libcxx initial import

llvm-svn: 103490

1 files changed, 101 insertions, 0 deletions

diff --git a/libcxx/src/chrono.cpp b/libcxx/src/chrono.cpp
new file mode 100644
index 00000000000..0130bd2ee15
--- /dev/null
+++ b/libcxx/src/chrono.cpp
@@ -0,0 +1,101 @@
+//===------------------------- chrono.cpp ---------------------------------===//
+//
+// ΚΚΚΚΚΚΚΚΚΚΚΚΚΚΚΚΚΚΚΚThe 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