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Add a first-class way of accessing caller's exports (#1290)

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* Add a first-class way of accessing caller's exports

This commit is a continuation of #1237 and updates the API of `Func` to
allow defining host functions which have easy access to a caller's
memory in particular. The new APIs look like so:

* The `Func::wrap*` family of functions was condensed into one
  `Func::wrap` function.
* The ABI layer of conversions in `WasmTy` were removed
* An optional `Caller<'_>` argument can be at the front of all
  host-defined functions now.

The old way the wasi bindings looked up memory has been removed and is
now replaced with the `Caller` type. The `Caller` type has a
`get_export` method on it which allows looking up a caller's export by
name, allowing you to get access to the caller's memory easily, and even
during instantiation.

* Add a temporary note

* Move some docs
This commit is contained in:
Alex Crichton
2020-03-18 16:57:31 -05:00
committed by GitHub
parent 1958e8af96
commit f63c3c814e
10 changed files with 550 additions and 509 deletions
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16
crates/wasi-common/wig/src/wasi.rs
View File

@@ -182,24 +182,26 @@ pub fn define_struct(args: TokenStream) -> TokenStream {
}
let format_str = format!("{}({})", name, formats.join(", "));
let wrap = format_ident!("wrap{}", shim_arg_decls.len() + 1);
ctor_externs.push(quote! {
let my_cx = cx.clone();
let #name_ident = wasmtime::Func::#wrap(
let #name_ident = wasmtime::Func::wrap(
store,
move |mem: crate::WasiCallerMemory #(,#shim_arg_decls)*| -> #ret_ty {
move |caller: wasmtime::Caller<'_> #(,#shim_arg_decls)*| -> #ret_ty {
log::trace!(
#format_str,
#(#format_args),*
);
unsafe {
let memory = match mem.get() {
Ok(e) => e,
Err(e) => #handle_early_error,
let memory = match caller.get_export("memory") {
Some(wasmtime::Extern::Memory(m)) => m,
_ => {
let e = wasi_common::wasi::__WASI_ERRNO_INVAL;
#handle_early_error
}
};
hostcalls::#name_ident(
&mut my_cx.borrow_mut(),
memory,
memory.data_unchecked_mut(),
#(#hostcall_args),*
) #cvt_ret
}