ValueKind
A ValueKind represents all of the possible types of a WebAssembly value. This is used to represent the type of various constructs such as Globals, or Function parameters/results.
| ValueKind | C# Type |
|---|---|
| Int32 | int |
| Int64 | long |
| Float32 | float |
| Float64 | double |
| V128 | Wasmtime.V128* |
| FuncRef | Wasmtime.Function |
| ExternRef | object* |
V128​
V128 is a 128 bit value type. C# has no built in equivalent to this type, instead the Wasmtime.V128 type provides a way to interact with values of this type.
ExternRef​
ExternRef represents an opaque reference to any data within WebAssembly. Any C# reference type (anything derived from object) can be passed as an ExternRef. WASM code cannot create new externref values. WASM code cannot do anything with an externref, other than pass it as an argument to other functions.
These properties make externref objects useful as "capabilities" which WASM can access. For example if you pass a GameObject into some WASM code as an externref and the same code later passes you back a GameObject you know that it must be an object you gave to the WASM earlier, because it is impossible for WASM to create new externref values.