1 files changed, 78 insertions, 0 deletions
diff --git a/tools/profiler/rust-api/src/profiler_state.rs b/tools/profiler/rust-api/src/profiler_state.rs
new file mode 100644
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+++ b/tools/profiler/rust-api/src/profiler_state.rs
@@ -0,0 +1,78 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Gecko profiler state.
+
+/// Whether the Gecko profiler is currently active.
+/// A typical use of this API:
+/// ```rust
+/// if gecko_profiler::is_active() {
+///   // do something.
+/// }
+/// ```
+///
+/// This implementation must be kept in sync with
+/// `mozilla::profiler::detail::RacyFeatures::IsActive`.
+#[cfg(feature = "enabled")]
+#[inline]
+pub fn is_active() -> bool {
+    use crate::gecko_bindings::structs::mozilla::profiler::detail;
+
+    let active_and_features = get_active_and_features();
+    (active_and_features & detail::RacyFeatures_Active) != 0
+}
+
+/// Always false when MOZ_GECKO_PROFILER is not defined.
+#[cfg(not(feature = "enabled"))]
+#[inline]
+pub fn is_active() -> bool {
+    false
+}
+
+/// Whether the Gecko Profiler can accept markers.
+/// Similar to `is_active`, but with some extra checks that determine if the
+/// profiler would currently store markers. So this should be used before
+/// doing some potentially-expensive work that's used in a marker. E.g.:
+///
+/// ```rust
+/// if gecko_profiler::can_accept_markers() {
+///   // Do something expensive and add the marker with that data.
+/// }
+/// ```
+///
+/// This implementation must be kept in sync with
+/// `mozilla::profiler::detail::RacyFeatures::IsActiveAndUnpaused`.
+#[cfg(feature = "enabled")]
+#[inline]
+pub fn can_accept_markers() -> bool {
+    use crate::gecko_bindings::structs::mozilla::profiler::detail;
+
+    let active_and_features = get_active_and_features();
+    (active_and_features & detail::RacyFeatures_Active) != 0
+        && (active_and_features & detail::RacyFeatures_Paused) == 0
+}
+
+/// Always false when MOZ_GECKO_PROFILER is not defined.
+#[cfg(not(feature = "enabled"))]
+#[inline]
+pub fn can_accept_markers() -> bool {
+    false
+}
+
+/// Returns the value of atomic `RacyFeatures::sActiveAndFeatures` from the C++ side.
+#[cfg(feature = "enabled")]
+#[inline]
+fn get_active_and_features() -> u32 {
+    use crate::gecko_bindings::structs::mozilla::profiler::detail;
+    use std::mem;
+    use std::sync::atomic::{AtomicU32, Ordering};
+
+    // This is reaching for the C++ atomic value instead of calling an FFI
+    // function to return this value. Because, calling an FFI function is much
+    // more expensive compared to this method. That's why it's worth to go with
+    // this solution for performance. But it's crucial to keep the implementation
+    // of this and the callers in sync with the C++ counterparts.
+    unsafe { mem::transmute::<_, &AtomicU32>(&detail::RacyFeatures_sActiveAndFeatures) }
+        .load(Ordering::Relaxed)
+}