Promise/A+ like javascript in cpp
Hi, Javascript Promise creates a task chain to help develop asynchronized application with single thread. I did not find a good implement of this kind of "Promise" in c++, so i create one named "promise-cpp" here -- https://github.com/xhawk18/promise-cpp with which, we can write asynchronized tasks like sequential flows. Here's an example of promisifed http client in boost::asio -- https://github.com/xhawk18/promise-cpp/blob/master/test/asio_http_client.cpp "promise-cpp" would be the best friend to boost::asio's asynchronized task for single thread, and it is not std::promise. Thanks for you reviewing this library and any suggestion will be appreciated!
On 26/07/2018 00:15, hawk x wrote:
Javascript Promise creates a task chain to help develop asynchronized application with single thread.
I did not find a good implement of this kind of "Promise" in c++
std::future::then was proposed for C++17, but didn't make it in. Boost does support it, however, as does an STL that implements the Concurrency TS (as std::experimental::future::then). https://www.boost.org/doc/libs/1_67_0/doc/html/thread/synchronization.html#t... Additionally, Boost.Asio supports using coroutines for implementing asynchronous tasks, which are even better than a then-chain and read even more like plain synchronous code. https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/overview/core/spaw... https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/example/cpp11/spaw... Currently coroutines are a pure library feature (supported by Boost.Context and Boost.Coroutine), but they are expected to be supported directly by C++20 compilers, and by C++17 compilers that implement the Coroutine TS (VS 2017 already supports co_await, for example). https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/overview/core/coro... https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/examples/cpp17_exa...
boost::coroutine and std::future are all excellent solutions for
concurrency programming.
But if there's many concurrent tasks, event-loop based multi-task in SINGLE
thread will have the best performance.
while std::future is designed for mulitthread, and std::future::then is not
suitable for event-loop based multi-task in SINGLE thread,
that's why I wrote "promise-cpp".
2018-07-27 8:50 GMT+08:00 Gavin Lambert via Boost
On 26/07/2018 00:15, hawk x wrote:
Javascript Promise creates a task chain to help develop asynchronized application with single thread.
I did not find a good implement of this kind of "Promise" in c++
std::future::then was proposed for C++17, but didn't make it in. Boost does support it, however, as does an STL that implements the Concurrency TS (as std::experimental::future::then).
https://www.boost.org/doc/libs/1_67_0/doc/html/thread/synchr onization.html#thread.synchronization.futures.then
Additionally, Boost.Asio supports using coroutines for implementing asynchronous tasks, which are even better than a then-chain and read even more like plain synchronous code.
https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/ overview/core/spawn.html
https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/ example/cpp11/spawn/echo_server.cpp
Currently coroutines are a pure library feature (supported by Boost.Context and Boost.Coroutine), but they are expected to be supported directly by C++20 compilers, and by C++17 compilers that implement the Coroutine TS (VS 2017 already supports co_await, for example).
https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/ overview/core/coroutines_ts.html
https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/ examples/cpp17_examples.html
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On 27/07/2018 14:13, hawk x wrote:
boost::coroutine and std::future are all excellent solutions for concurrency programming. But if there's many concurrent tasks, event-loop based multi-task in SINGLE thread will have the best performance.
coroutines can be used to manage concurrent tasks on a single thread. Boost.Asio is one way to manage those tasks with an event loop (simply have a single thread running the io_service/io_context); additional work can be posted both from "inside" and outside. Boost.Fiber (https://www.boost.org/doc/libs/1_67_0/libs/fiber/doc/html/index.html) is another way. This also supports futures, although not currently then-able ones.
On Fri, Jul 27, 2018, 1:58 AM Gavin Lambert via Boost
(https://www.boost.org/doc/libs/1_67_0/libs/fiber/doc/html/index.html) is another way. This also supports futures, although not currently then-able ones.
Boost.Fiber doesn't need fibers::future::then - just suspend the fiber. If you need more concurrency than that, launch another fiber. then() is redundant with coroutine and fiber concurrency.
participants (3)
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Gavin Lambert -
hawk x -
Nat Goodspeed