1//===------------------------- chrono.cpp ---------------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is dual licensed under the MIT and the University of Illinois Open
6// Source Licenses. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "chrono"
11#include <sys/time.h>        //for gettimeofday and timeval
12#ifdef __APPLE__
13#include <mach/mach_time.h>  // mach_absolute_time, mach_timebase_info_data_t
14#else  /* !__APPLE__ */
15#include <cerrno>  // errno
16#include <system_error>  // __throw_system_error
17#include <time.h>  // clock_gettime, CLOCK_MONOTONIC
18#endif  // __APPLE__
19
20_LIBCPP_BEGIN_NAMESPACE_STD
21
22namespace chrono
23{
24
25// system_clock
26
27const bool system_clock::is_steady;
28
29system_clock::time_point
30system_clock::now() _NOEXCEPT
31{
32    timeval tv;
33    gettimeofday(&tv, 0);
34    return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec));
35}
36
37time_t
38system_clock::to_time_t(const time_point& t) _NOEXCEPT
39{
40    return time_t(duration_cast<seconds>(t.time_since_epoch()).count());
41}
42
43system_clock::time_point
44system_clock::from_time_t(time_t t) _NOEXCEPT
45{
46    return system_clock::time_point(seconds(t));
47}
48
49// steady_clock
50
51const bool steady_clock::is_steady;
52
53#ifdef __APPLE__
54//   mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of
55//   nanoseconds since the computer booted up.  MachInfo.numer and MachInfo.denom
56//   are run time constants supplied by the OS.  This clock has no relationship
57//   to the Gregorian calendar.  It's main use is as a high resolution timer.
58
59// MachInfo.numer / MachInfo.denom is often 1 on the latest equipment.  Specialize
60//   for that case as an optimization.
61
62#pragma GCC visibility push(hidden)
63
64static
65steady_clock::rep
66steady_simplified()
67{
68    return static_cast<steady_clock::rep>(mach_absolute_time());
69}
70
71static
72double
73compute_steady_factor()
74{
75    mach_timebase_info_data_t MachInfo;
76    mach_timebase_info(&MachInfo);
77    return static_cast<double>(MachInfo.numer) / MachInfo.denom;
78}
79
80static
81steady_clock::rep
82steady_full()
83{
84    static const double factor = compute_steady_factor();
85    return static_cast<steady_clock::rep>(mach_absolute_time() * factor);
86}
87
88typedef steady_clock::rep (*FP)();
89
90static
91FP
92init_steady_clock()
93{
94    mach_timebase_info_data_t MachInfo;
95    mach_timebase_info(&MachInfo);
96    if (MachInfo.numer == MachInfo.denom)
97        return &steady_simplified;
98    return &steady_full;
99}
100
101#pragma GCC visibility pop
102
103steady_clock::time_point
104steady_clock::now() _NOEXCEPT
105{
106    static FP fp = init_steady_clock();
107    return time_point(duration(fp()));
108}
109
110#else  // __APPLE__
111// FIXME: We assume that clock_gettime(CLOCK_MONOTONIC) works on
112// non-apple systems.  Instead, we should check _POSIX_TIMERS and
113// _POSIX_MONOTONIC_CLOCK and fall back to something else if those
114// don't exist.
115
116// Warning:  If this is not truly steady, then it is non-conforming.  It is
117//  better for it to not exist and have the rest of libc++ use system_clock
118//  instead.
119
120steady_clock::time_point
121steady_clock::now() _NOEXCEPT
122{
123    struct timespec tp;
124    if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
125        __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
126    return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
127}
128#endif  // __APPLE__
129
130}
131
132_LIBCPP_END_NAMESPACE_STD
133