use crate::host::Externals;
use crate::isa;
use crate::module::ModuleInstance;
use crate::runner::{check_function_args, Interpreter, InterpreterState, StackRecycler};
use crate::types::ValueType;
use crate::value::RuntimeValue;
use crate::{Signature, Trap, TrapKind};
use alloc::{
borrow::Cow,
rc::{Rc, Weak},
vec::Vec,
};
use core::fmt;
use parity_wasm::elements::Local;
/// Reference to a function (See [`FuncInstance`] for details).
///
/// This reference has a reference-counting semantics.
///
/// [`FuncInstance`]: struct.FuncInstance.html
#[derive(Clone, Debug)]
pub struct FuncRef {
/// Function Instance
instance: Rc<FuncInstance>,
/// Function name and index for debug
info: Option<(usize, String)>,
}
impl FuncRef {
/// Get function info
pub fn info(&self) -> Option<&(usize, String)> {
self.info.as_ref()
}
/// Set function info
pub fn set_info(mut self, index: usize, name: String) -> Self {
self.info = Some((index, name));
self
}
}
impl ::core::ops::Deref for FuncRef {
type Target = FuncInstance;
fn deref(&self) -> &FuncInstance {
&self.instance
}
}
/// Runtime representation of a function.
///
/// Functions are the unit of organization of code in WebAssembly. Each function takes a sequence of values
/// as parameters and either optionally return a value or trap.
/// Functions can call other function including itself (i.e recursive calls are allowed) and imported functions
/// (i.e functions defined in another module or by the host environment).
///
/// Functions can be defined either:
///
/// - by a wasm module,
/// - by the host environment and passed to a wasm module as an import.
/// See more in [`Externals`].
///
/// [`Externals`]: trait.Externals.html
pub struct FuncInstance(FuncInstanceInternal);
#[derive(Clone)]
pub(crate) enum FuncInstanceInternal {
Internal {
signature: Rc<Signature>,
module: Weak<ModuleInstance>,
body: Rc<FuncBody>,
},
Host {
signature: Signature,
host_func_index: usize,
},
}
impl fmt::Debug for FuncInstance {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.as_internal() {
FuncInstanceInternal::Internal { ref signature, .. } => {
// We can't write description of self.module here, because it generate
// debug string for function instances and this will lead to infinite loop.
write!(f, "Internal {{ signature={:?} }}", signature,)
}
FuncInstanceInternal::Host { ref signature, .. } => {
write!(f, "Host {{ signature={:?} }}", signature)
}
}
}
}
impl FuncInstance {
/// Allocate a function instance for a host function.
///
/// When this function instance will be called by the wasm code,
/// the instance of [`Externals`] will be invoked by calling `invoke_index`
/// with specified `host_func_index` here.
/// This call will be made with the `signature` provided here.
///
/// [`Externals`]: trait.Externals.html
pub fn alloc_host(signature: Signature, host_func_index: usize) -> FuncRef {
let func = FuncInstanceInternal::Host {
signature,
host_func_index,
};
FuncRef {
instance: Rc::new(FuncInstance(func)),
info: None,
}
}
/// Returns [signature] of this function instance.
///
/// This function instance can only be called with matching signatures.
///
/// [signature]: struct.Signature.html
pub fn signature(&self) -> &Signature {
match *self.as_internal() {
FuncInstanceInternal::Internal { ref signature, .. } => signature,
FuncInstanceInternal::Host { ref signature, .. } => signature,
}
}
pub(crate) fn as_internal(&self) -> &FuncInstanceInternal {
&self.0
}
pub(crate) fn alloc_internal(
module: Weak<ModuleInstance>,
signature: Rc<Signature>,
body: FuncBody,
) -> FuncRef {
let func = FuncInstanceInternal::Internal {
signature,
module,
body: Rc::new(body),
};
FuncRef {
instance: Rc::new(FuncInstance(func)),
info: None,
}
}
pub(crate) fn body(&self) -> Option<Rc<FuncBody>> {
match *self.as_internal() {
FuncInstanceInternal::Internal { ref body, .. } => Some(Rc::clone(body)),
FuncInstanceInternal::Host { .. } => None,
}
}
/// Invoke this function.
///
/// # Errors
///
/// Returns `Err` if `args` types is not match function [`signature`] or
/// if [`Trap`] at execution time occured.
///
/// [`signature`]: #method.signature
/// [`Trap`]: #enum.Trap.html
pub fn invoke<E: Externals>(
func: &FuncRef,
args: &[RuntimeValue],
externals: &mut E,
) -> Result<Option<RuntimeValue>, Trap> {
check_function_args(func.signature(), args)?;
match *func.as_internal() {
FuncInstanceInternal::Internal { .. } => {
let mut interpreter = Interpreter::new(func, args, None)?;
let res = interpreter.start_execution(externals);
if let Err(trap) = res {
let mut stack = interpreter
.trace()
.iter()
.map(|n| {
if let Some(info) = n {
format!("{:#}[{}]", rustc_demangle::demangle(&info.1), info.0)
} else {
"<unknown>".to_string()
}
})
.collect::<Vec<_>>();
// Append the panicing trap
stack.append(&mut trap.wasm_trace().clone());
stack.reverse();
// Embed this info into the trap
Err(trap.set_wasm_trace(stack))
} else {
res
}
}
FuncInstanceInternal::Host {
ref host_func_index,
..
} => externals.invoke_index(*host_func_index, args.into()),
}
}
/// Invoke this function using recycled stacks.
///
/// # Errors
///
/// Same as [`invoke`].
///
/// [`invoke`]: #method.invoke
pub fn invoke_with_stack<E: Externals>(
func: &FuncRef,
args: &[RuntimeValue],
externals: &mut E,
stack_recycler: &mut StackRecycler,
) -> Result<Option<RuntimeValue>, Trap> {
check_function_args(func.signature(), args)?;
match *func.as_internal() {
FuncInstanceInternal::Internal { .. } => {
let mut interpreter = Interpreter::new(func, args, Some(stack_recycler))?;
let return_value = interpreter.start_execution(externals);
stack_recycler.recycle(interpreter);
return_value
}
FuncInstanceInternal::Host {
ref host_func_index,
..
} => externals.invoke_index(*host_func_index, args.into()),
}
}
/// Invoke the function, get a resumable handle. This handle can then be used to [`start_execution`]. If a
/// Host trap happens, caller can use [`resume_execution`] to feed the expected return value back in, and then
/// continue the execution.
///
/// This is an experimental API, and this functionality may not be available in other WebAssembly engines.
///
/// # Errors
///
/// Returns `Err` if `args` types is not match function [`signature`].
///
/// [`signature`]: #method.signature
/// [`Trap`]: #enum.Trap.html
/// [`start_execution`]: struct.FuncInvocation.html#method.start_execution
/// [`resume_execution`]: struct.FuncInvocation.html#method.resume_execution
pub fn invoke_resumable<'args>(
func: &FuncRef,
args: impl Into<Cow<'args, [RuntimeValue]>>,
) -> Result<FuncInvocation<'args>, Trap> {
let args = args.into();
check_function_args(func.signature(), &args)?;
match *func.as_internal() {
FuncInstanceInternal::Internal { .. } => {
let interpreter = Interpreter::new(func, &*args, None)?;
Ok(FuncInvocation {
kind: FuncInvocationKind::Internal(interpreter),
})
}
FuncInstanceInternal::Host {
ref host_func_index,
..
} => Ok(FuncInvocation {
kind: FuncInvocationKind::Host {
args,
host_func_index: *host_func_index,
finished: false,
},
}),
}
}
}
/// A resumable invocation error.
#[derive(Debug)]
pub enum ResumableError {
/// Trap happened.
Trap(Trap),
/// The invocation is not resumable.
///
/// Invocations are only resumable if a host function is called, and the host function returns a trap of `Host` kind. For other cases, this error will be returned. This includes:
/// - The invocation is directly a host function.
/// - The invocation has not been started.
/// - The invocation returns normally or returns any trap other than `Host` kind.
///
/// This error is returned by [`resume_execution`].
///
/// [`resume_execution`]: struct.FuncInvocation.html#method.resume_execution
NotResumable,
/// The invocation has already been started.
///
/// This error is returned by [`start_execution`].
///
/// [`start_execution`]: struct.FuncInvocation.html#method.start_execution
AlreadyStarted,
}
impl From<Trap> for ResumableError {
fn from(trap: Trap) -> Self {
ResumableError::Trap(trap)
}
}
/// A resumable invocation handle. This struct is returned by `FuncInstance::invoke_resumable`.
pub struct FuncInvocation<'args> {
kind: FuncInvocationKind<'args>,
}
enum FuncInvocationKind<'args> {
Internal(Interpreter),
Host {
args: Cow<'args, [RuntimeValue]>,
host_func_index: usize,
finished: bool,
},
}
impl<'args> FuncInvocation<'args> {
/// Whether this invocation is currently resumable.
pub fn is_resumable(&self) -> bool {
match &self.kind {
FuncInvocationKind::Internal(ref interpreter) => interpreter.state().is_resumable(),
FuncInvocationKind::Host { .. } => false,
}
}
/// If the invocation is resumable, the expected return value type to be feed back in.
pub fn resumable_value_type(&self) -> Option<ValueType> {
match &self.kind {
FuncInvocationKind::Internal(ref interpreter) => match interpreter.state() {
InterpreterState::Resumable(ref value_type) => *value_type,
_ => None,
},
FuncInvocationKind::Host { .. } => None,
}
}
/// Start the invocation execution.
pub fn start_execution<'externals, E: Externals + 'externals>(
&mut self,
externals: &'externals mut E,
) -> Result<Option<RuntimeValue>, ResumableError> {
match self.kind {
FuncInvocationKind::Internal(ref mut interpreter) => {
if interpreter.state() != &InterpreterState::Initialized {
return Err(ResumableError::AlreadyStarted);
}
Ok(interpreter.start_execution(externals)?)
}
FuncInvocationKind::Host {
ref args,
ref mut finished,
ref host_func_index,
} => {
if *finished {
return Err(ResumableError::AlreadyStarted);
}
*finished = true;
Ok(externals.invoke_index(*host_func_index, args.as_ref().into())?)
}
}
}
/// Resume an execution if a previous trap of Host kind happened.
///
/// `return_val` must be of the value type [`resumable_value_type`], defined by the host function import. Otherwise,
/// `UnexpectedSignature` trap will be returned. The current invocation must also be resumable
/// [`is_resumable`]. Otherwise, a `NotResumable` error will be returned.
///
/// [`resumable_value_type`]: #method.resumable_value_type
/// [`is_resumable`]: #method.is_resumable
pub fn resume_execution<'externals, E: Externals + 'externals>(
&mut self,
return_val: Option<RuntimeValue>,
externals: &'externals mut E,
) -> Result<Option<RuntimeValue>, ResumableError> {
if return_val.map(|v| v.value_type()) != self.resumable_value_type() {
return Err(ResumableError::Trap(Trap::new(
TrapKind::UnexpectedSignature,
)));
}
match &mut self.kind {
FuncInvocationKind::Internal(interpreter) => {
if interpreter.state().is_resumable() {
Ok(interpreter.resume_execution(return_val, externals)?)
} else {
Err(ResumableError::AlreadyStarted)
}
}
FuncInvocationKind::Host { .. } => Err(ResumableError::NotResumable),
}
}
}
#[derive(Clone, Debug)]
pub struct FuncBody {
pub locals: Vec<Local>,
pub code: isa::Instructions,
}