wasmtime/runtime/component/linker.rs
1use crate::component::func::HostFunc;
2use crate::component::instance::RuntimeImport;
3use crate::component::matching::{InstanceType, TypeChecker};
4use crate::component::types;
5use crate::component::{
6 Component, ComponentNamedList, Instance, InstancePre, Lift, Lower, ResourceType, Val,
7};
8use crate::hash_map::HashMap;
9use crate::prelude::*;
10use crate::{AsContextMut, Engine, Module, StoreContextMut};
11use alloc::sync::Arc;
12use core::marker;
13#[cfg(feature = "async")]
14use core::{future::Future, pin::Pin};
15use wasmtime_environ::component::{NameMap, NameMapIntern};
16use wasmtime_environ::PrimaryMap;
17
18/// A type used to instantiate [`Component`]s.
19///
20/// This type is used to both link components together as well as supply host
21/// functionality to components. Values are defined in a [`Linker`] by their
22/// import name and then components are instantiated with a [`Linker`] using the
23/// names provided for name resolution of the component's imports.
24///
25/// # Names and Semver
26///
27/// Names defined in a [`Linker`] correspond to import names in the Component
28/// Model. Names in the Component Model are allowed to be semver-qualified, for
29/// example:
30///
31/// * `wasi:cli/stdout@0.2.0`
32/// * `wasi:http/types@0.2.0-rc-2023-10-25`
33/// * `my:custom/plugin@1.0.0-pre.2`
34///
35/// These version strings are taken into account when looking up names within a
36/// [`Linker`]. You're allowed to define any number of versions within a
37/// [`Linker`] still, for example you can define `a:b/c@0.2.0`, `a:b/c@0.2.1`,
38/// and `a:b/c@0.3.0` all at the same time.
39///
40/// Specifically though when names are looked up within a linker, for example
41/// during instantiation, semver-compatible names are automatically consulted.
42/// This means that if you define `a:b/c@0.2.1` in a [`Linker`] but a component
43/// imports `a:b/c@0.2.0` then that import will resolve to the `0.2.1` version.
44///
45/// This lookup behavior relies on hosts being well-behaved when using Semver,
46/// specifically that interfaces once defined are never changed. This reflects
47/// how Semver works at the Component Model layer, and it's assumed that if
48/// versions are present then hosts are respecting this.
49///
50/// Note that this behavior goes the other direction, too. If a component
51/// imports `a:b/c@0.2.1` and the host has provided `a:b/c@0.2.0` then that
52/// will also resolve correctly. This is because if an API was defined at 0.2.0
53/// and 0.2.1 then it must be the same API.
54///
55/// This behavior is intended to make it easier for hosts to upgrade WASI and
56/// for guests to upgrade WASI. So long as the actual "meat" of the
57/// functionality is defined then it should align correctly and components can
58/// be instantiated.
59pub struct Linker<T> {
60 engine: Engine,
61 strings: Strings,
62 map: NameMap<usize, Definition>,
63 path: Vec<usize>,
64 allow_shadowing: bool,
65 _marker: marker::PhantomData<fn() -> T>,
66}
67
68impl<T> Clone for Linker<T> {
69 fn clone(&self) -> Linker<T> {
70 Linker {
71 engine: self.engine.clone(),
72 strings: self.strings.clone(),
73 map: self.map.clone(),
74 path: self.path.clone(),
75 allow_shadowing: self.allow_shadowing,
76 _marker: self._marker,
77 }
78 }
79}
80
81#[derive(Clone, Default)]
82pub struct Strings {
83 string2idx: HashMap<Arc<str>, usize>,
84 strings: Vec<Arc<str>>,
85}
86
87/// Structure representing an "instance" being defined within a linker.
88///
89/// Instances do not need to be actual [`Instance`]s and instead are defined by
90/// a "bag of named items", so each [`LinkerInstance`] can further define items
91/// internally.
92pub struct LinkerInstance<'a, T> {
93 engine: &'a Engine,
94 path: &'a mut Vec<usize>,
95 path_len: usize,
96 strings: &'a mut Strings,
97 map: &'a mut NameMap<usize, Definition>,
98 allow_shadowing: bool,
99 _marker: marker::PhantomData<fn() -> T>,
100}
101
102#[derive(Clone, Debug)]
103pub(crate) enum Definition {
104 Instance(NameMap<usize, Definition>),
105 Func(Arc<HostFunc>),
106 Module(Module),
107 Resource(ResourceType, Arc<crate::func::HostFunc>),
108}
109
110impl<T> Linker<T> {
111 /// Creates a new linker for the [`Engine`] specified with no items defined
112 /// within it.
113 pub fn new(engine: &Engine) -> Linker<T> {
114 Linker {
115 engine: engine.clone(),
116 strings: Strings::default(),
117 map: NameMap::default(),
118 allow_shadowing: false,
119 path: Vec::new(),
120 _marker: marker::PhantomData,
121 }
122 }
123
124 /// Returns the [`Engine`] this is connected to.
125 pub fn engine(&self) -> &Engine {
126 &self.engine
127 }
128
129 /// Configures whether or not name-shadowing is allowed.
130 ///
131 /// By default name shadowing is not allowed and it's an error to redefine
132 /// the same name within a linker.
133 pub fn allow_shadowing(&mut self, allow: bool) -> &mut Self {
134 self.allow_shadowing = allow;
135 self
136 }
137
138 /// Returns the "root instance" of this linker, used to define names into
139 /// the root namespace.
140 pub fn root(&mut self) -> LinkerInstance<'_, T> {
141 LinkerInstance {
142 engine: &self.engine,
143 path: &mut self.path,
144 path_len: 0,
145 strings: &mut self.strings,
146 map: &mut self.map,
147 allow_shadowing: self.allow_shadowing,
148 _marker: self._marker,
149 }
150 }
151
152 /// Returns a builder for the named instance specified.
153 ///
154 /// # Errors
155 ///
156 /// Returns an error if `name` is already defined within the linker.
157 pub fn instance(&mut self, name: &str) -> Result<LinkerInstance<'_, T>> {
158 self.root().into_instance(name)
159 }
160
161 fn typecheck<'a>(&'a self, component: &'a Component) -> Result<TypeChecker<'a>> {
162 let mut cx = TypeChecker {
163 engine: &self.engine,
164 types: component.types(),
165 strings: &self.strings,
166 imported_resources: Default::default(),
167 };
168
169 // Walk over the component's list of import names and use that to lookup
170 // the definition within this linker that it corresponds to. When found
171 // perform a typecheck against the component's expected type.
172 let env_component = component.env_component();
173 for (_idx, (name, ty)) in env_component.import_types.iter() {
174 let import = self.map.get(name, &self.strings);
175 cx.definition(ty, import)
176 .with_context(|| format!("component imports {desc} `{name}`, but a matching implementation was not found in the linker", desc = ty.desc()))?;
177 }
178 Ok(cx)
179 }
180
181 /// Returns the [`types::Component`] corresponding to `component` with resource
182 /// types imported by it replaced using imports present in [`Self`].
183 pub fn substituted_component_type(&self, component: &Component) -> Result<types::Component> {
184 let cx = self.typecheck(&component)?;
185 Ok(types::Component::from(
186 component.ty(),
187 &InstanceType {
188 types: cx.types,
189 resources: &cx.imported_resources,
190 },
191 ))
192 }
193
194 /// Performs a "pre-instantiation" to resolve the imports of the
195 /// [`Component`] specified with the items defined within this linker.
196 ///
197 /// This method will perform as much work as possible short of actually
198 /// instantiating an instance. Internally this will use the names defined
199 /// within this linker to satisfy the imports of the [`Component`] provided.
200 /// Additionally this will perform type-checks against the component's
201 /// imports against all items defined within this linker.
202 ///
203 /// Note that unlike internally in components where subtyping at the
204 /// interface-types layer is supported this is not supported here. Items
205 /// defined in this linker must match the component's imports precisely.
206 ///
207 /// # Errors
208 ///
209 /// Returns an error if this linker doesn't define a name that the
210 /// `component` imports or if a name defined doesn't match the type of the
211 /// item imported by the `component` provided.
212 pub fn instantiate_pre(&self, component: &Component) -> Result<InstancePre<T>> {
213 let cx = self.typecheck(&component)?;
214
215 // A successful typecheck resolves all of the imported resources used by
216 // this InstancePre. We keep a clone of this table in the InstancePre
217 // so that we can construct an InstanceType for typechecking.
218 let imported_resources = cx.imported_resources.clone();
219
220 // Now that all imports are known to be defined and satisfied by this
221 // linker a list of "flat" import items (aka no instances) is created
222 // using the import map within the component created at
223 // component-compile-time.
224 let env_component = component.env_component();
225 let mut imports = PrimaryMap::with_capacity(env_component.imports.len());
226 for (idx, (import, names)) in env_component.imports.iter() {
227 let (root, _) = &env_component.import_types[*import];
228
229 // This is the flattening process where we go from a definition
230 // optionally through a list of exported names to get to the final
231 // item.
232 let mut cur = self.map.get(root, &self.strings).unwrap();
233 for name in names {
234 cur = match cur {
235 Definition::Instance(map) => map.get(&name, &self.strings).unwrap(),
236 _ => unreachable!(),
237 };
238 }
239 let import = match cur {
240 Definition::Module(m) => RuntimeImport::Module(m.clone()),
241 Definition::Func(f) => RuntimeImport::Func(f.clone()),
242 Definition::Resource(t, dtor) => RuntimeImport::Resource {
243 ty: *t,
244 _dtor: dtor.clone(),
245 dtor_funcref: component.resource_drop_func_ref(dtor),
246 },
247
248 // This is guaranteed by the compilation process that "leaf"
249 // runtime imports are never instances.
250 Definition::Instance(_) => unreachable!(),
251 };
252 let i = imports.push(import);
253 assert_eq!(i, idx);
254 }
255 Ok(unsafe {
256 InstancePre::new_unchecked(component.clone(), Arc::new(imports), imported_resources)
257 })
258 }
259
260 /// Instantiates the [`Component`] provided into the `store` specified.
261 ///
262 /// This function will use the items defined within this [`Linker`] to
263 /// satisfy the imports of the [`Component`] provided as necessary. For more
264 /// information about this see [`Linker::instantiate_pre`] as well.
265 ///
266 /// # Errors
267 ///
268 /// Returns an error if this [`Linker`] doesn't define an import that
269 /// `component` requires or if it is of the wrong type. Additionally this
270 /// can return an error if something goes wrong during instantiation such as
271 /// a runtime trap or a runtime limit being exceeded.
272 pub fn instantiate(
273 &self,
274 store: impl AsContextMut<Data = T>,
275 component: &Component,
276 ) -> Result<Instance> {
277 assert!(
278 !store.as_context().async_support(),
279 "must use async instantiation when async support is enabled"
280 );
281 self.instantiate_pre(component)?.instantiate(store)
282 }
283
284 /// Instantiates the [`Component`] provided into the `store` specified.
285 ///
286 /// This is exactly like [`Linker::instantiate`] except for async stores.
287 ///
288 /// # Errors
289 ///
290 /// Returns an error if this [`Linker`] doesn't define an import that
291 /// `component` requires or if it is of the wrong type. Additionally this
292 /// can return an error if something goes wrong during instantiation such as
293 /// a runtime trap or a runtime limit being exceeded.
294 #[cfg(feature = "async")]
295 pub async fn instantiate_async(
296 &self,
297 store: impl AsContextMut<Data = T>,
298 component: &Component,
299 ) -> Result<Instance>
300 where
301 T: Send,
302 {
303 assert!(
304 store.as_context().async_support(),
305 "must use sync instantiation when async support is disabled"
306 );
307 self.instantiate_pre(component)?
308 .instantiate_async(store)
309 .await
310 }
311
312 /// Implement any imports of the given [`Component`] with a function which traps.
313 ///
314 /// By default a [`Linker`] will error when unknown imports are encountered when instantiating a [`Component`].
315 /// This changes this behavior from an instant error to a trap that will happen if the import is called.
316 pub fn define_unknown_imports_as_traps(&mut self, component: &Component) -> Result<()> {
317 use wasmtime_environ::component::ComponentTypes;
318 use wasmtime_environ::component::TypeDef;
319 // Recursively stub out all imports of the component with a function that traps.
320 fn stub_item<T>(
321 linker: &mut LinkerInstance<T>,
322 item_name: &str,
323 item_def: &TypeDef,
324 parent_instance: Option<&str>,
325 types: &ComponentTypes,
326 ) -> Result<()> {
327 // Skip if the item isn't an instance and has already been defined in the linker.
328 if !matches!(item_def, TypeDef::ComponentInstance(_)) && linker.get(item_name).is_some()
329 {
330 return Ok(());
331 }
332
333 match item_def {
334 TypeDef::ComponentFunc(_) => {
335 let fully_qualified_name = parent_instance
336 .map(|parent| format!("{parent}#{item_name}"))
337 .unwrap_or_else(|| item_name.to_owned());
338 linker.func_new(&item_name, move |_, _, _| {
339 bail!("unknown import: `{fully_qualified_name}` has not been defined")
340 })?;
341 }
342 TypeDef::ComponentInstance(i) => {
343 let instance = &types[*i];
344 let mut linker_instance = linker.instance(item_name)?;
345 for (export_name, export) in instance.exports.iter() {
346 stub_item(
347 &mut linker_instance,
348 export_name,
349 export,
350 Some(item_name),
351 types,
352 )?;
353 }
354 }
355 TypeDef::Resource(_) => {
356 let ty = crate::component::ResourceType::host::<()>();
357 linker.resource(item_name, ty, |_, _| Ok(()))?;
358 }
359 TypeDef::Component(_) | TypeDef::Module(_) => {
360 bail!("unable to define {} imports as traps", item_def.desc())
361 }
362 _ => {}
363 }
364 Ok(())
365 }
366
367 for (_, (import_name, import_type)) in &component.env_component().import_types {
368 stub_item(
369 &mut self.root(),
370 import_name,
371 import_type,
372 None,
373 component.types(),
374 )?;
375 }
376 Ok(())
377 }
378}
379
380impl<T> LinkerInstance<'_, T> {
381 fn as_mut(&mut self) -> LinkerInstance<'_, T> {
382 LinkerInstance {
383 engine: self.engine,
384 path: self.path,
385 path_len: self.path_len,
386 strings: self.strings,
387 map: self.map,
388 allow_shadowing: self.allow_shadowing,
389 _marker: self._marker,
390 }
391 }
392
393 /// Defines a new host-provided function into this [`Linker`].
394 ///
395 /// This method is used to give host functions to wasm components. The
396 /// `func` provided will be callable from linked components with the type
397 /// signature dictated by `Params` and `Return`. The `Params` is a tuple of
398 /// types that will come from wasm and `Return` is a value coming from the
399 /// host going back to wasm.
400 ///
401 /// Additionally the `func` takes a
402 /// [`StoreContextMut`](crate::StoreContextMut) as its first parameter.
403 ///
404 /// Note that `func` must be an `Fn` and must also be `Send + Sync +
405 /// 'static`. Shared state within a func is typically accessed with the `T`
406 /// type parameter from [`Store<T>`](crate::Store) which is accessible
407 /// through the leading [`StoreContextMut<'_, T>`](crate::StoreContextMut)
408 /// argument which can be provided to the `func` given here.
409 //
410 // TODO: needs more words and examples
411 pub fn func_wrap<F, Params, Return>(&mut self, name: &str, func: F) -> Result<()>
412 where
413 F: Fn(StoreContextMut<T>, Params) -> Result<Return> + Send + Sync + 'static,
414 Params: ComponentNamedList + Lift + 'static,
415 Return: ComponentNamedList + Lower + 'static,
416 {
417 self.insert(name, Definition::Func(HostFunc::from_closure(func)))?;
418 Ok(())
419 }
420
421 /// Defines a new host-provided async function into this [`Linker`].
422 ///
423 /// This is exactly like [`Self::func_wrap`] except it takes an async
424 /// host function.
425 #[cfg(feature = "async")]
426 pub fn func_wrap_async<Params, Return, F>(&mut self, name: &str, f: F) -> Result<()>
427 where
428 F: for<'a> Fn(
429 StoreContextMut<'a, T>,
430 Params,
431 ) -> Box<dyn Future<Output = Result<Return>> + Send + 'a>
432 + Send
433 + Sync
434 + 'static,
435 Params: ComponentNamedList + Lift + 'static,
436 Return: ComponentNamedList + Lower + 'static,
437 {
438 assert!(
439 self.engine.config().async_support,
440 "cannot use `func_wrap_async` without enabling async support in the config"
441 );
442 let ff = move |mut store: StoreContextMut<'_, T>, params: Params| -> Result<Return> {
443 let async_cx = store.as_context_mut().0.async_cx().expect("async cx");
444 let future = f(store.as_context_mut(), params);
445 unsafe { async_cx.block_on(Pin::from(future)) }?
446 };
447 self.func_wrap(name, ff)
448 }
449
450 /// Defines a new host-provided async function into this [`LinkerInstance`].
451 ///
452 /// This allows the caller to register host functions with the
453 /// LinkerInstance such that multiple calls to such functions can run
454 /// concurrently. This isn't possible with the existing func_wrap_async
455 /// method because it takes a function which returns a future that owns a
456 /// unique reference to the Store, meaning the Store can't be used for
457 /// anything else until the future resolves.
458 ///
459 /// Ideally, we'd have a way to thread a `StoreContextMut<T>` through an
460 /// arbitrary `Future` such that it has access to the `Store` only while
461 /// being polled (i.e. between, but not across, await points). However,
462 /// there's currently no way to express that in async Rust, so we make do
463 /// with a more awkward scheme: each function registered using
464 /// `func_wrap_concurrent` gets access to the `Store` twice: once before
465 /// doing any concurrent operations (i.e. before awaiting) and once
466 /// afterward. This allows multiple calls to proceed concurrently without
467 /// any one of them monopolizing the store.
468 #[cfg(feature = "component-model-async")]
469 pub fn func_wrap_concurrent<Params, Return, F, N, FN>(&mut self, name: &str, f: F) -> Result<()>
470 where
471 N: FnOnce(StoreContextMut<T>) -> Result<Return> + Send + Sync + 'static,
472 FN: Future<Output = N> + Send + Sync + 'static,
473 F: Fn(StoreContextMut<T>, Params) -> FN + Send + Sync + 'static,
474 Params: ComponentNamedList + Lift + 'static,
475 Return: ComponentNamedList + Lower + Send + Sync + 'static,
476 {
477 assert!(
478 self.engine.config().async_support,
479 "cannot use `func_wrap_concurrent` without enabling async support in the config"
480 );
481 _ = (name, f);
482 todo!()
483 }
484
485 /// Define a new host-provided function using dynamically typed values.
486 ///
487 /// The `name` provided is the name of the function to define and the
488 /// `func` provided is the host-defined closure to invoke when this
489 /// function is called.
490 ///
491 /// This function is the "dynamic" version of defining a host function as
492 /// compared to [`LinkerInstance::func_wrap`]. With
493 /// [`LinkerInstance::func_wrap`] a function's type is statically known but
494 /// with this method the `func` argument's type isn't known ahead of time.
495 /// That means that `func` can be by imported component so long as it's
496 /// imported as a matching name.
497 ///
498 /// Type information will be available at execution time, however. For
499 /// example when `func` is invoked the second argument, a `&[Val]` list,
500 /// contains [`Val`] entries that say what type they are. Additionally the
501 /// third argument, `&mut [Val]`, is the expected number of results. Note
502 /// that the expected types of the results cannot be learned during the
503 /// execution of `func`. Learning that would require runtime introspection
504 /// of a component.
505 ///
506 /// Return values, stored in the third argument of `&mut [Val]`, are
507 /// type-checked at runtime to ensure that they have the appropriate type.
508 /// A trap will be raised if they do not have the right type.
509 ///
510 /// # Examples
511 ///
512 /// ```
513 /// use wasmtime::{Store, Engine};
514 /// use wasmtime::component::{Component, Linker, Val};
515 ///
516 /// # fn main() -> wasmtime::Result<()> {
517 /// let engine = Engine::default();
518 /// let component = Component::new(
519 /// &engine,
520 /// r#"
521 /// (component
522 /// (import "thunk" (func $thunk))
523 /// (import "is-even" (func $is-even (param "x" u32) (result bool)))
524 ///
525 /// (core module $m
526 /// (import "" "thunk" (func $thunk))
527 /// (import "" "is-even" (func $is-even (param i32) (result i32)))
528 ///
529 /// (func (export "run")
530 /// call $thunk
531 ///
532 /// (call $is-even (i32.const 1))
533 /// if unreachable end
534 ///
535 /// (call $is-even (i32.const 2))
536 /// i32.eqz
537 /// if unreachable end
538 /// )
539 /// )
540 /// (core func $thunk (canon lower (func $thunk)))
541 /// (core func $is-even (canon lower (func $is-even)))
542 /// (core instance $i (instantiate $m
543 /// (with "" (instance
544 /// (export "thunk" (func $thunk))
545 /// (export "is-even" (func $is-even))
546 /// ))
547 /// ))
548 ///
549 /// (func (export "run") (canon lift (core func $i "run")))
550 /// )
551 /// "#,
552 /// )?;
553 ///
554 /// let mut linker = Linker::<()>::new(&engine);
555 ///
556 /// // Sample function that takes no arguments.
557 /// linker.root().func_new("thunk", |_store, params, results| {
558 /// assert!(params.is_empty());
559 /// assert!(results.is_empty());
560 /// println!("Look ma, host hands!");
561 /// Ok(())
562 /// })?;
563 ///
564 /// // This function takes one argument and returns one result.
565 /// linker.root().func_new("is-even", |_store, params, results| {
566 /// assert_eq!(params.len(), 1);
567 /// let param = match params[0] {
568 /// Val::U32(n) => n,
569 /// _ => panic!("unexpected type"),
570 /// };
571 ///
572 /// assert_eq!(results.len(), 1);
573 /// results[0] = Val::Bool(param % 2 == 0);
574 /// Ok(())
575 /// })?;
576 ///
577 /// let mut store = Store::new(&engine, ());
578 /// let instance = linker.instantiate(&mut store, &component)?;
579 /// let run = instance.get_typed_func::<(), ()>(&mut store, "run")?;
580 /// run.call(&mut store, ())?;
581 /// # Ok(())
582 /// # }
583 /// ```
584 pub fn func_new(
585 &mut self,
586 name: &str,
587 func: impl Fn(StoreContextMut<'_, T>, &[Val], &mut [Val]) -> Result<()> + Send + Sync + 'static,
588 ) -> Result<()> {
589 self.insert(name, Definition::Func(HostFunc::new_dynamic(func)))?;
590 Ok(())
591 }
592
593 /// Define a new host-provided async function using dynamic types.
594 ///
595 /// This is exactly like [`Self::func_new`] except it takes an async
596 /// host function.
597 #[cfg(feature = "async")]
598 pub fn func_new_async<F>(&mut self, name: &str, f: F) -> Result<()>
599 where
600 F: for<'a> Fn(
601 StoreContextMut<'a, T>,
602 &'a [Val],
603 &'a mut [Val],
604 ) -> Box<dyn Future<Output = Result<()>> + Send + 'a>
605 + Send
606 + Sync
607 + 'static,
608 {
609 assert!(
610 self.engine.config().async_support,
611 "cannot use `func_new_async` without enabling async support in the config"
612 );
613 let ff = move |mut store: StoreContextMut<'_, T>, params: &[Val], results: &mut [Val]| {
614 let async_cx = store.as_context_mut().0.async_cx().expect("async cx");
615 let future = f(store.as_context_mut(), params, results);
616 unsafe { async_cx.block_on(Pin::from(future)) }?
617 };
618 self.func_new(name, ff)
619 }
620
621 /// Defines a [`Module`] within this instance.
622 ///
623 /// This can be used to provide a core wasm [`Module`] as an import to a
624 /// component. The [`Module`] provided is saved within the linker for the
625 /// specified `name` in this instance.
626 pub fn module(&mut self, name: &str, module: &Module) -> Result<()> {
627 self.insert(name, Definition::Module(module.clone()))?;
628 Ok(())
629 }
630
631 /// Defines a new resource of a given [`ResourceType`] in this linker.
632 ///
633 /// This function is used to specify resources defined in the host.
634 ///
635 /// The `name` argument is the name to define the resource within this
636 /// linker.
637 ///
638 /// The `dtor` provided is a destructor that will get invoked when an owned
639 /// version of this resource is destroyed from the guest. Note that this
640 /// destructor is not called when a host-owned resource is destroyed as it's
641 /// assumed the host knows how to handle destroying its own resources.
642 ///
643 /// The `dtor` closure is provided the store state as the first argument
644 /// along with the representation of the resource that was just destroyed.
645 ///
646 /// [`Resource<U>`]: crate::component::Resource
647 ///
648 /// # Errors
649 ///
650 /// The provided `dtor` closure returns an error if something goes wrong
651 /// when a guest calls the `dtor` to drop a `Resource<T>` such as
652 /// a runtime trap or a runtime limit being exceeded.
653 pub fn resource(
654 &mut self,
655 name: &str,
656 ty: ResourceType,
657 dtor: impl Fn(StoreContextMut<'_, T>, u32) -> Result<()> + Send + Sync + 'static,
658 ) -> Result<()> {
659 let dtor = Arc::new(crate::func::HostFunc::wrap_inner(
660 &self.engine,
661 move |mut cx: crate::Caller<'_, T>, (param,): (u32,)| dtor(cx.as_context_mut(), param),
662 ));
663 self.insert(name, Definition::Resource(ty, dtor))?;
664 Ok(())
665 }
666
667 /// Identical to [`Self::resource`], except that it takes an async destructor.
668 #[cfg(feature = "async")]
669 pub fn resource_async<F>(&mut self, name: &str, ty: ResourceType, dtor: F) -> Result<()>
670 where
671 F: for<'a> Fn(
672 StoreContextMut<'a, T>,
673 u32,
674 ) -> Box<dyn Future<Output = Result<()>> + Send + 'a>
675 + Send
676 + Sync
677 + 'static,
678 {
679 assert!(
680 self.engine.config().async_support,
681 "cannot use `resource_async` without enabling async support in the config"
682 );
683 let dtor = Arc::new(crate::func::HostFunc::wrap_inner(
684 &self.engine,
685 move |mut cx: crate::Caller<'_, T>, (param,): (u32,)| {
686 let async_cx = cx.as_context_mut().0.async_cx().expect("async cx");
687 let future = dtor(cx.as_context_mut(), param);
688 match unsafe { async_cx.block_on(Pin::from(future)) } {
689 Ok(Ok(())) => Ok(()),
690 Ok(Err(trap)) | Err(trap) => Err(trap),
691 }
692 },
693 ));
694 self.insert(name, Definition::Resource(ty, dtor))?;
695 Ok(())
696 }
697
698 /// Defines a nested instance within this instance.
699 ///
700 /// This can be used to describe arbitrarily nested levels of instances
701 /// within a linker to satisfy nested instance exports of components.
702 pub fn instance(&mut self, name: &str) -> Result<LinkerInstance<'_, T>> {
703 self.as_mut().into_instance(name)
704 }
705
706 /// Same as [`LinkerInstance::instance`] except with different lifetime
707 /// parameters.
708 pub fn into_instance(mut self, name: &str) -> Result<Self> {
709 let name = self.insert(name, Definition::Instance(NameMap::default()))?;
710 self.map = match self.map.raw_get_mut(&name) {
711 Some(Definition::Instance(map)) => map,
712 _ => unreachable!(),
713 };
714 self.path.truncate(self.path_len);
715 self.path.push(name);
716 self.path_len += 1;
717 Ok(self)
718 }
719
720 fn insert(&mut self, name: &str, item: Definition) -> Result<usize> {
721 self.map
722 .insert(name, self.strings, self.allow_shadowing, item)
723 }
724
725 fn get(&self, name: &str) -> Option<&Definition> {
726 self.map.get(name, self.strings)
727 }
728}
729
730impl NameMapIntern for Strings {
731 type Key = usize;
732
733 fn intern(&mut self, string: &str) -> usize {
734 if let Some(idx) = self.string2idx.get(string) {
735 return *idx;
736 }
737 let string: Arc<str> = string.into();
738 let idx = self.strings.len();
739 self.strings.push(string.clone());
740 self.string2idx.insert(string, idx);
741 idx
742 }
743
744 fn lookup(&self, string: &str) -> Option<usize> {
745 self.string2idx.get(string).cloned()
746 }
747}