Trait PessimizeCast

Source

pub unsafe trait PessimizeCast {
    type Pessimized: Pessimize;

    // Required methods
    fn into_pessimize(self) -> Self::Pessimized;
    unsafe fn from_pessimize(x: Self::Pessimized) -> Self;
}

Expand description

Convert Self back and forth to a Pessimize impl (Pessimize impl helper)

While only a small number of Pessimize types are supported by inline assembly, many standard types can be losslessly converted to a lower-level type (or tuple of types) that implement Pessimize and back in such a way that the runtime costs should be optimized out.

This trait exposes that capability under a common abstraction vocabulary. Combined with the related BorrowPessimize trait, it enables implementation of Pessimize with increased safety reduced boilerplate.

§Safety

By implementing this trait, you guarantee that someone using it as documented will not trigger Undefined Behavior, since the safe Pessimize trait can be automatically implemented on top of it

Required Associated Types§

Source

type Pessimized: Pessimize

Pessimize type that can be converted to and from a Self value

Required Methods§

Source

fn into_pessimize(self) -> Self::Pessimized

Convert Self to Pessimized

Source

unsafe fn from_pessimize(x: Self::Pessimized) -> Self

Convert back from Pessimized to Self

§Safety

A correct implementation of this operation only needs to be safe for the intended purpose of converting Self to Pessimized using into_pessimize(), invoking Pessimize trait operations on the resulting value, and optionally converting the Pessimized value back to Self afterwards via from_pessimize().

The final from_pessimize() operation of this round trip must be performed in the same scope where the initial into_pessimize() operation was called, or a child scope thereof.

Even if Pessimized is Clone, it is strongly advised to treat the Pessimized value from into_pessimize() as a !Clone value: don’t clone or copy it, and stop using it after converting it back to Self. Otherwise, suprising (but safe) behavior may occur.

No other usage of from_pessimize() is safe. To give a few examples of incorrect usage of from_pessimize()…

Self may contain references to the surrounding stack frame, so even if Pessimized is 'static, letting a Pessimized escape the scope in which into_pessimize() was called before converting it back to Self is unsafe.
Self may contain !Clone data like &mut references, so even if Pessimized is Clone, converting two clones of a single Pessimized value back into Self is unsafe. In fact, even using the Pessimize implementation after converting one of the clones to Self is not guaranteed to produce the desired optimization barrier.
Self may be !Send, so even if Pessimized is Send, sending a Pessimized value to another thread before calling from_pessimize() on that separate thread is unsafe.
Even if two types share the same Pessimized representation, abusing the PessimizeCast trait to perform a cast operation, like casting a reference to another reference with different mutability or lifetime, is unsafe.

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Trait PessimizeCastCopy item path

§Safety

Required Associated Types§

type Pessimized: Pessimize

Required Methods§

fn into_pessimize(self) -> Self::Pessimized

unsafe fn from_pessimize(x: Self::Pessimized) -> Self

§Safety

Dyn Compatibility§

Implementations on Foreign Types§

impl PessimizeCast for bool

type Pessimized = u8

fn into_pessimize(self) -> u8

unsafe fn from_pessimize(inner: u8) -> Self

impl PessimizeCast for char

type Pessimized = u32

fn into_pessimize(self) -> u32

unsafe fn from_pessimize(inner: u32) -> Self

impl PessimizeCast for String

type Pessimized = Vec<u8>

fn into_pessimize(self) -> Vec<u8> ⓘ

unsafe fn from_pessimize(inner: Vec<u8>) -> Self

impl PessimizeCast for Layout

type Pessimized = (usize, usize)

fn into_pessimize(self) -> (usize, usize)

unsafe fn from_pessimize(inner: (usize, usize)) -> Self

impl PessimizeCast for float64x1x2_t

type Pessimized = (float64x1_t, float64x1_t)

fn into_pessimize(self) -> (float64x1_t, float64x1_t)

unsafe fn from_pessimize(inner: (float64x1_t, float64x1_t)) -> Self

impl PessimizeCast for float64x1x3_t

type Pessimized = (float64x1_t, float64x1_t, float64x1_t)

fn into_pessimize(self) -> (float64x1_t, float64x1_t, float64x1_t)

unsafe fn from_pessimize(inner: (float64x1_t, float64x1_t, float64x1_t)) -> Self

impl PessimizeCast for float64x1x4_t

type Pessimized = (float64x1_t, float64x1_t, float64x1_t, float64x1_t)

fn into_pessimize(self) -> (float64x1_t, float64x1_t, float64x1_t, float64x1_t)

unsafe fn from_pessimize( inner: (float64x1_t, float64x1_t, float64x1_t, float64x1_t), ) -> Self

impl PessimizeCast for float64x2x2_t

type Pessimized = (float64x2_t, float64x2_t)

fn into_pessimize(self) -> (float64x2_t, float64x2_t)

unsafe fn from_pessimize(inner: (float64x2_t, float64x2_t)) -> Self

impl PessimizeCast for float64x2x3_t

type Pessimized = (float64x2_t, float64x2_t, float64x2_t)

fn into_pessimize(self) -> (float64x2_t, float64x2_t, float64x2_t)

unsafe fn from_pessimize(inner: (float64x2_t, float64x2_t, float64x2_t)) -> Self

impl PessimizeCast for float64x2x4_t

type Pessimized = (float64x2_t, float64x2_t, float64x2_t, float64x2_t)

fn into_pessimize(self) -> (float64x2_t, float64x2_t, float64x2_t, float64x2_t)

unsafe fn from_pessimize( inner: (float64x2_t, float64x2_t, float64x2_t, float64x2_t), ) -> Self

impl PessimizeCast for Simd<f64, 1>

type Pessimized = float64x1_t

fn into_pessimize(self) -> float64x1_t

unsafe fn from_pessimize(inner: float64x1_t) -> Self

impl PessimizeCast for Simd<f64, 2>

type Pessimized = float64x2_t

fn into_pessimize(self) -> float64x2_t

unsafe fn from_pessimize(inner: float64x2_t) -> Self

impl PessimizeCast for Error

type Pessimized = ()

fn into_pessimize(self)

unsafe fn from_pessimize(inner: ()) -> Self

impl PessimizeCast for PhantomPinned

type Pessimized = ()

fn into_pessimize(self)

unsafe fn from_pessimize(inner: ()) -> Self

impl PessimizeCast for Ipv4Addr

type Pessimized = u32

fn into_pessimize(self) -> u32

unsafe fn from_pessimize(inner: u32) -> Self

impl PessimizeCast for SocketAddrV4

type Pessimized = (Ipv4Addr, u16)

fn into_pessimize(self) -> (Ipv4Addr, u16)

unsafe fn from_pessimize(inner: (Ipv4Addr, u16)) -> Self

impl PessimizeCast for RangeFull

type Pessimized = ()

fn into_pessimize(self)

unsafe fn from_pessimize(inner: ()) -> Self

impl PessimizeCast for AtomicBool

type Pessimized = bool

Trait PessimizeCast