time_utils.hpp

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// SPDX-License-Identifier: MIT
#pragma once
#ifndef TIME_SHIELD_HEADER_CORE_TIME_UTILS_HPP_INCLUDED
#define TIME_SHIELD_HEADER_CORE_TIME_UTILS_HPP_INCLUDED
 
 
#include "config.hpp"
#include "types.hpp"
#include "constants.hpp"
 
#include <chrono>
#include <limits>       // For std::numeric_limits
#include <ctime>        // For clock_t and timespec (POSIX)
#include <time.h>       // For clock(), times(), etc.
#include <mutex>        // For std::once_flag
 
#if TIME_SHIELD_PLATFORM_WINDOWS
#   ifndef WIN32_LEAN_AND_MEAN
#       define WIN32_LEAN_AND_MEAN
#   endif
#   ifndef NOMINMAX
#       define NOMINMAX
#   endif
#   include <Windows.h>
#elif TIME_SHIELD_PLATFORM_UNIX
#   include <unistd.h>
#   include <sys/resource.h>
#   include <sys/times.h>
#   include <time.h>
#else
#   error "Unsupported platform for get_cpu_time()"
#endif
 
namespace time_shield {
 
    inline struct timespec get_timespec_impl() noexcept {
        // https://en.cppreference.com/w/c/chrono/timespec_get
        struct timespec ts;
#       if defined(CLOCK_REALTIME)
        clock_gettime(CLOCK_REALTIME, &ts); // POSIX implementation
#       else
        timespec_get(&ts, TIME_UTC);
#       endif
        return ts;
    }
 
    inline int64_t now_realtime_us() {
#       if TIME_SHIELD_PLATFORM_WINDOWS
        static std::once_flag init_flag;
        static int64_t s_perf_freq = 0;
        static int64_t s_anchor_perf = 0;
        static int64_t s_anchor_realtime_us = 0;
 
        std::call_once(init_flag, []() {
            LARGE_INTEGER freq = {};
            LARGE_INTEGER counter = {};
            ::QueryPerformanceFrequency(&freq);
            ::QueryPerformanceCounter(&counter);
 
            s_perf_freq   = static_cast<int64_t>(freq.QuadPart);
            s_anchor_perf = static_cast<int64_t>(counter.QuadPart);
 
            FILETIME ft;
            ::GetSystemTimeAsFileTime(&ft);
 
            ULARGE_INTEGER uli;
            uli.LowPart  = ft.dwLowDateTime;
            uli.HighPart = ft.dwHighDateTime;
 
            // 100ns ticks since 1601-01-01 to 1970-01-01 (signed constant!)
            const int64_t k_epoch_diff_100ns = 116444736000000000LL;
 
            const int64_t filetime_100ns = static_cast<int64_t>(uli.QuadPart);
            // Convert 100ns since 1601 -> us since 1970
            s_anchor_realtime_us = (filetime_100ns - k_epoch_diff_100ns) / 10;
        });
 
        LARGE_INTEGER now = {};
        ::QueryPerformanceCounter(&now);
 
        const int64_t now_ticks   = static_cast<int64_t>(now.QuadPart);
        const int64_t delta_ticks = now_ticks - s_anchor_perf;
 
        // Avoid overflow of (delta_ticks * 1000000)
        const int64_t q = delta_ticks / s_perf_freq;
        const int64_t r = delta_ticks % s_perf_freq;
 
        const int64_t delta_us =
            q * 1000000LL + (r * 1000000LL) / s_perf_freq;
 
        return s_anchor_realtime_us + delta_us;
#       else
        static std::once_flag init_flag;
        static int64_t s_anchor_realtime_us = 0;
        static int64_t s_anchor_mono_ns = 0;
 
        std::call_once(init_flag, []() {
            struct timespec realtime_ts{};
            struct timespec mono_ts{};
 
#           if defined(CLOCK_MONOTONIC_RAW)
            clock_gettime(CLOCK_MONOTONIC_RAW, &mono_ts);
#           else
            clock_gettime(CLOCK_MONOTONIC, &mono_ts);
#           endif
            clock_gettime(CLOCK_REALTIME, &realtime_ts);
 
            s_anchor_realtime_us = static_cast<int64_t>(realtime_ts.tv_sec) * 1000000LL
                                 + realtime_ts.tv_nsec / 1000;
            s_anchor_mono_ns = static_cast<int64_t>(mono_ts.tv_sec) * 1000000000LL
                             + mono_ts.tv_nsec;
        });
 
        struct timespec mono_now_ts{};
#       if defined(CLOCK_MONOTONIC_RAW)
        clock_gettime(CLOCK_MONOTONIC_RAW, &mono_now_ts);
#       else
        clock_gettime(CLOCK_MONOTONIC, &mono_now_ts);
#       endif
 
        const int64_t mono_now_ns = static_cast<int64_t>(mono_now_ts.tv_sec) * 1000000000LL
                                  + mono_now_ts.tv_nsec;
        const int64_t delta_ns = mono_now_ns - s_anchor_mono_ns;
        return s_anchor_realtime_us + delta_ns / 1000;
#       endif
    }
 
    inline ts_t monotonic_sec() noexcept {
        const auto ticks = std::chrono::steady_clock::now().time_since_epoch();
        return static_cast<ts_t>(std::chrono::duration_cast<std::chrono::seconds>(ticks).count());
    }
 
    inline ts_ms_t monotonic_ms() noexcept {
        const auto ticks = std::chrono::steady_clock::now().time_since_epoch();
        return static_cast<ts_ms_t>(std::chrono::duration_cast<std::chrono::milliseconds>(ticks).count());
    }
 
    inline ts_us_t monotonic_us() noexcept {
        const auto ticks = std::chrono::steady_clock::now().time_since_epoch();
        return static_cast<ts_us_t>(std::chrono::duration_cast<std::chrono::microseconds>(ticks).count());
    }
 
    template<class T = int>
    inline T ns_of_sec() noexcept {
        const struct timespec ts = get_timespec_impl();
        return static_cast<T>(ts.tv_nsec);
    }
 
    template<class T = int>
    inline T us_of_sec() noexcept {
        const struct timespec ts = get_timespec_impl();
        return static_cast<T>(ts.tv_nsec / NS_PER_US);
    }
 
    template<class T = int>
    inline T ms_of_sec() noexcept {
        const struct timespec ts = get_timespec_impl();
        return static_cast<T>(ts.tv_nsec / NS_PER_MS);
    }
 
    inline ts_t ts() noexcept {
        const struct timespec ts = get_timespec_impl();
        return ts.tv_sec;
    }
 
    inline ts_t timestamp() noexcept {
        const struct timespec ts = get_timespec_impl();
        return ts.tv_sec;
    }
 
    inline fts_t fts() noexcept {
        const struct timespec ts = get_timespec_impl();
        return static_cast<fts_t>(ts.tv_sec) + static_cast<fts_t>(ts.tv_nsec) / static_cast<fts_t>(NS_PER_SEC);
    }
 
    inline fts_t ftimestamp() noexcept {
        const struct timespec ts = get_timespec_impl();
        return static_cast<fts_t>(ts.tv_sec) + static_cast<fts_t>(ts.tv_nsec) / static_cast<fts_t>(NS_PER_SEC);
    }
 
    inline ts_ms_t ts_ms() noexcept {
        const struct timespec ts = get_timespec_impl();
        return MS_PER_SEC * ts.tv_sec + ts.tv_nsec / NS_PER_MS;
    }
 
    inline ts_ms_t timestamp_ms() noexcept {
        const struct timespec ts = get_timespec_impl();
        return MS_PER_SEC * ts.tv_sec + ts.tv_nsec / NS_PER_MS;
    }
 
    inline ts_ms_t now() noexcept {
        const struct timespec ts = get_timespec_impl();
        return MS_PER_SEC * ts.tv_sec + ts.tv_nsec / NS_PER_MS;
    }
 
    inline ts_us_t ts_us() noexcept {
        const struct timespec ts = get_timespec_impl();
        return US_PER_SEC * ts.tv_sec + ts.tv_nsec / NS_PER_US;
    }
 
    inline ts_us_t timestamp_us() noexcept {
        const struct timespec ts = get_timespec_impl();
        return US_PER_SEC * ts.tv_sec + ts.tv_nsec / NS_PER_US;
    }
 
    inline double get_cpu_time() noexcept {
#   if TIME_SHIELD_PLATFORM_WINDOWS
        FILETIME create_time{}, exit_time{}, kernel_time{}, user_time{};
        if (GetProcessTimes(GetCurrentProcess(), &create_time, &exit_time, &kernel_time, &user_time)) {
            ULARGE_INTEGER li{};
            li.LowPart = user_time.dwLowDateTime;
            li.HighPart = user_time.dwHighDateTime;
            return static_cast<double>(li.QuadPart) / 10000000.0;
        }
#   elif   TIME_SHIELD_PLATFORM_UNIX
        // AIX, BSD, Cygwin, HP-UX, Linux, OSX, and Solaris
#       if defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0)
            clockid_t id = (clockid_t)-1;
#           if defined(_POSIX_CPUTIME) && (_POSIX_CPUTIME > 0)
                if (clock_getcpuclockid(0, &id) != 0) {
#                   if defined(CLOCK_PROCESS_CPUTIME_ID)
                        id = CLOCK_PROCESS_CPUTIME_ID;
#                   elif defined(CLOCK_VIRTUAL)
                        id = CLOCK_VIRTUAL;
#                   endif
                }
#           elif defined(CLOCK_PROCESS_CPUTIME_ID)
                id = CLOCK_PROCESS_CPUTIME_ID;
#           elif defined(CLOCK_VIRTUAL)
                id = CLOCK_VIRTUAL;
#           endif
            if (id != (clockid_t)-1) {
                struct timespec ts;
                if (clock_gettime(id, &ts) == 0) {
                    return static_cast<double>(ts.tv_sec) + static_cast<double>(ts.tv_nsec) / 1e9;
                }
            }
#       endif
 
#       if defined(RUSAGE_SELF)
            struct rusage usage{};
            if (getrusage(RUSAGE_SELF, &usage) == 0) {
                return static_cast<double>(usage.ru_utime.tv_sec) + static_cast<double>(usage.ru_utime.tv_usec) / 1e6;
            }
#       endif
 
#       if defined(_SC_CLK_TCK)
            struct tms t{};
            if (times(&t) != (clock_t)-1) {
                return static_cast<double>(t.tms_utime) / static_cast<double>(sysconf(_SC_CLK_TCK));
            }
#       endif
 
#       if defined(CLOCKS_PER_SEC)
            clock_t cl = clock();
            if (cl != (clock_t)-1) {
                return static_cast<double>(cl) / static_cast<double>(CLOCKS_PER_SEC);
            }
#       endif
#   else
#       warning "get_cpu_time() may not work correctly: unsupported platform"
#   endif
        return std::numeric_limits<double>::quiet_NaN();
    }
 
}; // namespace time_shield
 
#endif // TIME_SHIELD_HEADER_CORE_TIME_UTILS_HPP_INCLUDED