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48 lines
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1.8 KiB
Markdown
48 lines
No EOL
1.8 KiB
Markdown
# Zed's Plugin Runner
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Wasm plugins can be run through `wasmtime`, with supported for sandboxed system integration through WASI. There are three `plugin` crates that implement different things:
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1. `plugin_runtime` loads and runs compiled `Wasm` plugins, and handles setting up system bindings.
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2. `plugin` is the crate that Rust Wasm plugins should depend on. It re-exports some required crates (e.g. `serde`, `bincode`) and provides some necessary macros for generating bindings that `plugin_runtime` can hook into.
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3. `plugin_macros` implements the proc macros required by `plugin`, like the `#[bind]` attribute macro.
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## ABI
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The interface between the host Rust runtime ('Runtime') and plugins implemented in Wasm ('Plugin') is pretty simple.
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`Buffer` is a pair of two 4-byte (`u32`) fields, encoded as a single `u64`.
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```
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struct Buffer {
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ptr: u32,
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len: u32,
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}
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```
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All functions that Plugin exports must have the following properties:
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- Have the signature `fn(ptr: u64) -> u64`, where both the argument and return types are a `Buffer`:
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- The input `Buffer` will contain the input arguments serialized to `bincode`.
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- The output `Buffer` will contain the output arguments serialized to `bincode`.
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- Have a name starting with two underscores.
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Additionally, Plugin must export an:
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- `__alloc_buffer` function that, given a `u32` length, returns a `u32` pointer to a buffer of that length.
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Note that all of these requirements are automatically fullfilled for any Rust Wasm plugin that uses the `plugin` crate, and imports the `prelude`.
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Here's an example Rust Wasm plugin that doubles the value of every float in a `Vec<f64>` passed into it:
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```rust
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use plugin::prelude::*;
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#[bind]
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pub fn double(mut x: Vec<f64>) -> Vec<f64> {
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x.into_iter().map(|x| x * 2.0).collect()
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}
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```
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All the serialization code is automatically generated by `#[bind]`. |