Struct smol_str::SmolStr

pub struct SmolStr(_);

A SmolStr is a string type that has the following properties:

• size_of::<SmolStr>() == size_of::<String>()
• Clone is O(1)
• Strings are stack-allocated if they are:
  • Up to 22 bytes long
  • Longer than 22 bytes, but substrings of WS (see below). Such strings consist solely of consecutive newlines, followed by consecutive spaces
• If a string does not satisfy the aforementioned conditions, it is heap-allocated

Unlike String, however, SmolStr is immutable. The primary use case for SmolStr is a good enough default storage for tokens of typical programming languages. Strings consisting of a series of newlines, followed by a series of whitespace are a typical pattern in computer programs because of indentation. Note that a specialized interner might be a better solution for some use cases.

Methods

impl SmolStr

pub const fn new_inline_from_ascii(len: usize, bytes: &[u8]) -> SmolStr

Constructs an inline variant of SmolStr at compile time.

Parameters

• len: Must be short (≤ 22 bytes)
• bytes: Must be ASCII bytes, and there must be at least len of them. If len is smaller than the actual len of bytes, the string is truncated.

Returns

A constant SmolStr with inline data.

Examples

const IDENT: SmolStr = SmolStr::new_inline_from_ascii(5, b"hello");

Given a len smaller than the number of bytes in bytes, the string is cut off:

const SHORT: SmolStr = SmolStr::new_inline_from_ascii(5, b"hello world");
assert_eq!(SHORT.as_str(), "hello");

Compile-time errors

This will fail at compile-time with a message like "index out of bounds" on a _len_is_short because the string is too large:

const IDENT: SmolStr = SmolStr::new_inline_from_ascii(
    49,
    b"hello world, how are you doing this fine morning?",
);

Similarly, this will fail to compile with "index out of bounds" on an _is_ascii binding because it contains non-ASCII characters:

const IDENT: SmolStr = SmolStr::new_inline_from_ascii(
    2,
    &[209, 139],
);

Last but not least, given a len that is larger than the number of bytes in bytes, it will fail to compile with "index out of bounds: the len is 5 but the index is 5" on a binding called byte:

const IDENT: SmolStr = SmolStr::new_inline_from_ascii(10, b"hello");

pub fn new<T>(text: T) -> SmolStr where
    T: Into<String> + AsRef<str>, 

pub fn as_str(&self) -> &str

pub fn to_string(&self) -> String

pub fn len(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn is_heap_allocated(&self) -> bool

Trait Implementations

impl<T> From<T> for SmolStr where
    T: Into<String> + AsRef<str>, 

fn from(text: T) -> Self

Performs the conversion.

impl From<SmolStr> for String

fn from(text: SmolStr) -> Self

Performs the conversion.

impl Clone for SmolStr

fn clone(&self) -> SmolStr

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Default for SmolStr

fn default() -> SmolStr

Returns the "default value" for a type.

impl Eq for SmolStr

impl Ord for SmolStr

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

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

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

🔬 This is a nightly-only experimental API. (clamp)

Restrict a value to a certain interval.

impl PartialEq<SmolStr> for SmolStr

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

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<str> for SmolStr

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

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<SmolStr> for str

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

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<&'a str> for SmolStr

fn eq(&self, other: &&'a str) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<SmolStr> for &'a str

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

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<String> for SmolStr

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

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<SmolStr> for String

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

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<&'a String> for SmolStr

fn eq(&self, other: &&'a String) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<SmolStr> for &'a String

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

This method tests for self and other values to be equal, and is used by ==.

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialOrd<SmolStr> for SmolStr

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

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

#[must_use] fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use] fn le(&self, other: &Rhs) -> bool

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

#[must_use] fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use] fn ge(&self, other: &Rhs) -> bool

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

impl Display for SmolStr

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

Formats the value using the given formatter.

impl Debug for SmolStr

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

Formats the value using the given formatter.

impl Deref for SmolStr

type Target = str

The resulting type after dereferencing.

fn deref(&self) -> &str

Dereferences the value.

impl Hash for SmolStr

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

Feeds this value into the given [Hasher].

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

Feeds a slice of this type into the given [Hasher].

impl FromIterator<char> for SmolStr

fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> SmolStr

Creates a value from an iterator.

impl FromIterator<String> for SmolStr

fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> SmolStr

Creates a value from an iterator.

impl<'a> FromIterator<&'a String> for SmolStr

fn from_iter<I: IntoIterator<Item = &'a String>>(iter: I) -> SmolStr

Creates a value from an iterator.

impl<'a> FromIterator<&'a str> for SmolStr

fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> SmolStr

Creates a value from an iterator.

impl Borrow<str> for SmolStr

fn borrow(&self) -> &str

Immutably borrows from an owned value.