port subscriptions in from old branch

crates/wasi-c2/src/sched.rs

@@ -1,8 +1,15 @@
+use crate::file::WasiFile;
 use crate::Error;
+use cap_std::time::{SystemClock, SystemTime};
+use std::cell::Ref;
+pub mod subscription;
+
+use subscription::{
+    RwSubscription, Subscription, SubscriptionResult, SubscriptionSet, TimerSubscription,
+};
 
 pub trait WasiSched {
-    // XXX poll oneoff needs args and results.
-    fn poll_oneoff(&self) -> Result<(), Error>;
+    fn poll_oneoff(&self, subs: SubscriptionSet) -> Result<(), Error>;
     fn sched_yield(&self) -> Result<(), Error>;
 }
 
@@ -10,7 +17,7 @@ pub trait WasiSched {
 pub struct SyncSched {}
 
 impl WasiSched for SyncSched {
-    fn poll_oneoff(&self) -> Result<(), Error> {
+    fn poll_oneoff(&self, subs: SubscriptionSet) -> Result<(), Error> {
         todo!()
     }
     fn sched_yield(&self) -> Result<(), Error> {
@@ -18,3 +25,48 @@ impl WasiSched for SyncSched {
         Ok(())
     }
 }
+
+pub struct Userdata(u64);
+impl From<u64> for Userdata {
+    fn from(u: u64) -> Userdata {
+        Userdata(u)
+    }
+}
+impl From<Userdata> for u64 {
+    fn from(u: Userdata) -> u64 {
+        u.0
+    }
+}
+
+pub struct Poll<'a> {
+    subs: Vec<(Subscription<'a>, Userdata)>,
+}
+
+impl<'a> Poll<'a> {
+    pub fn new() -> Self {
+        Self { subs: Vec::new() }
+    }
+    pub fn subscribe_timer(&mut self, deadline: SystemTime, ud: Userdata) {
+        self.subs
+            .push((Subscription::Timer(TimerSubscription { deadline }), ud));
+    }
+    pub fn subscribe_read(&mut self, file: Ref<'a, dyn WasiFile>, ud: Userdata) {
+        self.subs
+            .push((Subscription::Read(RwSubscription::new(file)), ud));
+    }
+    pub fn subscribe_write(&mut self, file: Ref<'a, dyn WasiFile>, ud: Userdata) {
+        self.subs
+            .push((Subscription::Read(RwSubscription::new(file)), ud));
+    }
+    pub fn results(self, clock: &SystemClock) -> Vec<(SubscriptionResult, Userdata)> {
+        self.subs
+            .into_iter()
+            .filter_map(|(s, ud)| SubscriptionResult::from_subscription(s, clock).map(|r| (r, ud)))
+            .collect()
+    }
+    pub(crate) fn subscriptions(&'a mut self) -> SubscriptionSet<'a> {
+        SubscriptionSet {
+            subs: self.subs.iter().map(|(s, _ud)| s).collect(),
+        }
+    }
+}