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https://github.com/CarterLi/liburing4cpp

Modern C++ binding for liburing (io_uring) that features C++ coroutines support
https://github.com/CarterLi/liburing4cpp

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Modern C++ binding for liburing (io_uring) that features C++ coroutines support

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# liburing4cpp

Modern C++ binding for [liburing](https://github.com/axboe/liburing) that uses C++20 Coroutines ( but still compiles for `clang` at C++17 mode with `-fcoroutines-ts` )

Originally named liburing-http-demo ( this project was originally started for demo )

## Requirements

Requires the latest kernel ( currently 5.8 ). Since [io_uring](https://git.kernel.dk/cgit/liburing/) is in active development, we will drop old kernel support when every new linux kernel version is released ( before the next LTS version is released, maybe ).

Tested: `Ubuntu 5.9.0-050900rc6daily20200923-generic #202009222208 SMP Wed Sep 23 02:24:13 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux` with `clang version 10.0.0-4ubuntu1`

## First glance

```cpp
#include

using namespace std::literals;

int main() {
// You first need an io_service instance
uio::io_service service;

// In order to `co_await`, you must be in a coroutine.
// We use IIFE here for simplification
auto work = [&] () -> uio::task<> {
// Use Linux syscalls just as what you did before (except a little changes)
const auto str = "Hello world\n"sv;
co_await service.write(STDOUT_FILENO, str.data(), str.size(), 0);
}();

// At last, you need a loop to dispatch finished IO events
// It's usually called Event Loop (https://en.wikipedia.org/wiki/Event_loop)
service.run(work);
}
```

## Benchmarks

* Ubuntu 20.04.1 LTS
* Linux Ubuntu 5.9.0-050900rc6daily20200923-generic #202009222208 SMP Wed Sep 23 02:24:13 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
* Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz
* Compiler: clang version 10.0.0-4ubuntu1

### demo/bench

```
service.yield: 5436209973
plain IORING_OP_NOP: 5268565967
this_thread::yield: 4750992301
pause: 41557653
```

About 3% overhead

### demo/echo_server

* demo/echo_server 12345 ( C++, uses coroutines )
* [./io_uring_echo_server 12345](https://github.com/CarterLi/io_uring-echo-server) ( C, raw )

with `rust_echo_bench`: https://github.com/haraldh/rust_echo_bench
unit: request/sec

Also see [benchmarks for different opcodes](https://github.com/CarterLi/io_uring-echo-server#benchmarks)

#### command: `cargo run --release`

LANG | USE_LINK | USE_SPLICE | USE_POLL | operations | 1st | 2nd | 3rd | mid | rate
:-: | :-: | :-: | :-: | -: | -: | -: | -: | -: | -:
C | - | - | 0 | RECV-SEND | 114461 | 116797 | 112112 | 114461 | 100.00%
C | - | - | 1 | POLL-RECV-SEND | 109037 | 114893 | 117629 | 114893 | 100.38%
C++ | 0 | 0 | 0 | RECV-SEND | 117519 | 121139 | 120239 | 120239 | 105.05%
C++ | 0 | 1 | 0 | SPLICE-SPLICE | 90577 | 91912 | 92301 | 91912 | 80.30%
C++ | 1 | 1 | 0 | SPLICE-SPLICE | 93440 | 92619 | 94201 | 93440 | 81.63%
C++ | 0 | 0 | 1 | POLL-RECV-SEND | 107454 | 111525 | 111210 | 111210 | 97.16%
C++ | 0 | 1 | 1 | POLL-SPLICE-SPLICE | 89469 | 90663 | 89315 | 89469 | 78.17%
C++ | 1 | 1 | 1 | POLL-SPLICE-SPLICE | 87628 | 89099 | 88708 | 89099 | 77.84%

## Project Structure

### task.hpp

An awaitable class for C++2a coroutine functions. Originally modified from [gor_task.h](https://github.com/Quuxplusone/coro#taskh-gor_taskh)

NOTE: `task` is not lazily executed, which is easy to use of course, but also can be easily misused. The simplest code to crash your memory is:

```c++
{
char c;
service.read(STDIN_FILENO, &c, sizeof (c), 0);
}
```

The task instance returned by `service.read` is destructed, but the kernel task itself is **NOT** canceled. The memory of variable `c` will be written sometime. In this case, out-of-scope stack memory access will happen.

### io_service.hpp

Main [liburing](https://github.com/axboe/liburing) binding. Also provides some helper functions for working with posix interfaces easier.

### demo

Some examples

#### file_server.cpp

A simple http file server that returns file's content requested by clients

#### link_cp.cpp

A cp command inspired by original [liburing link-cp demo](https://github.com/axboe/liburing/blob/master/examples/link-cp.c)

#### http_client.cpp

A simple http client that sends `GET` http request

#### threading.cpp

A simple `async_invoke` implementation

#### test.cpp

Various simple tests

#### bench.cpp

Benchmarks

#### echo_server.cpp

Echo server, features IOSQE_IO_LINK and IOSQE_FIXED_FILE

See also https://github.com/frevib/io_uring-echo-server#benchmarks for benchmarking

## Build

This library is header only. It provides some demos, as well as some tests.

### Dependencies

This library has to be linked against [`liburing`](https://github.com/axboe/liburing),
and requires a recent version of GCC or Clang. For best results, please use GCC
10.3 (or later), or Clang 10.0.0 (or later)

**[Optional]** This library can be built with either `libc++` or `libstdc++`.
If you want to use `libc++`, you can install it with
```
sudo apt install clang libc++-dev libc++abi-dev`
```

### Building Demos & Tests

In order to build the demos, clone the repository and then run CMake in the
project's root directory:
```bash
git clone https://github.com/CarterLi/liburing4cpp.git
cd liburing4cpp
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --config Release
```
Optionally, you may also use CMake Presets instead (requires CMake version 3.19 or above)
```bash
git clone https://github.com/CarterLi/liburing4cpp.git
cd liburing4cpp
cmake --preset=Release
cmake --build --preset=Release
```

Binares are placed in the `build/` directory. You can then run tests via ctest:
```bash
ctest --test-dir build
```

## Using this library with CMake
When using CMake, you can automatically include this library as a dependency of
your project by using the FetchContent interface:

```cmake
include(FetchContent)
FetchContent_Declare(
liburing4cpp
GIT_REPOSITORY https://github.com/CarterLi/liburing4cpp.git
GIT_TAG async
)
FetchContent_MakeAvailable(liburing4cpp)
```
Then, just use `target_link_libraries`, which will ensure that liburing4cpp/include
is added to the list of includes for whatever target you're building.
```cmake
target_link_libraries(


liburing4cpp)
```

## License

MIT