chore: checkpoint before Python removal

vendor/num-bigint/benches/rng/mod.rs

@@ -0,0 +1,38 @@
+use rand::RngCore;
+
+pub(crate) fn get_rng() -> impl RngCore {
+    XorShiftStar {
+        a: 0x0123_4567_89AB_CDEF,
+    }
+}
+
+/// Simple `Rng` for benchmarking without additional dependencies
+struct XorShiftStar {
+    a: u64,
+}
+
+impl RngCore for XorShiftStar {
+    fn next_u32(&mut self) -> u32 {
+        self.next_u64() as u32
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        // https://en.wikipedia.org/wiki/Xorshift#xorshift*
+        self.a ^= self.a >> 12;
+        self.a ^= self.a << 25;
+        self.a ^= self.a >> 27;
+        self.a.wrapping_mul(0x2545_F491_4F6C_DD1D)
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        for chunk in dest.chunks_mut(8) {
+            let bytes = self.next_u64().to_le_bytes();
+            let slice = &bytes[..chunk.len()];
+            chunk.copy_from_slice(slice)
+        }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand::Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}