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1 | #ifndef OPENTRACING_UTIL_H |
2 | #define OPENTRACING_UTIL_H | |
3 | ||
4 | #include <opentracing/string_view.h> | |
5 | #include <opentracing/version.h> | |
6 | #include <chrono> | |
7 | #include <system_error> | |
8 | ||
9 | // expected uses a C++11 implementation that follows the std::expected standard | |
10 | // library proposal. | |
11 | // | |
12 | // See https://github.com/martinmoene/expected-lite | |
13 | // https://github.com/viboes/std-make/blob/master/doc/proposal/expected/d0323r2.md | |
14 | #include <opentracing/expected/expected.hpp> | |
15 | ||
16 | namespace opentracing { | |
17 | BEGIN_OPENTRACING_ABI_NAMESPACE | |
18 | using SystemClock = std::chrono::system_clock; | |
19 | using SteadyClock = std::chrono::steady_clock; | |
20 | using SystemTime = SystemClock::time_point; | |
21 | using SteadyTime = SteadyClock::time_point; | |
22 | ||
23 | // This is unsafe to do. | |
24 | // | |
25 | // This is like an unsafe std::reference_wrapper<> that allows taking | |
26 | // references to temporaries. It must only be used for temporary | |
27 | // SpanStartOption and SpanFinishOption objects. | |
28 | template <typename T> | |
29 | class option_wrapper { | |
30 | public: | |
31 | option_wrapper(const T &opt) : ptr_(&opt) {} | |
32 | ||
33 | // This will dangle unless it is only used for short-lived initializer lists. | |
34 | const T &get() const { return *ptr_; } | |
35 | ||
36 | private: | |
37 | const T *ptr_; | |
38 | }; | |
39 | ||
40 | // Support conversion between time_points from different clocks. There's no | |
41 | // standard way to get the difference in epochs between clocks, so this uses | |
42 | // an approximation suggested by Howard Hinnant. | |
43 | // | |
44 | // See https://stackoverflow.com/a/35282833/4447365 | |
45 | template <class ToClock, class FromClock, class Duration, | |
46 | typename std::enable_if< | |
47 | !std::is_same<FromClock, ToClock>::value>::type * = nullptr> | |
48 | typename ToClock::time_point convert_time_point( | |
49 | std::chrono::time_point<FromClock, Duration> from_time_point) { | |
50 | auto from_now = FromClock::now(); | |
51 | auto to_now = ToClock::now(); | |
52 | return to_now + std::chrono::duration_cast<typename ToClock::duration>( | |
53 | from_time_point - from_now); | |
54 | } | |
55 | ||
56 | template <class ToClock, class FromClock, class Duration, | |
57 | typename std::enable_if<std::is_same<FromClock, ToClock>::value>::type | |
58 | * = nullptr> | |
59 | typename ToClock::time_point convert_time_point( | |
60 | std::chrono::time_point<FromClock, Duration> from_time_point) { | |
61 | return std::chrono::time_point_cast<typename ToClock::time_point::duration>( | |
62 | from_time_point); | |
63 | } | |
64 | ||
65 | // std::error_code's have default comparison operators; however, they make use | |
66 | // of singleton addresses which can cause comparisons to fail when multiple | |
67 | // versions of the opentracing library are linked in. Since this is a common | |
68 | // deployment scenario when making OpenTracing plugins, we add this utility | |
69 | // function to make comparing std::error_code across libraries easier. | |
70 | // | |
71 | // Note: There's a proposed change to the C++ standard that addresses this | |
72 | // issue. See | |
73 | // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1196r0.html | |
74 | inline bool are_errors_equal(std::error_code lhs, | |
75 | std::error_code rhs) noexcept { | |
76 | return opentracing::string_view{lhs.category().name()} == | |
77 | opentracing::string_view{rhs.category().name()} && | |
78 | lhs.value() == rhs.value(); | |
79 | } | |
80 | ||
81 | END_OPENTRACING_ABI_NAMESPACE | |
82 | } // namespace opentracing | |
83 | ||
84 | #endif // OPENTRACING_UTIL_H |