napi-rs/crates/napi/src/tokio_runtime.rs

use std::future::Future;
use std::ptr;

use once_cell::sync::Lazy;
use tokio::runtime::Runtime;

use crate::{check_status, sys, JsDeferred, JsUnknown, NapiValue, Result};

pub(crate) static RT: Lazy<Runtime> =
  Lazy::new(|| tokio::runtime::Runtime::new().expect("Create tokio runtime failed"));

pub fn runtime() -> &'static Runtime {
  &RT
}

/// Spawns a future onto the Tokio runtime.
///
/// Depending on where you use it, you should await or abort the future in your drop function.
/// To avoid undefined behavior and memory corruptions.
pub fn spawn<F>(fut: F) -> tokio::task::JoinHandle<F::Output>
where
  F: 'static + Send + Future<Output = ()>,
{
  RT.spawn(fut)
}

/// Runs a future to completion
/// This is blocking, meaning that it pauses other execution until the future is complete,
/// only use it when it is absolutely necessary, in other places use async functions instead.
pub fn block_on<F>(fut: F) -> F::Output
where
  F: 'static + Send + Future<Output = ()>,
{
  RT.block_on(fut)
}

// This function's signature must be kept in sync with the one in lib.rs, otherwise napi
// will fail to compile with the `tokio_rt` feature.

/// If the feature `tokio_rt` has been enabled this will enter the runtime context and
/// then call the provided closure. Otherwise it will just call the provided closure.
#[inline]
pub fn within_runtime_if_available<F: FnOnce() -> T, T>(f: F) -> T {
  let _rt_guard = RT.enter();
  f()
}

#[allow(clippy::not_unsafe_ptr_arg_deref)]
pub fn execute_tokio_future<
  Data: 'static + Send,
  Fut: 'static + Send + Future<Output = Result<Data>>,
  Resolver: 'static + Send + Sync + FnOnce(sys::napi_env, Data) -> Result<sys::napi_value>,
>(
  env: sys::napi_env,
  fut: Fut,
  resolver: Resolver,
) -> Result<sys::napi_value> {
  let mut promise = ptr::null_mut();
  let mut deferred = ptr::null_mut();

  check_status!(unsafe { sys::napi_create_promise(env, &mut deferred, &mut promise) })?;

  let (deferred, promise) = JsDeferred::new(env)?;

  spawn(async move {
    match fut.await {
      Ok(v) => deferred.resolve(|env| {
        resolver(env.raw(), v).map(|v| unsafe { JsUnknown::from_raw_unchecked(env.raw(), v) })
      }),
      Err(e) => deferred.reject(e),
    }
  });

  Ok(promise.0.value)
}