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> 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 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
