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use std::{io::Write, sync::Arc};

use anyhow::Context;

use libloading::Library;

use tempfile::{NamedTempFile, TempPath};

use crate::context::{PluginContext, PluginPtrMut};

/// A native plugin loaded from a shared library

pub struct NativePlugin {

/// The tempfile containing the shared library.

tempfile: TempPath,

/// The plugin's shared library.

library: Library,

/// The plugin's exported quill_setup function.

///

/// Parameters:

/// 1. Host context pointer

/// 2. Pointer to bincode-encoded vtable

/// 3. Length of bincode-encoded vtable

enable: unsafe extern "C" fn(*const u8, *const u8, usize),

/// The plugin's exported quill_run_system function.

///

/// Parameters:

/// 1. Plugin data pointer for this system

run_system: unsafe extern "C" fn(*mut u8),

}

impl NativePlugin {

pub fn load(module: &[u8]) -> anyhow::Result<Self> {

// Libraries have to be loaded from files, so

// we'll create a tempfile containing the module bytes.

let mut tempfile = NamedTempFile::new()?;

tempfile.write_all(module)?;

tempfile.flush()?;

let path = tempfile.into_temp_path();

// SAFETY: Library::new() is unsafe because

// the loaded module can execute arbitrary

// code. Since native plugins are trusted,

// this is sound.

let library = unsafe { Library::new(&path)? };

// SAFETY: these functions will not be accessed after the plugin is unloaded.

let enable = unsafe {

*library

.get("quill_setup".as_bytes())

.context("plugin is missing quill_setup export")?

};

let run_system = unsafe {

*library

.get("quill_run_system".as_bytes())

.context("plugin is missing quill_run_system export")?

};

Ok(Self {

tempfile: path,

library,

enable,

run_system,

})

}

pub fn enable(&self, context: Arc<PluginContext>) {

let vtable = self.generate_vtable();

let context_ptr = Arc::as_ptr(&context);

// Ensure context stays alive

std::mem::forget(context);

// SAFETY: we assume the plugin is sound.

unsafe {

(self.enable)(

context_ptr.cast::<u8>(),

vtable.as_ptr(),

vtable.len() as usize,

)

}

fn generate_vtable(&self) -> Vec<u8> {

let vtable = crate::host_calls::generate_vtable();

bincode::serialize(&vtable).expect("can't serialize vtable")

}

pub fn run_system(&self, data: PluginPtrMut<u8>) {

// SAFETY: we assume the plugin is sound.

unsafe { (self.run_system)(data.as_native()) }

}

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