clock.cpp

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/*
    Copyright (c) 2010-2011 250bpm s.r.o.
    Copyright (c) 2010-2011 Other contributors as noted in the AUTHORS file

    This file is part of 0MQ.

    0MQ is free software; you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    0MQ is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "clock.hpp"
#include "platform.hpp"
#include "likely.hpp"
#include "config.hpp"
#include "err.hpp"

#include <stddef.h>

#if defined _MSC_VER
#include <intrin.h>
#endif

#if !defined ZMQ_HAVE_WINDOWS
#include <sys/time.h>
#endif

zmq::clock_t::clock_t () :
    last_tsc (rdtsc ()),
    last_time (now_us () / 1000)
{
}

zmq::clock_t::~clock_t ()
{
}

uint64_t zmq::clock_t::now_us ()
{
#if defined ZMQ_HAVE_WINDOWS

    //  Get the high resolution counter's accuracy.
    LARGE_INTEGER ticksPerSecond;
    QueryPerformanceFrequency (&ticksPerSecond);

    //  What time is it?
    LARGE_INTEGER tick;
    QueryPerformanceCounter (&tick);

    //  Convert the tick number into the number of seconds
    //  since the system was started.
    double ticks_div = (double) (ticksPerSecond.QuadPart / 1000000);     
    return (uint64_t) (tick.QuadPart / ticks_div);

#else

    //  Use POSIX gettimeofday function to get precise time.
    struct timeval tv;
    int rc = gettimeofday (&tv, NULL);
    errno_assert (rc == 0);
    return (tv.tv_sec * (uint64_t) 1000000 + tv.tv_usec);

#endif
}

uint64_t zmq::clock_t::now_ms ()
{
    uint64_t tsc = rdtsc ();

    //  If TSC is not supported, get precise time and chop off the microseconds.
    if (!tsc)
        return now_us () / 1000;

    //  If TSC haven't jumped back (in case of migration to a different
    //  CPU core) and if not too much time elapsed since last measurement,
    //  we can return cached time value.
    if (likely (tsc - last_tsc <= (clock_precision / 2) && tsc >= last_tsc))
        return last_time;

    last_tsc = tsc;
    last_time = now_us () / 1000;
    return last_time;
}

uint64_t zmq::clock_t::rdtsc ()
{
#if (defined _MSC_VER && (defined _M_IX86 || defined _M_X64))
    return __rdtsc ();
#elif (defined __GNUC__ && (defined __i386__ || defined __x86_64__))
    uint32_t low, high;
    __asm__ volatile ("rdtsc" : "=a" (low), "=d" (high));
    return (uint64_t) high << 32 | low;
#elif (defined __SUNPRO_CC && (__SUNPRO_CC >= 0x5100) && (defined __i386 || \
    defined __amd64 || defined __x86_64))
    union {
        uint64_t u64val;
        uint32_t u32val [2];
    } tsc;
    asm("rdtsc" : "=a" (tsc.u32val [0]), "=d" (tsc.u32val [1]));
    return tsc.u64val;
#elif defined(__s390__)
    uint64_t tsc;
    asm("\tstck\t%0\n" : "=Q" (tsc) : : "cc");
    tsc >>= 12;     /* convert to microseconds just to be consistent */
    return(tsc);
#else
    return 0;
#endif
}