bogo_alloc/
lib.rs

1use std::alloc::{GlobalAlloc, Layout};
2use std::sync::atomic::{AtomicBool, AtomicIsize, AtomicUsize, Ordering};
3use std::sync::Mutex;
4use nanorand::{Rng, WyRand};
5
6const ORD: Ordering = Ordering::Relaxed;
7
8/// Returns a totally memory safe allocator, with a fixed size heap-capacity
9pub struct BogoAlloc<const SIZE: usize> {
10	start: AtomicIsize,
11	size: AtomicUsize,
12	uninit: AtomicBool,
13	rand: Mutex<Option<WyRand>>,
14}
15
16impl<const SIZE: usize> BogoAlloc<SIZE> {
17	/// Creates a new uninitialized Allocator, which initializes itself when first used
18	pub const fn new() -> Self {
19		Self {
20			start: AtomicIsize::new(0),
21			size: AtomicUsize::new(0),
22			uninit: AtomicBool::new(true),
23			rand: Mutex::new(None),
24		}
25	}
26	/// Returns random integer from internal RNG
27	unsafe fn rand(&self) -> isize {
28		isize::from_le_bytes(self.rand.lock().unwrap().as_mut().unwrap_unchecked().rand())
29	}
30	/// Returns random address from within range
31	unsafe fn rand_addr(&self) -> isize {
32		self.rand().abs() % self.size.load(ORD) as isize
33	}
34}
35
36unsafe impl<const SIZE: usize> GlobalAlloc for BogoAlloc<SIZE> {
37	unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
38		// Only one call should allocate, the rest gets deferred and waits for this to complete
39		if self.uninit.swap(false, ORD) {
40			let size: usize = 2_usize.pow(SIZE as u32);
41			self.size.store(size, ORD);
42			*self.rand.lock().unwrap() = Some(WyRand::new());
43			self.start.store(libc::malloc(size.into()) as isize, ORD);
44		} else {
45			while self.start.load(ORD) == 0 {}
46		}
47		let align = layout.align() as isize;
48		let mut offset = self.rand_addr().saturating_sub(layout.size() as isize); // To ensure allocations end up within bounds
49		offset = (offset + align - 1) & !(align - 1); // Ensures the memory is aligned
50		(self.start.load(ORD) + offset) as *mut u8
51	}
52
53	unsafe fn dealloc(&self, _: *mut u8, _: Layout) {
54		// :)
55	}
56}
57
58
59#[cfg(test)]
60mod tests {
61	use crate::BogoAlloc;
62
63	#[global_allocator]
64	static A: BogoAlloc<32> = BogoAlloc::new();
65
66	#[test]
67	fn funny_values_everywhere() {
68		let vecs = (1..42).map(|i| vec![i; 1500]).collect::<Vec<_>>();
69		println!("{:?}", vecs);
70	}
71}
bogo_alloc/lib.rs

bogo_alloc/
lib.rs
