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Double Mapped Circular Buffer

  • Thread-safe.
  • Supports multiple readers.
  • Generic over the item type.
  • Provides access to all items (not n-1).
  • Supports Linux, macOS, Windows, and Android.
  • Sync, async, and non-blocking implementations.
  • Generic variant that allows specifying custom Notifiers to ease integration.
  • Underlying data structure (i.e., DoubleMappedBuffer) is exported to allow custom implementations. Apache 2.0 licensed Build Status


This circular buffer implementation maps the underlying buffer twice, back-to-back into the virtual address space of the process. This arrangement allows the circular buffer to present the available data sequentially, (i.e., as a slice) without having to worry about wrapping.


use vmcircbuffer::sync;

let mut w = sync::Circular::new::<u32>()?;
let mut r = w.add_reader();

// delay producing by 1 sec
let now = std::time::Instant::now();
let delay = std::time::Duration::from_millis(1000);

// producer thread
std::thread::spawn(move || {
    let w_buff = w.slice();
    for v in w_buff.iter_mut() {
        *v = 23;
    let l = w_buff.len();

// blocks until data becomes available
let r_buff = r.slice().unwrap();
assert!(now.elapsed() > delay);
for v in r_buff {
    assert_eq!(*v, 23);
let l = r_buff.len();


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the project, shall be licensed as Apache 2.0, without any additional terms or conditions.