Struct ClosureOnce 

pub struct ClosureOnce { /* private fields */ }

A closure that owns needs-drop data.

This allows the closure’s callback to take ownership of the data, in which case the userdata will be gone if called again.

Implementations

impl ClosureOnce

pub fn new<U: Any, R>( cif: Cif, callback: CallbackOnce<U, R>, userdata: U, ) -> Self

Creates a new closure with owned userdata.

Arguments

• cif — describes the calling convention and argument and result types
• callback — the function to call when the closure is invoked
• userdata — the value to pass to callback along with the arguments when the closure is called

Result

The new closure.

pub fn code_ptr(&self) -> &unsafe extern "C" fn()

Obtains the callable code pointer for a closure.

Safety

The result needs to be transmuted to the correct type before it can be called. If the type is wrong then undefined behavior will result.

pub unsafe fn instantiate_code_ptr<T>(&self) -> &T

Transmutes the callable code pointer for a closure to a reference to any type. This is intended to be used to transmute it to its correct function type in order to call it.

Safety

This method allows transmuting to a reference to any sized type, and cannot check whether the code pointer actually has that type. If the type is wrong then undefined behavior will result.

Trait Implementations

impl Debug for ClosureOnce

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

Formats the value using the given formatter.

impl Drop for ClosureOnce

fn drop(&mut self)

Executes the destructor for this type.