wasmi/src/host.rs

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use std::any::TypeId;
use value::RuntimeValue;
use Error;
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pub struct RuntimeArgs<'a>(&'a [RuntimeValue]);
impl<'a> From<&'a [RuntimeValue]> for RuntimeArgs<'a> {
fn from(inner: &'a [RuntimeValue]) -> Self {
RuntimeArgs(inner)
}
}
impl<'a> RuntimeArgs<'a> {
fn nth<T>(&self, idx: usize) -> Result<T, Error> where RuntimeValue: From<T> {
Err(Error::Value("Invalid cast".to_owned()))
}
}
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/// Custom user error.
pub trait HostError: 'static + ::std::fmt::Display + ::std::fmt::Debug {
#[doc(hidden)]
fn __private_get_type_id__(&self) -> TypeId {
TypeId::of::<Self>()
}
}
impl HostError {
/// Attempt to downcast this `HostError` to a concrete type by reference.
pub fn downcast_ref<T: HostError>(&self) -> Option<&T> {
if self.__private_get_type_id__() == TypeId::of::<T>() {
unsafe { Some(&*(self as *const HostError as *const T)) }
} else {
None
}
}
/// Attempt to downcast this `HostError` to a concrete type by mutable
/// reference.
pub fn downcast_mut<T: HostError>(&mut self) -> Option<&mut T> {
if self.__private_get_type_id__() == TypeId::of::<T>() {
unsafe { Some(&mut *(self as *mut HostError as *mut T)) }
} else {
None
}
}
}
pub trait Externals {
fn invoke_index(
&mut self,
index: usize,
args: &[RuntimeValue],
) -> Result<Option<RuntimeValue>, Error>;
}
pub struct NopExternals;
impl Externals for NopExternals {
fn invoke_index(
&mut self,
_index: usize,
_args: &[RuntimeValue],
) -> Result<Option<RuntimeValue>, Error> {
Err(Error::Trap("invoke index on no-op externals".into()))
}
}
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#[cfg(test)]
mod tests {
use value::RuntimeValue;
use super::RuntimeArgs;
#[test]
fn i32_runtime_args() {
let args: RuntimeArgs = (&[RuntimeValue::I32(0)][..]).into();
let val: i32 = args.nth(0).unwrap();
assert_eq!(val, 0);
}
}