1 #include <iostream>
2 #include <chrono>
3 #include <ratio>
4
5 // In NDK GCC 4.6 and below, "steady_clock" is called "monotonic_clock",
6 // and "is_steady" is called "is_monotonic". One may be tempted to use
7 // __GLIBCXX__ to detect it by doing
8 //
9 // # if __GLIBCXX__ < 20120920 /* 20120920 is the date of gcc-4.7 in NDK */
10 //
11 // But __GLIBCXX__ get date from gcc/DATESTAMP. Although it never changes
12 // (so far) once deposit in toolchain/gcc.git, it gets daily bump in upstream.
13 // Thus, this approach may not work in other gcc release.
14 //
15 // We can detect it by
16 //
17 // #if !(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
18 //
19 // But unfortunately clang uses gcc libstdc++ w/o defining __GNUC__ at all.
20 // Since clang now sides with gcc-4.7, we need the following intead
21 //
22 // #if !(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7) || defined(__clang__))
23 //
24 // This approach won't be valid if clang sides with gcc4.6 (in standalone mode, for
25 // example).
26 //
27 // ToDo: better approach
28
29 #if !(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7) || defined(__clang__))
30 namespace std {
31 namespace chrono {
32 typedef monotonic_clock steady_clock;
33 }
34 }
35 #define is_steady is_monotonic
36 #endif
37
38 template <typename C>
printClockData(bool & is_high_res,bool & is_steady)39 void printClockData (bool &is_high_res, bool &is_steady)
40 {
41 using namespace std;
42
43 cout << "- precision: ";
44 // if time unit is less or equal one millisecond
45 typedef typename C::period P;// type of time unit
46 if (ratio_less_equal<P,milli>::value) {
47 // convert to and print as milliseconds
48 typedef typename ratio_multiply<P,kilo>::type TT;
49 cout << fixed << double(TT::num)/TT::den
50 << " milliseconds" << endl;
51 is_high_res = true;
52 }
53 else {
54 // print as seconds
55 cout << fixed << double(P::num)/P::den << " seconds" << endl;
56 is_high_res = false;
57 }
58 cout << "- is_steady: " << boolalpha << C::is_steady << endl;
59 is_steady = C::is_steady;
60 }
61
main()62 int main()
63 {
64 bool is_high_res1, is_high_res2, is_high_res3, is_steady;
65 std::cout << "system_clock: " << std::endl;
66 printClockData<std::chrono::system_clock>(is_high_res1, is_steady);
67 std::cout << "\nhigh_resolution_clock: " << std::endl;
68 printClockData<std::chrono::high_resolution_clock>(is_high_res2, is_steady);
69 std::cout << "\nsteady_clock: " << std::endl;
70 printClockData<std::chrono::steady_clock>(is_high_res3, is_steady);
71
72 return (is_high_res1 && is_high_res2 && is_high_res3 && is_steady)? 0 : 1;
73 }
74