1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411
use crate::{ Extern, ExternType, Func, FuncType, GlobalType, ImportType, Instance, IntoFunc, Module, Store, }; use anyhow::{bail, Result}; use std::collections::hash_map::{Entry, HashMap}; use std::rc::Rc; /// Structure used to link wasm modules/instances together. /// /// This structure is used to assist in instantiating a [`Module`]. A `Linker` /// is a way of performing name resolution to make instantiating a module easier /// (as opposed to calling [`Instance::new`]). `Linker` is a name-based resolver /// where names are dynamically defined and then used to instantiate a /// [`Module`]. The goal of a `Linker` is to have a one-argument method, /// [`Linker::instantiate`], which takes a [`Module`] and produces an /// [`Instance`]. This method will automatically select all the right imports /// for the [`Module`] to be instantiated, and will otherwise return an error /// if an import isn't satisfied. /// /// ## Name Resolution /// /// As mentioned previously, `Linker` is a form of name resolver. It will be /// using the string-based names of imports on a module to attempt to select a /// matching item to hook up to it. This name resolution has two-levels of /// namespaces, a module level and a name level. Each item is defined within a /// module and then has its own name. This basically follows the wasm standard /// for modularization. /// /// Names in a `Linker` can be defined twice, but only for different signatures /// of items. This means that every item defined in a `Linker` has a unique /// name/type pair. For example you can define two functions with the module /// name `foo` and item name `bar`, so long as they have different function /// signatures. Currently duplicate memories and tables are not allowed, only /// one-per-name is allowed. /// /// Note that allowing duplicates by shadowing the previous definition can be /// controlled with the [`Linker::allow_shadowing`] method as well. pub struct Linker { store: Store, string2idx: HashMap<Rc<str>, usize>, strings: Vec<Rc<str>>, map: HashMap<ImportKey, Extern>, allow_shadowing: bool, } #[derive(Hash, PartialEq, Eq)] struct ImportKey { name: usize, module: usize, kind: ImportKind, } #[derive(Hash, PartialEq, Eq, Debug)] enum ImportKind { Func(FuncType), Global(GlobalType), Memory, Table, } impl Linker { /// Creates a new [`Linker`]. /// /// This function will create a new [`Linker`] which is ready to start /// linking modules. All items defined in this linker and produced by this /// linker will be connected with `store` and must come from the same /// `store`. /// /// # Examples /// /// ``` /// use wasmtime::{Linker, Store}; /// /// let store = Store::default(); /// let mut linker = Linker::new(&store); /// // ... /// ``` pub fn new(store: &Store) -> Linker { Linker { store: store.clone(), map: HashMap::new(), string2idx: HashMap::new(), strings: Vec::new(), allow_shadowing: false, } } /// Configures whether this [`Linker`] will shadow previous duplicate /// definitions of the same signature. /// /// By default a [`Linker`] will disallow duplicate definitions of the same /// signature. This method, however, can be used to instead allow duplicates /// and have the latest definition take precedence when linking modules. /// /// # Examples /// /// ``` /// # use wasmtime::*; /// # fn main() -> anyhow::Result<()> { /// # let store = Store::default(); /// let mut linker = Linker::new(&store); /// linker.func("", "", || {})?; /// /// // by default, duplicates are disallowed /// assert!(linker.func("", "", || {}).is_err()); /// /// // but shadowing can be configured to be allowed as well /// linker.allow_shadowing(true); /// linker.func("", "", || {})?; /// # Ok(()) /// # } /// ``` pub fn allow_shadowing(&mut self, allow: bool) -> &mut Linker { self.allow_shadowing = allow; self } /// Defines a new item in this [`Linker`]. /// /// This method will add a new definition, by name, to this instance of /// [`Linker`]. The `module` and `name` provided are what to name the /// `item`. /// /// # Errors /// /// Returns an error if the `module` and `name` already identify an item /// of the same type as the `item` provided and if shadowing is disallowed. /// For more information see the documentation on [`Linker`]. /// /// Also returns an error if `item` comes from a different store than this /// [`Linker`] was created with. /// /// # Examples /// /// ``` /// # use wasmtime::*; /// # fn main() -> anyhow::Result<()> { /// # let store = Store::default(); /// let mut linker = Linker::new(&store); /// let ty = GlobalType::new(ValType::I32, Mutability::Const); /// let global = Global::new(&store, ty, Val::I32(0x1234))?; /// linker.define("host", "offset", global)?; /// /// let wat = r#" /// (module /// (import "host" "offset" (global i32)) /// (memory 1) /// (data (global.get 0) "foo") /// ) /// "#; /// let module = Module::new(&store, wat)?; /// linker.instantiate(&module)?; /// # Ok(()) /// # } /// ``` pub fn define( &mut self, module: &str, name: &str, item: impl Into<Extern>, ) -> Result<&mut Self> { self._define(module, name, item.into()) } fn _define(&mut self, module: &str, name: &str, item: Extern) -> Result<&mut Self> { if !item.comes_from_same_store(&self.store) { bail!("all linker items must be from the same store"); } self.insert(module, name, &item.ty(), item)?; Ok(self) } /// Convenience wrapper to define a function import. /// /// This method is a convenience wrapper around [`Linker::define`] which /// internally delegates to [`Func::wrap`]. /// /// # Errors /// /// Returns an error if the `module` and `name` already identify an item /// of the same type as the `item` provided and if shadowing is disallowed. /// For more information see the documentation on [`Linker`]. /// /// # Examples /// /// ``` /// # use wasmtime::*; /// # fn main() -> anyhow::Result<()> { /// # let store = Store::default(); /// let mut linker = Linker::new(&store); /// linker.func("host", "double", |x: i32| x * 2)?; /// linker.func("host", "log_i32", |x: i32| println!("{}", x))?; /// linker.func("host", "log_str", |caller: Caller, ptr: i32, len: i32| { /// // ... /// })?; /// /// let wat = r#" /// (module /// (import "host" "double" (func (param i32) (result i32))) /// (import "host" "log_i32" (func (param i32))) /// (import "host" "log_str" (func (param i32 i32))) /// ) /// "#; /// let module = Module::new(&store, wat)?; /// linker.instantiate(&module)?; /// # Ok(()) /// # } /// ``` pub fn func<Params, Args>( &mut self, module: &str, name: &str, func: impl IntoFunc<Params, Args>, ) -> Result<&mut Self> { self._define(module, name, Func::wrap(&self.store, func).into()) } /// Convenience wrapper to define an entire [`Instance`] in this linker. /// /// This function is a convenience wrapper around [`Linker::define`] which /// will define all exports on `instance` into this linker. The module name /// for each export is `module_name`, and the name for each export is the /// name in the instance itself. /// /// # Errors /// /// Returns an error if the any item is redefined twice in this linker (for /// example the same `module_name` was already defined) and shadowing is /// disallowed, or if `instance` comes from a different [`Store`] than this /// [`Linker`] originally was created with. /// /// # Examples /// /// ``` /// # use wasmtime::*; /// # fn main() -> anyhow::Result<()> { /// # let store = Store::default(); /// let mut linker = Linker::new(&store); /// /// // Instantiate a small instance... /// let wat = r#"(module (func (export "run") ))"#; /// let module = Module::new(&store, wat)?; /// let instance = linker.instantiate(&module)?; /// /// // ... and inform the linker that the name of this instance is /// // `instance1`. This defines the `instance1::run` name for our next /// // module to use. /// linker.instance("instance1", &instance)?; /// /// let wat = r#" /// (module /// (import "instance1" "run" (func $instance1_run)) /// (func (export "run") /// call $instance1_run /// ) /// ) /// "#; /// let module = Module::new(&store, wat)?; /// let instance = linker.instantiate(&module)?; /// # Ok(()) /// # } /// ``` pub fn instance(&mut self, module_name: &str, instance: &Instance) -> Result<&mut Self> { if !Store::same(&self.store, instance.store()) { bail!("all linker items must be from the same store"); } for (export, item) in instance.module().exports().iter().zip(instance.exports()) { self.insert(module_name, export.name(), export.ty(), item.clone())?; } Ok(self) } fn insert(&mut self, module: &str, name: &str, ty: &ExternType, item: Extern) -> Result<()> { let key = self.import_key(module, name, ty); match self.map.entry(key) { Entry::Occupied(o) if !self.allow_shadowing => bail!( "import of `{}::{}` with kind {:?} defined twice", module, name, o.key().kind, ), Entry::Occupied(mut o) => { o.insert(item); } Entry::Vacant(v) => { v.insert(item); } } Ok(()) } fn import_key(&mut self, module: &str, name: &str, ty: &ExternType) -> ImportKey { ImportKey { module: self.intern_str(module), name: self.intern_str(name), kind: self.import_kind(ty), } } fn import_kind(&self, ty: &ExternType) -> ImportKind { match ty { ExternType::Func(f) => ImportKind::Func(f.clone()), ExternType::Global(f) => ImportKind::Global(f.clone()), ExternType::Memory(_) => ImportKind::Memory, ExternType::Table(_) => ImportKind::Table, } } fn intern_str(&mut self, string: &str) -> usize { if let Some(idx) = self.string2idx.get(string) { return *idx; } let string: Rc<str> = string.into(); let idx = self.strings.len(); self.strings.push(string.clone()); self.string2idx.insert(string, idx); idx } /// Attempts to instantiate the `module` provided. /// /// This method will attempt to assemble a list of imports that correspond /// to the imports required by the [`Module`] provided. This list /// of imports is then passed to [`Instance::new`] to continue the /// instantiation process. /// /// Each import of `module` will be looked up in this [`Linker`] and must /// have previously been defined. If it was previously defined with an /// incorrect signature or if it was not prevoiusly defined then an error /// will be returned because the import can not be satisfied. /// /// # Errors /// /// This method can fail because an import may not be found, or because /// instantiation itself may fail. For information on instantiation /// failures see [`Instance::new`]. /// /// # Examples /// /// ``` /// # use wasmtime::*; /// # fn main() -> anyhow::Result<()> { /// # let store = Store::default(); /// let mut linker = Linker::new(&store); /// linker.func("host", "double", |x: i32| x * 2)?; /// /// let wat = r#" /// (module /// (import "host" "double" (func (param i32) (result i32))) /// ) /// "#; /// let module = Module::new(&store, wat)?; /// linker.instantiate(&module)?; /// # Ok(()) /// # } /// ``` pub fn instantiate(&self, module: &Module) -> Result<Instance> { let mut imports = Vec::new(); for import in module.imports() { if let Some(item) = self.import_get(import) { imports.push(item.clone()); continue; } let mut options = String::new(); for i in self.map.keys() { if &*self.strings[i.module] != import.module() || &*self.strings[i.name] != import.name() { continue; } options.push_str(" * "); options.push_str(&format!("{:?}", i.kind)); options.push_str("\n"); } if options.len() == 0 { bail!( "unknown import: `{}::{}` has not been defined", import.module(), import.name() ) } bail!( "incompatible import type for `{}::{}` specified\n\ desired signature was: {:?}\n\ signatures available:\n\n{}", import.module(), import.name(), import.ty(), options, ) } Instance::new(module, &imports) } fn import_get(&self, import: &ImportType) -> Option<&Extern> { let key = ImportKey { module: *self.string2idx.get(import.module())?, name: *self.string2idx.get(import.name())?, kind: self.import_kind(import.ty()), }; self.map.get(&key) } /// Returns the [`Store`] that this linker is connected to. pub fn store(&self) -> &Store { &self.store } }