/* timed_thread.c: Abstraction layer for timed threads
 *
 * Copyright (C) 2006-2007 Philip Kovacs pkovacs@users.sourceforge.net
 *
 * This library 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.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA.
 *
 * vim: ts=4 sw=4 noet ai cindent syntax=c
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <pthread.h>
#include <assert.h>
#include <errno.h>
#include <time.h>
#include <unistd.h>
#ifndef HAVE_CLOCK_GETTIME
#include <sys/time.h>
#endif
#include "timed_thread.h"

/* Abstraction layer for timed threads */

static int now(struct timespec *);

/* private */
struct _timed_thread {
	pthread_t thread;				/* thread itself */
	pthread_attr_t thread_attr;		/* thread attributes */
	pthread_mutex_t cs_mutex;		/* critical section mutex */
	pthread_mutex_t runnable_mutex;	/* only for the runnable_cond */
	pthread_cond_t runnable_cond;	/* signalled to stop the thread */
	void *(*start_routine)(void *);	/* thread function to run */
	void *arg;						/* thread function argument */
	struct timespec interval_time;	/* interval_usecs as a struct timespec */
	struct timespec wait_time;		/* absolute future time next timed_thread_test will wait until */
	int pipefd[2];
	int die;
};

/* linked list of created threads */
typedef struct _timed_thread_list {
	timed_thread *p_timed_thread;
	timed_thread **addr_of_p_timed_thread;
	struct _timed_thread_list *next;
} timed_thread_node, timed_thread_list;

static timed_thread_list *p_timed_thread_list_head = NULL;
static timed_thread_list *p_timed_thread_list_tail = NULL;

int timed_thread_readfd(timed_thread *p_timed_thread)
{
	return p_timed_thread->pipefd[0];
}

static int now(struct timespec *abstime)
{
#ifndef HAVE_CLOCK_GETTIME
	struct timeval tv;
#endif

	if (!abstime) {
		return -1;
	}

#ifdef HAVE_CLOCK_GETTIME
	return clock_gettime(CLOCK_REALTIME, abstime);
#else
	/* fallback to gettimeofday () */
	if (gettimeofday(&tv, NULL) != 0) {
		return -1;
	}

	abstime->tv_sec = tv.tv_sec;
	abstime->tv_nsec = tv.tv_usec * 1000;
	return 0;
#endif
}

/* create a timed thread (object creation only) */
timed_thread *timed_thread_create(void *start_routine(void *), void *arg,
		unsigned int interval_usecs)
{
	timed_thread *p_timed_thread;

	assert(start_routine != NULL);
	assert(interval_usecs >= MINIMUM_INTERVAL_USECS);

	if ((p_timed_thread = calloc(sizeof(timed_thread), 1)) == 0) {
		return NULL;
	}

	/* create thread pipe (used to tell threads to die) */
	if (pipe(p_timed_thread->pipefd)) {
		return NULL;
	}

	/* init attributes, e.g. joinable thread */
	pthread_attr_init(&p_timed_thread->thread_attr);
	pthread_attr_setdetachstate(&p_timed_thread->thread_attr,
			PTHREAD_CREATE_JOINABLE);
	/* init mutexes */
	pthread_mutex_init(&p_timed_thread->cs_mutex, NULL);
	pthread_mutex_init(&p_timed_thread->runnable_mutex, NULL);
	/* init cond */
	pthread_cond_init(&p_timed_thread->runnable_cond, NULL);

	p_timed_thread->start_routine = start_routine;
	p_timed_thread->arg = arg;

	/* set wait time to current time */
	if (now(&p_timed_thread->wait_time)) {
		return NULL;
	}

	/* seconds portion of the microseconds interval */
	p_timed_thread->interval_time.tv_sec = (time_t) (interval_usecs / 1000000);
	/* remaining microseconds convert to nanoseconds */
	p_timed_thread->interval_time.tv_nsec =
		(long) ((interval_usecs % 1000000) * 1000);

	/* printf("interval_time.tv_sec = %li, .tv_nsec = %li\n",
	   p_timed_thread->interval_time.tv_sec,
	   p_timed_thread->interval_time.tv_nsec); */
	return p_timed_thread;
}

/* run a timed thread (drop the thread and run it) */
int timed_thread_run(timed_thread *p_timed_thread)
{
	return pthread_create(&p_timed_thread->thread, &p_timed_thread->thread_attr,
			p_timed_thread->start_routine, p_timed_thread->arg);
}

/* destroy a timed thread.
 * optional addr_of_p_timed_thread to set callers pointer to NULL as a
 * convenience. */
void timed_thread_destroy(timed_thread *p_timed_thread,
		timed_thread **addr_of_p_timed_thread)
{
	assert(p_timed_thread != NULL);
	assert((addr_of_p_timed_thread == NULL)
			|| (*addr_of_p_timed_thread == p_timed_thread));

	/* signal thread to stop */
	pthread_mutex_lock(&p_timed_thread->runnable_mutex);
	pthread_cond_signal(&p_timed_thread->runnable_cond);
	p_timed_thread->die = 1;
	pthread_mutex_unlock(&p_timed_thread->runnable_mutex);
	write(p_timed_thread->pipefd[1], "die", 3);

	/* join the terminating thread */
	if (p_timed_thread->thread) {
		pthread_join(p_timed_thread->thread, NULL);
	}

	/* clean up */
	pthread_attr_destroy(&p_timed_thread->thread_attr);
	pthread_mutex_destroy(&p_timed_thread->cs_mutex);
	pthread_mutex_destroy(&p_timed_thread->runnable_mutex);
	pthread_cond_destroy(&p_timed_thread->runnable_cond);

	free(p_timed_thread);
	if (addr_of_p_timed_thread) {
		*addr_of_p_timed_thread = NULL;
	}
}

/* lock a timed thread for critical section activity */
int timed_thread_lock(timed_thread *p_timed_thread)
{
	assert(p_timed_thread != NULL);

	return pthread_mutex_lock(&p_timed_thread->cs_mutex);
}

/* unlock a timed thread after critical section activity */
int timed_thread_unlock(timed_thread *p_timed_thread)
{
	assert(p_timed_thread != NULL);

	return pthread_mutex_unlock(&p_timed_thread->cs_mutex);
}

/* thread waits interval_usecs for runnable_cond to be signaled.
 * returns 1 if signaled, -1 on error, and 0 otherwise.
 * caller should call timed_thread_exit() on any non-zero return value. */
int timed_thread_test(timed_thread *p_timed_thread, int override_wait_time)
{
	struct timespec now_time;
	int rc;

	assert(p_timed_thread != NULL);

	/* acquire runnable_cond mutex */
	if (pthread_mutex_lock(&p_timed_thread->runnable_mutex)) {
		/* could not acquire runnable_cond mutex,
		 * so tell caller to exit thread */
		return -1;
	}

	if (p_timed_thread->die) {
		/* if we were kindly asked to die, then die */
		return 1;
	}

	if (override_wait_time && now(&p_timed_thread->wait_time)) {
		return -1;
	}

	/* release mutex and wait until future time for runnable_cond to signal */
	rc = pthread_cond_timedwait(&p_timed_thread->runnable_cond,
			&p_timed_thread->runnable_mutex, &p_timed_thread->wait_time);
	/* mutex re-acquired, so release it */
	pthread_mutex_unlock(&p_timed_thread->runnable_mutex);
	
	if (now(&now_time)) {
		return -1;
	}

	if (rc == 0) {
		/* runnable_cond was signaled, so tell caller to exit thread */
		return 1;
	}

	/* absolute future time for next pass */
	p_timed_thread->wait_time.tv_sec += p_timed_thread->interval_time.tv_sec;
	p_timed_thread->wait_time.tv_nsec += p_timed_thread->interval_time.tv_nsec;
	p_timed_thread->wait_time.tv_sec += p_timed_thread->wait_time.tv_nsec / 1000000000;
	p_timed_thread->wait_time.tv_nsec = p_timed_thread->wait_time.tv_nsec % 1000000000;

	/* ensure our future wait time is sane */
	if (p_timed_thread->wait_time.tv_sec > (now_time.tv_sec + p_timed_thread->interval_time.tv_sec) || p_timed_thread->wait_time.tv_sec < now_time.tv_sec) {
		p_timed_thread->wait_time.tv_sec = now_time.tv_sec + p_timed_thread->interval_time.tv_sec;
		p_timed_thread->wait_time.tv_nsec = now_time.tv_nsec + p_timed_thread->interval_time.tv_nsec;
		p_timed_thread->wait_time.tv_sec += p_timed_thread->wait_time.tv_nsec / 1000000000;
		p_timed_thread->wait_time.tv_nsec = p_timed_thread->wait_time.tv_nsec % 1000000000;
	}

	/* tell caller not to exit yet */
	return 0;
}

/* exit a timed thread */
void timed_thread_exit(timed_thread *p_timed_thread)
{
	assert(p_timed_thread != NULL);

	close(p_timed_thread->pipefd[0]);
	close(p_timed_thread->pipefd[1]);

	pthread_exit(NULL);
}

/* register a timed thread for future destruction via
 * timed_thread_destroy_registered_threads() */
int timed_thread_register(timed_thread *p_timed_thread,
		timed_thread **addr_of_p_timed_thread)
{
	timed_thread_node *p_node;

	assert((addr_of_p_timed_thread == NULL)
			|| (*addr_of_p_timed_thread == p_timed_thread));

	if ((p_node = calloc(sizeof(timed_thread_node), 1)) == 0) {
		return 0;
	}

	p_node->p_timed_thread = p_timed_thread;
	p_node->addr_of_p_timed_thread = addr_of_p_timed_thread;
	p_node->next = NULL;

	if (!p_timed_thread_list_tail) {
		/* first node of empty list */
		p_timed_thread_list_tail = p_node;
		p_timed_thread_list_head = p_node;
	} else {
		/* add node to tail of non-empty list */
		p_timed_thread_list_tail->next = p_node;
		p_timed_thread_list_tail = p_node;
	}

	return 0;
}

/* destroy all registered timed threads */
void timed_thread_destroy_registered_threads(void)
{
	timed_thread_node *p_node, *p_next;

	for (p_node = p_timed_thread_list_head; p_node; p_node = p_next) {
		p_next = p_node->next;
		timed_thread_destroy(p_node->p_timed_thread,
				p_node->addr_of_p_timed_thread);
		free(p_node);
		p_node = NULL;
	}

	p_timed_thread_list_head = NULL;
	p_timed_thread_list_tail = NULL;
}