Exports
In WebAssembly terms, Exports are the functions, tables, memories and globals a Wasm module or component exposes to external code. Module exports are, essentially, Wrappers, containing the various items that need to be exposed to the host environment. Exports from a component add another layer, working as a glue between Wasm and various programming languages, allowing for one way of using Wasm functions in non-JavaScript contexts.
Examples
Accessing exports might look something like this:
WebAssembly.instantiateStreaming(fetch("moduleOrComponent.wasm")).then(
(obj) => {
const exported_function = obj.instance.exports.aFunction;
const exported_table = obj.instance.exports.aTable;
const exported_memory = obj.instance.exports.memory;
const exported_global = obj.instance.exports.global;
// code to use exports goes here
}
);use anyhow::Result;
use wasmtime::*;
fn main() -> Result<(), Box<dyn Error>> {
let engine = Engine::default();
let module = Module::from_file(&engine, "module.wasm")?;
let mut store = Store::new(&engine, ());
let instance = Instance::new(&mut store, &module, &[])?;
// setting each export to a variable, with error handling.
let exported_function = instance.get_func(&mut store, "aFunction")
.expect("`testfunc` is not an export");
let test_table = instance.get_table(&mut store, "table")
.ok_or(anyhow::format_err!("failed to find `table` export"))?;
let test_memory = instance.get_memory(&mut store, "memory")
.ok_or(anyhow::format_err!("failed to find `memory` export"))?;
let test_shared_memory = instance.get_shared_memory(&mut store, "shared_memory")
.ok_or(anyhow::format_err!("failed to find `shared_memory` export"))?;
let test_global = instance.get_global(&mut store, "global")
.ok_or(anyhow::format_err!("failed to find `global` export"))?;
// code to use exports goes here
Ok(())
}
Additional reading
Read more about how to use exports in Mozilla’s WebAssembly documentation, here.
You can read about how WebAssembly imports are displayed in the Nor2 WASM Analyzer in the Exports page section of our WASM Analyzer documentation.