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//===------------------------- chrono.cpp ---------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "chrono"
#include <sys/time.h> //for gettimeofday and timeval
#ifdef __APPLE__
#include <mach/mach_time.h> // mach_absolute_time, mach_timebase_info_data_t
#else /* !__APPLE__ */
#include <cerrno> // errno
#include <system_error> // __throw_system_error
#include <time.h> // clock_gettime, CLOCK_MONOTONIC
#endif // __APPLE__
_LIBCPP_BEGIN_NAMESPACE_STD
namespace chrono
{
// system_clock
const bool system_clock::is_steady;
system_clock::time_point
system_clock::now() _NOEXCEPT
{
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) _NOEXCEPT
{
return time_t(duration_cast<seconds>(t.time_since_epoch()).count());
}
system_clock::time_point
system_clock::from_time_t(time_t t) _NOEXCEPT
{
return system_clock::time_point(seconds(t));
}
// steady_clock
const bool steady_clock::is_steady;
#ifdef __APPLE__
// 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
steady_clock::rep
steady_simplified()
{
return static_cast<steady_clock::rep>(mach_absolute_time());
}
static
double
compute_steady_factor()
{
mach_timebase_info_data_t MachInfo;
mach_timebase_info(&MachInfo);
return static_cast<double>(MachInfo.numer) / MachInfo.denom;
}
static
steady_clock::rep
steady_full()
{
static const double factor = compute_steady_factor();
return static_cast<steady_clock::rep>(mach_absolute_time() * factor);
}
typedef steady_clock::rep (*FP)();
static
FP
init_steady_clock()
{
mach_timebase_info_data_t MachInfo;
mach_timebase_info(&MachInfo);
if (MachInfo.numer == MachInfo.denom)
return &steady_simplified;
return &steady_full;
}
#pragma GCC visibility pop
steady_clock::time_point
steady_clock::now() _NOEXCEPT
{
static FP fp = init_steady_clock();
return time_point(duration(fp()));
}
#else // __APPLE__
// FIXME: We assume that clock_gettime(CLOCK_MONOTONIC) works on
// non-apple systems. Instead, we should check _POSIX_TIMERS and
// _POSIX_MONOTONIC_CLOCK and fall back to something else if those
// don't exist.
// Warning: If this is not truly steady, then it is non-conforming. It is
// better for it to not exist and have the rest of libc++ use system_clock
// instead.
steady_clock::time_point
steady_clock::now() _NOEXCEPT
{
struct timespec tp;
if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
__throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
}
#endif // __APPLE__
}
_LIBCPP_END_NAMESPACE_STD
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