library/alloc/src/collections/btree/testing/rng.rs

   1 /// XorShiftRng
   2 pub struct DeterministicRng {
   3     count: usize,
   4     x: u32,
   5     y: u32,
   6     z: u32,
   7     w: u32,
   8 }
   9
  10 impl DeterministicRng {
  11     pub fn new() -> Self {
  12         DeterministicRng { count: 0, x: 0x193a6754, y: 0xa8a7d469, z: 0x97830e05, w: 0x113ba7bb }
  13     }
  14
  15     /// Guarantees that each returned number is unique.
  16     pub fn next(&mut self) -> u32 {
  17         self.count += 1;
  18         assert!(self.count <= 70029);
  19         let x = self.x;
  20         let t = x ^ (x << 11);
  21         self.x = self.y;
  22         self.y = self.z;
  23         self.z = self.w;
  24         let w_ = self.w;
  25         self.w = w_ ^ (w_ >> 19) ^ (t ^ (t >> 8));
  26         self.w
  27     }
  28 }