Struct DelayBuffer 

pub struct DelayBuffer<T> { /* private fields */ }

A delay buffer that outputs items as they are pushed out by newer items.

This is equivalent to Apama’s rstream operator:

• retain 1 select rstream a delays output by 1 item
• When a new item arrives, the oldest item is output

Use cases:

• Compare current value with previous value
• Detect changes between consecutive aggregations
• Implement “previous” reference in expressions

Example

let mut delay = DelayBuffer::new(1);

// First item: nothing output (buffer filling)
assert_eq!(delay.push(10), None);

// Second item: first item output
assert_eq!(delay.push(20), Some(10));

// Third item: second item output
assert_eq!(delay.push(30), Some(20));

Implementations

impl<T: Clone> DelayBuffer<T>

pub fn new(delay: usize) -> Self

Create a new delay buffer with specified delay count.

A delay of 1 means the previous item is output when a new item arrives.

pub fn push(&mut self, item: T) -> Option<T>

Push a new item and potentially output a delayed item.

Returns Some(item) if there’s an item to output (buffer was full), or None if the buffer is still filling up.

pub fn current(&self) -> Option<&T>

Get the current item (most recent) without removing it.

pub fn previous(&self) -> Option<&T>

Get the previous item (one before current) without removing it.

pub fn oldest(&self) -> Option<&T>

Get the oldest item in the buffer (the one that would be output next).

pub fn is_ready(&self) -> bool

Check if the buffer is full (ready to output items).

pub fn len(&self) -> usize

Get the current number of items in the buffer.

pub fn is_empty(&self) -> bool

Check if the buffer is empty.

pub fn clear(&mut self)

Clear the buffer.

pub fn flush(&mut self) -> Vec<T>

Flush all items from the buffer, returning them in order.

Trait Implementations

impl<T: Clone> Clone for DelayBuffer<T>

fn clone(&self) -> DelayBuffer<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for DelayBuffer<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.