/*
 * Linux epoll() based ioloop handler.
 *
 * Copyright (c) 2004 Andrey Panin <pazke@donpac.ru>
 *
 * This software is released under the MIT license.
 */

#include "lib.h"
#include "array.h"
#include "fd-close-on-exec.h"
#include "ioloop-internal.h"
#include "ioloop-iolist.h"

#ifdef IOLOOP_EPOLL

#include <sys/epoll.h>
#include <unistd.h>

struct ioloop_handler_context {
	int epfd;

	unsigned int deleted_count;
	ARRAY_DEFINE(fd_index, struct io_list *);
	ARRAY_DEFINE(events, struct epoll_event);
};

void io_loop_handler_init(struct ioloop *ioloop)
{
	struct ioloop_handler_context *ctx;

	ioloop->handler_context = ctx = i_new(struct ioloop_handler_context, 1);

	i_array_init(&ctx->events, IOLOOP_INITIAL_FD_COUNT);
	i_array_init(&ctx->fd_index, IOLOOP_INITIAL_FD_COUNT);

	ctx->epfd = epoll_create(IOLOOP_INITIAL_FD_COUNT);
	if (ctx->epfd < 0)
		i_fatal("epoll_create(): %m");
	fd_close_on_exec(ctx->epfd, TRUE);
}

void io_loop_handler_deinit(struct ioloop *ioloop)
{
	struct ioloop_handler_context *ctx = ioloop->handler_context;
	struct io_list **list;
	unsigned int i, count;

	list = array_get_modifiable(&ctx->fd_index, &count);
	for (i = 0; i < count; i++)
		i_free(list[i]);

	if (close(ctx->epfd) < 0)
		i_error("close(epoll) failed: %m");
	array_free(&ioloop->handler_context->fd_index);
	array_free(&ioloop->handler_context->events);
	i_free(ioloop->handler_context);
}

#define IO_EPOLL_ERROR (EPOLLERR | EPOLLHUP)
#define IO_EPOLL_INPUT (EPOLLIN | EPOLLPRI | IO_EPOLL_ERROR)
#define IO_EPOLL_OUTPUT	(EPOLLOUT | IO_EPOLL_ERROR)

static int epoll_event_mask(struct io_list *list)
{
	int events = 0, i;
	struct io_file *io;

	for (i = 0; i < IOLOOP_IOLIST_IOS_PER_FD; i++) {
		io = list->ios[i];

		if (io == NULL)
			continue;

		if (io->io.condition & IO_READ)
			events |= IO_EPOLL_INPUT;
		if (io->io.condition & IO_WRITE)
			events |= IO_EPOLL_OUTPUT;
		if (io->io.condition & IO_ERROR)
			events |= IO_EPOLL_ERROR;
	}

	return events;
}

void io_loop_handle_add(struct io_file *io)
{
	struct ioloop_handler_context *ctx = io->io.ioloop->handler_context;
	struct io_list **list;
	struct epoll_event event;
	int op;
	bool first;

	list = array_idx_modifiable(&ctx->fd_index, io->fd);
	if (*list == NULL)
		*list = i_new(struct io_list, 1);

	first = ioloop_iolist_add(*list, io);

	memset(&event, 0, sizeof(event));
	event.data.ptr = *list;
	event.events = epoll_event_mask(*list);

	op = first ? EPOLL_CTL_ADD : EPOLL_CTL_MOD;

	if (epoll_ctl(ctx->epfd, op, io->fd, &event) < 0) {
		i_fatal("io_loop_handle_add: epoll_ctl(%d, %d): %m",
			op, io->fd);
	}

	if (first) {
		/* allow epoll_wait() to return the maximum number of events
		   by keeping space allocated for each file descriptor */
		if (ctx->deleted_count > 0)
			ctx->deleted_count--;
		else
			(void)array_append_space(&ctx->events);
	}
}

void io_loop_handle_remove(struct io_file *io, bool closed)
{
	struct ioloop_handler_context *ctx = io->io.ioloop->handler_context;
	struct io_list **list;
	struct epoll_event event;
	int op;
	bool last;

	list = array_idx_modifiable(&ctx->fd_index, io->fd);
	last = ioloop_iolist_del(*list, io);

	if (!closed) {
		memset(&event, 0, sizeof(event));
		event.data.ptr = *list;
		event.events = epoll_event_mask(*list);

		op = last ? EPOLL_CTL_DEL : EPOLL_CTL_MOD;

		if (epoll_ctl(ctx->epfd, op, io->fd, &event) < 0) {
			i_error("io_loop_handle_remove: epoll_ctl(%d, %d): %m",
				op, io->fd);
		}
	}
	if (last) {
		/* since we're not freeing memory in any case, just increase
		   deleted counter so next handle_add() can just decrease it
		   insteading of appending to the events array */
		ctx->deleted_count++;
	}
	i_free(io);
}

void io_loop_handler_run(struct ioloop *ioloop)
{
	struct ioloop_handler_context *ctx = ioloop->handler_context;
	struct epoll_event *events;
	const struct epoll_event *event;
	struct io_list *list;
	struct io_file *io;
	struct timeval tv;
	unsigned int events_count, t_id;
	int msecs, ret, i, j;
	bool call;

        /* get the time left for next timeout task */
	msecs = io_loop_get_wait_time(ioloop, &tv, NULL);

	events = array_get_modifiable(&ctx->events, &events_count);
	ret = epoll_wait(ctx->epfd, events, events_count, msecs);
	if (ret < 0 && errno != EINTR)
		i_fatal("epoll_wait(): %m");

	/* execute timeout handlers */
        io_loop_handle_timeouts(ioloop);

	if (!ioloop->running)
		return;

	for (i = 0; i < ret; i++) {
		/* io_loop_handle_add() may cause events array reallocation,
		   so we have use array_idx() */
		event = array_idx(&ctx->events, i);
		list = event->data.ptr;

		for (j = 0; j < IOLOOP_IOLIST_IOS_PER_FD; j++) {
			io = list->ios[j];
			if (io == NULL)
				continue;

			call = FALSE;
			if ((event->events & (EPOLLHUP | EPOLLERR)) != 0)
				call = TRUE;
			else if ((io->io.condition & IO_READ) != 0)
				call = (event->events & EPOLLIN) != 0;
			else if ((io->io.condition & IO_WRITE) != 0)
				call = (event->events & EPOLLOUT) != 0;
			else if ((io->io.condition & IO_ERROR) != 0)
				call = (event->events & IO_EPOLL_ERROR) != 0;

			if (call) {
				t_id = t_push();
				io->io.callback(io->io.context);
				if (t_pop() != t_id) {
					i_panic("Leaked a t_pop() call in "
						"I/O handler %p",
						(void *)io->io.callback);
				}
			}
		}
	}
}

#endif	/* IOLOOP_EPOLL */