More robust file implementation

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

Cargo.toml

@@ -27,10 +27,9 @@ unstable = []
 async-task = "1.0.0"
 cfg-if = "0.1.9"
 crossbeam-channel = "0.3.9"
-futures-channel-preview = "0.3.0-alpha.18"
 futures-core-preview = "0.3.0-alpha.18"
 futures-io-preview = "0.3.0-alpha.18"
-futures-timer = "0.3.0"
+futures-timer = "0.4.0"
 lazy_static = "1.3.0"
 log = { version = "0.4.8", features = ["kv_unstable"] }
 memchr = "2.2.1"

examples/print-file.rs

@@ -7,7 +7,7 @@ use async_std::io;
 use async_std::prelude::*;
 use async_std::task;
 
-const LEN: usize = 4 * 1024 * 1024; // 4 Mb
+const LEN: usize = 16 * 1024; // 16 Kb
 
 fn main() -> io::Result<()> {
     let path = args().nth(1).expect("missing path argument");

src/net/driver/mod.rs

@@ -213,7 +213,11 @@ impl<T: Evented> IoHandle<T> {
         let mut readiness = mio::Ready::from_usize(self.entry.readiness.load(Ordering::SeqCst));
 
         if (readiness & mask).is_empty() {
-            self.entry.readers.lock().unwrap().push(cx.waker().clone());
+            let mut list = self.entry.readers.lock().unwrap();
+            if list.iter().all(|w| !w.will_wake(cx.waker())) {
+                list.push(cx.waker().clone());
+            }
+
             readiness = mio::Ready::from_usize(self.entry.readiness.fetch_or(0, Ordering::SeqCst));
         }
 
@@ -250,7 +254,11 @@ impl<T: Evented> IoHandle<T> {
         let mut readiness = mio::Ready::from_usize(self.entry.readiness.load(Ordering::SeqCst));
 
         if (readiness & mask).is_empty() {
-            self.entry.writers.lock().unwrap().push(cx.waker().clone());
+            let mut list = self.entry.writers.lock().unwrap();
+            if list.iter().all(|w| !w.will_wake(cx.waker())) {
+                list.push(cx.waker().clone());
+            }
+
             readiness = mio::Ready::from_usize(self.entry.readiness.fetch_or(0, Ordering::SeqCst));
         }