text: #define _POSIX_C_SOURCE 200112L
  #include <limits.h>
  #include <string.h>
  #include <stdbool.h>
  #include <stdlib.h>
  #include <stdio.h>
  #include <poll.h>
  #include <time.h>
  #include <unistd.h>
  #include <wayland-client.h>
  #include "log.h"
  #include "loop.h"
  
  struct loop_fd_event {
  	void (*callback)(int fd, short mask, void *data);
  	void *data;
  	struct wl_list link; // struct loop_fd_event::link
  };
  
  struct loop_timer {
  	void (*callback)(void *data);
  	void *data;
  	struct timespec expiry;
  	struct wl_list link; // struct loop_timer::link
  };
  
  struct loop {
  	struct pollfd *fds;
  	int fd_length;
  	int fd_capacity;
  
  	struct wl_list fd_events; // struct loop_fd_event::link
  	struct wl_list timers; // struct loop_timer::link
  };
  
  struct loop *loop_create(void) {
  	struct loop *loop = calloc(1, sizeof(struct loop));
  	if (!loop) {
  		swaylock_log(LOG_ERROR, "Unable to allocate memory for loop");
  		return NULL;
  	}
  	loop->fd_capacity = 10;
  	loop->fds = malloc(sizeof(struct pollfd) * loop->fd_capacity);
  	wl_list_init(&loop->fd_events);
  	wl_list_init(&loop->timers);
  	return loop;
  }
  
  void loop_destroy(struct loop *loop) {
  	struct loop_fd_event *event = NULL, *tmp_event = NULL;
  	wl_list_for_each_safe(event, tmp_event, &loop->fd_events, link) {
  		wl_list_remove(&event->link);
  		free(event);
  	}
  	struct loop_timer *timer = NULL, *tmp_timer = NULL;
  	wl_list_for_each_safe(timer, tmp_timer, &loop->timers, link) {
  		wl_list_remove(&timer->link);
  		free(timer);
  	}
  	free(loop->fds);
  	free(loop);
  }
  
  void loop_poll(struct loop *loop) {
  	// Calculate next timer in ms
  	int ms = INT_MAX;
  	if (!wl_list_empty(&loop->timers)) {
  		struct timespec now;
  		clock_gettime(CLOCK_MONOTONIC, &now);
  		struct loop_timer *timer = NULL;
  		wl_list_for_each(timer, &loop->timers, link) {
  			int timer_ms = (timer->expiry.tv_sec - now.tv_sec) * 1000;
  			timer_ms += (timer->expiry.tv_nsec - now.tv_nsec) / 1000000;
  			if (timer_ms < ms) {
  				ms = timer_ms;
  			}
  		}
  	}
  	if (ms < 0) {
  		ms = 0;
  	}
  
  	poll(loop->fds, loop->fd_length, ms);
  
  	// Dispatch fds
  	size_t fd_index = 0;
  	struct loop_fd_event *event = NULL;
  	wl_list_for_each(event, &loop->fd_events, link) {
  		struct pollfd pfd = loop->fds[fd_index];
  
  		// Always send these events
  		unsigned events = pfd.events | POLLHUP | POLLERR;
  
  		if (pfd.revents & events) {
  			event->callback(pfd.fd, pfd.revents, event->data);
  		}
  
  		++fd_index;
  	}
  
  	// Dispatch timers
  	if (!wl_list_empty(&loop->timers)) {
  		struct timespec now;
  		clock_gettime(CLOCK_MONOTONIC, &now);
  		struct loop_timer *timer = NULL, *tmp_timer = NULL;
  		wl_list_for_each_safe(timer, tmp_timer, &loop->timers, link) {
  			bool expired = timer->expiry.tv_sec < now.tv_sec ||
  				(timer->expiry.tv_sec == now.tv_sec &&
  				 timer->expiry.tv_nsec < now.tv_nsec);
  			if (expired) {
  				timer->callback(timer->data);
  				loop_remove_timer(loop, timer);
  			}
  		}
  	}
  }
  
  void loop_add_fd(struct loop *loop, int fd, short mask,
  		void (*callback)(int fd, short mask, void *data), void *data) {
  	struct loop_fd_event *event = calloc(1, sizeof(struct loop_fd_event));
  	if (!event) {
  		swaylock_log(LOG_ERROR, "Unable to allocate memory for event");
  		return;
  	}
  	event->callback = callback;
  	event->data = data;
  	wl_list_insert(loop->fd_events.prev, &event->link);
  
  	struct pollfd pfd = {fd, mask, 0};
  
  	if (loop->fd_length == loop->fd_capacity) {
  		loop->fd_capacity += 10;
  		loop->fds = realloc(loop->fds,
  				sizeof(struct pollfd) * loop->fd_capacity);
  	}
  
  	loop->fds[loop->fd_length++] = pfd;
  }
  
  struct loop_timer *loop_add_timer(struct loop *loop, int ms,
  		void (*callback)(void *data), void *data) {
  	struct loop_timer *timer = calloc(1, sizeof(struct loop_timer));
  	if (!timer) {
  		swaylock_log(LOG_ERROR, "Unable to allocate memory for timer");
  		return NULL;
  	}
  	timer->callback = callback;
  	timer->data = data;
  
  	clock_gettime(CLOCK_MONOTONIC, &timer->expiry);
  	timer->expiry.tv_sec += ms / 1000;
  
  	long int nsec = (ms % 1000) * 1000000;
  	if (timer->expiry.tv_nsec + nsec >= 1000000000) {
  		timer->expiry.tv_sec++;
  		nsec -= 1000000000;
  	}
  	timer->expiry.tv_nsec += nsec;
  
  	wl_list_insert(&loop->timers, &timer->link);
  
  	return timer;
  }
  
  bool loop_remove_fd(struct loop *loop, int fd) {
  	size_t fd_index = 0;
  	struct loop_fd_event *event = NULL, *tmp_event = NULL;
  	wl_list_for_each_safe(event, tmp_event, &loop->fd_events, link) {
  		if (loop->fds[fd_index].fd == fd) {
  			wl_list_remove(&event->link);
  			free(event);
  
  			loop->fd_length--;
  			memmove(&loop->fds[fd_index], &loop->fds[fd_index + 1],
  					sizeof(struct pollfd) * (loop->fd_length - fd_index));
  			return true;
  		}
  		++fd_index;
  	}
  	return false;
  }
  
  bool loop_remove_timer(struct loop *loop, struct loop_timer *remove) {
  	struct loop_timer *timer = NULL, *tmp_timer = NULL;
  	wl_list_for_each_safe(timer, tmp_timer, &loop->timers, link) {
  		if (timer == remove) {
  			wl_list_remove(&timer->link);
  			free(timer);
  			return true;
  		}
  	}
  	return false;
  }
  