Stopwatch.h

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/*
 * Copyright (C) 1996-2025 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */
 
#ifndef SQUID_SRC_BASE_STOPWATCH_H
#define SQUID_SRC_BASE_STOPWATCH_H
 
#include <chrono>
#include <cstdint>
 
class Stopwatch
{
public:
    // std::clock() is not precise enough and raises (minor) overflow concerns;
    // clock_gettime(CLOCK_PROCESS_CPUTIME_ID) may not be portable, and both may
    // include CPU ticks accumulated by [AUFS] threads. When the code does
    // not sleep (i.e. always does something), wall clock time is better.
 
    // Do not be tempted by std::high_resolution_clock spelling! That clock has
    // unpredictable properties. It may not be steady (i.e. !is_steady). Its use
    // is discouraged[1,3]. In most implementations, the steady_clock resolution
    // is just as high[1,2,3].
    // [1]: https://en.cppreference.com/w/cpp/chrono/high_resolution_clock
    // [2]: https://howardhinnant.github.io/clock_survey.html
    // [3]: https://stackoverflow.com/questions/38252022/does-standard-c11-guarantee-that-high-resolution-clock-measure-real-time-non
 
    using Clock = std::chrono::steady_clock;
 
    Stopwatch();
 
    bool running() const { return resumes_ > pauses_; }
 
    bool ran() const { return resumes_ > 0; }
 
    Clock::duration total() const;
 
    void resume();
 
    void pause();
 
private:
    Clock::time_point runStart_; 
 
    Clock::duration subtotal_; 
 
    uint64_t resumes_ = 0; 
    uint64_t pauses_ = 0; 
};
 
#endif /* SQUID_SRC_BASE_STOPWATCH_H */