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use crate::sys::exports::Exports;
use crate::sys::externals::Extern;
use crate::sys::module::Module;
use crate::sys::store::Store;
use crate::sys::{HostEnvInitError, LinkError, RuntimeError};
use loupe::MemoryUsage;
use std::fmt;
use std::sync::{Arc, Mutex};
use thiserror::Error;
use wasmer_engine::Resolver;
use wasmer_vm::{InstanceHandle, VMContext};
/// A WebAssembly Instance is a stateful, executable
/// instance of a WebAssembly [`Module`].
///
/// Instance objects contain all the exported WebAssembly
/// functions, memories, tables and globals that allow
/// interacting with WebAssembly.
///
/// Spec: <https://webassembly.github.io/spec/core/exec/runtime.html#module-instances>
#[derive(Clone, MemoryUsage)]
pub struct Instance {
handle: Arc<Mutex<InstanceHandle>>,
module: Module,
/// The exports for an instance.
pub exports: Exports,
}
#[cfg(test)]
mod send_test {
use super::*;
fn is_send<T: Send>() -> bool {
true
}
#[test]
fn instance_is_send() {
assert!(is_send::<Instance>());
}
}
/// An error while instantiating a module.
///
/// This is not a common WebAssembly error, however
/// we need to differentiate from a `LinkError` (an error
/// that happens while linking, on instantiation), a
/// Trap that occurs when calling the WebAssembly module
/// start function, and an error when initializing the user's
/// host environments.
#[derive(Error, Debug)]
pub enum InstantiationError {
/// A linking ocurred during instantiation.
#[error(transparent)]
Link(LinkError),
/// A runtime error occured while invoking the start function
#[error(transparent)]
Start(RuntimeError),
/// The module was compiled with a CPU feature that is not available on
/// the current host.
#[error("missing requires CPU features: {0:?}")]
CpuFeature(String),
/// Error occurred when initializing the host environment.
#[error(transparent)]
HostEnvInitialization(HostEnvInitError),
}
impl From<wasmer_engine::InstantiationError> for InstantiationError {
fn from(other: wasmer_engine::InstantiationError) -> Self {
match other {
wasmer_engine::InstantiationError::Link(e) => Self::Link(e),
wasmer_engine::InstantiationError::Start(e) => Self::Start(e),
wasmer_engine::InstantiationError::CpuFeature(e) => Self::CpuFeature(e),
}
}
}
impl From<HostEnvInitError> for InstantiationError {
fn from(other: HostEnvInitError) -> Self {
Self::HostEnvInitialization(other)
}
}
impl Instance {
/// Creates a new `Instance` from a WebAssembly [`Module`] and a
/// set of imports resolved by the [`Resolver`].
///
/// The resolver can be anything that implements the [`Resolver`] trait,
/// so you can plug custom resolution for the imports, if you wish not
/// to use [`ImportObject`].
///
/// The [`ImportObject`] is the easiest way to provide imports to the instance.
///
/// [`ImportObject`]: crate::ImportObject
///
/// ```
/// # use wasmer::{imports, Store, Module, Global, Value, Instance};
/// # fn main() -> anyhow::Result<()> {
/// let store = Store::default();
/// let module = Module::new(&store, "(module)")?;
/// let imports = imports!{
/// "host" => {
/// "var" => Global::new(&store, Value::I32(2))
/// }
/// };
/// let instance = Instance::new(&module, &imports)?;
/// # Ok(())
/// # }
/// ```
///
/// ## Errors
///
/// The function can return [`InstantiationError`]s.
///
/// Those are, as defined by the spec:
/// * Link errors that happen when plugging the imports into the instance
/// * Runtime errors that happen when running the module `start` function.
pub fn new(
module: &Module,
resolver: &(dyn Resolver + Send + Sync),
) -> Result<Self, InstantiationError> {
let store = module.store();
let handle = module.instantiate(resolver)?;
let exports = module
.exports()
.map(|export| {
let name = export.name().to_string();
let export = handle.lookup(&name).expect("export");
let extern_ = Extern::from_vm_export(store, export.into());
(name, extern_)
})
.collect::<Exports>();
let instance = Self {
handle: Arc::new(Mutex::new(handle)),
module: module.clone(),
exports,
};
// # Safety
// `initialize_host_envs` should be called after instantiation but before
// returning an `Instance` to the user. We set up the host environments
// via `WasmerEnv::init_with_instance`.
//
// This usage is correct because we pass a valid pointer to `instance` and the
// correct error type returned by `WasmerEnv::init_with_instance` as a generic
// parameter.
unsafe {
instance
.handle
.lock()
.unwrap()
.initialize_host_envs::<HostEnvInitError>(&instance as *const _ as *const _)?;
}
Ok(instance)
}
/// Gets the [`Module`] associated with this instance.
pub fn module(&self) -> &Module {
&self.module
}
/// Returns the [`Store`] where the `Instance` belongs.
pub fn store(&self) -> &Store {
self.module.store()
}
#[doc(hidden)]
pub fn vmctx_ptr(&self) -> *mut VMContext {
self.handle.lock().unwrap().vmctx_ptr()
}
}
impl fmt::Debug for Instance {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Instance")
.field("exports", &self.exports)
.finish()
}
}