Minimal Worker support (#1476)

This adds the ability to spawn additional Isolates from Rust and send
and receive messages from them. This is preliminary work to support
running the typescript compiler in a separate isolate and thus support
native ES modules. Ref #975.

BUILD.gn

@@ -99,6 +99,7 @@ ts_sources = [
   "js/url.ts",
   "js/url_search_params.ts",
   "js/util.ts",
+  "js/workers.ts",
   "js/write_file.ts",
   "tsconfig.json",
 

js/globals.ts

@@ -19,6 +19,7 @@ import * as textEncoding from "./text_encoding";
 import * as timers from "./timers";
 import * as url from "./url";
 import * as urlSearchParams from "./url_search_params";
+import * as workers from "./workers";
 
 // These imports are not exposed and therefore are fine to just import the
 // symbols required.
@@ -86,3 +87,8 @@ window.TextEncoder = textEncoding.TextEncoder;
 export type TextEncoder = textEncoding.TextEncoder;
 window.TextDecoder = textEncoding.TextDecoder;
 export type TextDecoder = textEncoding.TextDecoder;
+
+window.workerMain = workers.workerMain;
+// TODO These shouldn't be available in main isolate.
+window.postMessage = workers.postMessage;
+window.close = workers.workerClose;

js/workers.ts

@@ -0,0 +1,75 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import * as dispatch from "./dispatch";
+import { libdeno } from "./libdeno";
+import * as msg from "gen/msg_generated";
+import * as flatbuffers from "./flatbuffers";
+import { assert, log } from "./util";
+import { globalEval } from "./global_eval";
+
+export async function postMessage(data: Uint8Array): Promise<void> {
+  const builder = flatbuffers.createBuilder();
+  msg.WorkerPostMessage.startWorkerPostMessage(builder);
+  const inner = msg.WorkerPostMessage.endWorkerPostMessage(builder);
+  const baseRes = await dispatch.sendAsync(
+    builder,
+    msg.Any.WorkerPostMessage,
+    inner,
+    data
+  );
+  assert(baseRes != null);
+}
+
+export async function getMessage(): Promise<null | Uint8Array> {
+  log("getMessage");
+  const builder = flatbuffers.createBuilder();
+  msg.WorkerGetMessage.startWorkerGetMessage(builder);
+  const inner = msg.WorkerGetMessage.endWorkerGetMessage(builder);
+  const baseRes = await dispatch.sendAsync(
+    builder,
+    msg.Any.WorkerGetMessage,
+    inner
+  );
+  assert(baseRes != null);
+  assert(
+    msg.Any.WorkerGetMessageRes === baseRes!.innerType(),
+    `base.innerType() unexpectedly is ${baseRes!.innerType()}`
+  );
+  const res = new msg.WorkerGetMessageRes();
+  assert(baseRes!.inner(res) != null);
+
+  const dataArray = res.dataArray();
+  if (dataArray == null) {
+    return null;
+  } else {
+    return new Uint8Array(dataArray!);
+  }
+}
+
+let isClosing = false;
+
+export function workerClose(): void {
+  isClosing = true;
+}
+
+export async function workerMain() {
+  log("workerMain");
+  libdeno.recv(dispatch.handleAsyncMsgFromRust);
+
+  // TODO avoid using globalEval to get Window. But circular imports if getting
+  // it from globals.ts
+  const window = globalEval("this");
+
+  while (!isClosing) {
+    const data = await getMessage();
+    if (data == null) {
+      log("workerMain got null message. quitting.");
+      break;
+    }
+    if (window["onmessage"]) {
+      const event = { data };
+      window.onmessage(event);
+    } else {
+      break;
+    }
+  }
+}

src/flags.rs

@@ -15,7 +15,7 @@ macro_rules! svec {
 }
 
 #[cfg_attr(feature = "cargo-clippy", allow(stutter))]
-#[derive(Debug, PartialEq, Default)]
+#[derive(Clone, Debug, PartialEq, Default)]
 pub struct DenoFlags {
   pub help: bool,
   pub log_debug: bool,

src/isolate.rs

@@ -12,6 +12,7 @@ use js_errors::JSError;
 use libdeno;
 use permissions::DenoPermissions;
 
+use futures::sync::mpsc as async_mpsc;
 use futures::Future;
 use libc::c_char;
 use libc::c_void;
@@ -23,6 +24,7 @@ use std::ffi::CString;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::mpsc;
 use std::sync::Arc;
+use std::sync::Mutex;
 use std::time::Duration;
 use std::time::Instant;
 use tokio;
@@ -53,6 +55,10 @@ pub struct Isolate {
   pub state: Arc<IsolateState>,
 }
 
+pub type WorkerSender = async_mpsc::Sender<Buf>;
+pub type WorkerReceiver = async_mpsc::Receiver<Buf>;
+pub type WorkerChannels = (WorkerSender, WorkerReceiver);
+
 // Isolate cannot be passed between threads but IsolateState can.
 // IsolateState satisfies Send and Sync.
 // So any state that needs to be accessed outside the main V8 thread should be
@@ -64,20 +70,35 @@ pub struct IsolateState {
   pub permissions: DenoPermissions,
   pub flags: flags::DenoFlags,
   pub metrics: Metrics,
+  pub worker_channels: Option<Mutex<WorkerChannels>>,
 }
 
 impl IsolateState {
-  pub fn new(flags: flags::DenoFlags, argv_rest: Vec<String>) -> Self {
+  pub fn new(
+    flags: flags::DenoFlags,
+    argv_rest: Vec<String>,
+    worker_channels: Option<WorkerChannels>,
+  ) -> Self {
     let custom_root = env::var("DENO_DIR").map(|s| s.into()).ok();
+
     Self {
       dir: deno_dir::DenoDir::new(flags.reload, custom_root).unwrap(),
       argv: argv_rest,
       permissions: DenoPermissions::new(&flags),
       flags,
       metrics: Metrics::default(),
+      worker_channels: worker_channels.map(|wc| Mutex::new(wc)),
     }
   }
 
+  #[cfg(test)]
+  pub fn mock() -> Arc<IsolateState> {
+    let argv = vec![String::from("./deno"), String::from("hello.js")];
+    // For debugging: argv.push_back(String::from("-D"));
+    let (flags, rest_argv, _) = flags::set_flags(argv).unwrap();
+    Arc::new(IsolateState::new(flags, rest_argv, None))
+  }
+
   #[inline]
   pub fn check_write(&self, filename: &str) -> DenoResult<()> {
     self.permissions.check_write(filename)
@@ -451,10 +472,7 @@ mod tests {
 
   #[test]
   fn test_dispatch_sync() {
-    let argv = vec![String::from("./deno"), String::from("hello.js")];
-    let (flags, rest_argv, _) = flags::set_flags(argv).unwrap();
-
-    let state = Arc::new(IsolateState::new(flags, rest_argv));
+    let state = IsolateState::mock();
     let snapshot = libdeno::deno_buf::empty();
     let isolate = Isolate::new(snapshot, state, dispatch_sync);
     tokio_util::init(|| {
@@ -493,9 +511,7 @@ mod tests {
 
   #[test]
   fn test_metrics_sync() {
-    let argv = vec![String::from("./deno"), String::from("hello.js")];
-    let (flags, rest_argv, _) = flags::set_flags(argv).unwrap();
-    let state = Arc::new(IsolateState::new(flags, rest_argv));
+    let state = IsolateState::mock();
     let snapshot = libdeno::deno_buf::empty();
     let isolate = Isolate::new(snapshot, state, metrics_dispatch_sync);
     tokio_util::init(|| {
@@ -529,9 +545,7 @@ mod tests {
 
   #[test]
   fn test_metrics_async() {
-    let argv = vec![String::from("./deno"), String::from("hello.js")];
-    let (flags, rest_argv, _) = flags::set_flags(argv).unwrap();
-    let state = Arc::new(IsolateState::new(flags, rest_argv));
+    let state = IsolateState::mock();
     let snapshot = libdeno::deno_buf::empty();
     let isolate = Isolate::new(snapshot, state, metrics_dispatch_async);
     tokio_util::init(|| {
@@ -619,7 +633,7 @@ mod tests {
     let argv = vec![String::from("./deno"), String::from(filename)];
     let (flags, rest_argv, _) = flags::set_flags(argv).unwrap();
 
-    let state = Arc::new(IsolateState::new(flags, rest_argv));
+    let state = Arc::new(IsolateState::new(flags, rest_argv, None));
     let snapshot = libdeno::deno_buf::empty();
     let isolate = Isolate::new(snapshot, state, dispatch_sync);
     tokio_util::init(|| {

src/main.rs

@@ -47,6 +47,7 @@ pub mod snapshot;
 mod tokio_util;
 mod tokio_write;
 pub mod version;
+mod workers;
 
 #[cfg(unix)]
 mod eager_unix;
@@ -96,7 +97,7 @@ fn main() {
     log::LevelFilter::Warn
   });
 
-  let state = Arc::new(isolate::IsolateState::new(flags, rest_argv));
+  let state = Arc::new(isolate::IsolateState::new(flags, rest_argv, None));
   let snapshot = snapshot::deno_snapshot();
   let isolate = isolate::Isolate::new(snapshot, state, ops::dispatch);
   tokio_util::init(|| {

src/msg.fbs

@@ -1,6 +1,9 @@
 union Any {
   Start,
   StartRes,
+  WorkerGetMessage,
+  WorkerGetMessageRes,
+  WorkerPostMessage,
   CodeFetch,
   CodeFetchRes,
   CodeCache,
@@ -149,6 +152,18 @@ table StartRes {
   v8_version: string;
 }
 
+table WorkerGetMessage {
+  unused: int8;
+}
+
+table WorkerGetMessageRes {
+  data: [ubyte];
+}
+
+table WorkerPostMessage {
+  // data passed thru the zero-copy data parameter.
+}
+
 table CodeFetch {
   specifier: string;
   referrer: string;

src/ops.rs

@@ -16,7 +16,10 @@ use version;
 
 use flatbuffers::FlatBufferBuilder;
 use futures;
+use futures::Async;
 use futures::Poll;
+use futures::Sink;
+use futures::Stream;
 use hyper;
 use hyper::rt::Future;
 use remove_dir_all::remove_dir_all;
@@ -34,6 +37,7 @@ use std::path::Path;
 use std::path::PathBuf;
 use std::process::Command;
 use std::str::FromStr;
+use std::sync::Arc;
 use std::time::UNIX_EPOCH;
 use std::time::{Duration, Instant};
 use tokio;
@@ -48,7 +52,7 @@ type OpResult = DenoResult<Buf>;
 // TODO Ideally we wouldn't have to box the Op being returned.
 // The box is just to make it easier to get a prototype refactor working.
 type OpCreator =
-  fn(state: &IsolateState, base: &msg::Base, data: libdeno::deno_buf)
+  fn(state: &Arc<IsolateState>, base: &msg::Base, data: libdeno::deno_buf)
     -> Box<Op>;
 
 #[inline]
@@ -113,8 +117,10 @@ pub fn dispatch(
       msg::Any::Stat => op_stat,
       msg::Any::Symlink => op_symlink,
       msg::Any::Truncate => op_truncate,
-      msg::Any::WriteFile => op_write_file,
+      msg::Any::WorkerGetMessage => op_worker_get_message,
+      msg::Any::WorkerPostMessage => op_worker_post_message,
       msg::Any::Write => op_write,
+      msg::Any::WriteFile => op_write_file,
       _ => panic!(format!(
         "Unhandled message {}",
         msg::enum_name_any(inner_type)
@@ -168,7 +174,7 @@ pub fn dispatch(
 }
 
 fn op_exit(
-  _config: &IsolateState,
+  _config: &Arc<IsolateState>,
   base: &msg::Base,
   _data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -177,7 +183,7 @@ fn op_exit(
 }
 
 fn op_start(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -238,19 +244,19 @@ fn serialize_response(
 }
 
 #[inline]
-fn ok_future(buf: Buf) -> Box<Op> {
+pub fn ok_future(buf: Buf) -> Box<Op> {
   Box::new(futures::future::ok(buf))
 }
 
 // Shout out to Earl Sweatshirt.
 #[inline]
-fn odd_future(err: DenoError) -> Box<Op> {
+pub fn odd_future(err: DenoError) -> Box<Op> {
   Box::new(futures::future::err(err))
 }
 
 // https://github.com/denoland/deno/blob/golang/os.go#L100-L154
 fn op_code_fetch(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -293,7 +299,7 @@ fn op_code_fetch(
 
 // https://github.com/denoland/deno/blob/golang/os.go#L156-L169
 fn op_code_cache(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -312,7 +318,7 @@ fn op_code_cache(
 }
 
 fn op_chdir(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -344,7 +350,7 @@ fn op_set_timeout(
 }
 
 fn op_set_env(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -360,7 +366,7 @@ fn op_set_env(
 }
 
 fn op_env(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -392,7 +398,7 @@ fn op_env(
 }
 
 fn op_fetch(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -479,7 +485,7 @@ where
 }
 
 fn op_make_temp_dir(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -528,7 +534,7 @@ fn op_make_temp_dir(
 }
 
 fn op_mkdir(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -548,7 +554,7 @@ fn op_mkdir(
 }
 
 fn op_chmod(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -581,7 +587,7 @@ fn op_chmod(
 }
 
 fn op_open(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -657,7 +663,7 @@ fn op_open(
 }
 
 fn op_close(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -674,7 +680,7 @@ fn op_close(
 }
 
 fn op_shutdown(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -700,7 +706,7 @@ fn op_shutdown(
 }
 
 fn op_read(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -738,7 +744,7 @@ fn op_read(
 }
 
 fn op_write(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -775,7 +781,7 @@ fn op_write(
 }
 
 fn op_remove(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -805,7 +811,7 @@ fn op_remove(
 
 // Prototype https://github.com/denoland/deno/blob/golang/os.go#L171-L184
 fn op_read_file(
-  _config: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -839,7 +845,7 @@ fn op_read_file(
 }
 
 fn op_copy_file(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -891,7 +897,7 @@ fn get_mode(_perm: &fs::Permissions) -> u32 {
 }
 
 fn op_cwd(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -917,7 +923,7 @@ fn op_cwd(
 }
 
 fn op_stat(
-  _config: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -964,7 +970,7 @@ fn op_stat(
 }
 
 fn op_read_dir(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1022,7 +1028,7 @@ fn op_read_dir(
 }
 
 fn op_write_file(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1042,7 +1048,7 @@ fn op_write_file(
 }
 
 fn op_rename(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1062,7 +1068,7 @@ fn op_rename(
 }
 
 fn op_symlink(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1091,7 +1097,7 @@ fn op_symlink(
 }
 
 fn op_read_link(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1124,7 +1130,7 @@ fn op_read_link(
 }
 
 fn op_repl_start(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1155,7 +1161,7 @@ fn op_repl_start(
 }
 
 fn op_repl_readline(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1193,7 +1199,7 @@ fn op_repl_readline(
 }
 
 fn op_truncate(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1216,7 +1222,7 @@ fn op_truncate(
 }
 
 fn op_listen(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1282,7 +1288,7 @@ fn new_conn(cmd_id: u32, tcp_stream: TcpStream) -> OpResult {
 }
 
 fn op_accept(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1308,7 +1314,7 @@ fn op_accept(
 }
 
 fn op_dial(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1332,7 +1338,7 @@ fn op_dial(
 }
 
 fn op_metrics(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1356,7 +1362,7 @@ fn op_metrics(
 }
 
 fn op_resources(
-  _state: &IsolateState,
+  _state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1408,7 +1414,7 @@ fn subprocess_stdio_map(v: msg::ProcessStdio) -> std::process::Stdio {
 }
 
 fn op_run(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1476,7 +1482,7 @@ fn op_run(
 }
 
 fn op_run_status(
-  state: &IsolateState,
+  state: &Arc<IsolateState>,
   base: &msg::Base,
   data: libdeno::deno_buf,
 ) -> Box<Op> {
@@ -1530,3 +1536,90 @@ fn op_run_status(
   });
   Box::new(future)
 }
+
+struct GetMessageFuture {
+  pub state: Arc<IsolateState>,
+}
+
+impl Future for GetMessageFuture {
+  type Item = Option<Buf>;
+  type Error = ();
+
+  fn poll(&mut self) -> Result<Async<Self::Item>, Self::Error> {
+    assert!(self.state.worker_channels.is_some());
+    match self.state.worker_channels {
+      None => panic!("expected worker_channels"),
+      Some(ref wc) => {
+        let mut wc = wc.lock().unwrap();
+        wc.1.poll()
+      }
+    }
+  }
+}
+
+fn op_worker_get_message(
+  state: &Arc<IsolateState>,
+  base: &msg::Base,
+  data: libdeno::deno_buf,
+) -> Box<Op> {
+  assert_eq!(data.len(), 0);
+  let cmd_id = base.cmd_id();
+
+  let op = GetMessageFuture {
+    state: state.clone(),
+  };
+  let op = op.map_err(move |_| -> DenoError { unimplemented!() });
+  let op = op.and_then(move |maybe_buf| -> DenoResult<Buf> {
+    debug!("op_worker_get_message");
+    let builder = &mut FlatBufferBuilder::new();
+
+    let data = maybe_buf.as_ref().map(|buf| builder.create_vector(buf));
+    let inner = msg::WorkerGetMessageRes::create(
+      builder,
+      &msg::WorkerGetMessageResArgs { data },
+    );
+    Ok(serialize_response(
+      cmd_id,
+      builder,
+      msg::BaseArgs {
+        inner: Some(inner.as_union_value()),
+        inner_type: msg::Any::WorkerGetMessageRes,
+        ..Default::default()
+      },
+    ))
+  });
+  Box::new(op)
+}
+
+fn op_worker_post_message(
+  state: &Arc<IsolateState>,
+  base: &msg::Base,
+  data: libdeno::deno_buf,
+) -> Box<Op> {
+  let cmd_id = base.cmd_id();
+
+  let d = Vec::from(data.as_ref()).into_boxed_slice();
+
+  assert!(state.worker_channels.is_some());
+  let tx = match state.worker_channels {
+    None => panic!("expected worker_channels"),
+    Some(ref wc) => {
+      let mut wc = wc.lock().unwrap();
+      wc.0.clone()
+    }
+  };
+  let op = tx.send(d);
+  let op = op.map_err(|e| errors::new(ErrorKind::Other, e.to_string()));
+  let op = op.and_then(move |_| -> DenoResult<Buf> {
+    let builder = &mut FlatBufferBuilder::new();
+
+    Ok(serialize_response(
+      cmd_id,
+      builder,
+      msg::BaseArgs {
+        ..Default::default()
+      },
+    ))
+  });
+  Box::new(op)
+}

src/resources.rs

@@ -10,10 +10,12 @@
 
 #[cfg(unix)]
 use eager_unix as eager;
+use errors;
 use errors::bad_resource;
 use errors::DenoError;
 use errors::DenoResult;
 use http_body::HttpBody;
+use isolate::WorkerChannels;
 use repl::Repl;
 use tokio_util;
 use tokio_write;
@@ -22,7 +24,10 @@ use futures;
 use futures::future::{Either, FutureResult};
 use futures::Future;
 use futures::Poll;
+use futures::Sink;
+use futures::Stream;
 use hyper;
+use isolate::Buf;
 use std;
 use std::collections::HashMap;
 use std::io::{Error, Read, Write};
@@ -96,6 +101,14 @@ enum Repr {
   ChildStdin(tokio_process::ChildStdin),
   ChildStdout(tokio_process::ChildStdout),
   ChildStderr(tokio_process::ChildStderr),
+  Worker(WorkerChannels),
+}
+
+/// If the given rid is open, this returns the type of resource, E.G. "worker".
+/// If the rid is closed or was never open, it returns None.
+pub fn get_type(rid: ResourceId) -> Option<String> {
+  let table = RESOURCE_TABLE.lock().unwrap();
+  table.get(&rid).map(inspect_repr)
 }
 
 pub fn table_entries() -> Vec<(u32, String)> {
@@ -131,6 +144,7 @@ fn inspect_repr(repr: &Repr) -> String {
     Repr::ChildStdin(_) => "childStdin",
     Repr::ChildStdout(_) => "childStdout",
     Repr::ChildStderr(_) => "childStderr",
+    Repr::Worker(_) => "worker",
   };
 
   String::from(h_repr)
@@ -138,7 +152,7 @@ fn inspect_repr(repr: &Repr) -> String {
 
 // Abstract async file interface.
 // Ideally in unix, if Resource represents an OS rid, it will be the same.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct Resource {
   pub rid: ResourceId,
 }
@@ -284,6 +298,54 @@ pub fn add_repl(repl: Repl) -> Resource {
   Resource { rid }
 }
 
+pub fn add_worker(wc: WorkerChannels) -> Resource {
+  let rid = new_rid();
+  let mut tg = RESOURCE_TABLE.lock().unwrap();
+  let r = tg.insert(rid, Repr::Worker(wc));
+  assert!(r.is_none());
+  Resource { rid }
+}
+
+pub fn worker_post_message(
+  rid: ResourceId,
+  buf: Buf,
+) -> futures::sink::Send<futures::sync::mpsc::Sender<Buf>> {
+  let mut table = RESOURCE_TABLE.lock().unwrap();
+  let maybe_repr = table.get_mut(&rid);
+  match maybe_repr {
+    Some(Repr::Worker(ref mut wc)) => {
+      // unwrap here is incorrect, but doing it anyway
+      wc.0.clone().send(buf)
+    }
+    _ => panic!("bad resource"), // futures::future::err(bad_resource()).into(),
+  }
+}
+
+pub struct WorkerReceiver {
+  rid: ResourceId,
+}
+
+// Invert the dumbness that tokio_process causes by making Child itself a future.
+impl Future for WorkerReceiver {
+  type Item = Option<Buf>;
+  type Error = DenoError;
+
+  fn poll(&mut self) -> Poll<Option<Buf>, DenoError> {
+    let mut table = RESOURCE_TABLE.lock().unwrap();
+    let maybe_repr = table.get_mut(&self.rid);
+    match maybe_repr {
+      Some(Repr::Worker(ref mut wc)) => wc.1.poll().map_err(|()| {
+        errors::new(errors::ErrorKind::Other, "recv msg error".to_string())
+      }),
+      _ => Err(bad_resource()),
+    }
+  }
+}
+
+pub fn worker_recv_message(rid: ResourceId) -> WorkerReceiver {
+  WorkerReceiver { rid }
+}
+
 #[cfg_attr(feature = "cargo-clippy", allow(stutter))]
 pub struct ChildResources {
   pub child_rid: ResourceId,

src/workers.rs

@@ -0,0 +1,148 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+
+#![allow(dead_code)]
+
+use isolate::Buf;
+use isolate::Isolate;
+use isolate::IsolateState;
+use isolate::WorkerChannels;
+use js_errors::JSError;
+use ops;
+use resources;
+use snapshot;
+use tokio_util;
+
+use futures::sync::mpsc;
+use futures::sync::oneshot;
+use futures::Future;
+use std::sync::Arc;
+use std::thread;
+
+/// Rust interface for WebWorkers.
+pub struct Worker {
+  isolate: Isolate,
+}
+
+impl Worker {
+  pub fn new(parent_state: &Arc<IsolateState>) -> (Self, WorkerChannels) {
+    let (worker_in_tx, worker_in_rx) = mpsc::channel::<Buf>(1);
+    let (worker_out_tx, worker_out_rx) = mpsc::channel::<Buf>(1);
+
+    let internal_channels = (worker_out_tx, worker_in_rx);
+    let external_channels = (worker_in_tx, worker_out_rx);
+
+    let state = Arc::new(IsolateState::new(
+      parent_state.flags.clone(),
+      parent_state.argv.clone(),
+      Some(internal_channels),
+    ));
+
+    let snapshot = snapshot::deno_snapshot();
+    let isolate = Isolate::new(snapshot, state, ops::dispatch);
+
+    let worker = Worker { isolate };
+    (worker, external_channels)
+  }
+
+  pub fn execute(&self, js_source: &str) -> Result<(), JSError> {
+    self.isolate.execute(js_source)
+  }
+
+  pub fn event_loop(&self) -> Result<(), JSError> {
+    self.isolate.event_loop()
+  }
+}
+
+fn spawn(state: Arc<IsolateState>, js_source: String) -> resources::Resource {
+  // TODO This function should return a Future, so that the caller can retrieve
+  // the JSError if one is thrown. Currently it just prints to stderr and calls
+  // exit(1).
+  // let (js_error_tx, js_error_rx) = oneshot::channel::<JSError>();
+  let (p, c) = oneshot::channel::<resources::Resource>();
+  let builder = thread::Builder::new().name("worker".to_string());
+  let _tid = builder
+    .spawn(move || {
+      let (worker, external_channels) = Worker::new(&state);
+
+      let mut resource = resources::add_worker(external_channels);
+      p.send(resource.clone()).unwrap();
+
+      tokio_util::init(|| {
+        (|| -> Result<(), JSError> {
+          worker.execute("workerMain()")?;
+          worker.execute(&js_source)?;
+          worker.event_loop()?;
+          Ok(())
+        })().or_else(|err: JSError| -> Result<(), JSError> {
+          eprintln!("{}", err.to_string());
+          std::process::exit(1)
+        }).unwrap();
+      });
+
+      resource.close();
+    }).unwrap();
+
+  let resource = c.wait().unwrap();
+
+  resource
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn test_spawn() {
+    let resource = spawn(
+      IsolateState::mock(),
+      r#"
+      onmessage = function(e) {
+        let s = new TextDecoder().decode(e.data);;
+        console.log("msg from main script", s);
+        if (s == "exit") {
+          close();
+          return;
+        } else {
+          console.assert(s === "hi");
+        }
+        postMessage(new Uint8Array([1, 2, 3]));
+        console.log("after postMessage");
+      }
+    "#.into(),
+    );
+    let msg = String::from("hi").into_boxed_str().into_boxed_bytes();
+
+    let r = resources::worker_post_message(resource.rid, msg).wait();
+    assert!(r.is_ok());
+
+    let maybe_msg =
+      resources::worker_recv_message(resource.rid).wait().unwrap();
+    assert!(maybe_msg.is_some());
+    assert_eq!(*maybe_msg.unwrap(), [1, 2, 3]);
+
+    let msg = String::from("exit").into_boxed_str().into_boxed_bytes();
+    let r = resources::worker_post_message(resource.rid, msg).wait();
+    assert!(r.is_ok());
+  }
+
+  #[test]
+  fn removed_from_resource_table_on_close() {
+    let resource =
+      spawn(IsolateState::mock(), "onmessage = () => close();".into());
+
+    assert_eq!(
+      resources::get_type(resource.rid),
+      Some("worker".to_string())
+    );
+
+    let msg = String::from("hi").into_boxed_str().into_boxed_bytes();
+    let r = resources::worker_post_message(resource.rid, msg).wait();
+    assert!(r.is_ok());
+    println!("rid {:?}", resource.rid);
+
+    // TODO Need a way to get a future for when a resource closes.
+    // For now, just sleep for a bit.
+    thread::sleep(std::time::Duration::from_millis(100));
+    assert_eq!(resources::get_type(resource.rid), None);
+  }
+}