Basic nonblocking I/O

examples/chan.rs

@@ -19,6 +19,8 @@ fn main() -> io::Result<()> {
     let dup = syscall::dup(server.as_raw_fd(), b"listen").map_err(from_syscall_error)?;
     let mut dup = unsafe { File::from_raw_fd(dup) };
 
+    println!("Testing basic I/O...");
+
     dup.write(b"abc")?;
     dup.flush()?;
 
@@ -26,7 +28,8 @@ fn main() -> io::Result<()> {
     assert_eq!(client.read(&mut buf)?, 3);
     assert_eq!(&buf[..3], b"abc");
 
-    // Tada, you can clone handles properly!
+    println!("Testing blocking I/O...");
+
     let mut client_clone = client.try_clone()?;
 
     let thread = thread::spawn(move || -> io::Result<()> {
@@ -36,11 +39,18 @@ fn main() -> io::Result<()> {
         Ok(())
     });
 
-    let mut buf = [0; 5];
     assert_eq!(dup.read(&mut buf)?, 3);
     assert_eq!(&buf[..3], b"def");
 
     thread.join().unwrap().unwrap();
 
+    println!("Testing non-blocking I/O...");
+
+    syscall::fcntl(client.as_raw_fd(), syscall::F_SETFL, syscall::O_NONBLOCK)
+        .map_err(from_syscall_error)?;
+    assert_eq!(client.read(&mut buf).unwrap_err().kind(), io::ErrorKind::WouldBlock);
+
+    println!("It works!");
+
     Ok(())
 }

src/scheme.rs

@@ -2,18 +2,28 @@ use std::collections::BTreeMap;
 use syscall::{flag::*, error::*, Error, SchemeBlockMut, Result};
 
 pub struct Handle {
+    flags: usize,
     path: Option<String>,
     remote: Option<usize>,
     buffer: Vec<u8>
 }
 impl Handle {
-    pub fn dup(&mut self) -> Self {
+    pub fn accept(&mut self) -> Self {
         Self {
+            flags: 0,
             path: None,
             remote: self.remote.take(),
             buffer: Vec::new()
         }
     }
+    pub fn copy(&self) -> Self {
+        Self {
+            flags: self.flags,
+            path: None,
+            remote: self.remote,
+            buffer: Vec::new()
+        }
+    }
 }
 
 #[derive(Default)]
@@ -35,6 +45,7 @@ impl SchemeBlockMut for ChanScheme {
         }
 
         let mut handle = Handle {
+            flags: 0,
             path: None,
             remote: None,
             buffer: Vec::new()
@@ -56,13 +67,13 @@ impl SchemeBlockMut for ChanScheme {
     fn dup(&mut self, id: usize, buf: &[u8]) -> Result<Option<usize>> {
         match buf {
             b"listen" => {
-                let mut remote = match self.handles.get(&id) {
-                    Some(ref handle) if handle.path.is_some() => handle.remote,
+                let mut handle = match self.handles.get(&id) {
+                    Some(ref handle) if handle.path.is_some() => handle.copy(),
                     _ => return Err(Error::new(EBADF))
                 };
-                if let Some(remote) = remote {
+                if let Some(remote) = handle.remote {
                     let new_id = self.next_id;
-                    let mut clone = self.handles.get_mut(&id).map(Handle::dup).unwrap();
+                    let mut clone = self.handles.get_mut(&id).map(Handle::accept).unwrap();
 
                     self.handles.insert(new_id, clone);
                     self.next_id += 1;
@@ -70,6 +81,8 @@ impl SchemeBlockMut for ChanScheme {
                     let mut remote = self.handles.get_mut(&remote).unwrap();
                     remote.remote = Some(new_id);
                     Ok(Some(new_id))
+                } else if handle.flags & O_NONBLOCK == O_NONBLOCK {
+                    Err(Error::new(EAGAIN))
                 } else {
                     Ok(None)
                 }
@@ -79,6 +92,19 @@ impl SchemeBlockMut for ChanScheme {
             }
         }
     }
+    fn fcntl(&mut self, id: usize, cmd: usize, arg: usize) -> Result<Option<usize>> {
+        match self.handles.get_mut(&id) {
+            Some(handle) => match cmd {
+                ::syscall::F_GETFL => Ok(Some(handle.flags)),
+                ::syscall::F_SETFL => {
+                    handle.flags = arg;
+                    Ok(Some(0))
+                },
+                _ => Err(Error::new(EINVAL))
+            },
+            _ => Err(Error::new(EBADF))
+        }
+    }
     fn write(&mut self, id: usize, buf: &[u8]) -> Result<Option<usize>> {
         let remote = match self.handles.get(&id) {
             Some(handle) if handle.path.is_none() => handle.remote,
@@ -106,13 +132,15 @@ impl SchemeBlockMut for ChanScheme {
         if handle.path.is_some() {
             // This is a listener, not a stream.
             Err(Error::new(EBADF))
-        } else if handle.buffer.is_empty() {
-            Ok(None)
-        } else {
+        } else if !handle.buffer.is_empty() {
             let len = buf.len().min(handle.buffer.len());
             buf[..len].copy_from_slice(&handle.buffer[..len]);
             handle.buffer.drain(..len);
             Ok(Some(len))
+        } else if handle.flags & O_NONBLOCK == O_NONBLOCK {
+            Err(Error::new(EAGAIN))
+        } else {
+            Ok(None)
         }
     }
     fn close(&mut self, id: usize) -> Result<Option<usize>> {