NanoSecondTimestamps
Capture, print and parse nanosecond UTC Timestmaps.
Overview
The nstimestamp utility provides a simplified wrapper around the Linux clock_gettime call. With a simpler, less rich, interface than std::chrono it can be used for:
- Capturing nanosecond timestamps
- Parsing string timestamps (including ISO8601 timestamps)
- Calculating the elapsed time between two stamps
- Reporting of timestamps (String formatting, as well component access: Year, Minute, nanosecond etc)
Example: Timestamp capture
Time eventTime;
// ...
eventTime.SetNow();
// ...
std::cout << "Event occurred: " << event.Timestamp() << std::endl;
Example: Wall time calculation
Time start;
benchmark();
Time stop;
std::cout << "Duration: " << stop.DiffUs(start) << "us" << std::endl;
Example: Parse timestamps
Time reftime("2014-04-03T10:11:02.294930Z");
std::cout << "Year: " << reftime.Year() << std::endl;
std::cout << "Month: " << reftime.Month() << std::endl;
std::cout << "Second: " << reftime.Second() << std::endl;
std::cout << "Micro Second: " << reftime.USec() << std::endl;
std::cout << "Seconds since the Epoch : " << reftime.EpochSecs << std::endl;
Performance - Event Capture
Capturing the current time with SetNow() is entirely equivalent to a naked clock_gettime call, and performs as such:
Benchmark | Time per itter |
---|---|
timestamp.SetNow() | 20ns |
updateTime = std::chrono::system_clock::now() | 20ns |
gettimeofday(&updateTime, NULL) | 18ns |
clock_gettime(CLOCK_REALTIME, &updateTime) | 18ns |
(Benchmarks are run 1 million times in a tight loop. Reported time is total time / 1e6)
As the Time class supports component level access, it has an additional struct of data. This is not initialised until (unless) needed, but does lead to a larger instance size. Consequently there is a slight impact to the construction benchmark:
Benchmark | Time per itter |
---|---|
timestamps.emplace_back() | 32ns |
events.emplace_back(std::chrono::system_clock::now()) | 24ns |
Performance - Timestamp Parsing
The string parsing logic has been optimized to allow rapid parsing of valid UTC timetamps.
Benchmark | Time per itter |
---|---|
Time(isotimestamp) | 19ns |
Time(nstimestamp) | 20ns |
Build Instructions
Prerequisites
nstimestamp is built for and tested for Linux. Other systems exposing a compatible clock_gettime method should also work.
Building and running the tests requires a modern installation of gtest.
Build and install.
#
# Setup the build
#
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX:PATH=<install path> .. .
#
# Build & Install
#
make
make install
Linking with CMake
The default installation exports a UtilTime package, which can be used to add the Time library as a dependency
find_package(UtilTime 0.1 REQUIRED)
target_link_libraries(Log PRIVATE UtilTime::Time)
Manually Linking against nstimestamp
The Time class is defined in util_time.h. The default installation will export a libTime.a which should be added to the link time dependencies