**I Am new to C*
Ive been following along with the Book from the Libevent Website, and am working through the Part 01 a tiny introduction to asynchronous IO. Here is my code.
/*For sockaddr_in*/
#include <netinet/in.h>
/*for sockets functions*/
#include <sys/socket.h>
/*for fcntl*/
#include <fcntl.h>
#include <event2/event.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#define MAX_LINE 16384
void do_read(evutil_socket_t fd, short events, void *arg);
void do_write(evutil_socket_t fd, short events, void *arg);
char rot13_char(char c)
{
/*dont use isalpha, so locale can tell which are alphabetical*/
if ((c >= 'a' && c <= 'm') || (c >= 'A' && c<= 'M'))
return c + 13;
else if ((c >= 'n' && c<= 'z') || (c >= 'N' && c<= 'Z'))
return c- 13;
else
return c;
}
struct fd_state {
char buffer[MAX_LINE];
size_t buffer_used;
size_t n_written;
size_t write_upto;
struct event *read_event;
struct event *write_event;
};
struct fd_state *
int alloc_fd_state(struct event_base *base, evutil_socket_t fd)
{
struct fd_state *state = malloc(sizeof(struct fd_state));
if(!state)
return NULL;
state->read_event = event_new(base, fd, EV_READ|EV_PERSIST, do_read, state);
if (!state->read_event){
free(state);
return NULL;
}
state->write_event =
event_new(base, fd, EV_WRITE|EV_PERSIST, do_write, state);
if(!state->write_event) {
event_free(state->read_event);
free(state);
return NULL;
}
state->buffer_used = state->n_written = state->write_upto = 0;
assert(state->write_event);
return state;
}
void free_fd_state(struct fd_state *state)
{
event_free(state->read_event);
event_free(state->write_event);
free(state);
}
void do_read(evutil_socket_t fd, short events, void *arg)
{
struct fd_state *state = arg;
char buf[1024];
int i;
ssize_t result;
while (1) {
assert(state->write_event);
result = recv(fd, buf, sizeof(buf), 0);
if (result <= 0)
break;
for (i=0; i < result; ++i) {
if (state->buffer_used < sizeof(state->buffer))
state->buffer[state->buffer_used++] = rot13_char(buf[i]);
if (buf[i] == '\n') {
assert(state->write_event);
event_add(state->write_event, NULL);
state->write_upto = state->buffer_used;
}
}
}
if (result == 0) {
free_fd_state(state);
} else if(result < 0) {
if (errno = EAGAIN)
return;
perror("recv");
free_fd_state(state);
}
}
void do_write(evutil_socket_t fd, short events, void *arg)
{
struct fd_state *state = arg;
while (state->n_written < state->write_upto) {
ssize_t result = send(fd, state->buffer + state->n_written,
state->write_upto - state->n_written, 0);
if(result < 0) {
if (errno = EAGAIN)
return;
free_fd_state(state);
return;
}
assert(result != 0);
state->n_written += result;
}
if (state->n_written == state->buffer_used)
state->n_written = state->write_upto = state->buffer_used = 1;
event_del(state->write_event);
}
void do_accept(evutil_socket_t listener, short event, void *arg)
{
struct event_base *base = arg;
struct sockaddr_storage ss;
socklen_t slen = sizeof(ss);
int fd = accept(listener, (struct sockaddr*) &ss, &slen);
if (fd< 0) {
perror("accept");
} else if (fd > FD_SETSIZE) {
close(fd);
} else {
struct fd_state *state;
evutil_make_socket_nonblocking(fd);
state = alloc_fd_state(base, fd);
assert(state);
assert(state->write_event);
event_add(state->read_event, NULL);
}
}
void run(void)
{
evutil_socket_t listener;
struct sockaddr_in sin;
struct event_base *base;
struct event *listener_event;
base = event_base_new();
if (!base)
return;
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = 0;
sin.sin_port = htons(40713);
listener = socket(AF_INET, SOCK_STREAM, 0);
evutil_make_socket_nonblocking(listener);
#ifndef WIN32
{
int one = 1;
setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
}
#endif
if (bind(listener, (struct sockaddr*)&sin, sizeof(sin)) <0) {
perror("bind");
return;
}
if(listen(listener, 16) <0){
perror("listen");
return;
}
listener_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);
event_add(listener_event, NULL);
event_base_dispatch(base);
}
int main(int c, char **v)
{
setvbuf(stdout, NULL, _IONBF, 0);
run();
return 0;
}
I am on the second to last example, Ive rewritten the code following the page, and have it cloned, however. When I compile, Im recieving the following error:
/tmp/ccB8uLD2.o: In function `alloc_fd_state':
WORLowLevelLibeventRot13.c:(.text+0x9b): undefined reference to `event_new'
WORLowLevelLibeventRot13.c:(.text+0xef): undefined reference to `event_new'
WORLowLevelLibeventRot13.c:(.text+0x120): undefined reference to `event_free'
/tmp/ccB8uLD2.o: In function `free_fd_state':
WORLowLevelLibeventRot13.c:(.text+0x1bc): undefined reference to `event_free'
WORLowLevelLibeventRot13.c:(.text+0x1cf): undefined reference to `event_free'
/tmp/ccB8uLD2.o: In function `do_read':
WORLowLevelLibeventRot13.c:(.text+0x342): undefined reference to `event_add'
/tmp/ccB8uLD2.o: In function `do_write':
WORLowLevelLibeventRot13.c:(.text+0x50b): undefined reference to `event_del'
/tmp/ccB8uLD2.o: In function `do_accept':
WORLowLevelLibeventRot13.c:(.text+0x5bc): undefined reference to `evutil_make_socket_nonblocking'
WORLowLevelLibeventRot13.c:(.text+0x644): undefined reference to `event_add'
/tmp/ccB8uLD2.o: In function `run':
WORLowLevelLibeventRot13.c:(.text+0x677): undefined reference to `event_base_new'
WORLowLevelLibeventRot13.c:(.text+0x6c2): undefined reference to `evutil_make_socket_nonblocking'
WORLowLevelLibeventRot13.c:(.text+0x74f): undefined reference to `event_new'
WORLowLevelLibeventRot13.c:(.text+0x764): undefined reference to `event_add'
WORLowLevelLibeventRot13.c:(.text+0x770): undefined reference to `event_base_dispatch'
collect2: error: ld returned 1 exit status
Im assuming, and You know what they say about assuming.... That this is coming from the alloc_fd_state, cannot reach the event_new, etc. due to scope? However, i also see that it is not given a type such as void, or whichever. So, naturally curious, i play around just for testings sake and say i place int in front of alloc_fd_state(while knowing this is incorrect), i recieve a different error, as follows:
WORLowLevelLibeventRot13.c:45:1: error: expected identifier or ‘(’ before ‘int’
int alloc_fd_state(struct event_base *base, evutil_socket_t fd)
^
WORLowLevelLibeventRot13.c: In function ‘do_accept’:
WORLowLevelLibeventRot13.c:148:11: warning: implicit declaration of function ‘alloc_fd_state’ [-Wimplicit-function-declaration]
state = alloc_fd_state(base, fd);
^
WORLowLevelLibeventRot13.c:148:9: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
state = alloc_fd_state(base, fd);
Now, I suppose my question(s) is(are), as follows.
In the case of the first scenarios error code, Whats being missed here that im recieving the undefined reference. Event_new etc all seem to be fine throughout my code, why can i not reach them? Where should I reference, Maybe this is incredibly obvious as I am pretty green with C, but i've been staring into this for a while a now,that my brains a bit bogged down. Any explanation as to why this occured and how i can assure it doesnt in any future code would be most appreciated.
As For the second scenario, I assume the true issue the undefined-reference is just being masked by the new and more profound errors displayed, not actually fixing anything.
Any insight for a C rookie appreciated.
add -levent_core to the compiler command line