Struct abi_stable::sabi_types::rsmallbox::RSmallBox[−][src]

#[repr(C)]
pub struct RSmallBox<T, Inline> { /* fields omitted */ }
Expand description

A box type which stores small values inline as an optimization.

Inline storage

The Inline type parameter is the storage space on the stack (as in inline with the RSmallBox struct) where small values get stored,instead of storing them on the heap.

It has to have an alignment greater than or equal to the value being stored, otherwise storing the value on the heap.

To ensure that the inline storage has enough alignemnt you can use one of the AlignTo* types from the (reexported) alignment submodule, or from abi_stable::inline_storage::alignment.

Examples

In a nonexhaustive enum

Using an RSmallBox to store a generic type in a nonexhaustive enum.

use abi_stable::{reexports::SelfOps, sabi_types::RSmallBox, std_types::RString, StableAbi};

#[repr(u8)]
#[derive(StableAbi, Debug, Clone, PartialEq)]
#[sabi(kind(WithNonExhaustive(
    // Determines the maximum size of this enum in semver compatible versions.
    // This is 7 usize large because:
    //    - The enum discriminant occupies 1 usize(because the enum is usize aligned).
    //    - RSmallBox<T,[usize;4]>: is 6 usize large
    size="[usize;7]",
    // Determines the traits that are required when wrapping this enum in NonExhaustive,
    // and are then available with it.
    traits(Debug,Clone,PartialEq),
)))]
pub enum SomeEnum<T> {
    #[doc(hidden)]
    __NonExhaustive,
    Foo,
    Bar,
    // This variant was added in a newer (compatible) version of the library.
    Baz(RSmallBox<T, [usize; 4]>),
}

impl<T> SomeEnum<T> {
    pub fn is_inline(&self) -> bool {
        match self {
            SomeEnum::__NonExhaustive => true,
            SomeEnum::Foo => true,
            SomeEnum::Bar => true,
            SomeEnum::Baz(rsbox) => RSmallBox::is_inline(rsbox),
        }
    }

    pub fn is_heap_allocated(&self) -> bool {
        !self.is_inline()
    }
}

#[repr(C)]
#[derive(StableAbi, Debug, Clone, PartialEq)]
pub struct FullName {
    pub name: RString,
    pub surname: RString,
}


let rstring = "Oh boy!"
    .piped(RString::from)
    .piped(RSmallBox::new)
    .piped(SomeEnum::Baz);

let full_name = FullName {
    name: "R__e".into(),
    surname: "L_____e".into(),
}
.piped(RSmallBox::new)
.piped(SomeEnum::Baz);

assert!(rstring.is_inline());
assert!(full_name.is_heap_allocated());

Trying out different Inline type parameters

This example demonstrates how changing the Inline type parameter can change whether an RString is stored inline or on the heap.

use abi_stable::{
    inline_storage::alignment::AlignToUsize, sabi_types::RSmallBox, std_types::RString,
    StableAbi,
};

use std::mem;

type JustRightInlineBox<T> = RSmallBox<T, AlignToUsize<[u8; mem::size_of::<usize>() * 4]>>;

let string = RString::from("What is that supposed to mean?");

let small = RSmallBox::<_, [usize; 3]>::new(string.clone());
let medium = RSmallBox::<_, [usize; 4]>::new(string.clone());
let large = RSmallBox::<_, [usize; 16]>::new(string.clone());
let not_enough_alignment = RSmallBox::<_, [u8; 64]>::new(string.clone());
let just_right = JustRightInlineBox::new(string.clone());

assert!(RSmallBox::is_heap_allocated(&small));
assert!(RSmallBox::is_inline(&medium));
assert!(RSmallBox::is_inline(&large));
assert!(RSmallBox::is_heap_allocated(&not_enough_alignment));
assert!(RSmallBox::is_inline(&just_right));

Implementations

Constructs this RSmallBox from a value.

Example
use abi_stable::{sabi_types::RSmallBox, std_types::RString};

let xbox = RSmallBox::<_, [usize; 4]>::new(RString::from("one"));

Gets a raw pointer into the underlying data.

Example
use abi_stable::{sabi_types::RSmallBox, std_types::RString};

let mut play = RSmallBox::<_, [usize; 4]>::new(RString::from("station"));

let play_addr = &mut play as *mut RSmallBox<_, _> as usize;
let heap_addr = RSmallBox::as_mut_ptr(&mut play) as usize;

assert_eq!(play_addr, heap_addr);

Gets a raw pointer into the underlying data.

Example
use abi_stable::{reexports::SelfOps, sabi_types::RSmallBox, std_types::RVec};

let mut generations = vec![1, 2, 3, 4, 5, 6, 7, 8]
    .piped(RVec::from)
    .piped(RSmallBox::<_, [usize; 2]>::new);

let generations_addr = &generations as *const RSmallBox<_, _> as usize;
let heap_addr = RSmallBox::as_ptr(&generations) as usize;

assert_ne!(generations_addr, heap_addr);

Constructs this RSmallBox from a MovePtr.

Example
use abi_stable::{pointer_trait::OwnedPointer, sabi_types::RSmallBox, std_types::RBox};

let rbox = RBox::new(1000_u64);
let rsbox: RSmallBox<u64, [u64; 1]> =
    rbox.in_move_ptr(|x| RSmallBox::<u64, [u64; 1]>::from_move_ptr(x));

assert_eq!(*rsbox, 1000_u64);
[src]

pub fn move_<Inline2>(this: Self) -> RSmallBox<T, Inline2> where
    Inline2: InlineStorage, 

Converts this RSmallBox into another one with a differnet inline size.

Example
use abi_stable::sabi_types::RSmallBox;

let old = RSmallBox::<u64, [u8; 4]>::new(599_u64);
assert!(!RSmallBox::is_inline(&old));

let new = RSmallBox::move_::<[u64; 1]>(old);
assert!(RSmallBox::is_inline(&new));
assert_eq!(*new, 599_u64);

Queries whether the value is stored inline.

Example
use abi_stable::{sabi_types::RSmallBox, std_types::RString};

let heap = RSmallBox::<u64, [u8; 4]>::new(599_u64);
assert!(!RSmallBox::is_inline(&heap));

let inline = RSmallBox::<RString, [usize; 4]>::new("hello".into());
assert!(RSmallBox::is_inline(&inline));

Queries whether the value is stored on the heap.

Example
use abi_stable::{sabi_types::RSmallBox, std_types::RHashMap};

let heap = RSmallBox::<_, [u8; 4]>::new(String::new());
assert!(RSmallBox::is_heap_allocated(&heap));

let inline = RSmallBox::<_, [usize; 3]>::new(RHashMap::<u8, ()>::new());
assert!(!RSmallBox::is_heap_allocated(&inline));

Unwraps this pointer into its owned value.

Example
use abi_stable::sabi_types::RSmallBox;

let rbox = RSmallBox::<_, [usize; 3]>::new(vec![0, 1, 2]);
assert_eq!(RSmallBox::into_inner(rbox), vec![0, 1, 2]);

Trait Implementations

Gets a mutable raw pointer to the value that this points to.

Converts this pointer to an RRef.

Gets a const raw pointer to the value that this points to.

Converts this pointer to an RRef.

The type of the pointer after it’s element type has been changed.

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unsafe fn transmute_element_(self) -> Self::TransmutedPtr

Transmutes the element type of this pointer.. Read more

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Returns the “default value” for a type. Read more

The resulting type after dereferencing.

Dereferences the value.

Mutably dereferences the value.

Deserialize this value from the given Serde deserializer. Read more

Formats the value using the given formatter. Read more

Executes the destructor for this type. Read more

Converts an RBox into an RSmallBox,currently this allocates.

Performs the conversion.

Converts a RSmallBox into an RBox,currently this allocates.

Performs the conversion.

The kind of the pointer. Read more

What this pointer points to. Read more

The value-level version of the Kind associated type. Read more

[src]

impl<T, Inline> GetStaticEquivalent_ for RSmallBox<T, Inline> where
    T: __StableAbi,
    Inline: __GetStaticEquivalent_, 

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

Gets a move pointer to the contents of this pointer. Read more

Deallocates the pointer without dropping its owned contents. Read more

Runs a callback with the contents of this pointer, and then deallocates it. Read more

Runs a callback with the contents of this pointer, and then deallocates it. Read more

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

This method tests for !=.

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

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

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

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

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

Serialize this value into the given Serde serializer. Read more

Whether this type has a single invalid bit-pattern. Read more

The layout of the type provided by implementors.

const-equivalents of the associated types.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

The owned type, stored in RCow::Owned

The borrowed type, stored in RCow::Borrowed

Performs the conversion.

This is always WithMetadata_<Self, Self>

Performs the conversion.

Gets a reference to a field, determined by offset. Read more

Gets a muatble reference to a field, determined by offset. Read more

Gets a const pointer to a field, the field is determined by offset. Read more

Gets a mutable pointer to a field, determined by offset. Read more

Replaces a field (determined by offset) with value, returning the previous value of the field. Read more

Swaps a field (determined by offset) with the same field in right. Read more

Gets a copy of a field (determined by offset). The field is determined by offset. Read more

Replaces a field (determined by offset) with value, returning the previous value of the field. Read more

Swaps a field (determined by offset) with the same field in right. Read more

Gets a copy of a field (determined by offset). The field is determined by offset. Read more

Compares the address of self with the address of other. Read more

Emulates the pipeline operator, allowing method syntax in more places. Read more

The same as piped except that the function takes &Self Useful for functions that take &Self instead of Self. Read more

The same as piped, except that the function takes &mut Self. Useful for functions that take &mut Self instead of Self. Read more

Mutates self using a closure taking self by mutable reference, passing it along the method chain. Read more

Observes the value of self, passing it along unmodified. Useful in long method chains. Read more

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fn into_<T>(self) -> T where
    Self: Into<T>, 

Performs a conversion with Into. using the turbofish .into_::<_>() syntax. Read more

[src]

fn as_ref_<T>(&self) -> &T where
    Self: AsRef<T>,
    T: ?Sized, 

Performs a reference to reference conversion with AsRef, using the turbofish .as_ref_::<_>() syntax. Read more

[src]

fn as_mut_<T>(&mut self) -> &mut T where
    Self: AsMut<T>,
    T: ?Sized, 

Performs a mutable reference to mutable reference conversion with AsMut, using the turbofish .as_mut_::<_>() syntax. Read more

[src]

fn drop_(self)

Drops self using method notation. Alternative to std::mem::drop. Read more

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

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

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

Converts the given value to a String. Read more

Transmutes the element type of this pointer.. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

This is always Self.

Converts a value back to the original type.

Converts a reference back to the original type.

Converts a mutable reference back to the original type.

This is supported on crate feature alloc only.

Converts a box back to the original type.

This is supported on crate feature alloc only.

Converts an Arc back to the original type. Read more

This is supported on crate feature alloc only.

Converts an Rc back to the original type. Read more

Converts a value back to the original type.

Converts a reference back to the original type.

Converts a mutable reference back to the original type.

This is supported on crate feature alloc only.

Converts a box back to the original type.

This is supported on crate feature alloc only.

Converts an Arc back to the original type.

This is supported on crate feature alloc only.

Converts an Rc back to the original type.