Struct wasmtime::Caller

pub struct Caller<'a> { /* fields omitted */ }

A structure representing the caller’s context when creating a function via Func::wrap.

This structure can be taken as the first parameter of a closure passed to Func::wrap, and it can be used to learn information about the caller of the function, such as the calling module’s memory, exports, etc.

The primary purpose of this structure is to provide access to the caller’s information, namely it’s exported memory and exported functions. This allows functions which take pointers as arguments to easily read the memory the pointers point into, or if a function is expected to call malloc in the wasm module to reserve space for the output you can do that.

Note that this Caller type a pretty temporary mechanism for accessing the caller’s information until interface types has been fully standardized and implemented. The interface types proposal will obsolete this type and this will be removed in the future at some point after interface types is implemented. If you’re relying on this Caller type it’s recommended to become familiar with interface types to ensure that your use case is covered by the proposal.

Implementations

impl Caller<'_>

pub fn get_export(&self, name: &str) -> Option<Extern>

Looks up an export from the caller’s module by the name given.

Note that this function is only implemented for the Extern::Memory and the Extern::Func types currently. No other exported structures can be acquired through this just yet, but this may be implemented in the future!

Note that when accessing and calling exported functions, one should adhere to the guidelines of the interface types proposal.

Return

If a memory or function export with the name provided was found, then it is returned as a Memory. There are a number of situations, however, where the memory or function may not be available:

• The caller instance may not have an export named name
• The export named name may not be an exported memory
• There may not be a caller available, for example if Func was called directly from host code.

It’s recommended to take care when calling this API and gracefully handling a None return value.

pub fn store(&self) -> &Store

Get a reference to the caller’s store.