linera_witty/wit_generation/
stub_instance.rs

1// Copyright (c) Zefchain Labs, Inc.
2// SPDX-License-Identifier: Apache-2.0
3
4//! Contains a [`StubInstance`] type and the code it requires to implement the necessary
5//! trait to be used as a Wasm instance type during compile time.
6
7use std::{borrow::Cow, marker::PhantomData};
8
9use crate::{
10    memory_layout::FlatLayout, GuestPointer, Instance, InstanceWithFunction, InstanceWithMemory,
11    Runtime, RuntimeError, RuntimeMemory,
12};
13
14/// A stub Wasm instance.
15///
16/// This is when a Wasm instance type is needed for type-checking but is not needed during
17/// runtime.
18pub struct StubInstance<UserData = ()> {
19    _user_data: PhantomData<UserData>,
20}
21
22impl<UserData> Default for StubInstance<UserData> {
23    fn default() -> Self {
24        StubInstance {
25            _user_data: PhantomData,
26        }
27    }
28}
29
30impl<UserData> Instance for StubInstance<UserData> {
31    type Runtime = StubRuntime;
32    type UserData = UserData;
33    type UserDataReference<'a> = &'a UserData
34    where
35        Self::UserData: 'a,
36        Self: 'a;
37    type UserDataMutReference<'a> = &'a mut UserData
38    where
39        Self::UserData: 'a,
40        Self: 'a;
41
42    fn load_export(&mut self, _name: &str) -> Option<()> {
43        unimplemented!("`StubInstance` can not be used as a real `Instance`");
44    }
45
46    fn user_data(&self) -> Self::UserDataReference<'_> {
47        unimplemented!("`StubInstance` can not be used as a real `Instance`");
48    }
49
50    fn user_data_mut(&mut self) -> Self::UserDataMutReference<'_> {
51        unimplemented!("`StubInstance` can not be used as a real `Instance`");
52    }
53}
54
55impl<Parameters, Results, UserData> InstanceWithFunction<Parameters, Results>
56    for StubInstance<UserData>
57where
58    Parameters: FlatLayout + 'static,
59    Results: FlatLayout + 'static,
60{
61    type Function = ();
62
63    fn function_from_export(
64        &mut self,
65        _name: <Self::Runtime as Runtime>::Export,
66    ) -> Result<Option<Self::Function>, RuntimeError> {
67        unimplemented!("`StubInstance` can not be used as a real `InstanceWithFunction`");
68    }
69
70    fn call(
71        &mut self,
72        _function: &Self::Function,
73        _parameters: Parameters,
74    ) -> Result<Results, RuntimeError> {
75        unimplemented!("`StubInstance` can not be used as a real `InstanceWithFunction`");
76    }
77}
78
79impl<UserData> InstanceWithMemory for StubInstance<UserData> {
80    fn memory_from_export(&self, _export: ()) -> Result<Option<StubMemory>, RuntimeError> {
81        unimplemented!("`StubInstance` can not be used as a real `InstanceWithMemory`");
82    }
83}
84
85/// A stub Wasm runtime.
86pub struct StubRuntime;
87
88impl Runtime for StubRuntime {
89    type Export = ();
90    type Memory = StubMemory;
91}
92
93/// A stub Wasm runtime memory.
94pub struct StubMemory;
95
96impl<UserData> RuntimeMemory<StubInstance<UserData>> for StubMemory {
97    fn read<'instance>(
98        &self,
99        _instance: &'instance StubInstance<UserData>,
100        _location: GuestPointer,
101        _length: u32,
102    ) -> Result<Cow<'instance, [u8]>, RuntimeError> {
103        unimplemented!("`StubMemory` can not be used as a real `RuntimeMemory`");
104    }
105
106    fn write(
107        &mut self,
108        _instance: &mut StubInstance<UserData>,
109        _location: GuestPointer,
110        _bytes: &[u8],
111    ) -> Result<(), RuntimeError> {
112        unimplemented!("`StubMemory` can not be used as a real `RuntimeMemory`");
113    }
114}
linera_witty/wit_generation/stub_instance.rs

linera_witty/wit_generation/
stub_instance.rs
