1 files changed, 128 insertions, 0 deletions
diff --git a/src/chrono.cpp b/src/chrono.cpp
new file mode 100644
index 0000000..416b950
--- /dev/null
+++ b/src/chrono.cpp
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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
+#if __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
+
+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
+
+#if __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 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