Struct SmallString 

pub struct SmallString<const MAX_LEN: usize, C: SmallChar = u16> { /* private fields */ }

A stack-allocated fixed-capacity string with explicit length.

This type stores characters in a fixed-size array and maintains an explicit length field, similar to ITensors.jl’s SmallString.

Type Parameters

• MAX_LEN: Maximum number of characters (default: 16, matching ITensors.jl)
• C: Character type (default: u16 for ITensors.jl compatibility)

Character Type Options

• u16 (default): 2 bytes per character, supports BMP (Basic Multilingual Plane)
  • Covers ASCII, Japanese, Chinese, Korean, and most practical characters
  • Does NOT support emoji or rare characters outside BMP
• char: 4 bytes per character, full Unicode support

Example

use tensor4all_core::smallstring::SmallString;

// Default: u16 characters (ITensors.jl compatible)
let s1 = SmallString::<16>::from_str("hello").unwrap();

// Explicit char type for full Unicode support
let s2 = SmallString::<16, char>::from_str("hello 😀").unwrap();

Implementations

impl<const MAX_LEN: usize, C: SmallChar> SmallString<MAX_LEN, C>

pub fn new() -> Self

Create an empty SmallString.

pub fn from_str(s: &str) -> Result<Self, SmallStringError>

Create a SmallString from a string slice.

Returns an error if:

• The string is longer than MAX_LEN characters
• Any character cannot be represented in the character type C

This function is allocation-free (no heap allocation).

pub fn as_str(&self) -> String

Convert to a String.

pub fn is_empty(&self) -> bool

Check if the string is empty.

pub fn len(&self) -> usize

Get the length of the string.

pub fn capacity(&self) -> usize

Get the maximum capacity.

pub fn get(&self, index: usize) -> Option<char>

Get a character at the given index.

pub fn as_slice(&self) -> &[C]

Get a reference to the internal data slice.

Trait Implementations

impl<const MAX_LEN: usize, C: Clone + SmallChar> Clone for SmallString<MAX_LEN, C>

fn clone(&self) -> SmallString<MAX_LEN, C>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<const MAX_LEN: usize, C: Debug + SmallChar> Debug for SmallString<MAX_LEN, C>

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

Formats the value using the given formatter.

impl<const MAX_LEN: usize, C: SmallChar> Default for SmallString<MAX_LEN, C>

fn default() -> Self

Returns the “default value” for a type.

impl<const MAX_LEN: usize, C: SmallChar> Display for SmallString<MAX_LEN, C>

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

Formats the value using the given formatter.

impl<const MAX_LEN: usize, C: SmallChar> Hash for SmallString<MAX_LEN, C>

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<const MAX_LEN: usize, C: SmallChar> Ord for SmallString<MAX_LEN, C>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<const MAX_LEN: usize, C: SmallChar> PartialEq for SmallString<MAX_LEN, C>

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<const MAX_LEN: usize, C: SmallChar> PartialOrd for SmallString<MAX_LEN, C>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<const MAX_LEN: usize, C: Copy + SmallChar> Copy for SmallString<MAX_LEN, C>

impl<const MAX_LEN: usize, C: SmallChar> Eq for SmallString<MAX_LEN, C>