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+/*
+ Copyright (c) 2007-2010 iMatix Corporation
+
+ This file is part of 0MQ.
+
+ 0MQ is free software; you can redistribute it and/or modify it under
+ the terms of the Lesser GNU 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
+ Lesser GNU General Public License for more details.
+
+ You should have received a copy of the Lesser GNU 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 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;
+#else
+ return 0;
+#endif
+}