Struct IterStringData 

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

Iterator-backed string vector.

Wraps an iterator producing String values and exposes it as an ALTREP character vector.

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: Iterator<Item = String> + 'static> AltString for IterStringData<I>

fn elt(x: SEXP, i: R_xlen_t) -> SEXP

Get string element at index. Returns CHARSXP. This is REQUIRED for ALTSTRING - there is no default.

const HAS_SET_ELT: bool = false

Set to true to register set_elt.

fn set_elt(_x: SEXP, _i: R_xlen_t, _v: SEXP)

Set element (for mutable strings).

const HAS_IS_SORTED: bool = false

Set to true to register is_sorted.

fn is_sorted(_x: SEXP) -> i32

Sortedness hint.

const HAS_NO_NA: bool = false

Set to true to register no_na.

fn no_na(_x: SEXP) -> i32

NA-free hint.

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: Iterator<Item = String> + 'static> AltVec for IterStringData<I>

const HAS_DATAPTR: bool = false

Set to true to register dataptr.

fn dataptr(_x: SEXP, _writable: bool) -> *mut c_void

Get raw data pointer.

const HAS_DATAPTR_OR_NULL: bool = false

Set to true to register dataptr_or_null.

fn dataptr_or_null(_x: SEXP) -> *const c_void

Get data pointer without forcing materialization.

const HAS_EXTRACT_SUBSET: bool = false

Set to true to register extract_subset.

fn extract_subset(_x: SEXP, _indx: SEXP, _call: SEXP) -> SEXP

Optimized subsetting.

impl<I: Iterator<Item = String> + 'static> Altrep for IterStringData<I>

const GUARD: AltrepGuard = crate::altrep_traits::AltrepGuard::RUnwind

The guard mode for all ALTREP trampolines on this type.

fn length(x: SEXP) -> R_xlen_t

Returns the length of the ALTREP vector. This is REQUIRED - R cannot determine vector length without it.

const HAS_SERIALIZED_STATE: bool = false

Set to true to register serialized_state.

fn serialized_state(_x: SEXP) -> SEXP

Return serialization state.

const HAS_UNSERIALIZE: bool = false

Set to true to register unserialize.

fn unserialize(_class: SEXP, _state: SEXP) -> SEXP

Reconstruct ALTREP from serialized state.

const HAS_UNSERIALIZE_EX: bool = false

Set to true to register unserialize_ex.

fn unserialize_ex( _class: SEXP, _state: SEXP, _attr: SEXP, _objf: i32, _levs: i32, ) -> SEXP

Extended unserialization with attributes.

const HAS_DUPLICATE: bool = false

Set to true to register duplicate.

fn duplicate(_x: SEXP, _deep: bool) -> SEXP

Duplicate the ALTREP object.

const HAS_DUPLICATE_EX: bool = false

Set to true to register duplicate_ex.

fn duplicate_ex(_x: SEXP, _deep: bool) -> SEXP

Extended duplication.

const HAS_COERCE: bool = false

Set to true to register coerce.

fn coerce(_x: SEXP, _to_type: SEXPTYPE) -> SEXP

Coerce to another type.

const HAS_INSPECT: bool = false

Set to true to register inspect.

fn inspect( _x: SEXP, _pre: i32, _deep: i32, _pvec: i32, _inspect_subtree: Option<unsafe extern "C-unwind" fn(SEXP, i32, i32, i32)>, ) -> bool

Custom inspection for .Internal(inspect()).

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.

impl<I: Iterator<Item = String> + 'static> InferBase for IterStringData<I>

const BASE: RBase = crate::altrep::RBase::String

The inferred R base type.

unsafe fn make_class( class_name: *const i8, pkg_name: *const i8, ) -> R_altrep_class_t

Create the ALTREP class handle.

unsafe fn install_methods(cls: R_altrep_class_t)

Install ALTREP methods on the class.

impl<I: Iterator<Item = String> + 'static> TypedExternal for IterStringData<I>

const TYPE_NAME: &'static str = "IterStringData"

The type name as a static string (for debugging and display)

const TYPE_NAME_CSTR: &'static [u8] = b"IterStringData\0"

The type name as a null-terminated C string (for R tag display)

const TYPE_ID_CSTR: &'static [u8] = b"miniextendr_api::altrep::IterStringData\0"

Namespaced type ID as a null-terminated C string (for type checking).