1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
|
/*
* Ouroboros - Copyright (C) 2016 - 2026
*
* Link capacity codes
*
* Dimitri Staessens <dimitri@ouroboros.rocks>
* Sander Vrijders <sander@ouroboros.rocks>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., http://www.fsf.org/about/contact/.
*/
/*
* Rate <-> 8-bit code (cap_enc / cap_dec): the high 6 bits hold a
* band e = floor(log2 rate), the low 2 a quarter k splitting the
* band at 256 * 2^(k/4) = {256, 304, 362, 431}; code = 4 * e + k.
* Capacity is only ever needed to order-of-magnitude accuracy.
*/
#include "cap.h"
uint8_t cap_enc(uint64_t rate)
{
static const uint16_t thr[3] = {304, 362, 431};
uint64_t r = rate; /* copy halved to find band */
unsigned e = 0; /* band: floor log2 rate */
unsigned k = 0; /* quarter within band 0..3 */
unsigned c; /* code = 4 * band + quarter */
uint16_t top; /* rate scaled to [256, 512) */
if (rate == 0)
return 0;
while (r > 1) {
r >>= 1;
e++;
}
if (e >= 8)
top = (uint16_t) (rate >> (e - 8));
else
top = (uint16_t) (rate << (8 - e));
while (k < 3 && top >= thr[k])
k++;
c = 4 * e + k;
if (c == 0)
c = 1; /* 0 means unknown */
return (uint8_t) c;
}
uint64_t cap_dec(uint8_t c)
{
static const uint16_t m[4] = {256, 304, 362, 431};
unsigned e = c >> 2; /* band = c >> 2 */
unsigned k = c & 3; /* quarter = c & 3 */
if (c == 0)
return 0;
if (e >= 8)
return (uint64_t) m[k] << (e - 8);
return ((uint64_t) m[k] << e) >> 8;
}
uint8_t cap_min(uint8_t a,
uint8_t b)
{
if (a == 0)
return b;
if (b == 0)
return a;
return a < b ? a : b;
}
void cap_stamp(uint8_t * pci,
uint8_t own)
{
if (own == 0)
return;
if (*pci == 0 || own < *pci)
*pci = own;
}
|
