C++ Timeouts

A portable, header-only C++11 timer component.

It manages a set of timeouts that, when expired, invoke a callback. It uses features of C++11 in order to avoid platform specific code.

It supports one-shot and periodic timeouts.

Documentation

Please see the documentation in cpptime.h for more detailed information about the implementation.

Implementation Status

We use this timer implementation in some of our products without issues. Judging from the GitHub stars and forks, it seems to be used in other projects as well. Since it was implemented in 2015 and has not seen many issue reports, we assume it is quite stable.

But note that this is not a guarantee and if you find any issues, please report them.

Use Cases and Limitations

Naturally the implementation makes some trade-offs. This makes it useful for some cases, and less so for others.

• The timer runs completely in user space. This makes it slightly less efficient than other solutions, such as timer_create() or timerfd_create(). However, in many cases, this overhead is acceptable.

• Given a C++11 capable compiler, the code is portable.

• The API to add or remove a timeout is arguably nicer than the platform specific alternatives. E.g.

timer.add(seconds(2), [](CppTime::timer_id) { ... });

• The implementation is small and easy to understand. You can change or extend it to make it better suitable for your use-cases.

Examples

A one shot timer.

using namespace std::chrono;
CppTime::Timer t;
t.add(seconds(2), [](CppTime::timer_id) { std::cout << "yes\n"; });
std::this_thread::sleep_for(seconds(3));

A periodic timer that is first executed after 2 seconds, and after this every second. The timeout event is then removed after 10 seconds. When a timeout event is removed, its attached handler is also freed to clean-up any attached resources.

using namespace std::chrono;
CppTime::Timer t;
auto id = t.add(seconds(2), [](CppTime::timer_id) { std::cout << "yes\n"; }, seconds(1));
std::this_thread::sleep_for(seconds(10));
t.remove(id);

See the tests for more examples.

Usage

To use the timer component, Simply copy cpptime.h into you project. Everything is contained in this single header file.

Tests can be compiled and executed with the following commands, assuming you are on a POSIX machine.

g++ -std=c++11 -Wall -Wextra -o test tests/timer_test.cpp -l pthread
./test

Possible Features

While the current implementation serves us well, there are some features that might potentially be interesting for other use cases. Contact us in case you are interested.

• Ability to have multiple timer components running.
• Distribute it as a header only library.
• Optionally avoid locking.
• API to use client thread instead of creating its own.
• API to use client mutex instead of its own.

Known issues

GCC up to version 10 (e.g. used in Ubuntu 20.04 LTS) has an issue where conditional_variable doesn't use the monotonic clock. This leads to unreliable programs when the system clock is moved backwards. See #5 for more details. The fix is to update to a GCC version with the fix applied, e.g. version 10 or greater.

Contributions

Contributions, suggestions, and feature requests are welcome. Please use the GitHub issue tracker.