1 files changed, 38 insertions, 0 deletions
diff --git a/third_party/rust/wgpu-hal/src/metal/time.rs b/third_party/rust/wgpu-hal/src/metal/time.rs
new file mode 100644
index 0000000000..5c6bec10cd
--- /dev/null
+++ b/third_party/rust/wgpu-hal/src/metal/time.rs
@@ -0,0 +1,38 @@
+//! Handling of global timestamps.
+
+#[repr(C)]
+#[derive(Debug)]
+struct MachTimebaseInfo {
+    numerator: u32,
+    denominator: u32,
+}
+extern "C" {
+    fn mach_timebase_info(out: *mut MachTimebaseInfo) -> u32;
+    fn mach_absolute_time() -> u64;
+}
+
+/// A timer which uses mach_absolute_time to get its time. This is what the metal callbacks use.
+#[derive(Debug)]
+pub struct PresentationTimer {
+    scale: MachTimebaseInfo,
+}
+impl PresentationTimer {
+    /// Generates a new timer.
+    pub fn new() -> Self {
+        // Default to 1 / 1 in case the call to timebase_info fails.
+        let mut scale = MachTimebaseInfo {
+            numerator: 1,
+            denominator: 1,
+        };
+        unsafe { mach_timebase_info(&mut scale) };
+
+        Self { scale }
+    }
+
+    /// Gets the current time in nanoseconds.
+    pub fn get_timestamp_ns(&self) -> u128 {
+        let time = unsafe { mach_absolute_time() };
+
+        (time as u128 * self.scale.numerator as u128) / self.scale.denominator as u128
+    }
+}