use std::cell::Cell; use std::ops::Range; pub trait RNG { fn next(&self) -> i32; fn range(&self, range: Range) -> i32 { range.start + ((self.next() & 0x7fffffff) % (range.len() as i32 + 1)) } } /// Deterministic XorShift-based random number generator pub struct XorShift(Cell); impl XorShift { pub fn new(seed: i32) -> Self { Self(Cell::new(seed as u64)) } pub fn next_u64(&self) -> u64 { let mut state = self.0.get(); state ^= state >> 12; state ^= state << 25; state ^= state >> 27; self.0.replace(state); state.wrapping_mul(0x2545F4914F6CDD1Du64) } #[inline] pub fn next_u32(&self) -> u32 { (self.next_u64() >> 32) as u32 } pub fn dump_state(&self) -> u64 { self.0.get() } pub fn load_state(&mut self, saved_state: u64) { self.0.replace(saved_state); } } impl RNG for XorShift { #[inline] fn next(&self) -> i32 { self.next_u32() as i32 } } #[derive(Debug, Clone)] pub struct Xoroshiro32PlusPlus(Cell<(u16, u16)>); impl Xoroshiro32PlusPlus { pub fn new(seed: u32) -> Xoroshiro32PlusPlus { Xoroshiro32PlusPlus(Cell::new(( (seed & 0xffff) as u16, (seed >> 16 & 0xffff) as u16 ))) } pub fn next_u16(&self) -> u16 { let mut state = self.0.get(); let result = (state.0.wrapping_add(state.1)).rotate_left(9).wrapping_add(state.0); state.1 ^= state.0; state.0 = state.0.rotate_left(13) ^ state.1 ^ (state.1 << 5); state.1 = state.1.rotate_left(10); self.0.replace(state); result } pub fn dump_state(&self) -> u32 { let state = self.0.get(); (state.0 as u32) | (state.1 as u32) << 16 } pub fn load_state(&mut self, state: u32) { self.0.replace(( (state & 0xffff) as u16, ((state >> 16) & 0xffff) as u16 )); } } impl RNG for Xoroshiro32PlusPlus { fn next(&self) -> i32 { ((self.next_u16() as u32) << 16 | self.next_u16() as u32) as i32 } }