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use crate::utils;
use proc_macro2::{Ident, Span, TokenStream};
use quote::{format_ident, quote};
enum Abi {
I32,
I64,
F32,
F64,
}
/// This is a single-use macro intended to be used in the `wasmtime-wasi` crate.
///
/// This macro will generate a structure, `Wasi`, which will create all the
/// functions necessary to bind wasi and hook everything up via the `wasmtime`
/// crate.
///
/// The generated shim functions here will also `trace!` their arguments for
/// logging purposes. Otherwise this is hopefully somewhat straightforward!
///
/// I'd recommend using `cargo +nightly expand` to explore the output of this
/// macro some more.
pub fn define_struct(args: TokenStream) -> TokenStream {
let path = utils::witx_path_from_args(args);
let doc = match witx::load(&[&path]) {
Ok(doc) => doc,
Err(e) => {
panic!("error opening file {}: {}", path.display(), e);
}
};
let mut fields = Vec::new();
let mut get_exports = Vec::new();
let mut ctor_externs = Vec::new();
let mut ctor_fields = Vec::new();
let mut linker_add = Vec::new();
for module in doc.modules() {
let module_name = module.name.as_str();
for func in module.funcs() {
let name = func.name.as_str();
let name_ident = Ident::new(name, Span::call_site());
fields.push(quote! { pub #name_ident: wasmtime::Func });
get_exports.push(quote! { #name => Some(&self.#name_ident) });
ctor_fields.push(name_ident.clone());
linker_add.push(quote! {
linker.define(#module_name, #name, self.#name_ident.clone())?;
});
// `proc_exit` is special; it's essentially an unwinding primitive,
// so we implement it in the runtime rather than use the implementation
// in wasi-common.
if name == "proc_exit" {
ctor_externs.push(quote! {
let #name_ident = wasmtime::Func::wrap(store, crate::wasi_proc_exit);
});
continue;
}
let mut shim_arg_decls = Vec::new();
let mut params = Vec::new();
let mut formats = Vec::new();
let mut format_args = Vec::new();
let mut hostcall_args = Vec::new();
for param in func.params.iter() {
let name = utils::param_name(param);
// Registers a new parameter to the shim we're making with the
// given `name`, the `abi_ty` wasm type and `hex` defines
// whether it's debug-printed in a hex format or not.
//
// This will register a whole bunch of things:
//
// * The cranelift type for the parameter
// * Syntax to specify the actual function parameter
// * How to log the parameter value in a call to `trace!`
// * How to actually pass this argument to the host
// implementation, converting as necessary.
let mut add_param = |name: &Ident, abi_ty: Abi, hex: bool| {
match abi_ty {
Abi::I32 => {
params.push(quote! { types::I32 });
shim_arg_decls.push(quote! { #name: i32 });
}
Abi::I64 => {
params.push(quote! { types::I64 });
shim_arg_decls.push(quote! { #name: i64 });
}
Abi::F32 => {
params.push(quote! { types::F32 });
shim_arg_decls.push(quote! { #name: f32 });
}
Abi::F64 => {
params.push(quote! { types::F64 });
shim_arg_decls.push(quote! { #name: f64 });
}
}
formats.push(format!("{}={}", name, if hex { "{:#x}" } else { "{}" },));
format_args.push(name.clone());
hostcall_args.push(quote! { #name as _ });
};
match &*param.tref.type_() {
witx::Type::Int(e) => match e.repr {
witx::IntRepr::U64 => add_param(&name, Abi::I64, false),
_ => add_param(&name, Abi::I32, false),
},
witx::Type::Enum(e) => match e.repr {
witx::IntRepr::U64 => add_param(&name, Abi::I64, false),
_ => add_param(&name, Abi::I32, false),
},
witx::Type::Flags(f) => match f.repr {
witx::IntRepr::U64 => add_param(&name, Abi::I64, true),
_ => add_param(&name, Abi::I32, true),
},
witx::Type::Builtin(witx::BuiltinType::Char8)
| witx::Type::Builtin(witx::BuiltinType::S8)
| witx::Type::Builtin(witx::BuiltinType::U8)
| witx::Type::Builtin(witx::BuiltinType::S16)
| witx::Type::Builtin(witx::BuiltinType::U16)
| witx::Type::Builtin(witx::BuiltinType::S32)
| witx::Type::Builtin(witx::BuiltinType::U32)
| witx::Type::Builtin(witx::BuiltinType::USize) => {
add_param(&name, Abi::I32, false);
}
witx::Type::Builtin(witx::BuiltinType::S64)
| witx::Type::Builtin(witx::BuiltinType::U64) => {
add_param(&name, Abi::I64, false);
}
witx::Type::Builtin(witx::BuiltinType::F32) => {
add_param(&name, Abi::F32, false);
}
witx::Type::Builtin(witx::BuiltinType::F64) => {
add_param(&name, Abi::F64, false);
}
// strings/arrays have an extra ABI parameter for the length
// of the array passed.
witx::Type::Builtin(witx::BuiltinType::String) | witx::Type::Array(_) => {
add_param(&name, Abi::I32, true);
let len = format_ident!("{}_len", name);
add_param(&len, Abi::I32, false);
}
witx::Type::ConstPointer(_)
| witx::Type::Handle(_)
| witx::Type::Pointer(_) => {
add_param(&name, Abi::I32, true);
}
witx::Type::Struct(_) | witx::Type::Union(_) => {
panic!("unsupported argument type")
}
}
}
let mut results = func.results.iter();
let mut ret_ty = quote! { () };
let mut cvt_ret = quote! {};
let mut returns = Vec::new();
let mut handle_early_error = quote! { panic!("error: {:?}", e) };
// The first result is returned bare right now...
if let Some(ret) = results.next() {
handle_early_error = quote! { return e.into() };
match &*ret.tref.type_() {
// Eventually we'll want to add support for more returned
// types, but for now let's just conform to what `*.witx`
// definitions currently use.
witx::Type::Enum(e) => match e.repr {
witx::IntRepr::U16 => {
returns.push(quote! { types::I32 });
ret_ty = quote! { i32 };
cvt_ret = quote! { .into() }
}
other => panic!("unsupported ret enum repr {:?}", other),
},
other => panic!("unsupported first return {:?}", other),
}
}
// ... and all remaining results are returned via out-poiners
for result in results {
let name = format_ident!("{}", result.name.as_str());
params.push(quote! { types::I32 });
shim_arg_decls.push(quote! { #name: i32 });
formats.push(format!("{}={{:#x}}", name));
format_args.push(name.clone());
hostcall_args.push(quote! { #name as u32 });
}
let format_str = format!("{}({})", name, formats.join(", "));
ctor_externs.push(quote! {
let my_cx = cx.clone();
let #name_ident = wasmtime::Func::wrap(
store,
move |caller: wasmtime::Caller<'_> #(,#shim_arg_decls)*| -> #ret_ty {
tracing::trace!(
#format_str,
#(#format_args),*
);
unsafe {
let memory = match caller.get_export("memory") {
Some(wasmtime::Extern::Memory(m)) => m,
_ => {
tracing::warn!("callee does not export a memory as \"memory\"");
let e = wasi_common::old::snapshot_0::wasi::__WASI_ERRNO_INVAL;
#handle_early_error
}
};
hostcalls::#name_ident(
&mut my_cx.borrow_mut(),
memory.data_unchecked_mut(),
#(#hostcall_args),*
) #cvt_ret
}
}
);
});
}
}
quote! {
/// An instantiated instance of the wasi exports.
///
/// This represents a wasi module which can be used to instantiate other
/// wasm modules. This structure exports all that various fields of the
/// wasi instance as fields which can be used to implement your own
/// instantiation logic, if necessary. Additionally [`Wasi::get_export`]
/// can be used to do name-based resolution.
pub struct Wasi {
#(#fields,)*
}
impl Wasi {
/// Creates a new [`Wasi`] instance.
///
/// External values are allocated into the `store` provided and
/// configuration of the wasi instance itself should be all
/// contained in the `cx` parameter.
pub fn new(store: &wasmtime::Store, cx: WasiCtx) -> Wasi {
let cx = std::rc::Rc::new(std::cell::RefCell::new(cx));
#(#ctor_externs)*
Wasi {
#(#ctor_fields,)*
}
}
/// Looks up a field called `name` in this structure, returning it
/// if found.
///
/// This is often useful when instantiating a `wasmtime` instance
/// where name resolution often happens with strings.
pub fn get_export(&self, name: &str) -> Option<&wasmtime::Func> {
match name {
#(#get_exports,)*
_ => None,
}
}
/// Adds all wasi items to the specified `Linker`.
pub fn add_to_linker(&self, linker: &mut wasmtime::Linker) -> anyhow::Result<()> {
#(#linker_add)*
Ok(())
}
}
}
}