1use std::{
2 collections::HashMap, fs::File, future::Future, marker::PhantomData, path::Path, pin::Pin,
3};
4
5use anyhow::{anyhow, Error};
6use serde::{de::DeserializeOwned, Serialize};
7
8use wasi_common::{dir, file};
9use wasmtime::IntoFunc;
10use wasmtime::{Caller, Config, Engine, Instance, Linker, Module, Store, TypedFunc};
11use wasmtime_wasi::{Dir, WasiCtx, WasiCtxBuilder};
12
13pub struct WasiResource(u32);
14
15pub struct WasiFn<A: Serialize, R: DeserializeOwned> {
16 function: TypedFunc<(u32, u32), u32>,
17 _function_type: PhantomData<fn(A) -> R>,
18}
19
20impl<A: Serialize, R: DeserializeOwned> Copy for WasiFn<A, R> {}
21
22impl<A: Serialize, R: DeserializeOwned> Clone for WasiFn<A, R> {
23 fn clone(&self) -> Self {
24 Self {
25 function: self.function,
26 _function_type: PhantomData,
27 }
28 }
29}
30
31// impl<A: Serialize, R: DeserializeOwned> WasiFn<A, R> {
32// #[inline(always)]
33// pub async fn call(&self, runtime: &mut Wasi, arg: A) -> Result<R, Error> {
34// runtime.call(self, arg).await
35// }
36// }
37
38pub struct Wasi {
39 engine: Engine,
40 module: Module,
41 store: Store<WasiCtx>,
42 instance: Instance,
43 alloc_buffer: TypedFunc<u32, u32>,
44 // free_buffer: TypedFunc<(u32, u32), ()>,
45}
46
47// type signature derived from:
48// https://docs.rs/wasmtime/latest/wasmtime/struct.Linker.html#method.func_wrap2_async
49// macro_rules! dynHostFunction {
50// () => {
51// Box<
52// dyn for<'a> Fn(Caller<'a, WasiCtx>, u32, u32)
53// -> Box<dyn Future<Output = u32> + Send + 'a>
54// + Send
55// + Sync
56// + 'static
57// >
58// };
59// }
60
61// macro_rules! implHostFunction {
62// () => {
63// impl for<'a> Fn(Caller<'a, WasiCtx>, u32, u32)
64// -> Box<dyn Future<Output = u32> + Send + 'a>
65// + Send
66// + Sync
67// + 'static
68// };
69// }
70
71// This type signature goodness gracious
72pub type HostFunction = Box<dyn IntoFunc<WasiCtx, (u32, u32), u32>>;
73
74pub struct WasiPluginBuilder {
75 // host_functions: HashMap<String, Box<dyn Fn(&str, &mut Linker<WasiCtx>) -> Result<(), Error>>>,
76 wasi_ctx: WasiCtx,
77 engine: Engine,
78 linker: Linker<WasiCtx>,
79}
80
81impl WasiPluginBuilder {
82 pub fn new(wasi_ctx: WasiCtx) -> Result<Self, Error> {
83 let mut config = Config::default();
84 config.async_support(true);
85 let engine = Engine::new(&config)?;
86 let mut linker = Linker::new(&engine);
87
88 Ok(WasiPluginBuilder {
89 // host_functions: HashMap::new(),
90 wasi_ctx,
91 engine,
92 linker,
93 })
94 }
95
96 pub fn new_with_default_ctx() -> Result<Self, Error> {
97 let wasi_ctx = WasiCtxBuilder::new()
98 .inherit_stdin()
99 .inherit_stderr()
100 .build();
101 Self::new(wasi_ctx)
102 }
103
104 pub fn host_function<A: Serialize, R: DeserializeOwned>(
105 mut self,
106 name: &str,
107 function: impl Fn(A) -> R + Send + Sync + 'static,
108 ) -> Result<Self, Error> {
109 self.linker
110 .func_wrap("env", name, move |ptr: u32, len: u32| {
111 // TODO: insert serialization code
112 function(todo!());
113 7u32
114 })?;
115 Ok(self)
116 }
117
118 pub async fn init<T: AsRef<[u8]>>(self, module: T) -> Result<Wasi, Error> {
119 Wasi::init(module.as_ref().to_vec(), self).await
120 }
121}
122
123// TODO: remove
124/// Represents a to-be-initialized plugin.
125/// Please use [`WasiPluginBuilder`], don't use this directly.
126pub struct WasiPlugin {
127 pub module: Vec<u8>,
128 pub wasi_ctx: WasiCtx,
129 pub host_functions:
130 HashMap<String, Box<dyn Fn(&str, &mut Linker<WasiCtx>) -> Result<(), Error>>>,
131}
132
133impl Wasi {
134 pub fn dump_memory(data: &[u8]) {
135 for (i, byte) in data.iter().enumerate() {
136 if i % 32 == 0 {
137 println!();
138 }
139 if i % 4 == 0 {
140 print!("|");
141 }
142 if *byte == 0 {
143 print!("__")
144 } else {
145 print!("{:02x}", byte);
146 }
147 }
148 println!();
149 }
150}
151
152impl Wasi {
153 async fn init(module: Vec<u8>, plugin: WasiPluginBuilder) -> Result<Self, Error> {
154 let engine = plugin.engine;
155 let mut linker = plugin.linker;
156
157 linker.func_wrap("env", "__hello", |x: u32| x * 2).unwrap();
158 linker.func_wrap("env", "__bye", |x: u32| x / 2).unwrap();
159
160 wasmtime_wasi::add_to_linker(&mut linker, |s| s)?;
161
162 let mut store: Store<_> = Store::new(&engine, plugin.wasi_ctx);
163 let module = Module::new(&engine, module)?;
164
165 linker.module_async(&mut store, "", &module).await?;
166 let instance = linker.instantiate_async(&mut store, &module).await?;
167
168 let alloc_buffer = instance.get_typed_func(&mut store, "__alloc_buffer")?;
169 // let free_buffer = instance.get_typed_func(&mut store, "__free_buffer")?;
170
171 Ok(Wasi {
172 engine,
173 module,
174 store,
175 instance,
176 alloc_buffer,
177 // free_buffer,
178 })
179 }
180
181 /// Attaches a file or directory the the given system path to the runtime.
182 /// Note that the resource must be freed by calling `remove_resource` afterwards.
183 pub fn attach_path<T: AsRef<Path>>(&mut self, path: T) -> Result<WasiResource, Error> {
184 // grab the WASI context
185 let ctx = self.store.data_mut();
186
187 // open the file we want, and convert it into the right type
188 // this is a footgun and a half
189 let file = File::open(&path).unwrap();
190 let dir = Dir::from_std_file(file);
191 let dir = Box::new(wasmtime_wasi::dir::Dir::from_cap_std(dir));
192
193 // grab an empty file descriptor, specify capabilities
194 let fd = ctx.table().push(Box::new(()))?;
195 let caps = dir::DirCaps::all();
196 let file_caps = file::FileCaps::all();
197
198 // insert the directory at the given fd,
199 // return a handle to the resource
200 ctx.insert_dir(fd, dir, caps, file_caps, path.as_ref().to_path_buf());
201 Ok(WasiResource(fd))
202 }
203
204 /// Returns `true` if the resource existed and was removed.
205 pub fn remove_resource(&mut self, resource: WasiResource) -> Result<(), Error> {
206 self.store
207 .data_mut()
208 .table()
209 .delete(resource.0)
210 .ok_or_else(|| anyhow!("Resource did not exist, but a valid handle was passed in"))?;
211 Ok(())
212 }
213
214 // pub fn with_resource<T>(
215 // &mut self,
216 // resource: WasiResource,
217 // callback: fn(&mut Self) -> Result<T, Error>,
218 // ) -> Result<T, Error> {
219 // let result = callback(self);
220 // self.remove_resource(resource)?;
221 // return result;
222 // }
223
224 // So this call function is kinda a dance, I figured it'd be a good idea to document it.
225 // the high level is we take a serde type, serialize it to a byte array,
226 // (we're doing this using bincode for now)
227 // then toss that byte array into webassembly.
228 // webassembly grabs that byte array, does some magic,
229 // and serializes the result into yet another byte array.
230 // we then grab *that* result byte array and deserialize it into a result.
231 //
232 // phew...
233 //
234 // now the problem is, webassambly doesn't support buffers.
235 // only really like i32s, that's it (yeah, it's sad. Not even unsigned!)
236 // (ok, I'm exaggerating a bit).
237 //
238 // the Wasm function that this calls must have a very specific signature:
239 //
240 // fn(pointer to byte array: i32, length of byte array: i32)
241 // -> pointer to (
242 // pointer to byte_array: i32,
243 // length of byte array: i32,
244 // ): i32
245 //
246 // This pair `(pointer to byte array, length of byte array)` is called a `Buffer`
247 // and can be found in the cargo_test plugin.
248 //
249 // so on the wasm side, we grab the two parameters to the function,
250 // stuff them into a `Buffer`,
251 // and then pray to the `unsafe` Rust gods above that a valid byte array pops out.
252 //
253 // On the flip side, when returning from a wasm function,
254 // we convert whatever serialized result we get into byte array,
255 // which we stuff into a Buffer and allocate on the heap,
256 // which pointer to we then return.
257 // Note the double indirection!
258 //
259 // So when returning from a function, we actually leak memory *twice*:
260 //
261 // 1) once when we leak the byte array
262 // 2) again when we leak the allocated `Buffer`
263 //
264 // This isn't a problem because Wasm stops executing after the function returns,
265 // so the heap is still valid for our inspection when we want to pull things out.
266
267 /// Takes an item, allocates a buffer, serializes the argument to that buffer,
268 /// and returns a (ptr, len) pair to that buffer.
269 async fn serialize_to_buffer<T: Serialize>(&mut self, item: T) -> Result<(u32, u32), Error> {
270 // serialize the argument using bincode
271 let item = bincode::serialize(&item)?;
272 let buffer_len = item.len() as u32;
273
274 // allocate a buffer and write the argument to that buffer
275 let buffer_ptr = self
276 .alloc_buffer
277 .call_async(&mut self.store, buffer_len)
278 .await?;
279 let plugin_memory = self
280 .instance
281 .get_memory(&mut self.store, "memory")
282 .ok_or_else(|| anyhow!("Could not grab slice of plugin memory"))?;
283 plugin_memory.write(&mut self.store, buffer_ptr as usize, &item)?;
284 Ok((buffer_ptr, buffer_len))
285 }
286
287 /// Takes a ptr to a (ptr, len) pair and returns the corresponding deserialized buffer
288 fn deserialize_from_buffer<R: DeserializeOwned>(&mut self, buffer: u32) -> Result<R, Error> {
289 // create a buffer to read the (ptr, length) pair into
290 // this is a total of 4 + 4 = 8 bytes.
291 let raw_buffer = &mut [0; 8];
292 let plugin_memory = self
293 .instance
294 .get_memory(&mut self.store, "memory")
295 .ok_or_else(|| anyhow!("Could not grab slice of plugin memory"))?;
296 plugin_memory.read(&mut self.store, buffer as usize, raw_buffer)?;
297
298 // use these bytes (wasm stores things little-endian)
299 // to get a pointer to the buffer and its length
300 let b = raw_buffer;
301 let buffer_ptr = u32::from_le_bytes([b[0], b[1], b[2], b[3]]) as usize;
302 let buffer_len = u32::from_le_bytes([b[4], b[5], b[6], b[7]]) as usize;
303 let buffer_end = buffer_ptr + buffer_len;
304
305 // read the buffer at this point into a byte array
306 // deserialize the byte array into the provided serde type
307 let result = &plugin_memory.data(&mut self.store)[buffer_ptr..buffer_end];
308 let result = bincode::deserialize(result)?;
309
310 // TODO: this is handled wasm-side, but I'd like to double-check
311 // // deallocate the argument buffer
312 // self.free_buffer.call(&mut self.store, arg_buffer);
313
314 Ok(result)
315 }
316
317 pub fn function<A: Serialize, R: DeserializeOwned, T: AsRef<str>>(
318 &mut self,
319 name: T,
320 ) -> Result<WasiFn<A, R>, Error> {
321 let fun_name = format!("__{}", name.as_ref());
322 let fun = self
323 .instance
324 .get_typed_func::<(u32, u32), u32, _>(&mut self.store, &fun_name)?;
325 Ok(WasiFn {
326 function: fun,
327 _function_type: PhantomData,
328 })
329 }
330
331 // TODO: dont' use as for conversions
332 pub async fn call<A: Serialize, R: DeserializeOwned>(
333 &mut self,
334 handle: &WasiFn<A, R>,
335 arg: A,
336 ) -> Result<R, Error> {
337 // dbg!(&handle.name);
338 // dbg!(serde_json::to_string(&arg)).unwrap();
339
340 // write the argument to linear memory
341 // this returns a (ptr, lentgh) pair
342 let arg_buffer = self.serialize_to_buffer(arg).await?;
343
344 // get the webassembly function we want to actually call
345 // TODO: precompute handle
346 // let fun_name = format!("__{}", handle);
347 // let fun = self
348 // .instance
349 // .get_typed_func::<(u32, u32), u32, _>(&mut self.store, &fun_name)?;
350 let fun = handle.function;
351
352 // call the function, passing in the buffer and its length
353 // this returns a ptr to a (ptr, lentgh) pair
354 let result_buffer = fun.call_async(&mut self.store, arg_buffer).await?;
355
356 self.deserialize_from_buffer(result_buffer)
357 }
358}