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/*
Copyright 2014 Martin Pärtel <martin.partel@gmail.com>
This file is part of bindfs.
bindfs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.
bindfs 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with bindfs. If not, see <http://www.gnu.org/licenses/>.
*/
#define _XOPEN_SOURCE 700 /* for gettimeofday() on freebsd, and for nanosleep() */
#include "rate_limiter.h"
#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <time.h>
#include <sys/time.h>
const double rate_limiter_idle_credit = -0.2;
double gettimeofday_clock()
{
struct timeval tv;
gettimeofday(&tv, NULL);
return tv.tv_sec + tv.tv_usec * 0.000001;
}
static void sleep_seconds(double s)
{
struct timespec ts;
ts.tv_sec = (time_t)s;
ts.tv_nsec = (long)((s - ts.tv_sec) * 1000000000L);
/* Guard against float imprecision */
if (ts.tv_nsec > 999999999L) {
ts.tv_nsec = 999999999L;
} else if (ts.tv_nsec < 0L) {
ts.tv_nsec = 0L;
}
nanosleep(&ts, NULL);
}
void rate_limiter_init(RateLimiter *limiter, double rate, double (*clock)())
{
limiter->rate = rate;
limiter->clock = clock;
limiter->last_modified = limiter->clock();
limiter->accumulated_sleep_time = rate_limiter_idle_credit;
pthread_mutexattr_t attr;
int status = pthread_mutexattr_init(&attr);
assert(status == 0);
status = pthread_mutex_init(&limiter->mutex, &attr);
assert(status == 0);
status = pthread_mutexattr_destroy(&attr);
assert(status == 0);
}
void rate_limiter_wait(RateLimiter* limiter, size_t size)
{
double time_to_sleep = rate_limiter_wait_nosleep(limiter, size);
sleep_seconds(time_to_sleep);
}
double rate_limiter_wait_nosleep(RateLimiter* limiter, size_t size)
{
int status = pthread_mutex_lock(&limiter->mutex);
assert(status == 0);
double time_to_add = size / limiter->rate;
double now = limiter->clock();
double elapsed = now - limiter->last_modified;
if (elapsed < 0) {
elapsed = 0;
}
double time_to_sleep = limiter->accumulated_sleep_time;
time_to_sleep -= elapsed;
if (time_to_sleep < rate_limiter_idle_credit) {
time_to_sleep = rate_limiter_idle_credit;
}
time_to_sleep += time_to_add;
limiter->accumulated_sleep_time = time_to_sleep;
limiter->last_modified = now;
status = pthread_mutex_unlock(&limiter->mutex);
assert(status == 0);
return time_to_sleep;
}
void rate_limiter_destroy(RateLimiter *limiter)
{
int status = pthread_mutex_destroy(&limiter->mutex);
assert(status == 0);
}
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