1 files changed, 28 insertions, 0 deletions
diff --git a/library/alloctests/testing/rng.rs b/library/alloctests/testing/rng.rs
new file mode 100644
index 00000000000..77d3348f38a
--- /dev/null
+++ b/library/alloctests/testing/rng.rs
@@ -0,0 +1,28 @@
+/// XorShiftRng
+pub(crate) struct DeterministicRng {
+    count: usize,
+    x: u32,
+    y: u32,
+    z: u32,
+    w: u32,
+}
+
+impl DeterministicRng {
+    pub(crate) fn new() -> Self {
+        DeterministicRng { count: 0, x: 0x193a6754, y: 0xa8a7d469, z: 0x97830e05, w: 0x113ba7bb }
+    }
+
+    /// Guarantees that each returned number is unique.
+    pub(crate) fn next(&mut self) -> u32 {
+        self.count += 1;
+        assert!(self.count <= 70029);
+        let x = self.x;
+        let t = x ^ (x << 11);
+        self.x = self.y;
+        self.y = self.z;
+        self.z = self.w;
+        let w_ = self.w;
+        self.w = w_ ^ (w_ >> 19) ^ (t ^ (t >> 8));
+        self.w
+    }
+}