diff options
| -rwxr-xr-x | src/lib.rs | 53 |
1 files changed, 31 insertions, 22 deletions
@@ -10,7 +10,7 @@ use core::{ cell::UnsafeCell, cmp, marker::PhantomData, - mem, + mem::{self, MaybeUninit}, sync::atomic::{AtomicUsize, Ordering}, }; @@ -38,7 +38,7 @@ pub struct RingBuffer<T> { // Backing store needs to be UnsafeCell to make sure it's not // stored in read-only data sections. - buf: UnsafeCell<[T; CAPACITY]>, + buf: UnsafeCell<MaybeUninit<[T; CAPACITY]>>, } impl<T> RingBuffer<T> @@ -46,14 +46,11 @@ where T: Copy, { /// Create a new RingBuffer. - /// - /// The `default` element isn't important, but is, unfortunately, - /// currently required to make stable rust happy. - pub const fn new(default: T) -> Self { + pub const fn new() -> Self { Self { head: AtomicUsize::new(0), tail: AtomicUsize::new(0), - buf: UnsafeCell::new([default; CAPACITY]), + buf: UnsafeCell::new(MaybeUninit::uninit()), } } @@ -132,8 +129,8 @@ where } else { let nh = (h + 1) % CAPACITY; let rc = unsafe { - let buf = &mut *rb.buf.get(); - Some(*buf.get_unchecked(h)) + let buf: &MaybeUninit<[T; CAPACITY]> = &*rb.buf.get(); + Some(Self::load_val_at(h, buf)) }; rb.head.store(nh, Ordering::SeqCst); rc @@ -154,9 +151,9 @@ where let len = cmp::min(mylen, buflen); unsafe { - let rbuf = &mut *rb.buf.get(); + let rbuf: &MaybeUninit<[T; CAPACITY]> = &*rb.buf.get(); for i in 0..len { - *buf.get_unchecked_mut(i) = *rbuf.get_unchecked(h); + *buf.get_unchecked_mut(i) = Self::load_val_at(h, rbuf); h = (h + 1) % CAPACITY; } } @@ -164,6 +161,12 @@ where rb.head.store(h, Ordering::SeqCst); len } + + #[inline(always)] + unsafe fn load_val_at(i: usize, buf: &MaybeUninit<[T; CAPACITY]>) -> T { + let b: &[T; CAPACITY] = &*buf.as_ptr(); + *b.get_unchecked(i) + } } impl<T> Iterator for Reader<'_, T> @@ -202,7 +205,7 @@ where } else { unsafe { let buf = &mut *rb.buf.get(); - *buf.get_unchecked_mut(t) = v; + Self::store_val_at(t, buf, v); } rb.tail.store(nt, Ordering::SeqCst); Ok(()) @@ -225,7 +228,7 @@ where unsafe { let rbuf = &mut *rb.buf.get(); for i in 0..len { - *rbuf.get_unchecked_mut(t) = *buf.get_unchecked(i); + Self::store_val_at(t, rbuf, *buf.get_unchecked(i)); t = (t + 1) % CAPACITY; } } @@ -233,6 +236,12 @@ where rb.tail.store(t, Ordering::SeqCst); len } + + #[inline(always)] + unsafe fn store_val_at(i: usize, buf: &mut MaybeUninit<[T; CAPACITY]>, val: T) { + let b: &mut [T; CAPACITY] = &mut *buf.as_mut_ptr(); + *b.get_unchecked_mut(i) = val + } } #[cfg(test)] @@ -241,7 +250,7 @@ mod test { #[test] fn detects_empty() { - let rb = RingBuffer::<bool>::new(false); + let rb = RingBuffer::<bool>::new(); let (mut rbr, mut rbw) = rb.split(); assert!(rbr.is_empty()); rbw.unshift(true).ok(); @@ -252,7 +261,7 @@ mod test { #[test] fn len_matches() { - let rb = RingBuffer::<bool>::new(false); + let rb = RingBuffer::<bool>::new(); let (mut rbr, mut rbw) = rb.split(); // Count length up. @@ -273,7 +282,7 @@ mod test { #[test] fn can_wrap() { - let rb = RingBuffer::<usize>::new(0); + let rb = RingBuffer::<usize>::new(); let (mut rbr, mut rbw) = rb.split(); // Make sure we can store n-1 elements. @@ -289,7 +298,7 @@ mod test { #[test] fn cannot_overwrite() { - let rb = RingBuffer::<usize>::new(0); + let rb = RingBuffer::<usize>::new(); let (mut rbr, mut rbw) = rb.split(); for i in 0..CAPACITY - 1 { @@ -304,7 +313,7 @@ mod test { #[test] fn can_iter() { - let rb = RingBuffer::<usize>::new(0); + let rb = RingBuffer::<usize>::new(); let (rbr, mut rbw) = rb.split(); for i in 0..CAPACITY - 1 { @@ -320,7 +329,7 @@ mod test { #[test] fn shift_into_smaller() { - let rb = RingBuffer::<usize>::new(0); + let rb = RingBuffer::<usize>::new(); let (mut rbr, mut rbw) = rb.split(); for i in 0..CAPACITY - 1 { assert_eq!(rbw.unshift(i), Ok(())); @@ -337,7 +346,7 @@ mod test { #[test] fn shift_into_bigger() { - let rb = RingBuffer::<usize>::new(0); + let rb = RingBuffer::<usize>::new(); let (mut rbr, mut rbw) = rb.split(); for i in 0..CAPACITY - 1 { assert_eq!(rbw.unshift(i), Ok(())); @@ -357,7 +366,7 @@ mod test { #[test] fn unshift_from_smaller() { - let rb = RingBuffer::<usize>::new(0); + let rb = RingBuffer::<usize>::new(); let (mut rbr, mut rbw) = rb.split(); let buf: [usize; CAPACITY / 2] = [0xdead; CAPACITY / 2]; @@ -370,7 +379,7 @@ mod test { #[test] fn unshift_from_bigger() { - let rb = RingBuffer::<usize>::new(0); + let rb = RingBuffer::<usize>::new(); let (mut rbr, mut rbw) = rb.split(); let buf: [usize; CAPACITY * 2] = [0xdead; CAPACITY * 2]; |