/
if (maConfigureServer(server, "selectEventLoop.conf", 0) < 0) {
fprintf(stderr,
"Can't configure the server. Error on line %d\n",
maGetConfigErrorLine(server));
exit(2);
}
/*
* Start serving pages. After this we are live.
*/
if (maStartServers(http) < 0) {
fprintf(stderr, "Can't start the server\n");
exit(2);
}
/*
* Service events. This call will block until the server is exited
* Call mprTerminate() at any time to instruct the server to exit.
*/
eventLoop();
/*
* Stop all HTTP services
*/
maStopServers(http);
/*
* Delete the server and http objects
*/
maDeleteServer(server);
maDeleteHttp(http);
/*
* Stop and delete the run-time services
*/
mprStopMpr();
mprDeleteMpr();
return 0;
}
/**********************************************************************/
/*
* Sample main event loop using select. This demonstrates how to
* integrate AppWeb with your applications event loop using select()
*/
static void eventLoop()
{
struct timeval timeout;
fd_set readFds, writeFds, exceptFds;
fd_set readInterest, writeInterest, exceptInterest;
#if WIN
fd_set *readp, *writep, *exceptp;
#endif
int maxFd, till, lastGet, readyFds;
lastGet = -1;
maxFd = 0;
FD_ZERO(&readInterest);
FD_ZERO(&writeInterest);
FD_ZERO(&exceptInterest);
while (!mprIsExiting()) {
if (mprRunTimers() > 0) {
till = 0;
} else {
till = mprGetIdleTime();
}
//
// This will run tasks if maxThreads == 0 (single threaded). If
// multithreaded, the thread pool will run tasks
//
if (mprRunTasks() > 0) { // Returns > 0 if more work to do
till = 0; // So don't block in select
}
//
// Mpr will populate with the FDs in use by MR on if necessary
//
if (mprGetFds(&readInterest, &writeInterest, &exceptInterest,
&maxFd, &lastGet)) {
//
// Masks have been rebuilt, so add user fds here ....
//
}
//
// Copy as select will modify readFds etc.
//
memcpy((void*) &readFds, (void*) &readInterest, sizeof(readFds));
memcpy((void*) &writeFds, (void*) &writeInterest, sizeof(readFds));
memcpy((void*) &exceptFds, (void*) &exceptInterest, sizeof(exceptFds));
timeout.tv_sec = till / 1000;
timeout.tv_usec = (till % 1000) * 1000;
#if WIN
//
// Windows does not accept empty descriptor arrays
//
readp = (readFds.fd_count == 0) ? 0 : &readFds;
writep = (writeFds.fd_count == 0) ? 0 : &writeFds;
exceptp = (exceptFds.fd_count == 0) ? 0 : &exceptFds;
readyFds = select(maxFd, readp, writep, exceptp, &timeout);
#else
readyFds = select(maxFd, &readFds, &writeFds, &exceptFds, &timeout);
#endif
if (readyFds > 0) {
mprServiceIO(readyFds, &readFds, &writeFds, &exceptFds);
}
}
}
/**********************************************************************/
#else /* MPR_FEATURE_C_API */
int main()
{
fprintf(stderr, "MPR_FEATURE_C_API is not defined in config.h\n");
exit(2);
}
#endif /* MPR_FEATURE_C_API */