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1 /*
2  * tc_core.c		TC core library.
3  *
4  *		This program is free software; you can redistribute it and/or
5  *		modify it under the terms of the GNU General Public License
6  *		as published by the Free Software Foundation; either version
7  *		2 of the License, or (at your option) any later version.
8  *
9  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10  *
11  */
12 
13 #include <stdio.h>
14 #include <stdlib.h>
15 #include <unistd.h>
16 #include <syslog.h>
17 #include <fcntl.h>
18 #include <math.h>
19 #include <sys/socket.h>
20 #include <netinet/in.h>
21 #include <arpa/inet.h>
22 #include <string.h>
23 
24 #include "tc_core.h"
25 
tc_setup_estimator(unsigned A,unsigned time_const,struct tc_estimator * est)26 int tc_setup_estimator(unsigned A, unsigned time_const, struct tc_estimator *est)
27 {
28 	for (est->interval=0; est->interval<=5; est->interval++) {
29 		if (A <= (1<<est->interval)*(TIME_UNITS_PER_SEC/4))
30 			break;
31 	}
32 	if (est->interval > 5)
33 		return -1;
34 	est->interval -= 2;
35 	for (est->ewma_log=1; est->ewma_log<32; est->ewma_log++) {
36 		double w = 1.0 - 1.0/(1<<est->ewma_log);
37 		if (A/(-log(w)) > time_const)
38 			break;
39 	}
40 	est->ewma_log--;
41 	if (est->ewma_log==0 || est->ewma_log >= 31)
42 		return -1;
43 	return 0;
44 }
45