--- /dev/null
+/*
+ * C eventloop example.
+ *
+ * Timer management is similar to eventloop.js but implemented in C.
+ * In particular, timer insertion is an O(n) operation; in a real world
+ * eventloop based on a heap insertion would be O(log N).
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <sys/time.h>
+#include <poll.h>
+
+#include "duktape.h"
+
+#define MAX_TIMERS 4096 /* this is quite excessive for embedded use, but good for testing */
+#define MIN_DELAY 1.0
+#define MIN_WAIT 1.0
+#define MAX_WAIT 60000.0
+#define MAX_EXPIRYS 10
+
+#define MAX_FDS 256
+
+typedef struct {
+ int64_t id; /* numeric ID (returned from e.g. setTimeout); zero if unused */
+ double target; /* next target time */
+ double delay; /* delay/interval */
+ int oneshot; /* oneshot=1 (setTimeout), repeated=0 (setInterval) */
+ int removed; /* timer has been requested for removal */
+
+ /* The callback associated with the timer is held in the "global stash",
+ * in <stash>.eventTimers[String(id)]. The references must be deleted
+ * when a timer struct is deleted.
+ */
+} ev_timer;
+
+/* Active timers. Dense list, terminates to end of list or first unused timer.
+ * The list is sorted by 'target', with lowest 'target' (earliest expiry) last
+ * in the list. When a timer's callback is being called, the timer is moved
+ * to 'timer_expiring' as it needs special handling should the user callback
+ * delete that particular timer.
+ */
+static ev_timer timer_list[MAX_TIMERS];
+static ev_timer timer_expiring;
+static int timer_count; /* last timer at timer_count - 1 */
+static int64_t timer_next_id = 1;
+
+/* Socket poll state. */
+static struct pollfd poll_list[MAX_FDS];
+static int poll_count = 0;
+
+/* Misc */
+static int exit_requested = 0;
+
+/* Get Javascript compatible 'now' timestamp (millisecs since 1970). */
+static double get_now(void) {
+ struct timeval tv;
+ int rc;
+
+ rc = gettimeofday(&tv, NULL);
+ if (rc != 0) {
+ /* Should never happen, so return whatever. */
+ return 0.0;
+ }
+ return ((double) tv.tv_sec) * 1000.0 + ((double) tv.tv_usec) / 1000.0;
+}
+
+static ev_timer *find_nearest_timer(void) {
+ /* Last timer expires first (list is always kept sorted). */
+ if (timer_count <= 0) {
+ return NULL;
+ }
+ return timer_list + timer_count - 1;
+}
+
+/* Bubble last timer on timer list backwards until it has been moved to
+ * its proper sorted position (based on 'target' time).
+ */
+static void bubble_last_timer(void) {
+ int i;
+ int n = timer_count;
+ ev_timer *t;
+ ev_timer tmp;
+
+ for (i = n - 1; i > 0; i--) {
+ /* Timer to bubble is at index i, timer to compare to is
+ * at i-1 (both guaranteed to exist).
+ */
+ t = timer_list + i;
+ if (t->target <= (t-1)->target) {
+ /* 't' expires earlier than (or same time as) 't-1', so we're done. */
+ break;
+ } else {
+ /* 't' expires later than 't-1', so swap them and repeat. */
+ memcpy((void *) &tmp, (void *) (t - 1), sizeof(ev_timer));
+ memcpy((void *) (t - 1), (void *) t, sizeof(ev_timer));
+ memcpy((void *) t, (void *) &tmp, sizeof(ev_timer));
+ }
+ }
+}
+
+static void expire_timers(duk_context *ctx) {
+ ev_timer *t;
+ int sanity = MAX_EXPIRYS;
+ double now;
+ int rc;
+
+ /* Because a user callback can mutate the timer list (by adding or deleting
+ * a timer), we expire one timer and then rescan from the end again. There
+ * is a sanity limit on how many times we do this per expiry round.
+ */
+
+ duk_push_global_stash(ctx);
+ duk_get_prop_string(ctx, -1, "eventTimers");
+
+ /* [ ... stash eventTimers ] */
+
+ now = get_now();
+ while (sanity-- > 0) {
+ /*
+ * If exit has been requested, exit without running further
+ * callbacks.
+ */
+
+ if (exit_requested) {
+#if 0
+ fprintf(stderr, "exit requested, exiting timer expiry loop\n");
+ fflush(stderr);
+#endif
+ break;
+ }
+
+ /*
+ * Expired timer(s) still exist?
+ */
+
+ if (timer_count <= 0) {
+ break;
+ }
+ t = timer_list + timer_count - 1;
+ if (t->target > now) {
+ break;
+ }
+
+ /*
+ * Move the timer to 'expiring' for the duration of the callback.
+ * Mark a one-shot timer deleted, compute a new target for an interval.
+ */
+
+ memcpy((void *) &timer_expiring, (void *) t, sizeof(ev_timer));
+ memset((void *) t, 0, sizeof(ev_timer));
+ timer_count--;
+ t = &timer_expiring;
+
+ if (t->oneshot) {
+ t->removed = 1;
+ } else {
+ t->target = now + t->delay; /* XXX: or t->target + t->delay? */
+ }
+
+ /*
+ * Call timer callback. The callback can operate on the timer list:
+ * add new timers, remove timers. The callback can even remove the
+ * expired timer whose callback we're calling. However, because the
+ * timer being expired has been moved to 'timer_expiring', we don't
+ * need to worry about the timer's offset changing on the timer list.
+ */
+
+#if 0
+ fprintf(stderr, "calling user callback for timer id %d\n", (int) t->id);
+ fflush(stderr);
+#endif
+
+ duk_push_number(ctx, (double) t->id);
+ duk_get_prop(ctx, -2); /* -> [ ... stash eventTimers func ] */
+ rc = duk_pcall(ctx, 0 /*nargs*/); /* -> [ ... stash eventTimers retval ] */
+ if (rc != 0) {
+#if 0
+ fprintf(stderr, "timer callback failed for timer %d: %s\n", (int) t->id, duk_to_string(ctx, -1));
+ fflush(stderr);
+#endif
+ }
+ duk_pop(ctx); /* ignore errors for now -> [ ... stash eventTimers ] */
+
+ if (t->removed) {
+ /* One-shot timer (always removed) or removed by user callback. */
+#if 0
+ fprintf(stderr, "deleting callback state for timer %d\n", (int) t->id);
+ fflush(stderr);
+#endif
+ duk_push_number(ctx, (double) t->id);
+ duk_del_prop(ctx, -2);
+ } else {
+ /* Interval timer, not removed by user callback. Queue back to
+ * timer list and bubble to its final sorted position.
+ */
+#if 0
+ fprintf(stderr, "queueing timer %d back into active list\n", (int) t->id);
+ fflush(stderr);
+#endif
+ if (timer_count >= MAX_TIMERS) {
+ duk_error(ctx, DUK_ERR_RANGE_ERROR, "out of timer slots");
+ }
+ memcpy((void *) (timer_list + timer_count), (void *) t, sizeof(ev_timer));
+ timer_count++;
+ bubble_last_timer();
+ }
+ }
+
+ memset((void *) &timer_expiring, 0, sizeof(ev_timer));
+
+ duk_pop_2(ctx); /* -> [ ... ] */
+}
+
+static void compact_poll_list(void) {
+ int i, j, n;
+
+ /* i = input index
+ * j = output index (initially same as i)
+ */
+
+ n = poll_count;
+ for (i = 0, j = 0; i < n; i++) {
+ struct pollfd *pfd = poll_list + i;
+ if (pfd->fd == 0) {
+ /* keep output index the same */
+#if 0
+ fprintf(stderr, "remove pollfd (index %d): fd=%d, events=%d, revents=%d\n",
+ i, pfd->fd, pfd->events, pfd->revents),
+ fflush(stderr);
+#endif
+
+ continue;
+ }
+#if 0
+ fprintf(stderr, "keep pollfd (index %d -> %d): fd=%d, events=%d, revents=%d\n",
+ i, j, pfd->fd, pfd->events, pfd->revents),
+ fflush(stderr);
+#endif
+ if (i != j) {
+ /* copy only if indices have diverged */
+ memcpy((void *) (poll_list + j), (void *) (poll_list + i), sizeof(struct pollfd));
+ }
+ j++;
+ }
+
+ if (j < poll_count) {
+ /* zeroize unused entries for sanity */
+ memset((void *) (poll_list + j), 0, (poll_count - j) * sizeof(struct pollfd));
+ }
+
+ poll_count = j;
+}
+
+int eventloop_run(duk_context *ctx) {
+ ev_timer *t;
+ double now;
+ double diff;
+ int timeout;
+ int rc;
+ int i, n;
+ int idx_eventloop;
+ int idx_fd_handler;
+
+ /* The Ecmascript poll handler is passed through EventLoop.fdPollHandler
+ * which c_eventloop.js sets before we come here.
+ */
+ duk_push_global_object(ctx);
+ duk_get_prop_string(ctx, -1, "EventLoop");
+ duk_get_prop_string(ctx, -1, "fdPollHandler"); /* -> [ global EventLoop fdPollHandler ] */
+ idx_fd_handler = duk_get_top_index(ctx);
+ idx_eventloop = idx_fd_handler - 1;
+
+ for (;;) {
+ /*
+ * Expire timers.
+ */
+
+ expire_timers(ctx);
+
+ /*
+ * If exit requested, bail out as fast as possible.
+ */
+
+ if (exit_requested) {
+#if 0
+ fprintf(stderr, "exit requested, exiting event loop\n");
+ fflush(stderr);
+#endif
+ break;
+ }
+
+ /*
+ * Compact poll list by removing pollfds with fd == 0.
+ */
+
+ compact_poll_list();
+
+ /*
+ * Determine poll() timeout (as close to poll() as possible as
+ * the wait is relative).
+ */
+
+ now = get_now();
+ t = find_nearest_timer();
+ if (t) {
+ diff = t->target - now;
+ if (diff < MIN_WAIT) {
+ diff = MIN_WAIT;
+ } else if (diff > MAX_WAIT) {
+ diff = MAX_WAIT;
+ }
+ timeout = (int) diff; /* clamping ensures that fits */
+ } else {
+ if (poll_count == 0) {
+#if 0
+ fprintf(stderr, "no timers and no sockets to poll, exiting\n");
+ fflush(stderr);
+#endif
+ break;
+ }
+ timeout = (int) MAX_WAIT;
+ }
+
+ /*
+ * Poll for activity or timeout.
+ */
+
+#if 0
+ fprintf(stderr, "going to poll, timeout %d ms, pollfd count %d\n", timeout, poll_count);
+ fflush(stderr);
+#endif
+
+ rc = poll(poll_list, poll_count, timeout);
+#if 0
+ fprintf(stderr, "poll rc: %d\n", rc);
+ fflush(stderr);
+#endif
+ if (rc < 0) {
+ /* error */
+ } else if (rc == 0) {
+ /* timeout */
+ } else {
+ /* 'rc' fds active */
+ }
+
+ /*
+ * Check socket activity, handle all sockets. Handling is offloaded to
+ * Ecmascript code (fd + revents).
+ *
+ * If FDs are removed from the poll list while we're processing callbacks,
+ * the entries are simply marked unused (fd set to 0) without actually
+ * removing them from the poll list. This ensures indices are not
+ * disturbed. The poll list is compacted before next poll().
+ */
+
+ n = (rc == 0 ? 0 : poll_count); /* if timeout, no need to check pollfd */
+ for (i = 0; i < n; i++) {
+ struct pollfd *pfd = poll_list + i;
+
+ if (pfd->fd == 0) {
+ /* deleted, perhaps by previous callback */
+ continue;
+ }
+
+ if (pfd->revents) {
+#if 0
+ fprintf(stderr, "fd %d has revents: %d\n", (int) pfd->fd, (int) pfd->revents);
+ fflush(stderr);
+#endif
+ duk_dup(ctx, idx_fd_handler);
+ duk_dup(ctx, idx_eventloop);
+ duk_push_int(ctx, pfd->fd);
+ duk_push_int(ctx, pfd->revents);
+ rc = duk_pcall_method(ctx, 2 /*nargs*/);
+ if (rc) {
+#if 0
+ fprintf(stderr, "fd callback failed for fd %d: %s\n", (int) pfd->fd, duk_to_string(ctx, -1));
+ fflush(stderr);
+#endif
+ }
+ duk_pop(ctx);
+
+ pfd->revents = 0;
+ }
+
+ }
+ }
+
+ duk_pop_n(ctx, 3);
+
+ return 0;
+}
+
+static int create_timer(duk_context *ctx) {
+ double delay;
+ int oneshot;
+ int idx;
+ int64_t timer_id;
+ double now;
+ ev_timer *t;
+
+ now = get_now();
+
+ /* indexes:
+ * 0 = function (callback)
+ * 1 = delay
+ * 2 = boolean: oneshot
+ */
+
+ delay = duk_require_number(ctx, 1);
+ if (delay < MIN_DELAY) {
+ delay = MIN_DELAY;
+ }
+ oneshot = duk_require_boolean(ctx, 2);
+
+ if (timer_count >= MAX_TIMERS) {
+ duk_error(ctx, DUK_ERR_RANGE_ERROR, "out of timer slots");
+ }
+ idx = timer_count++;
+ timer_id = timer_next_id++;
+ t = timer_list + idx;
+
+ memset((void *) t, 0, sizeof(ev_timer));
+ t->id = timer_id;
+ t->target = now + delay;
+ t->delay = delay;
+ t->oneshot = oneshot;
+ t->removed = 0;
+
+ /* Timer is now at the last position; use swaps to "bubble" it to its
+ * correct sorted position.
+ */
+
+ bubble_last_timer();
+
+ /* Finally, register the callback to the global stash 'eventTimers' object. */
+
+ duk_push_global_stash(ctx);
+ duk_get_prop_string(ctx, -1, "eventTimers"); /* -> [ func delay oneshot stash eventTimers ] */
+ duk_push_number(ctx, (double) timer_id);
+ duk_dup(ctx, 0);
+ duk_put_prop(ctx, -3); /* eventTimers[timer_id] = callback */
+
+ /* Return timer id. */
+
+ duk_push_number(ctx, (double) timer_id);
+#if 0
+ fprintf(stderr, "created timer id: %d\n", (int) timer_id);
+ fflush(stderr);
+#endif
+ return 1;
+}
+
+static int delete_timer(duk_context *ctx) {
+ int i, n;
+ int64_t timer_id;
+ ev_timer *t;
+ int found = 0;
+
+ /* indexes:
+ * 0 = timer id
+ */
+
+ timer_id = (int64_t) duk_require_number(ctx, 0);
+
+ /*
+ * Unlike insertion, deletion needs a full scan of the timer list
+ * and an expensive remove. If no match is found, nothing is deleted.
+ * Caller gets a boolean return code indicating match.
+ *
+ * When a timer is being expired and its user callback is running,
+ * the timer has been moved to 'timer_expiring' and its deletion
+ * needs special handling: just mark it to-be-deleted and let the
+ * expiry code remove it.
+ */
+
+ t = &timer_expiring;
+ if (t->id == timer_id) {
+ t->removed = 1;
+ duk_push_true(ctx);
+#if 0
+ fprintf(stderr, "deleted expiring timer id: %d\n", (int) timer_id);
+ fflush(stderr);
+#endif
+ return 1;
+ }
+
+ n = timer_count;
+ for (i = 0; i < n; i++) {
+ t = timer_list + i;
+ if (t->id == timer_id) {
+ found = 1;
+
+ /* Shift elements downwards to keep the timer list dense
+ * (no need if last element).
+ */
+ if (i < timer_count - 1) {
+ memmove((void *) t, (void *) (t + 1), (timer_count - i - 1) * sizeof(ev_timer));
+ }
+
+ /* Zero last element for clarity. */
+ memset((void *) (timer_list + n - 1), 0, sizeof(ev_timer));
+
+ /* Update timer_count. */
+ timer_count--;
+
+ /* The C state is now up-to-date, but we still need to delete
+ * the timer callback state from the global 'stash'.
+ */
+
+ duk_push_global_stash(ctx);
+ duk_get_prop_string(ctx, -1, "eventTimers"); /* -> [ timer_id stash eventTimers ] */
+ duk_push_number(ctx, (double) timer_id);
+ duk_del_prop(ctx, -2); /* delete eventTimers[timer_id] */
+
+#if 0
+ fprintf(stderr, "deleted timer id: %d\n", (int) timer_id);
+ fflush(stderr);
+#endif
+ break;
+ }
+ }
+
+#if 0
+ if (!found) {
+ fprintf(stderr, "trying to delete timer id %d, but not found; ignoring\n", (int) timer_id);
+ fflush(stderr);
+ }
+#endif
+
+ duk_push_boolean(ctx, found);
+ return 1;
+}
+
+static int listen_fd(duk_context *ctx) {
+ int fd = duk_require_int(ctx, 0);
+ int events = duk_require_int(ctx, 1);
+ int i, n;
+ struct pollfd *pfd;
+
+#if 0
+ fprintf(stderr, "listen_fd: fd=%d, events=%d\n", fd, events);
+ fflush(stderr);
+#endif
+ /* events == 0 means stop listening to the FD */
+
+ n = poll_count;
+ for (i = 0; i < n; i++) {
+ pfd = poll_list + i;
+ if (pfd->fd == fd) {
+#if 0
+ fprintf(stderr, "listen_fd: fd found at index %d\n", i);
+ fflush(stderr);
+#endif
+ if (events == 0) {
+ /* mark to-be-deleted, cleaned up by next poll */
+ pfd->fd = 0;
+ } else {
+ pfd->events = events;
+ }
+ return 0;
+ }
+ }
+
+ /* not found, append to list */
+#if 0
+ fprintf(stderr, "listen_fd: fd not found on list, add new entry\n");
+ fflush(stderr);
+#endif
+
+ if (poll_count >= MAX_FDS) {
+ duk_error(ctx, DUK_ERR_ERROR, "out of fd slots");
+ }
+
+ pfd = poll_list + poll_count;
+ pfd->fd = fd;
+ pfd->events = events;
+ pfd->revents = 0;
+ poll_count++;
+
+ return 0;
+}
+
+static int request_exit(duk_context *ctx) {
+ (void) ctx;
+ exit_requested = 1;
+ return 0;
+}
+
+static duk_function_list_entry eventloop_funcs[] = {
+ { "createTimer", create_timer, 3 },
+ { "deleteTimer", delete_timer, 1 },
+ { "listenFd", listen_fd, 2 },
+ { "requestExit", request_exit, 0 },
+ { NULL, NULL, 0 }
+};
+
+void eventloop_register(duk_context *ctx) {
+ memset((void *) timer_list, 0, MAX_TIMERS * sizeof(ev_timer));
+ memset((void *) &timer_expiring, 0, sizeof(ev_timer));
+ memset((void *) poll_list, 0, MAX_FDS * sizeof(struct pollfd));
+
+ /* Set global 'EventLoop'. */
+ duk_push_global_object(ctx);
+ duk_push_object(ctx);
+ duk_put_function_list(ctx, -1, eventloop_funcs);
+ duk_put_prop_string(ctx, -2, "EventLoop");
+ duk_pop(ctx);
+
+ /* Initialize global stash 'eventTimers'. */
+ duk_push_global_stash(ctx);
+ duk_push_object(ctx);
+ duk_put_prop_string(ctx, -2, "eventTimers");
+ duk_pop(ctx);
+}
projects / ceph.git / blobdiff