Epoll + Lua

epoll_http_server.c

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <sys/wait.h>

#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>
#include <math.h>

#define MAX_EVENTS 10
#define PORT 9136

const char str[] =
    "HTTP/1.1 200 OK\r\nDate: Mon, 23 May 2005 22:38:34 GMT\r\nContent-Type: application/json; charset=UTF-8\r\nContent-Encoding: UTF-8\r\nContent-Length: 28\r\nLast-Modified: Wed, 08 Jan 2003 23:11:55 GMT\r\nServer: Apache/1.3.3.7 (Unix) (Red-Hat/Linux)\r\nETag: \"3f80f-1b6-3e1cb03b\"\r\nAccept-Ranges: bytes\r\nConnection: close\r\n\r\n";

unsigned int req_seqnr = 0;

lua_State *L;

int execlua(char* ret) {
	char buff[256];
	int error;

	//lua_State *L;
	//L = luaL_newstate();
	//luaL_openlibs(L);

	sprintf(buff, "%s", "JSON = (loadfile \"JSON.lua\")() -- one-time load of the routines\nlocal raw_json_text = '{\"name\":\"johan\"}'\nlocal T = JSON:decode(raw_json_text) -- decode example\nT.id=1001\nprint(JSON:encode(T))\nstr = JSON:encode(T)\n");

	error = luaL_loadbuffer(L, buff, strlen(buff), "line") || lua_pcall(L, 0, 0, 0);
	if (error) {
		fprintf(stderr, "!! %s", lua_tostring(L, -1));
		lua_pop(L, 1);  /* pop error message from the stack */
	}

    lua_getglobal(L, "str");    

    const char *s = lua_tostring(L, -1);   /* any Lua string */
    
    //size_t l = lua_strlen(L, -1);          /* its length */
    sprintf(ret, "%s", s);
    /*
	while (fgets(buff, sizeof(buff), stdin) != NULL) {
		error = luaL_loadbuffer(L, buff, strlen(buff), "line") || lua_pcall(L, 0, 0, 0);
		if (error) {
			fprintf(stderr, "!! %s", lua_tostring(L, -1));
			lua_pop(L, 1);
		}
	}*/

	//lua_close(L);
}

/* 
    JSON: https://tools.ietf.org/html/rfc7159
*/

void setnonblocking(int sock)
{
    int opts;
    opts = fcntl(sock, F_GETFL);
    if (opts < 0) {
	    perror("fcntl(sock,GETFL)");
	    exit(1);
    }
    opts = opts | O_NONBLOCK;
    if (fcntl(sock, F_SETFL, opts) < 0) {
	    perror("fcntl(sock,SETFL,opts)");
	    exit(1);
    }
}

void do_use_fd(int client_fd)
{
    char buffer[1024];
    int len;
    if ((len = read(client_fd, buffer, 1024)) == -1) {
	    perror("read");
    }
    buffer[len] = 0;
    printf("#%d: Received:\n%s\n\n", ++req_seqnr, buffer);
    
    char luabuffer[1024];
    char repstr[1024];
    execlua(luabuffer);

    printf("--------\n%s\n----------\n", luabuffer);

    sprintf(repstr, "%s%s\r\n", str, luabuffer);
    
    printf("--------\n%s\n----------\n", repstr);

    if (send(client_fd, repstr, strlen(repstr), 0) == -1) {
	    perror("send");
    }

    close(client_fd);
}

int main(int argc, char **argv)
{

    L = luaL_newstate();
    luaL_openlibs(L);

    struct sockaddr_in serv;
    struct sockaddr_in addr;
    memset(&serv, 0, sizeof(serv));
    serv.sin_family = AF_INET;
    serv.sin_addr.s_addr = htonl(INADDR_ANY);
    serv.sin_port = htons(PORT);

    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    int addrlen = 0;

    bind(sockfd, (struct sockaddr *) &serv, sizeof(struct sockaddr));
    listen(sockfd, 1);

    struct epoll_event ev, events[MAX_EVENTS];
    int listen_sock, conn_sock, nfds, epollfd, n;

    epollfd = epoll_create1(0);
    if (epollfd == -1) {
	    perror("epoll_create1");
	    exit(EXIT_FAILURE);
    }
    listen_sock = sockfd;
    ev.events = EPOLLIN;
    ev.data.fd = listen_sock;
    if (epoll_ctl(epollfd, EPOLL_CTL_ADD, listen_sock, &ev) == -1) {
	    perror("epoll_ctl: listen_sock");
	    exit(EXIT_FAILURE);
    }

    for (;;) {
	nfds = epoll_wait(epollfd, events, MAX_EVENTS, -1);
	if (nfds == -1) {
	    perror("epoll_wait");
	    exit(EXIT_FAILURE);
	}
	for (n = 0; n < nfds; ++n) {
	    if (events[n].data.fd == listen_sock) {
		    conn_sock = accept(listen_sock, (struct sockaddr *) &addr, &addrlen);
		    if (conn_sock == -1) {
		        perror("accept");
		        exit(EXIT_FAILURE);
		    }
		    setnonblocking(conn_sock);
		    ev.events = EPOLLIN | EPOLLET;
		    ev.data.fd = conn_sock;
		    if (epoll_ctl(epollfd, EPOLL_CTL_ADD, conn_sock, &ev) == -1) {
		        perror("epoll_ctl: conn_sock");
		        exit(EXIT_FAILURE);
		    }
	        } else {
		        do_use_fd(events[n].data.fd);
	        }
	    }
    }

    return 0;
}