diff --git a/core/flags.rs b/core/flags.rs
new file mode 100644
index 0000000000..2da35734d4
--- /dev/null
+++ b/core/flags.rs
@@ -0,0 +1,84 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+//! This module wraps libdeno::deno_set_v8_flags
+use crate::libdeno::deno_set_v8_flags;
+use libc::c_char;
+use libc::c_int;
+use std::ffi::CStr;
+use std::ffi::CString;
+use std::mem;
+use std::vec::Vec;
+
+/// Pass the command line arguments to v8.
+/// Returns a vector of command line arguments that V8 did not understand.
+/// Translates --v8-options into a --help flag for V8.
+pub fn v8_set_flags(args: Vec<String>) -> Vec<String> {
+  // deno_set_v8_flags(int* argc, char** argv) mutates argc and argv to remove
+  // flags that v8 understands.
+  // First parse core args, then convert to a vector of C strings.
+  let (args, rest) = v8_set_flags_preprocess(args);
+
+  // Make a new array, that can be modified by V8::SetFlagsFromCommandLine(),
+  // containing mutable raw pointers to the individual command line args.
+  let mut raw_argv = args
+    .iter()
+    .map(|arg| CString::new(arg.as_str()).unwrap().into_bytes_with_nul())
+    .collect::<Vec<_>>();
+  let mut c_argv = raw_argv
+    .iter_mut()
+    .map(|arg| arg.as_mut_ptr() as *mut c_char)
+    .collect::<Vec<_>>();
+
+  // Store the length of the c_argv array in a local variable. We'll pass
+  // a pointer to this local variable to deno_set_v8_flags(), which then
+  // updates its value.
+  let mut c_argv_len = c_argv.len() as c_int;
+  // Let v8 parse the arguments it recognizes and remove them from c_argv.
+  unsafe { deno_set_v8_flags(&mut c_argv_len, c_argv.as_mut_ptr()) };
+  // If c_argv_len was updated we have to change the length of c_argv to match.
+  c_argv.truncate(c_argv_len as usize);
+  // Copy the modified arguments list into a proper rust vec and return it.
+  c_argv
+    .iter()
+    .map(|ptr| unsafe {
+      let cstr = CStr::from_ptr(*ptr as *const c_char);
+      let slice = cstr.to_str().unwrap();
+      slice.to_string()
+    }).chain(rest.into_iter())
+    .collect()
+}
+
+// Returns args passed to V8, followed by args passed to JS
+fn v8_set_flags_preprocess(args: Vec<String>) -> (Vec<String>, Vec<String>) {
+  let (rest, mut v8_args) =
+    args.into_iter().partition(|ref a| a.as_str() == "--help");
+
+  // Replace args being sent to V8
+  for a in &mut v8_args {
+    if a == "--v8-options" {
+      mem::swap(a, &mut String::from("--help"));
+    }
+  }
+  (v8_args, rest)
+}
+
+#[test]
+fn test_v8_set_flags_preprocess_1() {
+  let js_args = v8_set_flags_preprocess(vec![
+    "deno".to_string(),
+    "--v8-options".to_string(),
+  ]);
+  assert_eq!(
+    js_args,
+    (vec!["deno".to_string(), "--help".to_string()], vec![])
+  );
+}
+
+#[test]
+fn test_v8_set_flags_preprocess_2() {
+  let js_args =
+    v8_set_flags_preprocess(vec!["deno".to_string(), "--help".to_string()]);
+  assert_eq!(
+    js_args,
+    (vec!["deno".to_string()], vec!["--help".to_string()])
+  );
+}
diff --git a/core/http_bench.js b/core/http_bench.js
index 29a79c4362..aae15a72c6 100644
--- a/core/http_bench.js
+++ b/core/http_bench.js
@@ -1,24 +1,57 @@
 // This is not a real HTTP server. We read blindly one time into 'requestBuf',
 // then write this fixed 'responseBuf'. The point of this benchmark is to
 // exercise the event loop in a simple yet semi-realistic way.
-const shared32 = new Int32Array(libdeno.shared);
-
-const INDEX_NUM_RECORDS = 0;
-const INDEX_RECORDS = 1;
-const RECORD_OFFSET_PROMISE_ID = 0;
-const RECORD_OFFSET_OP = 1;
-const RECORD_OFFSET_ARG = 2;
-const RECORD_OFFSET_RESULT = 3;
-const RECORD_SIZE = 4;
 const OP_LISTEN = 1;
 const OP_ACCEPT = 2;
 const OP_READ = 3;
 const OP_WRITE = 4;
 const OP_CLOSE = 5;
+const INDEX_START = 0;
+const INDEX_END = 1;
+const NUM_RECORDS = 128;
+const RECORD_SIZE = 4;
 
-const NUM_RECORDS = (shared32.length - INDEX_RECORDS) / RECORD_SIZE;
-if (NUM_RECORDS != 100) {
-  throw Error("expected 100 entries");
+const shared32 = new Int32Array(libdeno.shared);
+
+function idx(i, off) {
+  return 2 + i * RECORD_SIZE + off;
+}
+
+function recordsPush(promiseId, opId, arg, result) {
+  let i = shared32[INDEX_END];
+  if (i >= NUM_RECORDS) {
+    return false;
+  }
+  shared32[idx(i, 0)] = promiseId;
+  shared32[idx(i, 1)] = opId;
+  shared32[idx(i, 2)] = arg;
+  shared32[idx(i, 3)] = result;
+  shared32[INDEX_END]++;
+  return true;
+}
+
+function recordsShift() {
+  if (shared32[INDEX_START] == shared32[INDEX_END]) {
+    return null;
+  }
+  const i = shared32[INDEX_START];
+  const record = {
+    promiseId: shared32[idx(i, 0)],
+    opId: shared32[idx(i, 1)],
+    arg: shared32[idx(i, 2)],
+    result: shared32[idx(i, 3)]
+  };
+  shared32[INDEX_START]++;
+  return record;
+}
+
+function recordsReset() {
+  shared32[INDEX_START] = 0;
+  shared32[INDEX_END] = 0;
+}
+
+function recordsSize() {
+  return shared32[INDEX_END] - shared32[INDEX_START];
 }
 
 const requestBuf = new Uint8Array(64 * 1024);
@@ -39,51 +72,35 @@ function createResolvable() {
   return Object.assign(promise, methods);
 }
 
-function setRecord(i, off, value) {
-  if (i >= NUM_RECORDS) {
-    throw Error("out of range");
-  }
-  shared32[INDEX_RECORDS + RECORD_SIZE * i + off] = value;
-}
-
-function getRecord(i, off) {
-  if (i >= NUM_RECORDS) {
-    throw Error("out of range");
-  }
-  return shared32[INDEX_RECORDS + RECORD_SIZE * i + off];
-}
-
 /** Returns Promise<number> */
-function sendAsync(op, arg, zeroCopyData) {
-  const id = nextPromiseId++;
+function sendAsync(opId, arg, zeroCopyData) {
+  const promiseId = nextPromiseId++;
   const p = createResolvable();
-  shared32[INDEX_NUM_RECORDS] = 1;
-  setRecord(0, RECORD_OFFSET_PROMISE_ID, id);
-  setRecord(0, RECORD_OFFSET_OP, op);
-  setRecord(0, RECORD_OFFSET_ARG, arg);
-  setRecord(0, RECORD_OFFSET_RESULT, -1);
-  promiseMap.set(id, p);
+  recordsReset();
+  recordsPush(promiseId, opId, arg, -1);
+  promiseMap.set(promiseId, p);
   libdeno.send(null, zeroCopyData);
   return p;
 }
 
 /** Returns u32 number */
-function sendSync(op, arg) {
-  shared32[INDEX_NUM_RECORDS] = 1;
-  setRecord(0, RECORD_OFFSET_PROMISE_ID, 0);
-  setRecord(0, RECORD_OFFSET_OP, op);
-  setRecord(0, RECORD_OFFSET_ARG, arg);
-  setRecord(0, RECORD_OFFSET_RESULT, -1);
+function sendSync(opId, arg) {
+  recordsReset();
+  recordsPush(0, opId, arg, -1);
   libdeno.send();
-  return getRecord(0, RECORD_OFFSET_RESULT);
+  if (recordsSize() != 1) {
+    throw Error("Expected sharedSimple to have size 1");
+  }
+  let { result } = recordsShift();
+  return result;
 }
 
 function handleAsyncMsgFromRust() {
-  for (let i = 0; i < shared32[INDEX_NUM_RECORDS]; i++) {
-    let id = getRecord(i, RECORD_OFFSET_PROMISE_ID);
-    const p = promiseMap.get(id);
-    promiseMap.delete(id);
-    p.resolve(getRecord(i, RECORD_OFFSET_RESULT));
+  while (recordsSize() > 0) {
+    const { promiseId, result } = recordsShift();
+    const p = promiseMap.get(promiseId);
+    promiseMap.delete(promiseId);
+    p.resolve(result);
   }
 }
 
@@ -132,7 +149,7 @@ async function serve(rid) {
 async function main() {
   libdeno.recv(handleAsyncMsgFromRust);
 
-  libdeno.print("http_bench.js start");
+  libdeno.print("http_bench.js start\n");
 
   const listenerRid = listen();
   libdeno.print(`listening http://127.0.0.1:4544/ rid = ${listenerRid}`);
diff --git a/core/http_bench.rs b/core/http_bench.rs
index 3da30433a0..8e5a0e10cf 100644
--- a/core/http_bench.rs
+++ b/core/http_bench.rs
@@ -12,18 +12,11 @@ extern crate log;
 #[macro_use]
 extern crate lazy_static;
 
-use deno_core::deno_buf;
-use deno_core::AsyncResult;
-use deno_core::Isolate;
-use deno_core::JSError;
-use deno_core::Op;
-use deno_core::RECORD_OFFSET_ARG;
-use deno_core::RECORD_OFFSET_OP;
-use deno_core::RECORD_OFFSET_PROMISE_ID;
-use deno_core::RECORD_OFFSET_RESULT;
+use deno_core::*;
 use futures::future::lazy;
 use std::collections::HashMap;
 use std::env;
+use std::mem;
 use std::net::SocketAddr;
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
@@ -36,11 +29,148 @@ const OP_READ: i32 = 3;
 const OP_WRITE: i32 = 4;
 const OP_CLOSE: i32 = 5;
 
+const INDEX_START: usize = 0;
+const INDEX_END: usize = 1;
+
+const NUM_RECORDS: usize = 128;
+const RECORD_SIZE: usize = 4;
+
+#[derive(Clone, Debug)]
+pub struct Record {
+  pub promise_id: i32,
+  pub op_id: i32,
+  pub arg: i32,
+  pub result: i32,
+}
+
+pub type HttpBenchOp = dyn Future<Item = i32, Error = std::io::Error> + Send;
+
+struct HttpBench {
+  shared32: Vec<i32>,
+}
+
+impl HttpBench {
+  fn new() -> Self {
+    let mut shared32 = Vec::<i32>::new();
+    let n = 2 + 4 * NUM_RECORDS;
+    shared32.resize(n, 0);
+    shared32[INDEX_START] = 0;
+    shared32[INDEX_END] = 0;
+    Self { shared32 }
+  }
+}
+
+fn idx(i: usize, off: usize) -> usize {
+  2 + i * RECORD_SIZE + off
+}
+
+impl Behavior<Record> for HttpBench {
+  fn startup_snapshot(&mut self) -> Option<deno_buf> {
+    None
+  }
+
+  fn startup_shared(&mut self) -> Option<deno_buf> {
+    let ptr = self.shared32.as_ptr() as *const u8;
+    let len = mem::size_of::<i32>() * self.shared32.len();
+    Some(unsafe { deno_buf::from_raw_parts(ptr, len) })
+  }
+
+  fn resolve(&mut self, _specifier: &str, _referrer: deno_mod) -> deno_mod {
+    // HttpBench doesn't do ES modules.
+    unimplemented!()
+  }
+
+  fn recv(
+    &mut self,
+    record: Record,
+    zero_copy_buf: deno_buf,
+  ) -> (bool, Box<Op<Record>>) {
+    let is_sync = record.promise_id == 0;
+    let http_bench_op = match record.op_id {
+      OP_LISTEN => {
+        assert!(is_sync);
+        op_listen()
+      }
+      OP_CLOSE => {
+        assert!(is_sync);
+        let rid = record.arg;
+        op_close(rid)
+      }
+      OP_ACCEPT => {
+        assert!(!is_sync);
+        let listener_rid = record.arg;
+        op_accept(listener_rid)
+      }
+      OP_READ => {
+        assert!(!is_sync);
+        let rid = record.arg;
+        op_read(rid, zero_copy_buf)
+      }
+      OP_WRITE => {
+        assert!(!is_sync);
+        let rid = record.arg;
+        op_write(rid, zero_copy_buf)
+      }
+      _ => panic!("bad op {}", record.op_id),
+    };
+    let mut record_a = record.clone();
+    let mut record_b = record.clone();
+
+    let op = Box::new(
+      http_bench_op
+        .and_then(move |result| {
+          record_a.result = result;
+          Ok(record_a)
+        }).or_else(|err| -> Result<Record, ()> {
+          eprintln!("unexpected err {}", err);
+          record_b.result = -1;
+          Ok(record_b)
+        }),
+    );
+    (is_sync, op)
+  }
+
+  fn records_reset(&mut self) {
+    self.shared32[INDEX_START] = 0;
+    self.shared32[INDEX_END] = 0;
+  }
+
+  fn records_push(&mut self, record: Record) -> bool {
+    debug!("push {:?}", record);
+    let i = self.shared32[INDEX_END] as usize;
+    if i >= NUM_RECORDS {
+      return false;
+    }
+    self.shared32[idx(i, 0)] = record.promise_id;
+    self.shared32[idx(i, 1)] = record.op_id;
+    self.shared32[idx(i, 2)] = record.arg;
+    self.shared32[idx(i, 3)] = record.result;
+    self.shared32[INDEX_END] += 1;
+    true
+  }
+
+  fn records_shift(&mut self) -> Option<Record> {
+    let i = self.shared32[INDEX_START] as usize;
+    if i == self.shared32[INDEX_END] as usize {
+      return None;
+    }
+    let record = Record {
+      promise_id: self.shared32[idx(i, 0)],
+      op_id: self.shared32[idx(i, 1)],
+      arg: self.shared32[idx(i, 2)],
+      result: self.shared32[idx(i, 3)],
+    };
+    self.shared32[INDEX_START] += 1;
+    Some(record)
+  }
+}
+
 fn main() {
   let js_source = include_str!("http_bench.js");
-  let isolate = deno_core::Isolate::new(recv_cb);
 
   let main_future = lazy(move || {
+    let isolate = deno_core::Isolate::new(HttpBench::new());
+
     // TODO currently isolate.execute() must be run inside tokio, hence the
     // lazy(). It would be nice to not have that contraint. Probably requires
     // using v8::MicrotasksPolicy::kExplicit
@@ -77,69 +207,7 @@ fn new_rid() -> i32 {
   rid as i32
 }
 
-fn recv_cb(isolate: &mut Isolate, zero_copy_buf: deno_buf) {
-  isolate.test_send_counter += 1; // TODO ideally store this in isolate.state?
-
-  let promise_id = isolate.shared.get_record(0, RECORD_OFFSET_PROMISE_ID);
-  let op_id = isolate.shared.get_record(0, RECORD_OFFSET_OP);
-  let arg = isolate.shared.get_record(0, RECORD_OFFSET_ARG);
-
-  // dbg!(promise_id);
-  // dbg!(op_id);
-  // dbg!(arg);
-
-  let is_sync = promise_id == 0;
-
-  if is_sync {
-    // sync ops
-    match op_id {
-      OP_CLOSE => {
-        debug!("close");
-        assert!(is_sync);
-        let mut table = RESOURCE_TABLE.lock().unwrap();
-        let r = table.remove(&arg);
-        isolate.shared.set_record(
-          0,
-          RECORD_OFFSET_RESULT,
-          if r.is_some() { 0 } else { -1 },
-        );
-      }
-      OP_LISTEN => {
-        debug!("listen");
-        assert!(is_sync);
-
-        let addr = "127.0.0.1:4544".parse::<SocketAddr>().unwrap();
-        let listener = tokio::net::TcpListener::bind(&addr).unwrap();
-        let rid = new_rid();
-        isolate.shared.set_record(0, RECORD_OFFSET_RESULT, rid);
-        let mut guard = RESOURCE_TABLE.lock().unwrap();
-        guard.insert(rid, Repr::TcpListener(listener));
-      }
-      _ => panic!("bad op"),
-    }
-  } else {
-    // async ops
-    let zero_copy_id = zero_copy_buf.zero_copy_id;
-    let op = match op_id {
-      OP_ACCEPT => {
-        let listener_rid = arg;
-        op_accept(listener_rid)
-      }
-      OP_READ => {
-        let rid = arg;
-        op_read(rid, zero_copy_buf)
-      }
-      OP_WRITE => {
-        let rid = arg;
-        op_write(rid, zero_copy_buf)
-      }
-      _ => panic!("bad op"),
-    };
-    isolate.add_op(promise_id, op, zero_copy_id);
-  }
-}
-
-fn op_accept(listener_rid: i32) -> Box<Op> {
+fn op_accept(listener_rid: i32) -> Box<HttpBenchOp> {
   debug!("accept {}", listener_rid);
   Box::new(
     futures::future::poll_fn(move || {
@@ -147,7 +215,7 @@ fn op_accept(listener_rid: i32) -> Box<Op> {
       let maybe_repr = table.get_mut(&listener_rid);
       match maybe_repr {
         Some(Repr::TcpListener(ref mut listener)) => listener.poll_accept(),
-        _ => panic!("bad rid"),
+        _ => panic!("bad rid {}", listener_rid),
       }
     }).and_then(move |(stream, addr)| {
       debug!("accept success {}", addr);
@@ -156,12 +224,36 @@ fn op_accept(listener_rid: i32) -> Box<Op> {
       let mut guard = RESOURCE_TABLE.lock().unwrap();
       guard.insert(rid, Repr::TcpStream(stream));
 
-      Ok(AsyncResult { result: rid })
+      Ok(rid as i32)
     }),
   )
 }
 
-fn op_read(rid: i32, mut zero_copy_buf: deno_buf) -> Box<Op> {
+fn op_listen() -> Box<HttpBenchOp> {
+  debug!("listen");
+
+  Box::new(lazy(move || {
+    let addr = "127.0.0.1:4544".parse::<SocketAddr>().unwrap();
+    let listener = tokio::net::TcpListener::bind(&addr).unwrap();
+    let rid = new_rid();
+
+    let mut guard = RESOURCE_TABLE.lock().unwrap();
+    guard.insert(rid, Repr::TcpListener(listener));
+    futures::future::ok(rid)
+  }))
+}
+
+fn op_close(rid: i32) -> Box<HttpBenchOp> {
+  debug!("close");
+  Box::new(lazy(move || {
+    let mut table = RESOURCE_TABLE.lock().unwrap();
+    let r = table.remove(&rid);
+    let result = if r.is_some() { 0 } else { -1 };
+    futures::future::ok(result)
+  }))
+}
+
+fn op_read(rid: i32, mut zero_copy_buf: deno_buf) -> Box<HttpBenchOp> {
   debug!("read rid={}", rid);
   Box::new(
     futures::future::poll_fn(move || {
@@ -175,14 +267,12 @@ fn op_read(rid: i32, mut zero_copy_buf: deno_buf) -> Box<Op> {
       }
     }).and_then(move |nread| {
       debug!("read success {}", nread);
-      Ok(AsyncResult {
-        result: nread as i32,
-      })
+      Ok(nread as i32)
     }),
   )
 }
 
-fn op_write(rid: i32, zero_copy_buf: deno_buf) -> Box<Op> {
+fn op_write(rid: i32, zero_copy_buf: deno_buf) -> Box<HttpBenchOp> {
   debug!("write rid={}", rid);
   Box::new(
     futures::future::poll_fn(move || {
@@ -196,9 +286,7 @@ fn op_write(rid: i32, zero_copy_buf: deno_buf) -> Box<Op> {
       }
     }).and_then(move |nwritten| {
       debug!("write success {}", nwritten);
-      Ok(AsyncResult {
-        result: nwritten as i32,
-      })
+      Ok(nwritten as i32)
     }),
   )
 }
diff --git a/core/isolate.rs b/core/isolate.rs
new file mode 100644
index 0000000000..cdda7b8153
--- /dev/null
+++ b/core/isolate.rs
@@ -0,0 +1,548 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+use crate::js_errors::JSError;
+use crate::libdeno;
+use crate::libdeno::deno_buf;
+use crate::libdeno::deno_mod;
+use futures::Async;
+use futures::Future;
+use futures::Poll;
+use libc::c_void;
+use std::ffi::CStr;
+use std::ffi::CString;
+use std::sync::{Once, ONCE_INIT};
+
+pub type Op<R> = dyn Future<Item = R, Error = ()> + Send;
+
+struct PendingOp<R> {
+  op: Box<Op<R>>,
+  polled_recently: bool,
+  zero_copy_id: usize, // non-zero if associated zero-copy buffer.
+}
+
+impl<R> Future for PendingOp<R> {
+  type Item = R;
+  type Error = ();
+
+  fn poll(&mut self) -> Poll<R, ()> {
+    // Do not call poll on ops we've already polled this turn.
+    if self.polled_recently {
+      Ok(Async::NotReady)
+    } else {
+      self.polled_recently = true;
+      let op = &mut self.op;
+      op.poll().map_err(|()| {
+        // Ops should not error. If an op experiences an error it needs to
+        // encode that error into the record R, so it can be returned to JS.
+        panic!("ops should not error")
+      })
+    }
+  }
+}
+
+pub trait Behavior<R> {
+  fn startup_snapshot(&mut self) -> Option<deno_buf>;
+  fn startup_shared(&mut self) -> Option<deno_buf>;
+
+  fn resolve(&mut self, specifier: &str, referrer: deno_mod) -> deno_mod;
+
+  fn recv(&mut self, record: R, zero_copy_buf: deno_buf) -> (bool, Box<Op<R>>);
+
+  /// Clears the shared buffer.
+  fn records_reset(&mut self);
+
+  /// Returns false if not enough room.
+  fn records_push(&mut self, record: R) -> bool;
+
+  /// Returns none if empty.
+  fn records_shift(&mut self) -> Option<R>;
+}
+
+pub struct Isolate<R, B: Behavior<R>> {
+  libdeno_isolate: *const libdeno::isolate,
+  behavior: B,
+  pending_ops: Vec<PendingOp<R>>,
+  polled_recently: bool,
+}
+
+unsafe impl<R, B: Behavior<R>> Send for Isolate<R, B> {}
+
+impl<R, B: Behavior<R>> Drop for Isolate<R, B> {
+  fn drop(&mut self) {
+    unsafe { libdeno::deno_delete(self.libdeno_isolate) }
+  }
+}
+
+static DENO_INIT: Once = ONCE_INIT;
+
+impl<R, B: Behavior<R>> Isolate<R, B> {
+  pub fn new(mut behavior: B) -> Self {
+    DENO_INIT.call_once(|| {
+      unsafe { libdeno::deno_init() };
+    });
+
+    let config = libdeno::deno_config {
+      will_snapshot: 0,
+      load_snapshot: match behavior.startup_snapshot() {
+        Some(s) => s,
+        None => libdeno::deno_buf::empty(),
+      },
+      shared: match behavior.startup_shared() {
+        Some(s) => s,
+        None => libdeno::deno_buf::empty(),
+      },
+      recv_cb: Self::pre_dispatch,
+    };
+    let libdeno_isolate = unsafe { libdeno::deno_new(config) };
+
+    Self {
+      libdeno_isolate,
+      behavior,
+      pending_ops: Vec::new(),
+      polled_recently: false,
+    }
+  }
+
+  extern "C" fn pre_dispatch(
+    user_data: *mut c_void,
+    control_buf: deno_buf,
+    zero_copy_buf: deno_buf,
+  ) {
+    let isolate = unsafe { Isolate::<R, B>::from_raw_ptr(user_data) };
+    assert_eq!(control_buf.len(), 0);
+    let zero_copy_id = zero_copy_buf.zero_copy_id;
+
+    let req_record = isolate.behavior.records_shift().unwrap();
+
+    isolate.behavior.records_reset();
+
+    let (is_sync, op) = isolate.behavior.recv(req_record, zero_copy_buf);
+    if is_sync {
+      let res_record = op.wait().unwrap();
+      let push_success = isolate.behavior.records_push(res_record);
+      assert!(push_success);
+      // TODO check that if JSError thrown during respond(), that it will be
+      // picked up.
+      let _ = isolate.respond();
+    } else {
+      isolate.pending_ops.push(PendingOp {
+        op,
+        polled_recently: false,
+        zero_copy_id,
+      });
+      isolate.polled_recently = false;
+    }
+  }
+
+  pub fn zero_copy_release(&self, zero_copy_id: usize) {
+    unsafe {
+      libdeno::deno_zero_copy_release(self.libdeno_isolate, zero_copy_id)
+    }
+  }
+
+  #[inline]
+  unsafe fn from_raw_ptr<'a>(ptr: *const c_void) -> &'a mut Self {
+    let ptr = ptr as *mut _;
+    &mut *ptr
+  }
+
+  #[inline]
+  fn as_raw_ptr(&self) -> *const c_void {
+    self as *const _ as *const c_void
+  }
+
+  pub fn execute(
+    &self,
+    js_filename: &str,
+    js_source: &str,
+  ) -> Result<(), JSError> {
+    let filename = CString::new(js_filename).unwrap();
+    let source = CString::new(js_source).unwrap();
+    unsafe {
+      libdeno::deno_execute(
+        self.libdeno_isolate,
+        self.as_raw_ptr(),
+        filename.as_ptr(),
+        source.as_ptr(),
+      )
+    };
+    if let Some(err) = self.last_exception() {
+      return Err(err);
+    }
+    Ok(())
+  }
+
+  fn last_exception(&self) -> Option<JSError> {
+    let ptr = unsafe { libdeno::deno_last_exception(self.libdeno_isolate) };
+    if ptr.is_null() {
+      None
+    } else {
+      let cstr = unsafe { CStr::from_ptr(ptr) };
+      let v8_exception = cstr.to_str().unwrap();
+      debug!("v8_exception\n{}\n", v8_exception);
+      let js_error = JSError::from_v8_exception(v8_exception).unwrap();
+      Some(js_error)
+    }
+  }
+
+  pub fn check_promise_errors(&self) {
+    unsafe {
+      libdeno::deno_check_promise_errors(self.libdeno_isolate);
+    }
+  }
+
+  fn respond(&mut self) -> Result<(), JSError> {
+    let buf = deno_buf::empty();
+    unsafe {
+      libdeno::deno_respond(self.libdeno_isolate, self.as_raw_ptr(), buf)
+    }
+    if let Some(err) = self.last_exception() {
+      Err(err)
+    } else {
+      Ok(())
+    }
+  }
+
+  /// Low-level module creation.
+  /// You probably want to use IsolateState::mod_execute instead.
+  pub fn mod_new(
+    &self,
+    main: bool,
+    name: &str,
+    source: &str,
+  ) -> Result<deno_mod, JSError> {
+    let name_ = CString::new(name.to_string()).unwrap();
+    let name_ptr = name_.as_ptr() as *const libc::c_char;
+
+    let source_ = CString::new(source.to_string()).unwrap();
+    let source_ptr = source_.as_ptr() as *const libc::c_char;
+
+    let id = unsafe {
+      libdeno::deno_mod_new(self.libdeno_isolate, main, name_ptr, source_ptr)
+    };
+    if let Some(js_error) = self.last_exception() {
+      assert_eq!(id, 0);
+      return Err(js_error);
+    }
+
+    Ok(id)
+  }
+
+  pub fn mod_get_imports(&self, id: deno_mod) -> Vec<String> {
+    let len =
+      unsafe { libdeno::deno_mod_imports_len(self.libdeno_isolate, id) };
+    let mut out = Vec::new();
+    for i in 0..len {
+      let specifier_ptr =
+        unsafe { libdeno::deno_mod_imports_get(self.libdeno_isolate, id, i) };
+      let specifier_c: &CStr = unsafe { CStr::from_ptr(specifier_ptr) };
+      let specifier: &str = specifier_c.to_str().unwrap();
+
+      out.push(specifier.to_string());
+    }
+    out
+  }
+
+  pub fn mod_instantiate(&self, id: deno_mod) -> Result<(), JSError> {
+    unsafe {
+      libdeno::deno_mod_instantiate(
+        self.libdeno_isolate,
+        self.as_raw_ptr(),
+        id,
+        Self::resolve_cb,
+      )
+    };
+    if let Some(js_error) = self.last_exception() {
+      return Err(js_error);
+    }
+    Ok(())
+  }
+
+  pub fn mod_evaluate(&self, id: deno_mod) -> Result<(), JSError> {
+    unsafe {
+      libdeno::deno_mod_evaluate(self.libdeno_isolate, self.as_raw_ptr(), id)
+    };
+    if let Some(js_error) = self.last_exception() {
+      return Err(js_error);
+    }
+    Ok(())
+  }
+
+  /// Called during mod_instantiate() only.
+  extern "C" fn resolve_cb(
+    user_data: *mut libc::c_void,
+    specifier_ptr: *const libc::c_char,
+    referrer: deno_mod,
+  ) -> deno_mod {
+    let isolate = unsafe { Isolate::<R, B>::from_raw_ptr(user_data) };
+    let specifier_c: &CStr = unsafe { CStr::from_ptr(specifier_ptr) };
+    let specifier: &str = specifier_c.to_str().unwrap();
+    isolate.behavior.resolve(specifier, referrer)
+  }
+}
+
+struct LockerScope {
+  libdeno_isolate: *const libdeno::isolate,
+}
+
+impl LockerScope {
+  fn new(libdeno_isolate: *const libdeno::isolate) -> LockerScope {
+    unsafe { libdeno::deno_lock(libdeno_isolate) }
+    LockerScope { libdeno_isolate }
+  }
+}
+
+impl Drop for LockerScope {
+  fn drop(&mut self) {
+    unsafe { libdeno::deno_unlock(self.libdeno_isolate) }
+  }
+}
+
+impl<R, B: Behavior<R>> Future for Isolate<R, B> {
+  type Item = ();
+  type Error = JSError;
+
+  fn poll(&mut self) -> Poll<(), JSError> {
+    // Lock the current thread for V8.
+    let _locker = LockerScope::new(self.libdeno_isolate);
+
+    // Clear poll_recently state both on the Isolate itself and
+    // on the pending ops.
+    self.polled_recently = false;
+    for pending in self.pending_ops.iter_mut() {
+      pending.polled_recently = false;
+    }
+
+    while !self.polled_recently {
+      let mut completed_count = 0;
+
+      debug!("poll loop");
+
+      self.polled_recently = true;
+
+      self.behavior.records_reset();
+
+      let mut i = 0;
+      while i != self.pending_ops.len() {
+        let pending = &mut self.pending_ops[i];
+        match pending.poll() {
+          Err(()) => panic!("unexpectd error"),
+          Ok(Async::NotReady) => {
+            i += 1;
+          }
+          Ok(Async::Ready(record)) => {
+            let completed = self.pending_ops.remove(i);
+            completed_count += 1;
+
+            if completed.zero_copy_id > 0 {
+              self.zero_copy_release(completed.zero_copy_id);
+            }
+
+            self.behavior.records_push(record);
+          }
+        }
+      }
+
+      if completed_count > 0 {
+        debug!("respond");
+        self.respond()?;
+        debug!("after respond");
+      }
+    }
+
+    self.check_promise_errors();
+    if let Some(err) = self.last_exception() {
+      return Err(err);
+    }
+
+    // We're idle if pending_ops is empty.
+    if self.pending_ops.is_empty() {
+      Ok(futures::Async::Ready(()))
+    } else {
+      Ok(futures::Async::NotReady)
+    }
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+  use std::collections::HashMap;
+
+  fn js_check(r: Result<(), JSError>) {
+    if let Err(e) = r {
+      panic!(e.to_string());
+    }
+  }
+
+  struct TestBehavior {
+    recv_count: usize,
+    resolve_count: usize,
+    push_count: usize,
+    shift_count: usize,
+    reset_count: usize,
+    mod_map: HashMap<String, deno_mod>,
+  }
+
+  impl TestBehavior {
+    fn new() -> Self {
+      Self {
+        recv_count: 0,
+        resolve_count: 0,
+        push_count: 0,
+        shift_count: 0,
+        reset_count: 0,
+        mod_map: HashMap::new(),
+      }
+    }
+
+    fn register(&mut self, name: &str, id: deno_mod) {
+      self.mod_map.insert(name.to_string(), id);
+    }
+  }
+
+  impl Behavior<()> for TestBehavior {
+    fn startup_snapshot(&mut self) -> Option<deno_buf> {
+      None
+    }
+
+    fn startup_shared(&mut self) -> Option<deno_buf> {
+      None
+    }
+
+    fn recv(
+      &mut self,
+      _record: (),
+      _zero_copy_buf: deno_buf,
+    ) -> (bool, Box<Op<()>>) {
+      self.recv_count += 1;
+      (false, Box::new(futures::future::ok(())))
+    }
+
+    fn resolve(&mut self, specifier: &str, _referrer: deno_mod) -> deno_mod {
+      self.resolve_count += 1;
+      match self.mod_map.get(specifier) {
+        Some(id) => *id,
+        None => 0,
+      }
+    }
+
+    fn records_reset(&mut self) {
+      self.reset_count += 1;
+    }
+
+    fn records_push(&mut self, _record: ()) -> bool {
+      self.push_count += 1;
+      true
+    }
+
+    fn records_shift(&mut self) -> Option<()> {
+      self.shift_count += 1;
+      Some(())
+    }
+  }
+
+  #[test]
+  fn test_recv() {
+    let behavior = TestBehavior::new();
+    let isolate = Isolate::new(behavior);
+    js_check(isolate.execute(
+      "filename.js",
+      r#"
+        libdeno.send();
+        async function main() {
+          libdeno.send();
+        }
+        main();
+        "#,
+    ));
+    assert_eq!(isolate.behavior.recv_count, 2);
+  }
+
+  #[test]
+  fn test_mods() {
+    let behavior = TestBehavior::new();
+    let mut isolate = Isolate::new(behavior);
+    let mod_a = isolate
+      .mod_new(
+        true,
+        "a.js",
+        r#"
+        import { b } from 'b.js'
+        if (b() != 'b') throw Error();
+        libdeno.send();
+      "#,
+      ).unwrap();
+    assert_eq!(isolate.behavior.recv_count, 0);
+    assert_eq!(isolate.behavior.resolve_count, 0);
+
+    let imports = isolate.mod_get_imports(mod_a);
+    assert_eq!(imports, vec!["b.js".to_string()]);
+
+    let mod_b = isolate
+      .mod_new(false, "b.js", "export function b() { return 'b' }")
+      .unwrap();
+    let imports = isolate.mod_get_imports(mod_b);
+    assert_eq!(imports.len(), 0);
+
+    js_check(isolate.mod_instantiate(mod_b));
+    assert_eq!(isolate.behavior.recv_count, 0);
+    assert_eq!(isolate.behavior.resolve_count, 0);
+
+    isolate.behavior.register("b.js", mod_b);
+    js_check(isolate.mod_instantiate(mod_a));
+    assert_eq!(isolate.behavior.recv_count, 0);
+    assert_eq!(isolate.behavior.resolve_count, 1);
+
+    js_check(isolate.mod_evaluate(mod_a));
+    assert_eq!(isolate.behavior.recv_count, 1);
+    assert_eq!(isolate.behavior.resolve_count, 1);
+  }
+
+  #[test]
+  fn test_poll_async_immediate_ops() {
+    let behavior = TestBehavior::new();
+    let mut isolate = Isolate::new(behavior);
+
+    js_check(isolate.execute(
+      "setup.js",
+      r#"
+        let nrecv = 0;
+        libdeno.recv(() => {
+          nrecv++;
+        });
+        function assertEq(actual, expected) {
+          if (expected != actual) {
+            throw Error(`actual ${actual} expected ${expected} `);
+          }
+        }
+        "#,
+    ));
+    assert_eq!(isolate.behavior.recv_count, 0);
+    js_check(isolate.execute(
+      "check1.js",
+      r#"
+        assertEq(nrecv, 0);
+        libdeno.send();
+        assertEq(nrecv, 0);
+        "#,
+    ));
+    assert_eq!(isolate.behavior.recv_count, 1);
+    assert_eq!(Ok(Async::Ready(())), isolate.poll());
+    assert_eq!(isolate.behavior.recv_count, 1);
+    js_check(isolate.execute(
+      "check2.js",
+      r#"
+        assertEq(nrecv, 1);
+        libdeno.send();
+        assertEq(nrecv, 1);
+        "#,
+    ));
+    assert_eq!(isolate.behavior.recv_count, 2);
+    assert_eq!(Ok(Async::Ready(())), isolate.poll());
+    js_check(isolate.execute("check3.js", "assertEq(nrecv, 2)"));
+    assert_eq!(isolate.behavior.recv_count, 2);
+    // We are idle, so the next poll should be the last.
+    assert_eq!(Ok(Async::Ready(())), isolate.poll());
+  }
+
+}
diff --git a/core/lib.rs b/core/lib.rs
index 6416704e27..66233ddfcc 100644
--- a/core/lib.rs
+++ b/core/lib.rs
@@ -1,364 +1,28 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
 #[macro_use]
 extern crate log;
 extern crate futures;
 extern crate libc;
 
+mod flags;
+mod isolate;
 mod js_errors;
 mod libdeno;
-mod shared;
 
+pub use crate::flags::v8_set_flags;
+pub use crate::isolate::*;
 pub use crate::js_errors::*;
 pub use crate::libdeno::deno_buf;
-pub use crate::shared::*;
-use futures::Async;
-use futures::Future;
-use futures::Poll;
-use libc::c_void;
-use std::collections::HashMap;
-use std::ffi::CStr;
-use std::ffi::CString;
-use std::sync::{Once, ONCE_INIT};
+pub use crate::libdeno::deno_mod;
 
-pub struct Isolate {
-  libdeno_isolate: *const libdeno::isolate,
-  pending_ops: HashMap<i32, PendingOp>, // promise_id -> op
-  polled_recently: bool,
-  recv_cb: RecvCallback,
-
-  pub shared: Shared,
-  pub test_send_counter: u32, // TODO only used for testing- REMOVE.
+pub fn v8_version() -> &'static str {
+  use std::ffi::CStr;
+  let version = unsafe { libdeno::deno_v8_version() };
+  let c_str = unsafe { CStr::from_ptr(version) };
+  c_str.to_str().unwrap()
 }
 
-pub type RecvCallback = fn(isolate: &mut Isolate, zero_copy_buf: deno_buf);
-
-pub const NUM_RECORDS: usize = 100;
-
-// TODO rename to AsyncResult
-pub struct AsyncResult {
-  pub result: i32,
-}
-
-pub type Op = dyn Future<Item = AsyncResult, Error = std::io::Error> + Send;
-
-struct PendingOp {
-  op: Box<Op>,
-  polled_recently: bool,
-  zero_copy_id: usize, // non-zero if associated zero-copy buffer.
-}
-
-static DENO_INIT: Once = ONCE_INIT;
-
-unsafe impl Send for Isolate {}
-
-impl Isolate {
-  pub fn new(recv_cb: RecvCallback) -> Self {
-    DENO_INIT.call_once(|| {
-      unsafe { libdeno::deno_init() };
-    });
-
-    // Allocate unmanaged memory for the shared buffer by creating a Vec<u8>,
-    // grabbing the raw pointer, and then leaking the Vec so it is never freed.
-    let mut shared = Shared::new();
-    let shared_deno_buf = shared.as_deno_buf();
-
-    let config = libdeno::deno_config {
-      will_snapshot: 0,
-      load_snapshot: deno_buf::empty(), // TODO
-      shared: shared_deno_buf,
-      recv_cb: pre_dispatch,
-    };
-    let libdeno_isolate = unsafe { libdeno::deno_new(config) };
-
-    Self {
-      pending_ops: HashMap::new(),
-      polled_recently: false,
-      libdeno_isolate,
-      test_send_counter: 0,
-      recv_cb,
-      shared,
-    }
-  }
-
-  fn zero_copy_release(&self, zero_copy_id: usize) {
-    unsafe {
-      libdeno::deno_zero_copy_release(self.libdeno_isolate, zero_copy_id)
-    }
-  }
-
-  pub fn add_op(
-    self: &mut Self,
-    promise_id: i32,
-    op: Box<Op>,
-    zero_copy_id: usize,
-  ) {
-    debug!("add_op {}", zero_copy_id);
-    self.pending_ops.insert(
-      promise_id,
-      PendingOp {
-        op,
-        polled_recently: false,
-        zero_copy_id,
-      },
-    );
-    self.polled_recently = false;
-  }
-
-  #[inline]
-  pub unsafe fn from_raw_ptr<'a>(ptr: *const c_void) -> &'a mut Self {
-    let ptr = ptr as *mut _;
-    &mut *ptr
-  }
-
-  #[inline]
-  pub fn as_raw_ptr(&self) -> *const c_void {
-    self as *const _ as *const c_void
-  }
-
-  pub fn execute(
-    &self,
-    js_filename: &str,
-    js_source: &str,
-  ) -> Result<(), JSError> {
-    let filename = CString::new(js_filename).unwrap();
-    let source = CString::new(js_source).unwrap();
-    unsafe {
-      libdeno::deno_execute(
-        self.libdeno_isolate,
-        self.as_raw_ptr(),
-        filename.as_ptr(),
-        source.as_ptr(),
-      )
-    };
-    if let Some(err) = self.last_exception() {
-      return Err(err);
-    }
-    Ok(())
-  }
-
-  pub fn last_exception(&self) -> Option<JSError> {
-    let ptr = unsafe { libdeno::deno_last_exception(self.libdeno_isolate) };
-    if ptr.is_null() {
-      None
-    } else {
-      let cstr = unsafe { CStr::from_ptr(ptr) };
-      let v8_exception = cstr.to_str().unwrap();
-      debug!("v8_exception\n{}\n", v8_exception);
-      let js_error = JSError::from_v8_exception(v8_exception).unwrap();
-      Some(js_error)
-    }
-  }
-
-  fn check_promise_errors(&self) {
-    unsafe {
-      libdeno::deno_check_promise_errors(self.libdeno_isolate);
-    }
-  }
-
-  fn respond(&mut self) -> Result<(), JSError> {
-    let buf = deno_buf::empty();
-    unsafe {
-      libdeno::deno_respond(self.libdeno_isolate, self.as_raw_ptr(), buf)
-    }
-    if let Some(err) = self.last_exception() {
-      Err(err)
-    } else {
-      Ok(())
-    }
-  }
-}
-
-struct LockerScope {
-  libdeno_isolate: *const libdeno::isolate,
-}
-
-impl LockerScope {
-  fn new(isolate: &Isolate) -> LockerScope {
-    let libdeno_isolate = isolate.libdeno_isolate;
-    unsafe { libdeno::deno_lock(libdeno_isolate) }
-    LockerScope { libdeno_isolate }
-  }
-}
-
-impl Drop for LockerScope {
-  fn drop(&mut self) {
-    unsafe { libdeno::deno_unlock(self.libdeno_isolate) }
-  }
-}
-
-impl Future for Isolate {
-  type Item = ();
-  type Error = JSError;
-
-  fn poll(&mut self) -> Poll<(), JSError> {
-    // Lock the current thread for V8.
-    let _locker = LockerScope::new(self);
-
-    // Clear
-    self.polled_recently = false;
-    for (_, pending) in self.pending_ops.iter_mut() {
-      pending.polled_recently = false;
-    }
-
-    while !self.polled_recently {
-      let mut complete = HashMap::<i32, AsyncResult>::new();
-
-      self.polled_recently = true;
-      for (promise_id, pending) in self.pending_ops.iter_mut() {
-        // Do not call poll on futures we've already polled this turn.
-        if pending.polled_recently {
-          continue;
-        }
-        pending.polled_recently = true;
-
-        let promise_id = *promise_id;
-        let op = &mut pending.op;
-        match op.poll() {
-          Err(op_err) => {
-            eprintln!("op err {:?}", op_err);
-            complete.insert(promise_id, AsyncResult { result: -1 });
-            debug!("pending op {} complete err", promise_id);
-          }
-          Ok(Async::Ready(async_result)) => {
-            complete.insert(promise_id, async_result);
-            debug!("pending op {} complete ready", promise_id);
-          }
-          Ok(Async::NotReady) => {
-            debug!("pending op {} not ready", promise_id);
-            continue;
-          }
-        }
-      }
-
-      self.shared.set_num_records(complete.len() as i32);
-      if complete.len() > 0 {
-        // self.zero_copy_release() and self.respond() need Locker.
-        let mut i = 0;
-        for (promise_id, async_result) in complete.iter_mut() {
-          let pending = self.pending_ops.remove(promise_id).unwrap();
-
-          if pending.zero_copy_id > 0 {
-            self.zero_copy_release(pending.zero_copy_id);
-          }
-
-          self
-            .shared
-            .set_record(i, RECORD_OFFSET_PROMISE_ID, *promise_id);
-          self
-            .shared
-            .set_record(i, RECORD_OFFSET_RESULT, async_result.result);
-          i += 1;
-        }
-        self.respond()?;
-      }
-    }
-
-    self.check_promise_errors();
-    if let Some(err) = self.last_exception() {
-      return Err(err);
-    }
-
-    // We're idle if pending_ops is empty.
-    if self.pending_ops.is_empty() {
-      Ok(futures::Async::Ready(()))
-    } else {
-      Ok(futures::Async::NotReady)
-    }
-  }
-}
-
-extern "C" fn pre_dispatch(
-  user_data: *mut c_void,
-  control_buf: deno_buf,
-  zero_copy_buf: deno_buf,
-) {
-  let isolate = unsafe { Isolate::from_raw_ptr(user_data) };
-  assert_eq!(control_buf.len(), 0);
-  (isolate.recv_cb)(isolate, zero_copy_buf);
-}
-
-#[cfg(test)]
-mod tests {
-  use super::*;
-
-  fn inc_counter(isolate: &mut Isolate, zero_copy_buf: deno_buf) {
-    assert_eq!(zero_copy_buf.len(), 0);
-    isolate.test_send_counter += 1; // TODO ideally store this in isolate.state?
-  }
-
-  fn js_check(r: Result<(), JSError>) {
-    if let Err(e) = r {
-      panic!(e.to_string());
-    }
-  }
-
-  #[test]
-  fn test_execute() {
-    let isolate = Isolate::new(inc_counter);
-    js_check(isolate.execute(
-      "filename.js",
-      r#"
-        libdeno.send();
-        async function main() {
-          libdeno.send();
-        }
-        main();
-        "#,
-    ));
-    // We expect that main is executed even tho we didn't poll.
-    assert_eq!(isolate.test_send_counter, 2);
-  }
-
-  fn async_immediate(isolate: &mut Isolate, zero_copy_buf: deno_buf) {
-    assert_eq!(zero_copy_buf.len(), 0);
-    isolate.test_send_counter += 1; // TODO ideally store this in isolate.state?
-
-    let promise_id = 0;
-    let op = Box::new(futures::future::ok(AsyncResult { result: 0 }));
-    isolate.add_op(promise_id, op, zero_copy_buf.zero_copy_id);
-  }
-
-  #[test]
-  fn test_poll_async_immediate_ops() {
-    let mut isolate = Isolate::new(async_immediate);
-    js_check(isolate.execute(
-      "setup.js",
-      r#"
-        let nrecv = 0;
-        libdeno.recv(() => {
-          nrecv++;
-        });
-        function assertEq(actual, expected) {
-          if (expected != actual) {
-            throw Error(`actual ${actual} expected ${expected} `);
-          }
-        }
-        "#,
-    ));
-    assert_eq!(isolate.test_send_counter, 0);
-    js_check(isolate.execute(
-      "check1.js",
-      r#"
-        assertEq(nrecv, 0);
-        libdeno.send();
-        assertEq(nrecv, 0);
-        "#,
-    ));
-    assert_eq!(isolate.test_send_counter, 1);
-    assert_eq!(Ok(Async::Ready(())), isolate.poll());
-    assert_eq!(isolate.test_send_counter, 1);
-    js_check(isolate.execute(
-      "check2.js",
-      r#"
-        assertEq(nrecv, 1);
-        libdeno.send();
-        assertEq(nrecv, 1);
-        "#,
-    ));
-    assert_eq!(isolate.test_send_counter, 2);
-    assert_eq!(Ok(Async::Ready(())), isolate.poll());
-    js_check(isolate.execute("check3.js", "assertEq(nrecv, 2)"));
-    assert_eq!(isolate.test_send_counter, 2);
-    // We are idle, so the next poll should be the last.
-    assert_eq!(Ok(Async::Ready(())), isolate.poll());
-  }
+#[test]
+fn test_v8_version() {
+  assert!(v8_version().len() > 3);
 }
diff --git a/src/flags.rs b/src/flags.rs
index 376e0ab95b..471fc58ede 100644
--- a/src/flags.rs
+++ b/src/flags.rs
@@ -1,14 +1,7 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-use crate::libdeno;
-
+use deno_core::v8_set_flags;
 use getopts;
 use getopts::Options;
-use libc::c_char;
-use libc::c_int;
-use std::ffi::CStr;
-use std::ffi::CString;
-use std::mem;
-use std::vec::Vec;
 
 // Creates vector of strings, Vec<String>
 #[cfg(test)]
@@ -291,80 +284,3 @@ fn test_set_flags_8() {
     }
   )
 }
-
-// Returns args passed to V8, followed by args passed to JS
-fn v8_set_flags_preprocess(args: Vec<String>) -> (Vec<String>, Vec<String>) {
-  let (rest, mut v8_args) =
-    args.into_iter().partition(|ref a| a.as_str() == "--help");
-
-  // Replace args being sent to V8
-  for a in &mut v8_args {
-    if a == "--v8-options" {
-      mem::swap(a, &mut String::from("--help"));
-    }
-  }
-  (v8_args, rest)
-}
-
-#[test]
-fn test_v8_set_flags_preprocess_1() {
-  let js_args = v8_set_flags_preprocess(vec![
-    "deno".to_string(),
-    "--v8-options".to_string(),
-  ]);
-  assert_eq!(
-    js_args,
-    (vec!["deno".to_string(), "--help".to_string()], vec![])
-  );
-}
-
-#[test]
-fn test_v8_set_flags_preprocess_2() {
-  let js_args =
-    v8_set_flags_preprocess(vec!["deno".to_string(), "--help".to_string()]);
-  assert_eq!(
-    js_args,
-    (vec!["deno".to_string()], vec!["--help".to_string()])
-  );
-}
-
-// Pass the command line arguments to v8.
-// Returns a vector of command line arguments that v8 did not understand.
-#[cfg_attr(feature = "cargo-clippy", allow(stutter))]
-pub fn v8_set_flags(args: Vec<String>) -> Vec<String> {
-  // deno_set_v8_flags(int* argc, char** argv) mutates argc and argv to remove
-  // flags that v8 understands.
-  // First parse core args, then convert to a vector of C strings.
-  let (args, rest) = v8_set_flags_preprocess(args);
-
-  // Make a new array, that can be modified by V8::SetFlagsFromCommandLine(),
-  // containing mutable raw pointers to the individual command line args.
-  let mut raw_argv = args
-    .iter()
-    .map(|arg| CString::new(arg.as_str()).unwrap().into_bytes_with_nul())
-    .collect::<Vec<_>>();
-  let mut c_argv = raw_argv
-    .iter_mut()
-    .map(|arg| arg.as_mut_ptr() as *mut c_char)
-    .collect::<Vec<_>>();
-
-  // Store the length of the c_argv array in a local variable. We'll pass
-  // a pointer to this local variable to deno_set_v8_flags(), which then
-  // updates its value.
-  let mut c_argv_len = c_argv.len() as c_int;
-  // Let v8 parse the arguments it recognizes and remove them from c_argv.
-  unsafe {
-    libdeno::deno_set_v8_flags(&mut c_argv_len, c_argv.as_mut_ptr());
-  };
-  // If c_argv_len was updated we have to change the length of c_argv to match.
-  c_argv.truncate(c_argv_len as usize);
-  // Copy the modified arguments list into a proper rust vec and return it.
-  c_argv
-    .iter()
-    .map(|ptr| unsafe {
-      let cstr = CStr::from_ptr(*ptr as *const c_char);
-      let slice = cstr.to_str().unwrap();
-      slice.to_string()
-    }).chain(rest.into_iter())
-    .collect()
-}
diff --git a/src/version.rs b/src/version.rs
index 1cf0822576..e6ec9008b0 100644
--- a/src/version.rs
+++ b/src/version.rs
@@ -1,12 +1,6 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-use crate::libdeno;
-
-use std::ffi::CStr;
-
 pub const DENO: &str = env!("CARGO_PKG_VERSION");
 
 pub fn v8() -> &'static str {
-  let version = unsafe { libdeno::deno_v8_version() };
-  let c_str = unsafe { CStr::from_ptr(version) };
-  c_str.to_str().unwrap()
+  deno_core::v8_version()
 }