diff options
Diffstat (limited to 'library/alloc/src/collections/btree/testing/rng.rs')
-rw-r--r-- | library/alloc/src/collections/btree/testing/rng.rs | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/library/alloc/src/collections/btree/testing/rng.rs b/library/alloc/src/collections/btree/testing/rng.rs new file mode 100644 index 000000000..ecf543bee --- /dev/null +++ b/library/alloc/src/collections/btree/testing/rng.rs @@ -0,0 +1,28 @@ +/// XorShiftRng +pub struct DeterministicRng { + count: usize, + x: u32, + y: u32, + z: u32, + w: u32, +} + +impl DeterministicRng { + pub fn new() -> Self { + DeterministicRng { count: 0, x: 0x193a6754, y: 0xa8a7d469, z: 0x97830e05, w: 0x113ba7bb } + } + + /// Guarantees that each returned number is unique. + pub 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 + } +} |