implement simple event loop abstraction

1 files changed, 73 insertions, 0 deletions

diff --git a/src/event_loop.rs b/src/event_loop.rs
new file mode 100644
index 0000000..2300513
--- /dev/null
+++ b/src/event_loop.rs
@@ -0,0 +1,73 @@
+use std::collections::HashMap;
+use std::io;
+use std::os::fd::RawFd;
+
+use anyhow::Result;
+
+pub struct EventLoop<D> {
+    pollfds: Vec<libc::pollfd>,
+    cbs: HashMap<RawFd, Box<dyn FnMut(&mut D) -> Result<Action>>>,
+}
+
+pub enum Action {
+    Keep,
+    Unregister,
+}
+
+impl<D> EventLoop<D> {
+    pub fn new() -> Self {
+        Self {
+            pollfds: Vec::new(),
+            cbs: HashMap::new(),
+        }
+    }
+
+    pub fn register_with_fd<F>(&mut self, fd: RawFd, cb: F)
+    where
+        F: FnMut(&mut D) -> Result<Action> + 'static,
+    {
+        self.cbs.insert(fd, Box::new(cb));
+    }
+
+    pub fn run(&mut self, state: &mut D) -> Result<()> {
+        if self.cbs.is_empty() {
+            return Ok(());
+        }
+
+        self.pollfds.clear();
+        for &fd in self.cbs.keys() {
+            self.pollfds.push(libc::pollfd {
+                fd,
+                events: libc::POLLIN,
+                revents: 0,
+            });
+        }
+
+        loop {
+            let result =
+                unsafe { libc::poll(self.pollfds.as_mut_ptr(), self.pollfds.len() as _, -1) };
+            if result == -1 {
+                let err = io::Error::last_os_error();
+                if err.kind() == io::ErrorKind::Interrupted {
+                    continue;
+                }
+                return Err(err.into());
+            }
+            break;
+        }
+
+        for fd in &self.pollfds {
+            if fd.revents != 0 {
+                let mut cb = self.cbs.remove(&fd.fd).unwrap();
+                match cb(state)? {
+                    Action::Keep => {
+                        self.cbs.insert(fd.fd, cb);
+                    }
+                    Action::Unregister => (),
+                }
+            }
+        }
+
+        Ok(())
+    }
+}