shoney.arickathil
6b8b41ce06
- http: connection, listener, request, response, route updates - pg: protocol improvements - runtime: eventfd, netpoll (epoll/io_uring), scheduler, signalfd, timerfd - shard: cross-shard job improvements - wal: replay and recovery fixes
66 lines
2 KiB
Rust
66 lines
2 KiB
Rust
//! `eventfd(2)` wrapper — counter semaphore exposed as a file descriptor.
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//!
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//! Used as the cross-flow wake-up primitive: any code path that needs the
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//! event loop to come back and run something writes a `1` to the eventfd,
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//! which becomes readable on the loop's next `wait_once`.
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//!
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//! Ported from `.dev/reference/crates/wo-event/src/eventfd.rs` with an added
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//! `AsRawFd` impl so callers can drop the fd straight into `EventLoop`.
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use std::io;
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use std::os::unix::io::{AsRawFd, RawFd};
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pub struct EventFd {
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fd: RawFd,
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}
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impl EventFd {
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/// Create a non-blocking, close-on-exec eventfd with initial counter 0.
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pub fn new() -> io::Result<Self> {
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let fd = unsafe { libc::eventfd(0, libc::EFD_NONBLOCK | libc::EFD_CLOEXEC) };
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if fd < 0 { return Err(io::Error::last_os_error()); }
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Ok(Self { fd })
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}
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/// Add `val` to the counter. Wakes any waiter when the counter goes 0→non-zero.
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pub fn write(&self, val: u64) -> io::Result<()> {
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let buf = val.to_ne_bytes();
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let ret = unsafe {
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libc::write(self.fd, buf.as_ptr() as *const libc::c_void, 8)
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};
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if ret < 0 { Err(io::Error::last_os_error()) } else { Ok(()) }
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}
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/// Atomically read and zero the counter. Returns `EAGAIN` if the
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/// counter is already 0 (since we set `EFD_NONBLOCK`).
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pub fn read(&self) -> io::Result<u64> {
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let mut buf = [0u8; 8];
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let ret = unsafe {
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libc::read(self.fd, buf.as_mut_ptr() as *mut libc::c_void, 8)
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};
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if ret < 0 { Err(io::Error::last_os_error()) } else { Ok(u64::from_ne_bytes(buf)) }
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}
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}
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impl AsRawFd for EventFd {
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fn as_raw_fd(&self) -> RawFd { self.fd }
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}
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impl Drop for EventFd {
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fn drop(&mut self) {
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unsafe { libc::close(self.fd) };
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn writes_accumulate() {
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let efd = EventFd::new().unwrap();
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efd.write(5).unwrap();
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efd.write(3).unwrap();
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assert_eq!(efd.read().unwrap(), 8);
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}
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}
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