Struct compact::COption

pub struct COption<T: Compact + Clone>(pub Option<T>);

A wrapper to make an Option of a nontrivial Compact possible. Unfortunately, we can't blanket-impl that, since that overlaps (for the compiler) with the impl for trivial Copy types...

Methods from Deref<Target = Option<T>>

pub fn is_some(&self) -> bool

Returns true if the option is a Some value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_some(), true);

let x: Option<u32> = None;
assert_eq!(x.is_some(), false);

pub fn is_none(&self) -> bool

Returns true if the option is a None value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_none(), false);

let x: Option<u32> = None;
assert_eq!(x.is_none(), true);

pub fn as_ref(&self) -> Option<&T>

Converts from Option<T> to Option<&T>.

Examples

Convert an Option<String> into an Option<usize>, preserving the original. The map method takes the self argument by value, consuming the original, so this technique uses as_ref to first take an Option to a reference to the value inside the original.

let text: Option<String> = Some("Hello, world!".to_string());
// First, cast `Option<String>` to `Option<&String>` with `as_ref`,
// then consume *that* with `map`, leaving `text` on the stack.
let text_length: Option<usize> = text.as_ref().map(|s| s.len());
println!("still can print text: {:?}", text);

pub fn as_mut(&mut self) -> Option<&mut T>

Converts from Option<T> to Option<&mut T>.

Examples

let mut x = Some(2);
match x.as_mut() {
    Some(v) => *v = 42,
    None => {},
}
assert_eq!(x, Some(42));

pub fn as_pin_mut(self: PinMut<'a, Option<T>>) -> Option<PinMut<'a, T>>

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

Converts from Option<T> to Option<PinMut<'_, T>>

Important traits for Iter<'a, A>

impl<'a, A> Iterator for Iter<'a, A> type Item = &'a A;

pub fn iter(&self) -> Iter<T>

Returns an iterator over the possibly contained value.

Examples

let x = Some(4);
assert_eq!(x.iter().next(), Some(&4));

let x: Option<u32> = None;
assert_eq!(x.iter().next(), None);

Important traits for IterMut<'a, A>

impl<'a, A> Iterator for IterMut<'a, A> type Item = &'a mut A;

pub fn iter_mut(&mut self) -> IterMut<T>

Returns a mutable iterator over the possibly contained value.

Examples

let mut x = Some(4);
match x.iter_mut().next() {
    Some(v) => *v = 42,
    None => {},
}
assert_eq!(x, Some(42));

let mut x: Option<u32> = None;
assert_eq!(x.iter_mut().next(), None);

Important traits for &'a mut R

impl<'a, R> Read for &'a mut R where
    R: Read + ?Sized, impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized, impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;

pub fn get_or_insert(&mut self, v: T) -> &mut T

Inserts v into the option if it is None, then returns a mutable reference to the contained value.

Examples

let mut x = None;

{
    let y: &mut u32 = x.get_or_insert(5);
    assert_eq!(y, &5);

    *y = 7;
}

assert_eq!(x, Some(7));

Important traits for &'a mut R

impl<'a, R> Read for &'a mut R where
    R: Read + ?Sized, impl<'a, W> Write for &'a mut W where
    W: Write + ?Sized, impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;

pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut T where     F: FnOnce() -> T,

Inserts a value computed from f into the option if it is None, then returns a mutable reference to the contained value.

Examples

let mut x = None;

{
    let y: &mut u32 = x.get_or_insert_with(|| 5);
    assert_eq!(y, &5);

    *y = 7;
}

assert_eq!(x, Some(7));

pub fn take(&mut self) -> Option<T>

Takes the value out of the option, leaving a None in its place.

Examples

let mut x = Some(2);
x.take();
assert_eq!(x, None);

let mut x: Option<u32> = None;
x.take();
assert_eq!(x, None);

Trait Implementations

impl<T: Clone + Compact + Clone> Clone for CompactOption<T>

fn clone(&self) -> CompactOption<T>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Default + Compact + Clone> Default for CompactOption<T>

fn default() -> CompactOption<T>

Returns the "default value" for a type.

impl<T: Compact + Clone> Deref for CompactOption<T>

type Target = Option<T>

The resulting type after dereferencing.

fn deref(&self) -> &Option<T>

Dereferences the value.

impl<T: Compact + Clone> DerefMut for CompactOption<T>

fn deref_mut(&mut self) -> &mut Option<T>

Mutably dereferences the value.

impl<T: Clone + Compact> Compact for CompactOption<T>

fn is_still_compact(&self) -> bool

Is the object's dynamic part stored compactly?

fn dynamic_size_bytes(&self) -> usize

Size of the dynamic part in bytes

unsafe fn compact(source: *mut Self, dest: *mut Self, new_dynamic_part: *mut u8)

Copy the static part of source to dest and compactly store the dynamic part of source as the new dynamic part of dest at new_dynamic_part. This semantically moves source into dest.

unsafe fn decompact(source: *const Self) -> Self

Creates a clone of self with the dynamic part guaranteed to be stored freely.

fn total_size_bytes(&self) -> usize

Total size of the object (static part + dynamic part)

unsafe fn behind(ptr: *mut Self) -> *mut u8

Get a pointer to behind the static part of self (commonly used place for the dynamic part)

unsafe fn compact_behind(source: *mut Self, dest: *mut Self)

Like compact with new_dynamic_part set to dest.behind()