1/*
2 * nghttp2 - HTTP/2 C Library
3 *
4 * Copyright (c) 2023 nghttp2 contributors
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining
7 * a copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sublicense, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be
15 * included in all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
19 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
21 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
22 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
23 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24 */
25#include "nghttp2_ratelim.h"
26#include "nghttp2_helper.h"
27
28void nghttp2_ratelim_init(nghttp2_ratelim *rl, uint64_t burst, uint64_t rate) {
29  rl->val = rl->burst = burst;
30  rl->rate = rate;
31  rl->tstamp = 0;
32}
33
34void nghttp2_ratelim_update(nghttp2_ratelim *rl, uint64_t tstamp) {
35  uint64_t d, gain;
36
37  if (tstamp == rl->tstamp) {
38    return;
39  }
40
41  if (tstamp > rl->tstamp) {
42    d = tstamp - rl->tstamp;
43  } else {
44    d = 1;
45  }
46
47  rl->tstamp = tstamp;
48
49  if (UINT64_MAX / d < rl->rate) {
50    rl->val = rl->burst;
51
52    return;
53  }
54
55  gain = rl->rate * d;
56
57  if (UINT64_MAX - gain < rl->val) {
58    rl->val = rl->burst;
59
60    return;
61  }
62
63  rl->val += gain;
64  rl->val = nghttp2_min(rl->val, rl->burst);
65}
66
67int nghttp2_ratelim_drain(nghttp2_ratelim *rl, uint64_t n) {
68  if (rl->val < n) {
69    return -1;
70  }
71
72  rl->val -= n;
73
74  return 0;
75}
76