Struct wasmtime::Func

pub struct Func { /* fields omitted */ }

A WebAssembly function which can be called.

This type can represent a number of callable items, such as:

• An exported function from a WebAssembly module.
• A user-defined function used to satisfy an import.

These types of callable items are all wrapped up in this Func and can be used to both instantiate an Instance as well as be extracted from an Instance.

Func and Clone

Functions are internally reference counted so you can clone a Func. The cloning process only performs a shallow clone, so two cloned Func instances are equivalent in their functionality.

Methods

impl Func

pub fn new(
    store: &Store,
    ty: FuncType,
    callable: Rc<dyn Callable + 'static>
) -> Self

Creates a new Func with the given arguments, typically to create a user-defined function to pass as an import to a module.

• store - a cache of data where information is stored, typically shared with a Module.

• ty - the signature of this function, used to indicate what the inputs and outputs are, which must be WebAssembly types.

• callable - a type implementing the Callable trait which is the implementation of this Func value.

Note that the implementation of callable must adhere to the ty signature given, error or traps may occur if it does not respect the ty signature.

pub fn ty(&self) -> &FuncType

Returns the underlying wasm type that this Func has.

pub fn param_arity(&self) -> usize

Returns the number of parameters that this function takes.

pub fn result_arity(&self) -> usize

Returns the number of results this function produces.

pub fn call(&self, params: &[Val]) -> Result<Box<[Val]>, Trap>

Invokes this function with the params given, returning the results and any trap, if one occurs.

The params here must match the type signature of this Func, or a trap will occur. If a trap occurs while executing this function, then a trap will also be returned.

This function should not panic unless the underlying function itself initiates a panic.

Trait Implementations

impl Clone for Func

fn clone(&self) -> Func

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Func

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

Formats the value using the given formatter.

impl From<Func> for Extern

fn from(r: Func) -> Self

Performs the conversion.

impl From<Func> for Val

fn from(val: Func) -> Val

Performs the conversion.