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#ifndef OPENTRACING_UTIL_H
#define OPENTRACING_UTIL_H
#include <opentracing/string_view.h>
#include <opentracing/version.h>
#include <chrono>
#include <system_error>
// expected uses a C++11 implementation that follows the std::expected standard
// library proposal.
//
// See https://github.com/martinmoene/expected-lite
// https://github.com/viboes/std-make/blob/master/doc/proposal/expected/d0323r2.md
#include <opentracing/expected/expected.hpp>
namespace opentracing {
BEGIN_OPENTRACING_ABI_NAMESPACE
using SystemClock = std::chrono::system_clock;
using SteadyClock = std::chrono::steady_clock;
using SystemTime = SystemClock::time_point;
using SteadyTime = SteadyClock::time_point;
// This is unsafe to do.
//
// This is like an unsafe std::reference_wrapper<> that allows taking
// references to temporaries. It must only be used for temporary
// SpanStartOption and SpanFinishOption objects.
template <typename T>
class option_wrapper {
public:
option_wrapper(const T &opt) : ptr_(&opt) {}
// This will dangle unless it is only used for short-lived initializer lists.
const T &get() const { return *ptr_; }
private:
const T *ptr_;
};
// Support conversion between time_points from different clocks. There's no
// standard way to get the difference in epochs between clocks, so this uses
// an approximation suggested by Howard Hinnant.
//
// See https://stackoverflow.com/a/35282833/4447365
template <class ToClock, class FromClock, class Duration,
typename std::enable_if<
!std::is_same<FromClock, ToClock>::value>::type * = nullptr>
typename ToClock::time_point convert_time_point(
std::chrono::time_point<FromClock, Duration> from_time_point) {
auto from_now = FromClock::now();
auto to_now = ToClock::now();
return to_now + std::chrono::duration_cast<typename ToClock::duration>(
from_time_point - from_now);
}
template <class ToClock, class FromClock, class Duration,
typename std::enable_if<std::is_same<FromClock, ToClock>::value>::type
* = nullptr>
typename ToClock::time_point convert_time_point(
std::chrono::time_point<FromClock, Duration> from_time_point) {
return std::chrono::time_point_cast<typename ToClock::time_point::duration>(
from_time_point);
}
// std::error_code's have default comparison operators; however, they make use
// of singleton addresses which can cause comparisons to fail when multiple
// versions of the opentracing library are linked in. Since this is a common
// deployment scenario when making OpenTracing plugins, we add this utility
// function to make comparing std::error_code across libraries easier.
//
// Note: There's a proposed change to the C++ standard that addresses this
// issue. See
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1196r0.html
inline bool are_errors_equal(std::error_code lhs,
std::error_code rhs) noexcept {
return opentracing::string_view{lhs.category().name()} ==
opentracing::string_view{rhs.category().name()} &&
lhs.value() == rhs.value();
}
END_OPENTRACING_ABI_NAMESPACE
} // namespace opentracing
#endif // OPENTRACING_UTIL_H
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