tarsnap/libcperciva/events/events.c

#include <sys/time.h>

#include <signal.h>
#include <stdlib.h>
#include <string.h>

#include "mpool.h"

#include "events.h"
#include "events_internal.h"

/* Event structure. */
struct eventrec {
	int (* func)(void *);
	void * cookie;
};

MPOOL(eventrec, struct eventrec, 4096);

/* Zero timeval, for use with non-blocking event runs. */
static const struct timeval tv_zero = {0, 0};

/* We want to interrupt a running event loop. */
static volatile sig_atomic_t interrupt_requested = 0;

/**
 * events_mkrec(func, cookie):
 * Package ${func}, ${cookie} into a struct eventrec.
 */
struct eventrec *
events_mkrec(int (* func)(void *), void * cookie)
{
	struct eventrec * r;

	/* Allocate structure. */
	if ((r = mpool_eventrec_malloc()) == NULL)
		goto err0;

	/* Initialize. */
	r->func = func;
	r->cookie = cookie;

	/* Success! */
	return (r);

err0:
	/* Failure! */
	return (NULL);
}

/**
 * events_freerec(r):
 * Free the eventrec ${r}.
 */
void
events_freerec(struct eventrec * r)
{

	mpool_eventrec_free(r);
}

/* Do an event.  This makes events_run cleaner. */
static inline int
doevent(struct eventrec * r)
{
	int rc;

	/* Invoke the callback. */
	rc = (r->func)(r->cookie);

	/* Free the event record. */
	mpool_eventrec_free(r);

	/* Return the status code from the callback. */
	return (rc);
}

/**
 * events_run(void):
 * Run events.  Events registered via events_immediate_register() will be run
 * first, in order of increasing ${prio} values; then events associated with
 * ready sockets registered via events_network_register(); finally, events
 * associated with expired timers registered via events_timer_register() will
 * be run.  If any event function returns a non-zero result, no further events
 * will be run and said non-zero result will be returned; on error,
 * -1 will be returned.  May be interrupted by events_interrupt(), in which
 * case 0 will be returned.  If there are runnable events, events_run() is
 * guaranteed to run at least one; but it may return while there are still
 * more runnable events.
 */
static int
events_run_internal(void)
{
	struct eventrec * r;
	struct timeval * tv;
	struct timeval tv2;
	int rc = 0;

	/* If we have any immediate events, process them and return. */
	if ((r = events_immediate_get()) != NULL) {
		while (r != NULL) {
			/* Process the event. */
			if ((rc = doevent(r)) != 0)
				goto done;

			/* Interrupt loop if requested. */
			if (interrupt_requested)
				goto done;

			/* Get the next event. */
			r = events_immediate_get();
		}

		/* We've processed at least one event; time to return. */
		goto done;
	}

	/*
	 * Figure out the maximum duration to block, and wait up to that
	 * duration for network events to become available.
	 */
	if (events_timer_min(&tv))
		goto err0;
	if (events_network_select(tv, &interrupt_requested))
		goto err1;
	free(tv);

	/*
	 * Check for available immediate events, network events, and timer
	 * events, in that order of priority; exit only when no more events
	 * are available or when interrupted.
	 */
	do {
		/* Interrupt loop if requested. */
		if (interrupt_requested)
			goto done;

		/* Run an immediate event, if one is available. */
		if ((r = events_immediate_get()) != NULL) {
			if ((rc = doevent(r)) != 0)
				goto done;
			continue;
		}

		/* Run a network event, if one is available. */
		if ((r = events_network_get()) != NULL) {
			if ((rc = doevent(r)) != 0)
				goto done;
			continue;
		}

		/* Check if any new network events are available. */
		memcpy(&tv2, &tv_zero, sizeof(struct timeval));
		if (events_network_select(&tv2, &interrupt_requested))
			goto err0;
		if ((r = events_network_get()) != NULL) {
			if ((rc = doevent(r)) != 0)
				goto done;
			continue;
		}

		/* Run a timer event, if one is available. */
		if (events_timer_get(&r))
			goto err0;
		if (r != NULL) {
			if ((rc = doevent(r)) != 0)
				goto done;
			continue;
		}

		/* No events available. */
		break;
	} while (1);

done:
	/* Success! */
	return (rc);

err1:
	free(tv);
err0:
	/* Failure! */
	return (-1);
}

/* Wrapper function for events_run to reset interrupt_requested. */
int
events_run(void)
{
	int rc;

	/* Call the real function. */
	rc = events_run_internal();

	/* Reset interrupt_requested after quitting the loop. */
	interrupt_requested = 0;

	/* Return status. */
	return (rc);
}

/**
 * events_spin(done):
 * Call events_run() until ${done} is non-zero (and return 0), an error occurs
 * (and return -1), or a callback returns a non-zero status (and return the
 * status code from the callback).  May be interrupted by events_interrupt()
 * (and return 0).
 */
int
events_spin(const int * done)
{
	int rc = 0;

	/* Loop until we're done or have a non-zero status. */
	while ((done[0] == 0) && (rc == 0) && (interrupt_requested == 0)) {
		/* Run events. */
		rc = events_run_internal();
	}

	/* Reset interrupt_requested after quitting the loop. */
	interrupt_requested = 0;

	/* Return status code. */
	return (rc);
}

/**
 * events_interrupt(void):
 * Halt the event loop after finishing the current event.  This function can
 * be safely called from within a signal handler.
 */
void
events_interrupt(void)
{

	/* Interrupt the event loop. */
	interrupt_requested = 1;
}

/**
 * events_shutdown(void):
 * Deprecated function; does nothing.
 */
void
events_shutdown(void)
{
}