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 "cerrno"        // errno
12 #include "system_error"  // __throw_system_error
13 #include <time.h>        // clock_gettime, CLOCK_MONOTONIC and CLOCK_REALTIME
14 
15 #if !defined(CLOCK_REALTIME)
16 #include <sys/time.h>        // for gettimeofday and timeval
17 #endif
18 
19 #if !defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK) && !defined(CLOCK_MONOTONIC)
20 #if __APPLE__
21 #include <mach/mach_time.h>  // mach_absolute_time, mach_timebase_info_data_t
22 #else
23 #error "Monotonic clock not implemented"
24 #endif
25 #endif
26 
27 _LIBCPP_BEGIN_NAMESPACE_STD
28 
29 namespace chrono
30 {
31 
32 // system_clock
33 
34 const bool system_clock::is_steady;
35 
36 system_clock::time_point
now()37 system_clock::now() _NOEXCEPT
38 {
39 #ifdef CLOCK_REALTIME
40     struct timespec tp;
41     if (0 != clock_gettime(CLOCK_REALTIME, &tp))
42         __throw_system_error(errno, "clock_gettime(CLOCK_REALTIME) failed");
43     return time_point(seconds(tp.tv_sec) + microseconds(tp.tv_nsec / 1000));
44 #else  // !CLOCK_REALTIME
45     timeval tv;
46     gettimeofday(&tv, 0);
47     return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec));
48 #endif  // CLOCK_REALTIME
49 }
50 
51 time_t
to_time_t(const time_point & t)52 system_clock::to_time_t(const time_point& t) _NOEXCEPT
53 {
54     return time_t(duration_cast<seconds>(t.time_since_epoch()).count());
55 }
56 
57 system_clock::time_point
from_time_t(time_t t)58 system_clock::from_time_t(time_t t) _NOEXCEPT
59 {
60     return system_clock::time_point(seconds(t));
61 }
62 
63 #ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK
64 // steady_clock
65 //
66 // Warning:  If this is not truly steady, then it is non-conforming.  It is
67 //  better for it to not exist and have the rest of libc++ use system_clock
68 //  instead.
69 
70 const bool steady_clock::is_steady;
71 
72 #ifdef CLOCK_MONOTONIC
73 
74 steady_clock::time_point
now()75 steady_clock::now() _NOEXCEPT
76 {
77     struct timespec tp;
78     if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
79         __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
80     return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
81 }
82 
83 #elif defined(__APPLE__)
84 
85 //   mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of
86 //   nanoseconds since the computer booted up.  MachInfo.numer and MachInfo.denom
87 //   are run time constants supplied by the OS.  This clock has no relationship
88 //   to the Gregorian calendar.  It's main use is as a high resolution timer.
89 
90 // MachInfo.numer / MachInfo.denom is often 1 on the latest equipment.  Specialize
91 //   for that case as an optimization.
92 
93 #pragma GCC visibility push(hidden)
94 
95 static
96 steady_clock::rep
steady_simplified()97 steady_simplified()
98 {
99     return static_cast<steady_clock::rep>(mach_absolute_time());
100 }
101 
102 static
103 double
compute_steady_factor()104 compute_steady_factor()
105 {
106     mach_timebase_info_data_t MachInfo;
107     mach_timebase_info(&MachInfo);
108     return static_cast<double>(MachInfo.numer) / MachInfo.denom;
109 }
110 
111 static
112 steady_clock::rep
steady_full()113 steady_full()
114 {
115     static const double factor = compute_steady_factor();
116     return static_cast<steady_clock::rep>(mach_absolute_time() * factor);
117 }
118 
119 typedef steady_clock::rep (*FP)();
120 
121 static
122 FP
init_steady_clock()123 init_steady_clock()
124 {
125     mach_timebase_info_data_t MachInfo;
126     mach_timebase_info(&MachInfo);
127     if (MachInfo.numer == MachInfo.denom)
128         return &steady_simplified;
129     return &steady_full;
130 }
131 
132 #pragma GCC visibility pop
133 
134 steady_clock::time_point
now()135 steady_clock::now() _NOEXCEPT
136 {
137     static FP fp = init_steady_clock();
138     return time_point(duration(fp()));
139 }
140 
141 #else
142 #error "Monotonic clock not implemented"
143 #endif
144 
145 #endif // !_LIBCPP_HAS_NO_MONOTONIC_CLOCK
146 
147 }
148 
149 _LIBCPP_END_NAMESPACE_STD
150