'Turning a function call which takes a callback into a coroutine

I am exploring and trying to learn C++ Coroutines (added in C++20). An SDK I am using has asynchronous API calls which all take a callback, the callbacks are invoked on some background thread managed by the SDK.


namespace third_party {

bool api_call(const std::string& some_parameter, const std::function<void(std::error_code)>& callback);

} // namespace third_party

I would like wrap this API call into something which can be awaited instead:


namespace my_third_party_sdk_wrapper {

cppcoro::task<std::error_code> api_call(const std::string& some_parameter);
cppcoro::task<std::error_code> api_call(const std::string& some_parameter, cppcoro::cancellation_token token);

} // namespace my_third_party_sdk_wrapper

I am considering using the cppcoro lib but that isn't a requirement unless the implementation of the wrapper gets much simpler by doing so.

The problem is I cannot figure out how implement the wrapper.

c++c++20c++-coroutine


Solution 1:[1]

a simple (running) example on cppreference.com, "switch_to_new_thread": https://en.cppreference.com/w/cpp/language/coroutines

open are two problems:

  • passing a parameter to the callback
  • chaining the callbacks down the callstack

this code shows a solution https://wandbox.org/permlink/OGjmtFWsgjnn3GxX

look for latest version here: https://github.com/andreaspfaffenbichler/Continuation/blob/master/Continuation.cpp

Sources

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Source: Stack Overflow

Solution Source
Solution 1

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