Struct IterStringData 

pub struct IterStringData<I>
where
    I: Iterator<Item = String>,
{
    state: IterState<I, String>,
}

Iterator-backed string vector data adaptor.

Wraps an iterator producing String values and implements the data-level traits (AltrepLen + AltStringData) for backing an ALTREP character vector. To expose it to R, wrap it in a #[derive(AltrepString)] + #[altrep(manual)] struct (see the module docs).

Performance Warning

Unlike other Iter*Data types, accessing ANY element forces full materialization of the entire iterator. This is because R’s AltStringData::elt() returns a borrowed &str, which requires stable storage. The internal RefCell cannot provide the required lifetime, so all strings must be materialized upfront.

This means:

• elt(0) on a million-element iterator will generate ALL million strings
• There is no lazy evaluation benefit for string iterators
• Memory usage equals the full vector regardless of access patterns

For truly lazy string ALTREP, consider implementing a custom type that stores strings in a way that allows borrowing without full materialization (e.g., arena allocation or caching generated strings incrementally).

Example

use miniextendr_api::altrep_data::IterStringData;

let iter = (0..5).map(|x| format!("item_{}", x));
let data = IterStringData::from_iter(iter, 5);
// First access to ANY element will materialize all 5 strings

Fields

state: IterState<I, String>

Implementations

impl<I> IterStringData<I>

where I: Iterator<Item = String>,

pub fn from_iter(iter: I, len: usize) -> Self

Create from an iterator with explicit length.

impl<I> IterStringData<I>

where I: ExactSizeIterator<Item = String>,

pub fn from_exact_iter(iter: I) -> Self

Create from an ExactSizeIterator (length auto-detected).

Trait Implementations

impl<I> AltStringData for IterStringData<I>

where I: Iterator<Item = String>,

fn elt(&self, i: usize) -> Option<&str>

Get the string element at index i.

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

Optional: sortedness hint.

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

Optional: does this vector contain any NA values?

impl<I> AltrepLen for IterStringData<I>

where I: Iterator<Item = String>,

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.