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-rw-r--r--third_party/rust/crossbeam-channel/src/flavors/never.rs110
1 files changed, 110 insertions, 0 deletions
diff --git a/third_party/rust/crossbeam-channel/src/flavors/never.rs b/third_party/rust/crossbeam-channel/src/flavors/never.rs
new file mode 100644
index 0000000000..277a61dc1c
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+++ b/third_party/rust/crossbeam-channel/src/flavors/never.rs
@@ -0,0 +1,110 @@
+//! Channel that never delivers messages.
+//!
+//! Messages cannot be sent into this kind of channel.
+
+use std::marker::PhantomData;
+use std::time::Instant;
+
+use crate::context::Context;
+use crate::err::{RecvTimeoutError, TryRecvError};
+use crate::select::{Operation, SelectHandle, Token};
+use crate::utils;
+
+/// This flavor doesn't need a token.
+pub(crate) type NeverToken = ();
+
+/// Channel that never delivers messages.
+pub(crate) struct Channel<T> {
+ _marker: PhantomData<T>,
+}
+
+impl<T> Channel<T> {
+ /// Creates a channel that never delivers messages.
+ #[inline]
+ pub(crate) fn new() -> Self {
+ Channel {
+ _marker: PhantomData,
+ }
+ }
+
+ /// Attempts to receive a message without blocking.
+ #[inline]
+ pub(crate) fn try_recv(&self) -> Result<T, TryRecvError> {
+ Err(TryRecvError::Empty)
+ }
+
+ /// Receives a message from the channel.
+ #[inline]
+ pub(crate) fn recv(&self, deadline: Option<Instant>) -> Result<T, RecvTimeoutError> {
+ utils::sleep_until(deadline);
+ Err(RecvTimeoutError::Timeout)
+ }
+
+ /// Reads a message from the channel.
+ #[inline]
+ pub(crate) unsafe fn read(&self, _token: &mut Token) -> Result<T, ()> {
+ Err(())
+ }
+
+ /// Returns `true` if the channel is empty.
+ #[inline]
+ pub(crate) fn is_empty(&self) -> bool {
+ true
+ }
+
+ /// Returns `true` if the channel is full.
+ #[inline]
+ pub(crate) fn is_full(&self) -> bool {
+ true
+ }
+
+ /// Returns the number of messages in the channel.
+ #[inline]
+ pub(crate) fn len(&self) -> usize {
+ 0
+ }
+
+ /// Returns the capacity of the channel.
+ #[inline]
+ pub(crate) fn capacity(&self) -> Option<usize> {
+ Some(0)
+ }
+}
+
+impl<T> SelectHandle for Channel<T> {
+ #[inline]
+ fn try_select(&self, _token: &mut Token) -> bool {
+ false
+ }
+
+ #[inline]
+ fn deadline(&self) -> Option<Instant> {
+ None
+ }
+
+ #[inline]
+ fn register(&self, _oper: Operation, _cx: &Context) -> bool {
+ self.is_ready()
+ }
+
+ #[inline]
+ fn unregister(&self, _oper: Operation) {}
+
+ #[inline]
+ fn accept(&self, token: &mut Token, _cx: &Context) -> bool {
+ self.try_select(token)
+ }
+
+ #[inline]
+ fn is_ready(&self) -> bool {
+ false
+ }
+
+ #[inline]
+ fn watch(&self, _oper: Operation, _cx: &Context) -> bool {
+ self.is_ready()
+ }
+
+ #[inline]
+ fn unwatch(&self, _oper: Operation) {}
+}