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poll.c
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poll.c
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/*
* ISC License
*
* Copyright (c) 2021, Tommi Leino <namhas@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "evsrc.h"
#include "event.h"
#include <poll.h>
#include <unistd.h>
#include <signal.h>
#include <limits.h>
#include <errno.h>
#include <stdlib.h>
#include <assert.h>
#define FD_CHUNK 1024
struct event {
struct pollfd *pfd;
struct evsrc **evsrc;
int *remaining;
int n;
int alloc;
int lowest_timeout;
};
static int lowest_timeout(struct event *);
static void dispatch_timers();
static struct event *_ev;
struct event *
event_create()
{
struct event *ev;
/*
* Unfortunately it is still a portability mess regarding timers
* and event handling. For making it working in most platforms,
* we rely on alarm(3) i.e. we rely on signals, and as we rely
* on signals we have to rely on globals. For this reason there
* can be only one instance of the event object. For a better
* implementation, see kqueue.c or implement conditional compiling
* for timerfd_create(2) that works in Linux.
*/
if (_ev != NULL)
assert(0);
ev = calloc(1, sizeof(struct event));
if (ev == NULL)
return NULL;
ev->pfd = calloc(ev->alloc, sizeof(struct pollfd));
if (ev->pfd == NULL) {
event_free(ev);
return NULL;
}
ev->evsrc = calloc(ev->alloc, sizeof(struct evsrc *));
if (ev->evsrc == NULL) {
event_free(ev);
return NULL;
}
_ev = ev;
signal(SIGALRM, dispatch_timers);
return ev;
}
static void
dispatch_timers()
{
int i;
struct evsrc *evsrc;
struct event *ev = _ev;
assert(_ev != NULL);
for (i = 0; i < ev->n; i++) {
evsrc = ev->evsrc[i];
if (evsrc->type == EVSRC_TIMER) {
if (evsrc->remaining > 0)
evsrc->remaining--;
if (evsrc->remaining == 0) {
evsrc->readcb(evsrc, evsrc->data);
evsrc->remaining = evsrc->value / 1000;
}
}
}
ev->lowest_timeout = lowest_timeout(ev);
if (ev->lowest_timeout > 0)
alarm(ev->lowest_timeout);
else
alarm(0);
}
void
event_free(struct event *ev)
{
free(ev->pfd);
free(ev->evsrc);
free(ev);
}
static int
lowest_timeout(struct event *ev)
{
int i;
int lowest = INT_MAX;
struct evsrc *evsrc;
for (i = 0; i < ev->n; i++) {
evsrc = ev->evsrc[i];
if (evsrc->type == EVSRC_TIMER && evsrc->remaining < lowest)
lowest = evsrc->remaining;
}
return lowest;
}
int
event_add_evsrc(struct event *ev, struct evsrc *evsrc)
{
struct pollfd *pfd;
struct evsrc *src;
evsrc->ev = ev;
if (ev->n == ev->alloc) {
ev->alloc *= 2;
if (ev->alloc == 0)
ev->alloc = FD_CHUNK;
ev->pfd = realloc(ev->pfd,
ev->alloc * sizeof(struct pollfd));
if (ev->pfd == NULL)
return -1;
ev->evsrc = realloc(ev->evsrc,
ev->alloc * sizeof(struct evsrc *));
if (ev->evsrc == NULL)
return -1;
}
ev->evsrc[ev->n] = evsrc;
pfd = &ev->pfd[ev->n];
ev->n++;
switch (evsrc->type) {
case EVSRC_FD:
pfd->fd = evsrc->value;
pfd->events = POLLIN;
break;
case EVSRC_TIMER:
pfd->fd = 0;
pfd->events = 0;
evsrc->remaining = evsrc->value / 1000;
if (evsrc->remaining <= 0)
evsrc->remaining = 1;
ev->lowest_timeout = lowest_timeout(ev);
if (ev->lowest_timeout > 0)
alarm(ev->lowest_timeout);
break;
default:
assert(0);
break;
}
return 0;
}
int
event_dispatch(struct event *ev)
{
int nready;
int i, nevents;
struct evsrc *evsrc;
struct pollfd *pfd;
#ifndef INFTIM
#define INFTIM -1
#endif
nready = poll(ev->pfd, ev->n, INFTIM);
if (nready == -1 && errno == EINTR)
return 0;
else if (nready == -1)
return -1;
for (i = 0; i < nready; i++) {
pfd = &ev->pfd[i];
evsrc = ev->evsrc[i];
if (pfd->revents & (POLLIN | POLLHUP)) {
evsrc->readcb(evsrc, evsrc->data);
break;
}
}
return 0;
}
#ifdef TEST
int
readcb(struct evsrc *evsrc, void *data)
{
printf("Got event\n");
sleep(1);
return 0;
}
int
timercb(struct evsrc *evsrc, void *data)
{
printf("Got timer event\n");
return 0;
}
int
main(int argc, char *argv[])
{
struct event *ev;
struct evsrc *fdsrc, *timersrc;
ev = event_create();
if (ev == NULL)
err(1, "event_create");
fdsrc = evsrc_create_fd(0, readcb, NULL);
if (fdsrc == NULL)
err(1, "evsrc_create");
timersrc = evsrc_create_timer(1000, timercb, NULL);
if (timersrc == NULL)
err(1, "evsrc_create");
if (event_add_evsrc(ev, fdsrc) != 0)
err(1, "event_add_evsrc");
if (event_add_evsrc(ev, timersrc) != 0)
err(1, "event_add_evsrc");
for (;;)
if (event_dispatch(ev) == -1)
err(1, "event_dispatch");
event_free(ev);
}
#endif