Struct StreamingRealData 

pub struct StreamingRealData<F: Fn(usize, &mut [f64]) -> usize> {
    len: usize,
    reader: F,
    cache: RefCell<BTreeMap<usize, Vec<f64>>>,
    chunk_size: usize,
}

Streaming data adaptor for ALTREP real (f64) vectors.

Elements are loaded on-demand via a reader closure in fixed-size chunks. Chunks are cached in a BTreeMap for repeated access.

Reader Contract

The reader F(start, buf) -> count fills buf with elements starting at index start and returns the number of elements actually written.

Example

use miniextendr_api::altrep_data::StreamingRealData;

let data = StreamingRealData::new(1000, 64, |start, buf| {
    let count = buf.len().min(1000 - start);
    for (i, slot) in buf[..count].iter_mut().enumerate() {
        *slot = (start + i) as f64 * 0.1;
    }
    count
});

Fields

len: usize

reader: F

cache: RefCell<BTreeMap<usize, Vec<f64>>>

chunk_size: usize

Implementations

impl<F: Fn(usize, &mut [f64]) -> usize> StreamingRealData<F>

pub fn new(len: usize, chunk_size: usize, reader: F) -> Self

Create a new streaming real data source.

• len: total number of elements
• chunk_size: number of elements per cache chunk
• reader: closure that fills a buffer starting at a given index

fn ensure_chunk(&self, chunk_idx: usize)

Load a chunk into the cache if not already present.

Trait Implementations

impl<F: Fn(usize, &mut [f64]) -> usize> AltRealData for StreamingRealData<F>

fn elt(&self, i: usize) -> f64

Get the real element at index i.

fn get_region(&self, start: usize, len: usize, buf: &mut [f64]) -> usize

Optional: bulk read into buffer (clamped to available data).

fn as_slice(&self) -> Option<&[f64]>

Optional: return a pointer to contiguous data if available.

fn is_sorted(&self) -> Option<Sortedness>

Optional: sortedness hint.

fn no_na(&self) -> Option<bool>

Optional: does this vector contain any NA values?

fn sum(&self, _na_rm: bool) -> Option<f64>

Optional: optimized sum.

fn min(&self, _na_rm: bool) -> Option<f64>

Optional: optimized min.

fn max(&self, _na_rm: bool) -> Option<f64>

Optional: optimized max.

impl<F: Fn(usize, &mut [f64]) -> usize> AltrepLen for StreamingRealData<F>

fn len(&self) -> usize

Returns the length of this ALTREP vector.

fn is_empty(&self) -> bool

Returns true if the vector is empty.

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.