/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2013 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <sys/epoll.h>
#include <sys/timerfd.h>
#include <sys/wait.h>

#include "macro.h"
#include "refcnt.h"
#include "prioq.h"
#include "hashmap.h"
#include "util.h"
#include "time-util.h"

#include "sd-event.h"

#define EPOLL_QUEUE_MAX 64

typedef enum EventSourceType {
        SOURCE_IO,
        SOURCE_MONOTONIC,
        SOURCE_REALTIME,
        SOURCE_SIGNAL,
        SOURCE_CHILD,
        SOURCE_DEFER
} EventSourceType;

struct sd_event_source {
        RefCount n_ref;

        sd_event *event;
        void *userdata;
        sd_prepare_handler_t prepare;

        EventSourceType type:4;
        sd_event_mute_t mute:3;
        bool pending:1;

        int priority;
        unsigned pending_index;
        unsigned prepare_index;
        unsigned pending_iteration;
        unsigned prepare_iteration;

        union {
                struct {
                        sd_io_handler_t callback;
                        int fd;
                        uint32_t events;
                        uint32_t revents;
                        bool registered:1;
                } io;
                struct {
                        sd_time_handler_t callback;
                        usec_t next;
                        unsigned prioq_index;
                } time;
                struct {
                        sd_signal_handler_t callback;
                        struct signalfd_siginfo siginfo;
                        int sig;
                } signal;
                struct {
                        sd_child_handler_t callback;
                        siginfo_t siginfo;
                        pid_t pid;
                        int options;
                } child;
                struct {
                        sd_defer_handler_t callback;
                } defer;
        };
};

struct sd_event {
        RefCount n_ref;

        int epoll_fd;
        int signal_fd;
        int realtime_fd;
        int monotonic_fd;

        Prioq *pending;
        Prioq *prepare;
        Prioq *monotonic;
        Prioq *realtime;

        sigset_t sigset;
        sd_event_source **signal_sources;

        Hashmap *child_sources;
        unsigned n_unmuted_child_sources;

        unsigned iteration;
        unsigned processed_children;

        usec_t realtime_next, monotonic_next;

        bool quit;
};

static int pending_prioq_compare(const void *a, const void *b) {
        const sd_event_source *x = a, *y = b;

        assert(x->pending);
        assert(y->pending);

        /* Unmuted ones first */
        if (x->mute != SD_EVENT_MUTED && y->mute == SD_EVENT_MUTED)
                return -1;
        if (x->mute == SD_EVENT_MUTED && y->mute != SD_EVENT_MUTED)
                return 1;

        /* Lower priority values first */
        if (x->priority < y->priority)
                return -1;
        if (x->priority > y->priority)
                return 1;

        /* Older entries first */
        if (x->pending_iteration < y->pending_iteration)
                return -1;
        if (x->pending_iteration > y->pending_iteration)
                return 1;

        /* Stability for the rest */
        if (x < y)
                return -1;
        if (y > x)
                return 1;

        return 0;
}

static int prepare_prioq_compare(const void *a, const void *b) {
        const sd_event_source *x = a, *y = b;

        assert(x->prepare);
        assert(y->prepare);

        /* Move most recently prepared ones last, so that we can stop
         * preparing as soon as we hit one that has already been
         * prepared in the current iteration */
        if (x->prepare_iteration < y->prepare_iteration)
                return -1;
        if (x->prepare_iteration > y->prepare_iteration)
                return 1;

        /* Unmuted ones first */
        if (x->mute != SD_EVENT_MUTED && y->mute == SD_EVENT_MUTED)
                return -1;
        if (x->mute == SD_EVENT_MUTED && y->mute != SD_EVENT_MUTED)
                return 1;

        /* Lower priority values first */
        if (x->priority < y->priority)
                return -1;
        if (x->priority > y->priority)
                return 1;

        /* Stability for the rest */
        if (x < y)
                return -1;
        if (y > x)
                return 1;

        return 0;
}

static int time_prioq_compare(const void *a, const void *b) {
        const sd_event_source *x = a, *y = b;

        assert(x->type == SOURCE_MONOTONIC || x->type == SOURCE_REALTIME);
        assert(y->type == SOURCE_MONOTONIC || y->type == SOURCE_REALTIME);

        /* Unmuted ones first */
        if (x->mute != SD_EVENT_MUTED && y->mute == SD_EVENT_MUTED)
                return -1;
        if (x->mute == SD_EVENT_MUTED && y->mute != SD_EVENT_MUTED)
                return 1;

        /* Move the pending ones to the end */
        if (!x->pending && y->pending)
                return -1;
        if (x->pending && !y->pending)
                return 1;

        /* Order by time */
        if (x->time.next < y->time.next)
                return -1;
        if (x->time.next > y->time.next)
                return -1;

        /* Stability for the rest */
        if (x < y)
                return -1;
        if (y > x)
                return 1;

        return 0;
}

static void event_free(sd_event *e) {
        assert(e);

        if (e->epoll_fd >= 0)
                close_nointr_nofail(e->epoll_fd);

        if (e->signal_fd >= 0)
                close_nointr_nofail(e->signal_fd);

        if (e->realtime_fd >= 0)
                close_nointr_nofail(e->realtime_fd);

        if (e->monotonic_fd >= 0)
                close_nointr_nofail(e->monotonic_fd);

        prioq_free(e->pending);
        prioq_free(e->prepare);
        prioq_free(e->monotonic);
        prioq_free(e->realtime);

        free(e->signal_sources);

        hashmap_free(e->child_sources);
        free(e);
}

int sd_event_new(sd_event** ret) {
        sd_event *e;
        int r;

        if (!ret)
                return -EINVAL;

        e = new0(sd_event, 1);
        if (!e)
                return -ENOMEM;

        e->n_ref = REFCNT_INIT;
        e->signal_fd = e->realtime_fd = e->monotonic_fd = e->epoll_fd = -1;
        e->realtime_next = e->monotonic_next = (usec_t) -1;

        assert_se(sigemptyset(&e->sigset) == 0);

        e->pending = prioq_new(pending_prioq_compare);
        if (!e->pending) {
                r = -ENOMEM;
                goto fail;
        }

        e->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
        if (e->epoll_fd < 0) {
                r = -errno;
                goto fail;
        }

        *ret = e;
        return 0;

fail:
        event_free(e);
        return r;
}

sd_event* sd_event_ref(sd_event *e) {
        if (!e)
                return NULL;

        assert_se(REFCNT_INC(e->n_ref) >= 2);

        return e;
}

sd_event* sd_event_unref(sd_event *e) {
        if (!e)
                return NULL;

        if (REFCNT_DEC(e->n_ref) <= 0)
                event_free(e);

        return NULL;
}

static int source_io_unregister(sd_event_source *s) {
        int r;

        assert(s);
        assert(s->type == SOURCE_IO);

        if (!s->io.registered)
                return 0;

        r = epoll_ctl(s->event->epoll_fd, EPOLL_CTL_DEL, s->io.fd, NULL);
        if (r < 0)
                return -errno;

        s->io.registered = false;
        return 0;
}

static int source_io_register(sd_event_source *s, sd_event_mute_t m, uint32_t events) {
        struct epoll_event ev = {};
        int r;

        assert(s);
        assert(s->type == SOURCE_IO);
        assert(m != SD_EVENT_MUTED);

        ev.events = events;
        ev.data.ptr = s;

        if (m == SD_EVENT_ONESHOT)
                ev.events |= EPOLLONESHOT;

        if (s->io.registered)
                r = epoll_ctl(s->event->epoll_fd, EPOLL_CTL_MOD, s->io.fd, &ev);
        else
                r = epoll_ctl(s->event->epoll_fd, EPOLL_CTL_ADD, s->io.fd, &ev);

        if (r < 0)
                return -errno;

        s->io.registered = true;

        return 0;
}

static void source_free(sd_event_source *s) {
        assert(s);

        if (s->event) {
                switch (s->type) {

                case SOURCE_IO:
                        if (s->io.fd >= 0)
                                source_io_unregister(s);

                        break;

                case SOURCE_MONOTONIC:
                        prioq_remove(s->event->monotonic, s, &s->time.prioq_index);
                        break;

                case SOURCE_REALTIME:
                        prioq_remove(s->event->realtime, s, &s->time.prioq_index);
                        break;

                case SOURCE_SIGNAL:
                        if (s->signal.sig > 0) {
                                if (s->signal.sig != SIGCHLD || s->event->n_unmuted_child_sources == 0)
                                        assert_se(sigdelset(&s->event->sigset, s->signal.sig) == 0);

                                if (s->event->signal_sources)
                                        s->event->signal_sources[s->signal.sig] = NULL;
                        }

                        break;

                case SOURCE_CHILD:
                        if (s->child.pid > 0) {
                                if (s->mute != SD_EVENT_MUTED) {
                                        assert(s->event->n_unmuted_child_sources > 0);
                                        s->event->n_unmuted_child_sources--;
                                }

                                if (!s->event->signal_sources || !s->event->signal_sources[SIGCHLD])
                                        assert_se(sigdelset(&s->event->sigset, SIGCHLD) == 0);

                                hashmap_remove(s->event->child_sources, INT_TO_PTR(s->child.pid));
                        }

                        break;
                }

                if (s->pending)
                        prioq_remove(s->event->pending, s, &s->pending_index);

                if (s->prepare)
                        prioq_remove(s->event->prepare, s, &s->prepare_index);

                sd_event_unref(s->event);
        }

        free(s);
}

static int source_set_pending(sd_event_source *s, bool b) {
        int r;

        assert(s);

        if (s->pending == b)
                return 0;

        s->pending = b;

        if (b) {
                s->pending_iteration = s->event->iteration;

                r = prioq_put(s->event->pending, s, &s->pending_index);
                if (r < 0) {
                        s->pending = false;
                        return r;
                }
        } else
                assert_se(prioq_remove(s->event->pending, s, &s->pending_index));

        return 0;
}

static sd_event_source *source_new(sd_event *e, EventSourceType type) {
        sd_event_source *s;

        assert(e);

        s = new0(sd_event_source, 1);
        if (!s)
                return NULL;

        s->n_ref = REFCNT_INIT;
        s->event = sd_event_ref(e);
        s->type = type;
        s->mute = SD_EVENT_UNMUTED;
        s->pending_index = s->prepare_index = PRIOQ_IDX_NULL;

        return s;
}

int sd_event_add_io(
                sd_event *e,
                int fd,
                uint32_t events,
                sd_io_handler_t callback,
                void *userdata,
                sd_event_source **ret) {

        sd_event_source *s;
        int r;

        if (!e)
                return -EINVAL;
        if (fd < 0)
                return -EINVAL;
        if (events & ~(EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLPRI|EPOLLERR|EPOLLHUP))
                return -EINVAL;
        if (!callback)
                return -EINVAL;
        if (!ret)
                return -EINVAL;

        s = source_new(e, SOURCE_IO);
        if (!s)
                return -ENOMEM;

        s->io.fd = fd;
        s->io.events = events;
        s->io.callback = callback;
        s->userdata = userdata;

        r = source_io_register(s, s->mute, events);
        if (r < 0) {
                source_free(s);
                return -errno;
        }

        *ret = s;
        return 0;
}

static int event_setup_timer_fd(
                sd_event *e,
                EventSourceType type,
                int *timer_fd,
                clockid_t id) {

        struct epoll_event ev = {};
        int r, fd;

        assert(e);
        assert(timer_fd);

        if (_likely_(*timer_fd >= 0))
                return 0;

        fd = timerfd_create(id, TFD_NONBLOCK|TFD_CLOEXEC);
        if (fd < 0)
                return -errno;

        ev.events = EPOLLIN;
        ev.data.ptr = INT_TO_PTR(type);

        r = epoll_ctl(e->epoll_fd, EPOLL_CTL_ADD, fd, &ev);
        if (r < 0) {
                close_nointr_nofail(fd);
                return -errno;
        }

        *timer_fd = fd;
        return 0;
}

static int event_add_time_internal(
                sd_event *e,
                EventSourceType type,
                int *timer_fd,
                clockid_t id,
                Prioq **prioq,
                uint64_t usec,
                sd_time_handler_t callback,
                void *userdata,
                sd_event_source **ret) {

        sd_event_source *s;
        int r;

        if (!e)
                return -EINVAL;
        if (!callback)
                return -EINVAL;
        if (!ret)
                return -EINVAL;

        assert(timer_fd);
        assert(prioq);

        if (!*prioq) {
                *prioq = prioq_new(time_prioq_compare);
                if (!*prioq)
                        return -ENOMEM;
        }

        if (*timer_fd < 0) {
                r = event_setup_timer_fd(e, type, timer_fd, id);
                if (r < 0)
                        return r;
        }

        s = source_new(e, type);
        if (!s)
                return -ENOMEM;

        s->time.next = usec;
        s->time.callback = callback;
        s->time.prioq_index = PRIOQ_IDX_NULL;
        s->userdata = userdata;

        r = prioq_put(*prioq, s, &s->time.prioq_index);
        if (r < 0) {
                source_free(s);
                return r;
        }

        *ret = s;
        return 0;
}

int sd_event_add_monotonic(sd_event *e, uint64_t usec, sd_time_handler_t callback, void *userdata, sd_event_source **ret) {
        return event_add_time_internal(e, SOURCE_MONOTONIC, &e->monotonic_fd, CLOCK_MONOTONIC, &e->monotonic, usec, callback, userdata, ret);
}

int sd_event_add_realtime(sd_event *e, uint64_t usec, sd_time_handler_t callback, void *userdata, sd_event_source **ret) {
        return event_add_time_internal(e, SOURCE_REALTIME, &e->realtime_fd, CLOCK_REALTIME, &e->realtime, usec, callback, userdata, ret);
}

static int event_update_signal_fd(sd_event *e) {
        struct epoll_event ev = {};
        bool add_to_epoll;
        int r;

        assert(e);

        add_to_epoll = e->signal_fd < 0;

        r = signalfd(e->signal_fd, &e->sigset, SFD_NONBLOCK|SFD_CLOEXEC);
        if (r < 0)
                return -errno;

        e->signal_fd = r;

        if (!add_to_epoll)
                return 0;

        ev.events = EPOLLIN;
        ev.data.ptr = INT_TO_PTR(SOURCE_SIGNAL);

        r = epoll_ctl(e->epoll_fd, EPOLL_CTL_ADD, e->signal_fd, &ev);
        if (r < 0) {
                close_nointr_nofail(e->signal_fd);
                e->signal_fd = -1;

                return -errno;
        }

        return 0;
}

int sd_event_add_signal(sd_event *e, int sig, sd_signal_handler_t callback, void *userdata, sd_event_source **ret) {
        sd_event_source *s;
        int r;

        if (!e)
                return -EINVAL;
        if (sig <= 0)
                return -EINVAL;
        if (sig >= _NSIG)
                return -EINVAL;
        if (!callback)
                return -EINVAL;
        if (!ret)
                return -EINVAL;

        if (!e->signal_sources) {
                e->signal_sources = new0(sd_event_source*, _NSIG);
                if (!e->signal_sources)
                        return -ENOMEM;
        } else if (e->signal_sources[sig])
                return -EBUSY;

        s = source_new(e, SOURCE_SIGNAL);
        if (!s)
                return -ENOMEM;

        s->signal.sig = sig;
        s->signal.callback = callback;
        s->userdata = userdata;

        e->signal_sources[sig] = s;
        assert_se(sigaddset(&e->sigset, sig) == 0);

        if (sig != SIGCHLD || e->n_unmuted_child_sources == 0) {
                r = event_update_signal_fd(e);
                if (r < 0) {
                        source_free(s);
                        return r;
                }
        }

        *ret = s;
        return 0;
}

int sd_event_add_child(sd_event *e, pid_t pid, int options, sd_child_handler_t callback, void *userdata, sd_event_source **ret) {
        sd_event_source *s;
        int r;

        if (!e)
                return -EINVAL;
        if (pid <= 1)
                return -EINVAL;
        if (options & ~(WEXITED|WSTOPPED|WCONTINUED))
                return -EINVAL;
        if (!callback)
                return -EINVAL;
        if (!ret)
                return -EINVAL;

        r = hashmap_ensure_allocated(&e->child_sources, trivial_hash_func, trivial_compare_func);
        if (r < 0)
                return r;

        if (hashmap_contains(e->child_sources, INT_TO_PTR(pid)))
                return -EBUSY;

        s = source_new(e, SOURCE_CHILD);
        if (!s)
                return -ENOMEM;

        s->child.pid = pid;
        s->child.options = options;
        s->child.callback = callback;
        s->userdata = userdata;

        r = hashmap_put(e->child_sources, INT_TO_PTR(pid), s);
        if (r < 0) {
                source_free(s);
                return r;
        }

        e->n_unmuted_child_sources ++;

        assert_se(sigaddset(&e->sigset, SIGCHLD) == 0);

        if (!e->signal_sources || !e->signal_sources[SIGCHLD]) {
                r = event_update_signal_fd(e);
                if (r < 0) {
                        source_free(s);
                        return -errno;
                }
        }

        *ret = s;
        return 0;
}

int sd_event_add_defer(sd_event *e, sd_defer_handler_t callback, void *userdata, sd_event_source **ret) {
        sd_event_source *s;
        int r;

        if (!e)
                return -EINVAL;
        if (!ret)
                return -EINVAL;

        s = source_new(e, SOURCE_DEFER);
        if (!s)
                return -ENOMEM;

        s->defer.callback = callback;
        s->userdata = userdata;

        r = source_set_pending(s, true);
        if (r < 0) {
                source_free(s);
                return r;
        }

        *ret = s;
        return 0;
}

sd_event_source* sd_event_source_ref(sd_event_source *s) {
        if (!s)
                return NULL;

        assert_se(REFCNT_INC(s->n_ref) >= 2);

        return s;
}

sd_event_source* sd_event_source_unref(sd_event_source *s) {
        if (!s)
                return NULL;

        if (REFCNT_DEC(s->n_ref) <= 0)
                source_free(s);

        return NULL;
}

int sd_event_source_get_pending(sd_event_source *s) {
        if (!s)
                return -EINVAL;

        return s->pending;
}

int sd_event_source_get_io_fd(sd_event_source *s) {
        if (!s)
                return -EINVAL;
        if (s->type != SOURCE_IO)
                return -EDOM;

        return s->io.fd;
}

int sd_event_source_get_io_events(sd_event_source *s, uint32_t* events) {
        if (!s)
                return -EINVAL;
        if (s->type != SOURCE_IO)
                return -EDOM;
        if (!events)
                return -EINVAL;

        *events = s->io.events;
        return 0;
}

int sd_event_source_set_io_events(sd_event_source *s, uint32_t events) {
        int r;

        if (!s)
                return -EINVAL;
        if (!s->type != SOURCE_IO)
                return -EDOM;
        if (events & ~(EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLPRI|EPOLLERR|EPOLLHUP))
                return -EINVAL;

        if (s->io.events == events)
                return 0;

        if (s->mute != SD_EVENT_MUTED) {
                r = source_io_register(s, s->io.events, events);
                if (r < 0)
                        return r;
        }

        s->io.events = events;

        return 0;
}

int sd_event_source_get_io_revents(sd_event_source *s, uint32_t* revents) {
        if (!s)
                return -EINVAL;
        if (s->type != SOURCE_IO)
                return -EDOM;
        if (!revents)
                return -EINVAL;
        if (!s->pending)
                return -ENODATA;

        *revents = s->io.revents;
        return 0;
}

int sd_event_source_get_signal(sd_event_source *s) {
        if (!s)
                return -EINVAL;
        if (s->type != SOURCE_SIGNAL)
                return -EDOM;

        return s->signal.sig;
}

int sd_event_source_get_priority(sd_event_source *s, int *priority) {
        if (!s)
                return -EINVAL;

        return s->priority;
}

int sd_event_source_set_priority(sd_event_source *s, int priority) {
        if (!s)
                return -EINVAL;

        if (s->priority == priority)
                return 0;

        s->priority = priority;

        if (s->pending)
                assert_se(prioq_reshuffle(s->event->pending, s, &s->pending_index) == 0);

        if (s->prepare)
                assert_se(prioq_reshuffle(s->event->prepare, s, &s->prepare_index) == 0);

        return 0;
}

int sd_event_source_get_mute(sd_event_source *s, sd_event_mute_t *m) {
        if (!s)
                return -EINVAL;
        if (!m)
                return -EINVAL;

        *m = s->mute;
        return 0;
}

int sd_event_source_set_mute(sd_event_source *s, sd_event_mute_t m) {
        int r;

        if (!s)
                return -EINVAL;
        if (m != SD_EVENT_MUTED && m != SD_EVENT_UNMUTED && !SD_EVENT_ONESHOT)
                return -EINVAL;

        if (s->mute == m)
                return 0;

        if (m == SD_EVENT_MUTED) {

                switch (s->type) {

                case SOURCE_IO:
                        r = source_io_unregister(s);
                        if (r < 0)
                                return r;

                        s->mute = m;
                        break;

                case SOURCE_MONOTONIC:
                        s->mute = m;
                        prioq_reshuffle(s->event->monotonic, s, &s->time.prioq_index);
                        break;

                case SOURCE_REALTIME:
                        s->mute = m;
                        prioq_reshuffle(s->event->realtime, s, &s->time.prioq_index);
                        break;

                case SOURCE_SIGNAL:
                        s->mute = m;
                        if (s->signal.sig != SIGCHLD || s->event->n_unmuted_child_sources == 0) {
                                assert_se(sigdelset(&s->event->sigset, s->signal.sig) == 0);
                                event_update_signal_fd(s->event);
                        }

                        break;

                case SOURCE_CHILD:
                        s->mute = m;

                        assert(s->event->n_unmuted_child_sources > 0);
                        s->event->n_unmuted_child_sources--;

                        if (!s->event->signal_sources || !s->event->signal_sources[SIGCHLD]) {
                                assert_se(sigdelset(&s->event->sigset, SIGCHLD) == 0);
                                event_update_signal_fd(s->event);
                        }

                        break;

                case SOURCE_DEFER:
                        s->mute = m;
                        break;
                }

        } else {
                switch (s->type) {

                case SOURCE_IO:
                        r = source_io_register(s, m, s->io.events);
                        if (r < 0)
                                return r;

                        s->mute = m;
                        break;

                case SOURCE_MONOTONIC:
                        s->mute = m;
                        prioq_reshuffle(s->event->monotonic, s, &s->time.prioq_index);
                        break;

                case SOURCE_REALTIME:
                        s->mute = m;
                        prioq_reshuffle(s->event->realtime, s, &s->time.prioq_index);
                        break;

                case SOURCE_SIGNAL:
                        s->mute = m;

                        if (s->signal.sig != SIGCHLD || s->event->n_unmuted_child_sources == 0)  {
                                assert_se(sigaddset(&s->event->sigset, s->signal.sig) == 0);
                                event_update_signal_fd(s->event);
                        }
                        break;

                case SOURCE_CHILD:
                        s->mute = m;

                        if (s->mute == SD_EVENT_MUTED) {
                                s->event->n_unmuted_child_sources++;

                                if (!s->event->signal_sources || !s->event->signal_sources[SIGCHLD]) {
                                        assert_se(sigaddset(&s->event->sigset, SIGCHLD) == 0);
                                        event_update_signal_fd(s->event);
                                }
                        }
                        break;

                case SOURCE_DEFER:
                        s->mute = m;
                        break;
                }
        }

        if (s->pending)
                prioq_reshuffle(s->event->pending, s, &s->pending_index);

        if (s->prepare)
                prioq_reshuffle(s->event->prepare, s, &s->prepare_index);

        return 0;
}

int sd_event_source_get_time(sd_event_source *s, uint64_t *usec) {
        if (!s)
                return -EINVAL;
        if (!usec)
                return -EINVAL;
        if (s->type != SOURCE_REALTIME && s->type != SOURCE_MONOTONIC)
                return -EDOM;

        *usec = s->time.next;
        return 0;
}

int sd_event_source_set_time(sd_event_source *s, uint64_t usec) {
        if (!s)
                return -EINVAL;
        if (s->type != SOURCE_REALTIME && s->type != SOURCE_MONOTONIC)
                return -EDOM;

        if (s->time.next == usec)
                return 0;

        s->time.next = usec;

        if (s->type == SOURCE_REALTIME)
                prioq_reshuffle(s->event->realtime, s, &s->time.prioq_index);
        else
                prioq_reshuffle(s->event->monotonic, s, &s->time.prioq_index);

        return 0;
}

int sd_event_source_set_prepare(sd_event_source *s, sd_prepare_handler_t callback) {
        int r;

        if (!s)
                return -EINVAL;

        if (s->prepare == callback)
                return 0;

        if (callback && s->prepare) {
                s->prepare = callback;
                return 0;
        }

        r = prioq_ensure_allocated(&s->event->prepare, prepare_prioq_compare);
        if (r < 0)
                return r;

        s->prepare = callback;

        if (callback) {
                r = prioq_put(s->event->prepare, s, &s->prepare_index);
                if (r < 0)
                        return r;
        } else
                prioq_remove(s->event->prepare, s, &s->prepare_index);

        return 0;
}

void* sd_event_source_get_userdata(sd_event_source *s) {
        if (!s)
                return NULL;

        return s->userdata;
}

static int event_arm_timer(
                sd_event *e,
                int timer_fd,
                Prioq *prioq,
                usec_t *next) {

        struct itimerspec its = {};
        sd_event_source *s;
        int r;

        assert_se(e);
        assert_se(next);

        s = prioq_peek(prioq);
        if (!s || s->mute == SD_EVENT_MUTED)
                return 0;

        if (*next == s->time.next)
                return 0;

        assert_se(timer_fd >= 0);

        if (s->time.next == 0) {
                /* We don' want to disarm here, just mean some time looooong ago. */
                its.it_value.tv_sec = 0;
                its.it_value.tv_nsec = 1;
        } else
                timespec_store(&its.it_value, s->time.next);

        r = timerfd_settime(timer_fd, TFD_TIMER_ABSTIME, &its, NULL);
        if (r < 0)
                return r;

        *next = s->time.next;
        return 0;
}

static int process_io(sd_event *e, sd_event_source *s, uint32_t events) {
        assert(e);
        assert(s);
        assert(s->type == SOURCE_IO);

        s->io.revents = events;

        /*
           If this is a oneshot event source, then we added it to the
           epoll with EPOLLONESHOT, hence we know it's not registered
           anymore. We can save a syscall here...
        */

        if (s->mute == SD_EVENT_ONESHOT)
                s->io.registered = false;

        return source_set_pending(s, true);
}

static int flush_timer(sd_event *e, int fd, uint32_t events) {
        uint64_t x;
        ssize_t ss;

        assert(e);

        if (events != EPOLLIN)
                return -EIO;

        ss = read(fd, &x, sizeof(x));
        if (ss < 0) {
                if (errno == EAGAIN || errno == EINTR)
                        return 0;

                return -errno;
        }

        if (ss != sizeof(x))
                return -EIO;

        return 0;
}

static int process_timer(sd_event *e, usec_t n, Prioq *prioq) {
        sd_event_source *s;
        int r;

        assert(e);

        for (;;) {
                s = prioq_peek(prioq);
                if (!s ||
                    s->time.next > n ||
                    s->mute == SD_EVENT_MUTED ||
                    s->pending)
                        break;

                r = source_set_pending(s, true);
                if (r < 0)
                        return r;

                r = prioq_reshuffle(prioq, s, &s->time.prioq_index);
                if (r < 0)
                        return r;
        }

        return 0;
}

static int process_child(sd_event *e) {
        sd_event_source *s;
        Iterator i;
        int r;

        assert(e);

        /*
           So, this is ugly. We iteratively invoke waitid() with P_PID
           + WNOHANG for each PID we wait for, instead of using
           P_ALL. This is because we only want to get child
           information of very specific child processes, and not all
           of them. We might not have processed the SIGCHLD even of a
           previous invocation and we don't want to maintain a
           unbounded *per-child* event queue, hence we really don't
           want anything flushed out of the kernel's queue that we
           don't care about. Since this is O(n) this means that if you
           have a lot of processes you probably want to handle SIGCHLD
           yourself.
        */

        HASHMAP_FOREACH(s, e->child_sources, i) {
                assert(s->type == SOURCE_CHILD);

                if (s->pending)
                        continue;

                if (s->mute == SD_EVENT_MUTED)
                        continue;

                zero(s->child.siginfo);
                r = waitid(P_PID, s->child.pid, &s->child.siginfo, WNOHANG|s->child.options);
                if (r < 0)
                        return -errno;

                if (s->child.siginfo.si_pid != 0) {
                        r = source_set_pending(s, true);
                        if (r < 0)
                                return r;
                }
        }

        e->processed_children = e->iteration;
        return 0;
}

static int process_signal(sd_event *e, uint32_t events) {
        struct signalfd_siginfo si;
        bool read_one = false;
        ssize_t ss;
        int r;

        if (events != EPOLLIN)
                return -EIO;

        for (;;) {
                sd_event_source *s;

                ss = read(e->signal_fd, &si, sizeof(si));
                if (ss < 0) {
                        if (errno == EAGAIN || errno == EINTR)
                                return read_one;

                        return -errno;
                }

                if (ss != sizeof(si))
                        return -EIO;

                read_one = true;

                if (si.ssi_signo == SIGCHLD) {
                        r = process_child(e);
                        if (r < 0)
                                return r;
                        if (r > 0 || !e->signal_sources[si.ssi_signo])
                                continue;
                } else {
                        s = e->signal_sources[si.ssi_signo];
                        if (!s)
                                return -EIO;
                }

                s->signal.siginfo = si;
                r = source_set_pending(s, true);
                if (r < 0)
                        return r;
        }


        return 0;
}

static int source_dispatch(sd_event_source *s) {
        int r;

        assert(s);
        assert(s->pending);

        r = source_set_pending(s, false);
        if (r < 0)
                return r;

        if (s->mute == SD_EVENT_ONESHOT) {
                r = sd_event_source_set_mute(s, SD_EVENT_MUTED);
                if (r < 0)
                        return r;
        }

        switch (s->type) {

        case SOURCE_IO:
                r = s->io.callback(s, s->io.fd, s->io.revents, s->userdata);
                break;

        case SOURCE_MONOTONIC:
                r = s->time.callback(s, s->time.next, s->userdata);
                break;

        case SOURCE_REALTIME:
                r = s->time.callback(s, s->time.next, s->userdata);
                break;

        case SOURCE_SIGNAL:
                r = s->signal.callback(s, &s->signal.siginfo, s->userdata);
                break;

        case SOURCE_CHILD:
                r = s->child.callback(s, &s->child.siginfo, s->userdata);
                break;

        case SOURCE_DEFER:
                r = s->defer.callback(s, s->userdata);
                break;
        }

        return r;
}

static int event_prepare(sd_event *e) {
        int r;

        assert(e);

        for (;;) {
                sd_event_source *s;

                s = prioq_peek(e->prepare);
                if (!s || s->prepare_iteration == e->iteration || s->mute == SD_EVENT_MUTED)
                        break;

                s->prepare_iteration = e->iteration;
                r = prioq_reshuffle(e->prepare, s, &s->prepare_index);
                if (r < 0)
                        return r;

                assert(s->prepare);
                r = s->prepare(s, s->userdata);
                if (r < 0)
                        return r;

        }

        return 0;
}

int sd_event_run(sd_event *e, uint64_t timeout) {
        struct epoll_event ev_queue[EPOLL_QUEUE_MAX];
        sd_event_source *p;
        int r, i, m;
        dual_timestamp n;

        if (!e)
                return -EINVAL;
        if (e->quit)
                return -ESTALE;

        e->iteration++;

        r = event_prepare(e);
        if (r < 0)
                return r;

        r = event_arm_timer(e, e->monotonic_fd, e->monotonic, &e->monotonic_next);
        if (r < 0)
                return r;

        r = event_arm_timer(e, e->realtime_fd, e->realtime, &e->realtime_next);
        if (r < 0)
                return r;

        if (e->iteration == 1 && !hashmap_isempty(e->child_sources))
                /* On the first iteration, there might be already some
                 * zombies for us to care for, hence, don't wait */
                timeout = 0;
        else {
                p = prioq_peek(e->pending);
                if (p && p->mute != SD_EVENT_MUTED)
                        timeout = 0;
        }

        m = epoll_wait(e->epoll_fd, ev_queue, EPOLL_QUEUE_MAX, timeout == (uint64_t) -1 ? -1 : (int) ((timeout + USEC_PER_MSEC - 1) / USEC_PER_MSEC));
        if (m < 0)
                return m;

        dual_timestamp_get(&n);

        for (i = 0; i < m; i++) {

                if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_MONOTONIC))
                        r = flush_timer(e, e->monotonic_fd, ev_queue[i].events);
                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_REALTIME))
                        r = flush_timer(e, e->realtime_fd, ev_queue[i].events);
                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_SIGNAL))
                        r = process_signal(e, ev_queue[i].events);
                else
                        r = process_io(e, ev_queue[i].data.ptr, ev_queue[i].events);

                if (r < 0)
                        return r;
        }

        r = process_timer(e, n.monotonic, e->monotonic);
        if (r < 0)
                return r;

        r = process_timer(e, n.realtime, e->realtime);
        if (r < 0)
                return r;

        if (e->iteration == 1 && e->processed_children != 1) {
                /* On the first iteration, make sure we really process
                 * all children which might already be zombies. */
                r = process_child(e);
                if (r < 0)
                        return r;
        }

        p = prioq_peek(e->pending);
        if (!p || p->mute == SD_EVENT_MUTED)
                return 0;

        return source_dispatch(p);
}

int sd_event_loop(sd_event *e) {
        int r;

        if (!e)
                return -EINVAL;

        while (!e->quit) {
                r = sd_event_run(e, (uint64_t) -1);
                if (r < 0)
                        return r;
        }

        return 0;
}

int sd_event_quit(sd_event *e) {
        if (!e)
                return EINVAL;

        return e->quit;
}

int sd_event_request_quit(sd_event *e) {
        if (!e)
                return -EINVAL;

        e->quit = true;
        return 0;
}

sd_event *sd_event_get(sd_event_source *s) {
        if (!s)
                return NULL;

        return s->event;
}