Add portable-atomic feature

Cargo.toml

@@ -26,14 +26,14 @@ license.workspace = true
 
 [features]
 default = ["std"]
-std = ["alloc", "portable-atomic/std"]
+std = ["alloc", "portable-atomic?/std"]
 alloc = []
 bench = []
 test_local = []
 
 [dependencies]
 crossbeam-utils = { version = "0.8", default-features = false }
-portable-atomic  = "1"
+portable-atomic = { version = "1", default-features = false, optional = true }
 
 [dev-dependencies]
 once_mut = "0.1.0"

README.md

@@ -31,7 +31,7 @@ Lock-free SPSC FIFO ring buffer with direct access to inner data.
 + Different types of buffers and underlying storages.
 + Can be used without `std` and even without `alloc` (using only statically-allocated memory).
 + Async and blocking versions (see [this section](#derived-crates)).
-+ Uses the `portable-atomic` crate to allow usage on smaller systems without CAS operations.
++ Can optionally use the [`portable-atomic`](https://crates.io/crates/portable-atomic) crate to allow usage on smaller systems without CAS operations.
 
 # Usage
 

scripts/test.sh

@@ -2,6 +2,7 @@
 
 cargo test && \
 cargo test --features test_local && \
+cargo test --features portable-atomic && \
 cargo check --no-default-features --features alloc && \
 cargo check --no-default-features && \
 cd async && \

src/rb/shared.rs

@@ -12,12 +12,15 @@ use crate::{
 };
 #[cfg(feature = "alloc")]
 use alloc::{boxed::Box, sync::Arc};
+#[cfg(not(feature = "portable-atomic"))]
+use core::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use core::{
  mem::{ManuallyDrop, MaybeUninit},
  num::NonZeroUsize,
  ptr,
 };
 use crossbeam_utils::CachePadded;
+#[cfg(feature = "portable-atomic")]
 use portable_atomic::{AtomicBool, AtomicUsize, Ordering};
 
 /// Ring buffer that can be shared between threads.