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//===------------------------- chrono.cpp ---------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "chrono"
#include <sys/time.h> //for gettimeofday and timeval
#include <mach/mach_time.h> // mach_absolute_time, mach_timebase_info_data_t
_LIBCPP_BEGIN_NAMESPACE_STD
namespace chrono
{
// system_clock
system_clock::time_point
system_clock::now()
{
timeval tv;
gettimeofday(&tv, 0);
return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec));
}
time_t
system_clock::to_time_t(const time_point& t)
{
return time_t(duration_cast<seconds>(t.time_since_epoch()).count());
}
system_clock::time_point
system_clock::from_time_t(time_t t)
{
return system_clock::time_point(seconds(t));
}
// monotonic_clock
// mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of
// nanoseconds since the computer booted up. MachInfo.numer and MachInfo.denom
// are run time constants supplied by the OS. This clock has no relationship
// to the Gregorian calendar. It's main use is as a high resolution timer.
// MachInfo.numer / MachInfo.denom is often 1 on the latest equipment. Specialize
// for that case as an optimization.
#pragma GCC visibility push(hidden)
static
monotonic_clock::rep
monotonic_simplified()
{
return mach_absolute_time();
}
static
double
compute_monotonic_factor()
{
mach_timebase_info_data_t MachInfo;
mach_timebase_info(&MachInfo);
return static_cast<double>(MachInfo.numer) / MachInfo.denom;
}
static
monotonic_clock::rep
monotonic_full()
{
static const double factor = compute_monotonic_factor();
return static_cast<monotonic_clock::rep>(mach_absolute_time() * factor);
}
typedef monotonic_clock::rep (*FP)();
static
FP
init_monotonic_clock()
{
mach_timebase_info_data_t MachInfo;
mach_timebase_info(&MachInfo);
if (MachInfo.numer == MachInfo.denom)
return &monotonic_simplified;
return &monotonic_full;
}
#pragma GCC visiblity pop
monotonic_clock::time_point
monotonic_clock::now()
{
static FP fp = init_monotonic_clock();
return time_point(duration(fp()));
}
}
_LIBCPP_END_NAMESPACE_STD
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