1 files changed, 72 insertions, 0 deletions
diff --git a/library/std/src/sys/itron/wait_flag.rs b/library/std/src/sys/itron/wait_flag.rs
new file mode 100644
index 000000000..e432edd20
--- /dev/null
+++ b/library/std/src/sys/itron/wait_flag.rs
@@ -0,0 +1,72 @@
+use crate::mem::MaybeUninit;
+use crate::time::Duration;
+
+use super::{
+    abi,
+    error::{expect_success, fail},
+    time::with_tmos,
+};
+
+const CLEAR: abi::FLGPTN = 0;
+const RAISED: abi::FLGPTN = 1;
+
+/// A thread parking primitive that is not susceptible to race conditions,
+/// but provides no atomic ordering guarantees and allows only one `raise` per wait.
+pub struct WaitFlag {
+    flag: abi::ID,
+}
+
+impl WaitFlag {
+    /// Creates a new wait flag.
+    pub fn new() -> WaitFlag {
+        let flag = expect_success(
+            unsafe {
+                abi::acre_flg(&abi::T_CFLG {
+                    flgatr: abi::TA_FIFO | abi::TA_WSGL | abi::TA_CLR,
+                    iflgptn: CLEAR,
+                })
+            },
+            &"acre_flg",
+        );
+
+        WaitFlag { flag }
+    }
+
+    /// Wait for the wait flag to be raised.
+    pub fn wait(&self) {
+        let mut token = MaybeUninit::uninit();
+        expect_success(
+            unsafe { abi::wai_flg(self.flag, RAISED, abi::TWF_ORW, token.as_mut_ptr()) },
+            &"wai_flg",
+        );
+    }
+
+    /// Wait for the wait flag to be raised or the timeout to occur.
+    ///
+    /// Returns whether the flag was raised (`true`) or the operation timed out (`false`).
+    pub fn wait_timeout(&self, dur: Duration) -> bool {
+        let mut token = MaybeUninit::uninit();
+        let res = with_tmos(dur, |tmout| unsafe {
+            abi::twai_flg(self.flag, RAISED, abi::TWF_ORW, token.as_mut_ptr(), tmout)
+        });
+
+        match res {
+            abi::E_OK => true,
+            abi::E_TMOUT => false,
+            error => fail(error, &"twai_flg"),
+        }
+    }
+
+    /// Raise the wait flag.
+    ///
+    /// Calls to this function should be balanced with the number of successful waits.
+    pub fn raise(&self) {
+        expect_success(unsafe { abi::set_flg(self.flag, RAISED) }, &"set_flg");
+    }
+}
+
+impl Drop for WaitFlag {
+    fn drop(&mut self) {
+        expect_success(unsafe { abi::del_flg(self.flag) }, &"del_flg");
+    }
+}