Add WASI support by tokio_wasi (#11)

* Try to add WASI target support.

* Enable tokio_wasi by wasi feature.

* Add the impl for wasi environment.

* Use target_os instead of feature.

* Remove unused tokio_wasi module, use offical tokio instead.

* Use same original `tokio`.

* Pin tokio's version.

Cargo.toml

@@ -12,22 +12,27 @@ repository = "https://github.com/futursolo/prokio"
 rust-version = "1.60.0"
 
 [dependencies]
-futures = { version = "0.3", default-features = false, features = ["std", "async-await"] }
+futures = { version = "0.3", default-features = false, features = [
+  "std",
+  "async-await",
+] }
 pin-project = "1.0.11"
 pinned = "0.1.0"
+once_cell = "1"
+
+[target.'cfg(all(target_arch = "wasm32", not(target_os = "wasi")))'.dependencies]
+wasm-bindgen-futures = { version = "0.4" }
+gloo = { version = "0.11" }
 
-[target.'cfg(target_arch = "wasm32")'.dependencies]
-wasm-bindgen-futures = "0.4"
-gloo = "0.8"
+[target.'cfg(any(not(target_arch = "wasm32"), target_os = "wasi"))'.dependencies]
+tokio = { version = "1.35", features = ["rt", "time"] }
+tokio-stream = { version = "0.1.14", features = ["time"] }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 num_cpus = "1.13"
-once_cell = "1"
-tokio = { version = "1.21.1", features = ["rt", "time"] }
-tokio-stream = { version = "0.1", features = ["time"] }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
-tokio = { version = "1.19", features = ["full"] }
+tokio = { version = "1", features = ["full"] }
 
 [features]
 default = []

src/lib.rs

@@ -56,10 +56,10 @@ pub mod fmt;
 pub mod pinned;
 pub mod time;
 
-#[cfg(target_arch = "wasm32")]
+#[cfg(all(target_arch = "wasm32", not(target_os = "wasi")))]
 #[path = "rt_wasm_bindgen/mod.rs"]
 mod imp;
-#[cfg(not(target_arch = "wasm32"))]
+#[cfg(any(not(target_arch = "wasm32"), target_os = "wasi"))]
 #[path = "rt_tokio/mod.rs"]
 mod imp;
 

src/rt_tokio/mod.rs

@@ -14,7 +14,15 @@ use local_worker::LocalWorker;
 pub(crate) fn get_default_runtime_size() -> usize {
     // We use num_cpus as std::thread::available_parallelism() does not take
     // system resource constraint (e.g.: cgroups) into consideration.
-    num_cpus::get()
+    #[cfg(not(target_os = "wasi"))]
+    {
+        num_cpus::get()
+    }
+    // WASI does not support multi-threading at this moment.
+    #[cfg(target_os = "wasi")]
+    {
+        1
+    }
 }
 
 #[inline(always)]