--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/lfprng/src/lib.rs Sat Oct 13 18:32:41 2018 +0200
@@ -0,0 +1,65 @@
+pub struct LaggedFibonacciPRNG {
+ circular_buffer: [u32; 64],
+ index: usize,
+}
+
+impl LaggedFibonacciPRNG {
+ fn new(init_values: &[u8]) -> Self {
+ let mut buf = [0xa98765 + 68; 64];
+
+ for i in 0..std::cmp::min(init_values.len(), 54) {
+ buf[i] = init_values[i] as u32;
+ }
+
+ let mut prng = Self {
+ circular_buffer: buf,
+ index: 54,
+ };
+
+ for i in 0..2048 {
+ prng.get_next();
+ }
+
+ prng
+ }
+
+ #[inline]
+ fn get_next(&mut self) -> u32 {
+ self.index = (self.index + 1) & 0x3f;
+ self.circular_buffer[self.index] = (self.circular_buffer[(self.index + 40) & 0x3f]
+ + self.circular_buffer[(self.index + 9) & 0x3f])
+ & 0x7fffffff;
+
+ self.circular_buffer[self.index]
+ }
+
+ #[inline]
+ fn get_random(&mut self, modulo: u32) -> u32 {
+ self.get_next();
+ self.get_next() % modulo
+ }
+
+ #[inline]
+ fn add_randomness(&mut self, value: u32) {
+ self.index = (self.index + 1) & 0x3f;
+ self.circular_buffer[self.index] ^= value;
+ }
+}
+
+#[cfg(test)]
+#[test]
+fn compatibility() {
+ let mut prng = LaggedFibonacciPRNG::new("{052e2aee-ce41-4720-97bd-559a413bf866}".as_bytes());
+
+ assert_eq!(prng.get_random(1000), 418);
+ assert_eq!(prng.get_random(1000000), 554064);
+ assert_eq!(prng.get_random(0xffffffff), 239515837);
+
+ prng.add_randomness(123);
+
+ for i in 0..=100000 {
+ prng.get_random(2);
+ }
+
+ assert_eq!(prng.get_random(0xffffffff), 525333582);
+}