FadingCounter.cc
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1/*
2 * Copyright (C) 1996-2022 The Squid Software Foundation and contributors
3 *
4 * Squid software is distributed under GPLv2+ license and includes
5 * contributions from numerous individuals and organizations.
6 * Please see the COPYING and CONTRIBUTORS files for details.
7 */
8
9#include "squid.h"
10#include "base/TextException.h"
11#include "debug/Stream.h"
12#include "FadingCounter.h"
13#include "time/gadgets.h"
14
15#include <cmath>
16
17FadingCounter::FadingCounter(): horizon(-1), precision(10), delta(-1),
18 lastTime(0), total(0)
19{
20 counters.reserve(precision);
21 while (counters.size() < static_cast<unsigned int>(precision))
22 counters.push_back(0);
23}
24
26{
27 for (int i = 0; i < precision; ++i)
28 counters[i] = 0;
30 total = 0;
31}
32
33void FadingCounter::configure(double newHorizon)
34{
35 if (fabs(newHorizon - horizon) >= 1e-3) { // diff exceeds one millisecond
36 clear(); // for simplicity
37 horizon = newHorizon;
38 delta = horizon / precision; // may become negative or zero
39 }
40}
41
42int FadingCounter::count(int howMany)
43{
44 Must(howMany >= 0);
45
46 if (delta < 0)
47 return total += howMany; // forget nothing
48
49 if (horizon < 1e-3) // (e.g., zero)
50 return howMany; // remember nothing
51
52 const double deltas = (current_dtime - lastTime) / delta;
53 if (deltas >= precision || current_dtime < lastTime) {
54 clear(); // forget all values
55 } else {
56 // forget stale values, if any
57 // fmod() or "current_dtime/delta" will overflow int for small deltas
58 const int lastSlot = static_cast<int>(fmod(lastTime, horizon) / delta);
59 const int staleSlots = static_cast<int>(deltas);
60 for (int i = 0, s = lastSlot + 1; i < staleSlots; ++i, ++s) {
61 const int idx = s % precision;
62 total -= counters[idx];
63 counters[idx] = 0;
64 Must(total >= 0);
65 }
66 }
67
68 // apply new information
70 const int curSlot = static_cast<int>(fmod(lastTime, horizon) / delta);
71 counters[curSlot % precision] += howMany;
72 total += howMany;
73 Must(total >= 0);
74
75 return total;
76}
77
#define Must(condition)
Definition: TextException.h:71
std::vector< int > counters
events per delta (possibly stale)
Definition: FadingCounter.h:36
int total
number of remembered events (possibly stale)
Definition: FadingCounter.h:37
int count(int howMany)
count fresh, return #events remembered
double horizon
read-only memory horizon in seconds; older events are forgotten
Definition: FadingCounter.h:29
void clear()
forgets all events
double delta
sub-interval duration = horizon/precision
Definition: FadingCounter.h:33
void configure(double horizonSeconds)
0=remember nothing; -1=forget nothing; new value triggers clear()
double lastTime
time of the last update
Definition: FadingCounter.h:35
const int precision
#counting slots, controls measur. accuracy
Definition: FadingCounter.h:32
double current_dtime
the current UNIX time in seconds (with microsecond precision)
Definition: stub_libtime.cc:19

 

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