53 lines
1.2 KiB
Rust
53 lines
1.2 KiB
Rust
use std::any::TypeId;
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use value::RuntimeValue;
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use Error;
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/// Custom user error.
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pub trait HostError: 'static + ::std::fmt::Display + ::std::fmt::Debug {
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#[doc(hidden)]
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fn __private_get_type_id__(&self) -> TypeId {
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TypeId::of::<Self>()
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}
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}
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impl HostError {
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/// Attempt to downcast this `HostError` to a concrete type by reference.
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pub fn downcast_ref<T: HostError>(&self) -> Option<&T> {
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if self.__private_get_type_id__() == TypeId::of::<T>() {
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unsafe { Some(&*(self as *const HostError as *const T)) }
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} else {
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None
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}
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}
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/// Attempt to downcast this `HostError` to a concrete type by mutable
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/// reference.
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pub fn downcast_mut<T: HostError>(&mut self) -> Option<&mut T> {
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if self.__private_get_type_id__() == TypeId::of::<T>() {
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unsafe { Some(&mut *(self as *mut HostError as *mut T)) }
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} else {
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None
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}
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}
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}
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pub trait Externals {
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fn invoke_index(
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&mut self,
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index: usize,
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args: &[RuntimeValue],
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) -> Result<Option<RuntimeValue>, Error>;
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}
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pub struct NopExternals;
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impl Externals for NopExternals {
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fn invoke_index(
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&mut self,
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_index: usize,
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_args: &[RuntimeValue],
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) -> Result<Option<RuntimeValue>, Error> {
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Err(Error::Trap("invoke index on no-op externals".into()))
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}
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}
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