[ios] duration to time interval fix #8276
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@fabian-guerra, thanks for your PR! By analyzing this pull request, we identified @incanus, @boundsj and @1ec5 to be potential reviewers. |
| { | ||
| return duration.count(); | ||
| std::chrono::nanoseconds nano(duration.count()); | ||
| std::chrono::seconds sec = std::chrono::duration_cast<std::chrono::seconds>(nano); |
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FYI, since this is Objective-C++ code, you could condense these lines somewhat by passing duration.count() directly into the duration_cast. You can also use auto instead of declaring the local variable to be of type std::chrono::seconds. What you’ve got is totally reasonable, though.
| #import <XCTest/XCTest.h> | ||
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| #include <mbgl/util/chrono.hpp> | ||
| #import "../../darwin/src/NSDate+MGLAdditions.h" |
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Since NSDate+MGLAdditions.h is shared between iOS and macOS, the tests should be shared as well. Can you move this file to platform/darwin/test/ and add it to macos.xcodeproj?
| mbgl::Duration duration = MGLDurationFromTimeInterval(timeInterval); | ||
| NSTimeInterval durationTimeInterval = MGLTimeIntervalFromDuration(duration); | ||
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| mbgl::Duration durationInNanoseconds(5000000000); |
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Since chrono.hpp imports <chrono>, you can write using namespace std::chrono_literals; at the top, then use auto expectedDuration = 5000000000ns; or even mbgl::Duration expectedDuration = 5s;.
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Actually, sharing the tests between iOS and macOS is pretty important, so if you could take care of that, that’d be 👌. |
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| { | ||
| return duration.count(); | ||
| std::chrono::nanoseconds nano(duration.count()); |
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This implementation makes the unsafe assumption that mbgl::Duration's count is in nanoseconds. mbgl::Duration is a typedef to std::chrono::steady_clock::duration, and std::chrono::steady_clock does not specify a particular tick period.
In addition, this implementation truncates any fractional seconds in the duration. NSTimeInterval is a floating-point type, and so the conversion should be expected to preserve fractional seconds.
I believe the correct conversion is as follows (but don't trust me -- write some more tests 😄):
NSTimeInterval MGLTimeIntervalFromDuration(mbgl::Duration duration)
{
std::chrono::duration<NSTimeInterval, std::ratio<1>>(duration).count();
}
Fixes #8264