Struct TypedFunc
pub struct TypedFunc<Params, Return> { /* private fields */ }
Expand description
A statically-typed version of Func
which takes Params
as input and
returns Return
.
This is an efficient way to invoke a WebAssembly component where if the inputs and output are statically known this can eschew the vast majority of machinery and checks when calling WebAssembly. This is the most optimized way to call a WebAssembly component.
Note that like Func
this is a pointer within a Store
and usage will panic if used with the wrong store.
This type is primarily created with the Func::typed
API.
See ComponentType
for more information about supported types.
Implementations§
§impl<Params, Return> TypedFunc<Params, Return>
impl<Params, Return> TypedFunc<Params, Return>
pub unsafe fn new_unchecked(func: Func) -> TypedFunc<Params, Return>
pub unsafe fn new_unchecked(func: Func) -> TypedFunc<Params, Return>
Creates a new TypedFunc
from the provided component Func
,
unsafely asserting that the underlying function takes Params
as
input and returns Return
.
§Unsafety
This is an unsafe function because it does not verify that the Func
provided actually implements this signature. It’s up to the caller to
have performed some other sort of check to ensure that the signature is
correct.
pub fn call(
&self,
store: impl AsContextMut,
params: Params,
) -> Result<Return, Error>
pub fn call( &self, store: impl AsContextMut, params: Params, ) -> Result<Return, Error>
Calls the underlying WebAssembly component function using the provided
params
as input.
This method is used to enter into a component. Execution happens within
the store
provided. The params
are copied into WebAssembly memory
as appropriate and a core wasm function is invoked.
§Post-return
In the component model each function can have a “post return” specified
which allows cleaning up the arguments returned to the host. For example
if WebAssembly returns a string to the host then it might be a uniquely
allocated string which, after the host finishes processing it, needs to
be deallocated in the wasm instance’s own linear memory to prevent
memory leaks in wasm itself. The post-return
canonical abi option is
used to configured this.
To accommodate this feature of the component model after invoking a
function via TypedFunc::call
you must next invoke
TypedFunc::post_return
. Note that the return value of the function
should be processed between these two function calls. The return value
continues to be usable from an embedder’s perspective after
post_return
is called, but after post_return
is invoked it may no
longer retain the same value that the wasm module originally returned.
Also note that TypedFunc::post_return
must be invoked irrespective
of whether the canonical ABI option post-return
was configured or not.
This means that embedders must unconditionally call
TypedFunc::post_return
when a function returns. If this function
call returns an error, however, then TypedFunc::post_return
is not
required.
§Errors
This function can return an error for a number of reasons:
- If the wasm itself traps during execution.
- If the wasm traps while copying arguments into memory.
- If the wasm provides bad allocation pointers when copying arguments into memory.
- If the wasm returns a value which violates the canonical ABI.
- If this function’s instances cannot be entered, for example if the instance is currently calling a host function.
- If a previous function call occurred and the corresponding
post_return
hasn’t been invoked yet.
In general there are many ways that things could go wrong when copying
types in and out of a wasm module with the canonical ABI, and certain
error conditions are specific to certain types. For example a
WebAssembly module can’t return an invalid char
. When allocating space
for this host to copy a string into the returned pointer must be
in-bounds in memory.
If an error happens then the error should contain detailed enough information to understand which part of the canonical ABI went wrong and what to inspect.
§Panics
Panics if this is called on a function in an asynchronous store. This
only works with functions defined within a synchronous store. Also
panics if store
does not own this function.
pub async fn call_async<T>(
&self,
store: impl AsContextMut<Data = T>,
params: Params,
) -> Result<Return, Error>
pub async fn call_async<T>( &self, store: impl AsContextMut<Data = T>, params: Params, ) -> Result<Return, Error>
Exactly like Self::call
, except for use on asynchronous stores.
§Panics
Panics if this is called on a function in a synchronous store. This
only works with functions defined within an asynchronous store. Also
panics if store
does not own this function.
pub fn post_return(&self, store: impl AsContextMut) -> Result<(), Error>
pub fn post_return(&self, store: impl AsContextMut) -> Result<(), Error>
pub async fn post_return_async<T>(
&self,
store: impl AsContextMut<Data = T>,
) -> Result<(), Error>where
T: Send,
pub async fn post_return_async<T>(
&self,
store: impl AsContextMut<Data = T>,
) -> Result<(), Error>where
T: Send,
Trait Implementations§
impl<Params, Return> Copy for TypedFunc<Params, Return>
Auto Trait Implementations§
impl<Params, Return> Freeze for TypedFunc<Params, Return>
impl<Params, Return> RefUnwindSafe for TypedFunc<Params, Return>where
Params: RefUnwindSafe,
Return: RefUnwindSafe,
impl<Params, Return> Send for TypedFunc<Params, Return>
impl<Params, Return> Sync for TypedFunc<Params, Return>
impl<Params, Return> Unpin for TypedFunc<Params, Return>
impl<Params, Return> UnwindSafe for TypedFunc<Params, Return>where
Params: UnwindSafe,
Return: UnwindSafe,
Blanket Implementations§
Source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
Source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
Source§impl<T> Instrument for T
impl<T> Instrument for T
Source§fn instrument(self, span: Span) -> Instrumented<Self> ⓘ
fn instrument(self, span: Span) -> Instrumented<Self> ⓘ
Source§fn in_current_span(self) -> Instrumented<Self> ⓘ
fn in_current_span(self) -> Instrumented<Self> ⓘ
Source§impl<T> IntoEither for T
impl<T> IntoEither for T
Source§fn into_either(self, into_left: bool) -> Either<Self, Self> ⓘ
fn into_either(self, into_left: bool) -> Either<Self, Self> ⓘ
self
into a Left
variant of Either<Self, Self>
if into_left
is true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read moreSource§fn into_either_with<F>(self, into_left: F) -> Either<Self, Self> ⓘ
fn into_either_with<F>(self, into_left: F) -> Either<Self, Self> ⓘ
self
into a Left
variant of Either<Self, Self>
if into_left(&self)
returns true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read more