signal: add SignalKind Hash/Eq impls and c_int conversion (#4540)

tokio/src/signal/unix.rs

@@ -60,7 +60,7 @@ impl Init for OsExtraData {
 }
 
 /// Represents the specific kind of signal to listen for.
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
 pub struct SignalKind(libc::c_int);
 
 impl SignalKind {
@@ -84,6 +84,17 @@ impl SignalKind {
         Self(signum as libc::c_int)
     }
 
+    /// Get the signal's numeric value.
+    ///
+    /// ```rust
+    /// # use tokio::signal::unix::SignalKind;
+    /// let kind = SignalKind::interrupt();
+    /// assert_eq!(kind.as_raw_value(), libc::SIGINT);
+    /// ```
+    pub fn as_raw_value(&self) -> std::os::raw::c_int {
+        self.0
+    }
+
     /// Represents the SIGALRM signal.
     ///
     /// On Unix systems this signal is sent when a real-time timer has expired.
@@ -190,6 +201,18 @@ impl SignalKind {
     }
 }
 
+impl From<std::os::raw::c_int> for SignalKind {
+    fn from(signum: std::os::raw::c_int) -> Self {
+        Self::from_raw(signum as libc::c_int)
+    }
+}
+
+impl From<SignalKind> for std::os::raw::c_int {
+    fn from(kind: SignalKind) -> Self {
+        kind.as_raw_value()
+    }
+}
+
 pub(crate) struct SignalInfo {
     event_info: EventInfo,
     init: Once,
@@ -474,4 +497,15 @@ mod tests {
         )
         .unwrap_err();
     }
+
+    #[test]
+    fn from_c_int() {
+        assert_eq!(SignalKind::from(2), SignalKind::interrupt());
+    }
+
+    #[test]
+    fn into_c_int() {
+        let value: std::os::raw::c_int = SignalKind::interrupt().into();
+        assert_eq!(value, libc::SIGINT as _);
+    }
 }