time.cpp

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/*
 * Zth (libzth), a cooperative userspace multitasking library.
 * Copyright (C) 2019-2022  Jochem Rutgers
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */
 
#include <libzth/macros.h>
#include <libzth/init.h>
#include <libzth/time.h>
#include <libzth/util.h>
#include <cerrno>
 
#ifdef ZTH_OS_MAC
#       include <mach/mach_time.h>
#endif
 
#ifdef ZTH_OS_MAC
 
#       ifdef ZTH_CUSTOM_CLOCK_GETTIME
static mach_timebase_info_data_t clock_info;
static uint64_t mach_clock_start;
 
static void clock_global_init()
{
        mach_timebase_info(&clock_info);
        mach_clock_start = mach_absolute_time();
}
ZTH_INIT_CALL(clock_global_init)
 
int clock_gettime(int clk_id, struct timespec* res)
{
        if(unlikely(!res))
                return EFAULT;
 
        zth_assert(clk_id == CLOCK_MONOTONIC);
        uint64_t c = (mach_absolute_time() - mach_clock_start);
        uint64_t ns;
        if(unlikely(clock_info.numer != clock_info.denom)) // For all recent Mac OSX versions,
                                                           // mach_absolute_time() is in ns.
        {
                uint64_t chigh = (c >> 32u) * clock_info.numer;
                uint64_t chighrem = ((chigh % clock_info.denom) << 32u) / clock_info.denom;
                chigh /= clock_info.denom;
                uint64_t clow =
                        (c & (((uint64_t)1 << 32u) - 1)) * clock_info.numer / clock_info.denom;
                clow += chighrem;
                ns = (chigh << 32u)
                     + clow; // 64-bit ns gives us more than 500 y before wrap-around.
        } else {
                ns = c;
        }
 
        // Split in sec + nsec
        res->tv_nsec = (long)(ns % zth::TimeInterval::BILLION);
        res->tv_sec = (time_t)(ns / zth::TimeInterval::BILLION);
        return 0;
}
#       endif // ZTH_CUSTOM_CLOCK_GETTIME
 
int clock_nanosleep(int clk_id, int flags, struct timespec const* request, struct timespec* remain)
{
        if(unlikely(!request))
                return EFAULT;
        if(unlikely(clk_id != CLOCK_MONOTONIC || flags != TIMER_ABSTIME))
                return EINVAL;
 
        struct timespec now;
        int res = clock_gettime(CLOCK_MONOTONIC, &now);
        if(unlikely(res))
                return res;
 
        if(now.tv_sec > request->tv_sec)
                // No need to sleep.
                return 0;
 
        time_t sec = request->tv_sec - now.tv_sec;
        if(sec == 0 && request->tv_nsec <= now.tv_nsec) {
                // No need to sleep.
                return 0;
        } else if(sec < std::numeric_limits<useconds_t>::max() / 1000000 - 1) {
                useconds_t us = (useconds_t)(sec * 1000000);
                us += (useconds_t)((request->tv_nsec - now.tv_nsec) / 1000);
                if(likely(!usleep(us)))
                        return 0;
        } else {
                // Overflow, sleep (almost) infinitely.
                if(likely(!usleep(std::numeric_limits<useconds_t>::max())))
                        return 0;
        }
 
        if(remain) {
                struct timespec intr;
                if((res = clock_gettime(CLOCK_MONOTONIC, &intr)))
                        return res;
 
                remain->tv_sec = intr.tv_sec - now.tv_sec;
                remain->tv_nsec = intr.tv_nsec - now.tv_nsec;
                if(remain->tv_nsec < 0) {
                        remain->tv_nsec += 1000000000L;
                        remain->tv_sec--;
                }
        }
 
        return EINTR;
}
#endif
 
#ifdef ZTH_OS_WINDOWS
// When using gcc and MinGW, clock_nanosleep() only accepts CLOCK_REALTIME, but we use
// CLOCK_MONOTONIC.
int clock_nanosleep(
        clockid_t clock_id, int flags, const struct timespec* request, struct timespec* remain)
{
        if(unlikely(!request))
                return EFAULT;
        if(unlikely(clock_id != CLOCK_MONOTONIC || flags != TIMER_ABSTIME))
                return EINVAL;
 
        struct timespec t;
        int res = clock_gettime(CLOCK_MONOTONIC, &t);
        if(unlikely(res))
                return res;
 
        if(t.tv_sec > request->tv_sec)
                return 0;
        if(t.tv_sec == request->tv_sec && t.tv_nsec > request->tv_nsec)
                return 0;
 
        t.tv_sec = request->tv_sec - t.tv_sec;
        t.tv_nsec = request->tv_nsec - t.tv_nsec;
        if(t.tv_nsec < 0) {
                t.tv_nsec += 1000000000L;
                t.tv_sec--;
        }
 
        return nanosleep(&t, remain) ? errno : 0;
}
#endif
 
#ifdef ZTH_OS_BAREMETAL
// Clock functions are typically not provided by the std library.
 
// As there is no OS, just do polling for the clock. Please provide a more accurate one, when
// appropriate.
__attribute__((weak)) int clock_nanosleep(
        int clk_id, int flags, struct timespec const* request, struct timespec* UNUSED_PAR(remain))
{
        if(unlikely(!request))
                return EFAULT;
        if(unlikely(clk_id != CLOCK_MONOTONIC || flags != TIMER_ABSTIME))
                return EINVAL;
 
        while(true) {
                struct timespec now;
                int res = clock_gettime(CLOCK_MONOTONIC, &now);
                if(unlikely(res))
                        return res;
                else if(now.tv_sec > request->tv_sec)
                        return 0;
                else if(now.tv_sec == request->tv_sec && now.tv_nsec >= request->tv_nsec)
                        return 0;
                // else just keep polling...
        }
}
#endif
 
#ifdef ZTH_OS_MAC
namespace zth {
zth::Timestamp startTime;
}
 
static void startTimeInit()
{
        zth::startTime = zth::Timestamp::now();
}
ZTH_INIT_CALL(startTimeInit)
#else  // !ZTH_OS_MAC
zth::Timestamp startTime_;
 
static void startTimeInit()
{
        startTime_ = zth::Timestamp::now();
}
ZTH_INIT_CALL(startTimeInit)
 
// Let the const zth::startTime alias to the non-const startTime_.
namespace zth {
extern Timestamp const __attribute__((alias("startTime_"))) startTime;
}
#endif // ZTH_OS_MAC