/*
    * uloop - event loop implementation
    *
    * Copyright (C) 2010-2016 Felix Fietkau <nbd@openwrt.org>
    *
    * 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 <sys/time.h>
  #include <sys/types.h>
  
  #include <unistd.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <errno.h>
  #include <poll.h>
  #include <string.h>
  #include <fcntl.h>
  #include <stdbool.h>
  #include <limits.h>
  #include <signal.h>
  
  #include "uloop.h"
  #include "utils.h"
  
  #ifdef USE_KQUEUE
  #include <sys/event.h>
  #endif
  #ifdef USE_EPOLL
  #include <sys/epoll.h>
  #include <sys/timerfd.h>
  #endif
  #include <sys/wait.h>
  
  struct uloop_fd_event {
          struct uloop_fd *fd;
          unsigned int events;
  };
  
  struct uloop_fd_stack {
          struct uloop_fd_stack *next;
          struct uloop_fd *fd;
          unsigned int events;
  };
  
  static struct uloop_fd_stack *fd_stack = NULL;
  
  #define ULOOP_MAX_EVENTS 10
  
  static struct list_head timeouts = LIST_HEAD_INIT(timeouts);
  static struct list_head processes = LIST_HEAD_INIT(processes);
  static struct list_head signals = LIST_HEAD_INIT(signals);
  
  /*
   * Entries the signal and process dispatch loops are about to visit. A callback
   * may delete (and free) an arbitrary sibling entry; the matching *_delete()
   * advances these so the loops never dereference a freed entry.
   */
  static struct uloop_signal *signal_next;
  static struct uloop_process *process_next;
  
  static int poll_fd = -1;
  bool uloop_cancelled = false;
  bool uloop_handle_sigchld = true;
  static int uloop_status = 0;
  static volatile sig_atomic_t do_sigchld = 0;
  
  static struct uloop_fd_event cur_fds[ULOOP_MAX_EVENTS];
  static int cur_fd, cur_nfds;
  static int uloop_run_depth = 0;
  
  uloop_fd_handler uloop_fd_set_cb = NULL;
  
  int uloop_fd_add(struct uloop_fd *sock, unsigned int flags);
  
  #ifdef USE_KQUEUE
  #include "uloop-kqueue.c"
  #endif
  
  #ifdef USE_EPOLL
  #include "uloop-epoll.c"
  #endif
  
  static void set_signo(uint64_t *signums, int signo)
  {
          if (signo >= 1 && signo <= 64)
                  *signums |= (UINT64_C(1) << (signo - 1));
  }
  
  static bool get_signo(uint64_t signums, int signo)
 {
         return (signo >= 1) && (signo <= 64) && (signums & (UINT64_C(1) << (signo - 1)));
 }
 
 static struct uloop_signal *uloop_signal_next_entry(struct uloop_signal *s)
 {
         if (list_is_last(&s->list, &signals))
                 return NULL;
 
         return list_next_entry(s, list);
 }
 
 static void signal_consume(struct uloop_fd *fd, unsigned int events)
 {
         struct uloop_signal *usig;
         uint64_t signums = 0;
         uint8_t buf[32];
         ssize_t nsigs;
 
         do {
                 nsigs = read(fd->fd, buf, sizeof(buf));
 
                 for (ssize_t i = 0; i < nsigs; i++)
                         set_signo(&signums, buf[i]);
         }
         while (nsigs > 0);
 
         signal_next = list_empty(&signals) ? NULL :
                 list_first_entry(&signals, struct uloop_signal, list);
 
         while ((usig = signal_next) != NULL) {
                 signal_next = uloop_signal_next_entry(usig);
                 if (get_signo(signums, usig->signo))
                         usig->cb(usig);
         }
 }
 
 static int waker_pipe = -1;
 static struct uloop_fd waker_fd = {
         .fd = -1,
         .cb = signal_consume,
 };
 
 static void waker_init_fd(int fd)
 {
         int flags;
 
         flags = fcntl(fd, F_GETFD);
         if (flags >= 0)
                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 
         flags = fcntl(fd, F_GETFL);
         if (flags >= 0)
                 fcntl(fd, F_SETFL, flags | O_NONBLOCK);
 }
 
 static int waker_init(void)
 {
         int fds[2];
 
         if (waker_pipe >= 0)
                 return 0;
 
         if (pipe(fds) < 0)
                 return -1;
 
         waker_init_fd(fds[0]);
         waker_init_fd(fds[1]);
         waker_pipe = fds[1];
 
         waker_fd.fd = fds[0];
         waker_fd.cb = signal_consume;
         uloop_fd_add(&waker_fd, ULOOP_READ);
 
         return 0;
 }
 
 static void uloop_setup_signals(bool add);
 
 int uloop_init(void)
 {
         if (uloop_init_pollfd() < 0)
                 return -1;
 
         if (waker_init() < 0) {
                 uloop_done();
                 return -1;
         }
 
         uloop_setup_signals(true);
 
         return 0;
 }
 
 static bool uloop_fd_stack_event(struct uloop_fd *fd, int events)
 {
         struct uloop_fd_stack *cur;
 
         /*
          * Do not buffer events for level-triggered fds, they will keep firing.
          * Caller needs to take care of recursion issues.
          */
         if (!(fd->flags & ULOOP_EDGE_TRIGGER))
                 return false;
 
         for (cur = fd_stack; cur; cur = cur->next) {
                 if (cur->fd != fd)
                         continue;
 
                 if (events < 0)
                         cur->fd = NULL;
                 else
                         cur->events |= events | ULOOP_EVENT_BUFFERED;
 
                 return true;
         }
 
         return false;
 }
 
 static void uloop_run_events(int64_t timeout)
 {
         struct uloop_fd_event *cur;
         struct uloop_fd *fd;
 
         if (!cur_nfds) {
                 cur_fd = 0;
                 cur_nfds = uloop_fetch_events(timeout);
                 if (cur_nfds < 0)
                         cur_nfds = 0;
         }
 
         while (cur_nfds > 0) {
                 struct uloop_fd_stack stack_cur;
                 unsigned int events;
 
                 cur = &cur_fds[cur_fd++];
                 cur_nfds--;
 
                 fd = cur->fd;
                 events = cur->events;
                 if (!fd)
                         continue;
 
                 if (!fd->cb)
                         continue;
 
                 if (uloop_fd_stack_event(fd, cur->events))
                         continue;
 
                 stack_cur.next = fd_stack;
                 stack_cur.fd = fd;
                 fd_stack = &stack_cur;
                 do {
                         stack_cur.events = 0;
                         fd->cb(fd, events);
                         events = stack_cur.events & ULOOP_EVENT_MASK;
                 } while (stack_cur.fd && events);
                 fd_stack = stack_cur.next;
 
                 return;
         }
 }
 
 int uloop_fd_add(struct uloop_fd *sock, unsigned int flags)
 {
         int fl;
         int ret;
 
         if (!(flags & (ULOOP_READ | ULOOP_WRITE | ULOOP_PRIORITY)))
                 return uloop_fd_delete(sock);
 
         if (!sock->registered && !(flags & ULOOP_BLOCKING)) {
                 fl = fcntl(sock->fd, F_GETFL, 0);
                 if (fl >= 0)
                         fcntl(sock->fd, F_SETFL, fl | O_NONBLOCK);
         }
 
         ret = register_poll(sock, flags);
         if (ret < 0)
                 goto out;
 
         if (uloop_fd_set_cb)
                 uloop_fd_set_cb(sock, flags);
 
         sock->flags = flags;
         sock->registered = true;
         sock->eof = false;
         sock->error = false;
 
 out:
         return ret;
 }
 
 int uloop_fd_delete(struct uloop_fd *fd)
 {
         int ret;
         int i;
 
         for (i = 0; i < cur_nfds; i++) {
                 if (cur_fds[cur_fd + i].fd != fd)
                         continue;
 
                 cur_fds[cur_fd + i].fd = NULL;
         }
 
         if (!fd->registered)
                 return 0;
 
         if (uloop_fd_set_cb)
                 uloop_fd_set_cb(fd, 0);
 
         fd->registered = false;
         uloop_fd_stack_event(fd, -1);
         ret = __uloop_fd_delete(fd);
         fd->flags = 0;
 
         return ret;
 }
 
 static int64_t tv_diff(struct timeval *t1, struct timeval *t2)
 {
         return
                 (t1->tv_sec - t2->tv_sec) * 1000 +
                 (t1->tv_usec - t2->tv_usec) / 1000;
 }
 
 int uloop_timeout_add(struct uloop_timeout *timeout)
 {
         struct uloop_timeout *tmp;
         struct list_head *h = &timeouts;
 
         if (timeout->pending)
                 return -1;
 
         list_for_each_entry(tmp, &timeouts, list) {
                 if (tv_diff(&tmp->time, &timeout->time) > 0) {
                         h = &tmp->list;
                         break;
                 }
         }
 
         list_add_tail(&timeout->list, h);
         timeout->pending = true;
 
         return 0;
 }
 
 static void uloop_gettime(struct timeval *tv)
 {
         struct timespec ts;
 
         clock_gettime(CLOCK_MONOTONIC, &ts);
         tv->tv_sec = ts.tv_sec;
         tv->tv_usec = ts.tv_nsec / 1000;
 }
 
 int uloop_timeout_set(struct uloop_timeout *timeout, int msecs)
 {
         struct timeval *time = &timeout->time;
 
         if (timeout->pending)
                 uloop_timeout_cancel(timeout);
 
         uloop_gettime(time);
 
         time->tv_sec += msecs / 1000;
         time->tv_usec += (msecs % 1000) * 1000;
 
         if (time->tv_usec > 1000000) {
                 time->tv_sec++;
                 time->tv_usec -= 1000000;
         }
 
         return uloop_timeout_add(timeout);
 }
 
 int uloop_timeout_cancel(struct uloop_timeout *timeout)
 {
         if (!timeout->pending)
                 return -1;
 
         list_del(&timeout->list);
         timeout->pending = false;
 
         return 0;
 }
 
 int uloop_timeout_remaining(struct uloop_timeout *timeout)
 {
         int64_t td;
         struct timeval now;
 
         if (!timeout->pending)
                 return -1;
 
         uloop_gettime(&now);
 
         td = tv_diff(&timeout->time, &now);
 
         if (td > INT_MAX)
                 return INT_MAX;
         else if (td < INT_MIN)
                 return INT_MIN;
         else
                 return (int)td;
 }
 
 int64_t uloop_timeout_remaining64(struct uloop_timeout *timeout)
 {
         struct timeval now;
 
         if (!timeout->pending)
                 return -1;
 
         uloop_gettime(&now);
 
         return tv_diff(&timeout->time, &now);
 }
 
 int uloop_process_add(struct uloop_process *p)
 {
         struct uloop_process *tmp;
         struct list_head *h = &processes;
 
         if (p->pending)
                 return -1;
 
         list_for_each_entry(tmp, &processes, list) {
                 if (tmp->pid > p->pid) {
                         h = &tmp->list;
                         break;
                 }
         }
 
         list_add_tail(&p->list, h);
         p->pending = true;
 
         return 0;
 }
 
 static struct uloop_process *uloop_process_next_entry(struct uloop_process *p)
 {
         if (list_is_last(&p->list, &processes))
                 return NULL;
 
         return list_next_entry(p, list);
 }
 
 int uloop_process_delete(struct uloop_process *p)
 {
         if (!p->pending)
                 return -1;
 
         if (process_next == p)
                 process_next = uloop_process_next_entry(p);
 
         list_del(&p->list);
         p->pending = false;
 
         return 0;
 }
 
 static void uloop_handle_processes(void)
 {
         struct uloop_process *p;
         pid_t pid;
         int ret;
 
         do_sigchld = 0;
 
         while (1) {
                 pid = waitpid(-1, &ret, WNOHANG);
                 if (pid < 0 && errno == EINTR)
                         continue;
 
                 if (pid <= 0)
                         break;
 
                 process_next = list_empty(&processes) ? NULL :
                         list_first_entry(&processes, struct uloop_process, list);
 
                 while ((p = process_next) != NULL) {
                         process_next = uloop_process_next_entry(p);
 
                         if (p->pid < pid)
                                 continue;
 
                         if (p->pid > pid)
                                 break;
 
                         uloop_process_delete(p);
                         p->cb(p, ret);
                 }
         }
 
         process_next = NULL;
 }
 
 int uloop_interval_set(struct uloop_interval *timer, unsigned int msecs)
 {
         return timer_register(timer, msecs);
 }
 
 int uloop_interval_cancel(struct uloop_interval *timer)
 {
         return timer_remove(timer);
 }
 
 int64_t uloop_interval_remaining(struct uloop_interval *timer)
 {
         return timer_next(timer);
 }
 
 static void uloop_signal_wake(int signo)
 {
         uint8_t sigbyte = signo;
 
         if (signo == SIGCHLD)
                 do_sigchld = 1;
 
         do {
                 if (write(waker_pipe, &sigbyte, 1) < 0) {
                         if (errno == EINTR)
                                 continue;
                 }
                 break;
         } while (1);
 }
 
 static void uloop_handle_sigint(int signo)
 {
         uloop_status = signo;
         uloop_cancelled = true;
         uloop_signal_wake(signo);
 }
 
 static void uloop_install_handler(int signum, void (*handler)(int), struct sigaction* old, bool add)
 {
         struct sigaction s;
         struct sigaction *act;
 
         act = NULL;
         sigaction(signum, NULL, &s);
 
         if (add) {
                 if (s.sa_handler == SIG_DFL) { /* Do not override existing custom signal handlers */
                         memcpy(old, &s, sizeof(struct sigaction));
                         s.sa_handler = handler;
                         s.sa_flags = 0;
                         act = &s;
                 }
         }
         else if (s.sa_handler == handler) { /* Do not restore if someone modified our handler */
                         act = old;
         }
 
         if (act != NULL)
                 sigaction(signum, act, NULL);
 }
 
 static void uloop_ignore_signal(int signum, bool ignore)
 {
         struct sigaction s;
         void *new_handler = NULL;
 
         sigaction(signum, NULL, &s);
 
         if (ignore) {
                 if (s.sa_handler == SIG_DFL) /* Ignore only if there isn't any custom handler */
                         new_handler = SIG_IGN;
         } else {
                 if (s.sa_handler == SIG_IGN) /* Restore only if noone modified our SIG_IGN */
                         new_handler = SIG_DFL;
         }
 
         if (new_handler) {
                 s.sa_handler = new_handler;
                 s.sa_flags = 0;
                 sigaction(signum, &s, NULL);
         }
 }
 
 static void uloop_setup_signals(bool add)
 {
         static struct sigaction old_sigint, old_sigchld, old_sigterm;
 
         uloop_install_handler(SIGINT, uloop_handle_sigint, &old_sigint, add);
         uloop_install_handler(SIGTERM, uloop_handle_sigint, &old_sigterm, add);
 
         if (uloop_handle_sigchld)
                 uloop_install_handler(SIGCHLD, uloop_signal_wake, &old_sigchld, add);
 
         uloop_ignore_signal(SIGPIPE, add);
 }
 
 int uloop_signal_add(struct uloop_signal *s)
 {
         struct list_head *h = &signals;
         struct uloop_signal *tmp;
         struct sigaction sa;
 
         if (s->pending)
                 return -1;
 
         list_for_each_entry(tmp, &signals, list) {
                 if (tmp->signo > s->signo) {
                         h = &tmp->list;
                         break;
                 }
         }
 
         list_add_tail(&s->list, h);
         s->pending = true;
 
         sigaction(s->signo, NULL, &s->orig);
 
         if (s->orig.sa_handler != uloop_signal_wake) {
                 sa.sa_handler = uloop_signal_wake;
                 sa.sa_flags = 0;
                 sigemptyset(&sa.sa_mask);
                 sigaction(s->signo, &sa, NULL);
         }
 
         return 0;
 }
 
 int uloop_signal_delete(struct uloop_signal *s)
 {
         struct uloop_signal *tmp;
 
         if (!s->pending)
                 return -1;
 
         if (signal_next == s)
                 signal_next = uloop_signal_next_entry(s);
 
         list_del(&s->list);
         s->pending = false;
 
         /* Only the first watcher registered for a signal saved the real
          * original disposition; later ones saved uloop_signal_wake. */
         if (s->orig.sa_handler == uloop_signal_wake)
                 return 0;
 
         list_for_each_entry(tmp, &signals, list) {
                 if (tmp->signo != s->signo)
                         continue;
 
                 /* Other watchers remain for this signal, hand the saved
                  * disposition over to one of them so it can be restored once
                  * the last watcher is removed. */
                 tmp->orig = s->orig;
                 return 0;
         }
 
         sigaction(s->signo, &s->orig, NULL);
 
         return 0;
 }
 
 int uloop_get_next_timeout(void)
 {
         struct uloop_timeout *timeout;
         struct timeval tv;
         int64_t diff;
 
         if (list_empty(&timeouts))
                 return -1;
 
         uloop_gettime(&tv);
 
         timeout = list_first_entry(&timeouts, struct uloop_timeout, list);
         diff = tv_diff(&timeout->time, &tv);
         if (diff < 0)
                 return 0;
         if (diff > INT_MAX)
                 return INT_MAX;
 
         return diff;
 }
 
 static void uloop_process_timeouts(void)
 {
         struct uloop_timeout *t;
         struct timeval tv;
 
         if (list_empty(&timeouts))
                 return;
 
         uloop_gettime(&tv);
         while (!list_empty(&timeouts)) {
                 t = list_first_entry(&timeouts, struct uloop_timeout, list);
 
                 if (tv_diff(&t->time, &tv) > 0)
                         break;
 
                 uloop_timeout_cancel(t);
                 if (t->cb)
                         t->cb(t);
         }
 }
 
 static void uloop_clear_timeouts(void)
 {
         struct uloop_timeout *t, *tmp;
 
         list_for_each_entry_safe(t, tmp, &timeouts, list)
                 uloop_timeout_cancel(t);
 }
 
 static void uloop_clear_processes(void)
 {
         struct uloop_process *p, *tmp;
 
         list_for_each_entry_safe(p, tmp, &processes, list)
                 uloop_process_delete(p);
 }
 
 bool uloop_cancelling(void)
 {
         return uloop_run_depth > 0 && uloop_cancelled;
 }
 
 int uloop_run_timeout(int timeout)
 {
         int next_time = 0;
 
         uloop_run_depth++;
 
         uloop_status = 0;
         uloop_cancelled = false;
         do {
                 uloop_process_timeouts();
 
                 if (do_sigchld)
                         uloop_handle_processes();
 
                 if (uloop_cancelled)
                         break;
 
                 next_time = uloop_get_next_timeout();
                 if (timeout >= 0 && (next_time < 0 || timeout < next_time))
                                 next_time = timeout;
                 uloop_run_events(next_time);
         } while (!uloop_cancelled && timeout < 0);
 
         --uloop_run_depth;
 
         return uloop_status;
 }
 
 void uloop_done(void)
 {
         uloop_setup_signals(false);
 
         if (poll_fd >= 0) {
                 close(poll_fd);
                 poll_fd = -1;
         }
 
         if (waker_pipe >= 0) {
                 uloop_fd_delete(&waker_fd);
                 close(waker_pipe);
                 close(waker_fd.fd);
                 waker_pipe = -1;
         }
 
         uloop_clear_timeouts();
         uloop_clear_processes();
 }
 

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