From bbe2004f5d2b434fe5942fc3c8954a297b317fd0 Mon Sep 17 00:00:00 2001
From: Bert Belder <bertbelder@gmail.com>
Date: Fri, 8 Feb 2019 20:32:17 -0800
Subject: [PATCH] Shared buffer fixes (#1644)

* makes `libdeno.shared` a `SharedArrayBuffer` instead of a regular `ArrayBuffer`.
* fixes `libdeno.shared` becoming undefined after accessing it once.
---
 libdeno/binding.cc      |  9 +++++----
 libdeno/internal.h      |  3 ++-
 libdeno/libdeno_test.cc | 13 +++++++++++++
 libdeno/libdeno_test.js |  3 ++-
 4 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/libdeno/binding.cc b/libdeno/binding.cc
index 961fd17978..78e4cad296 100644
--- a/libdeno/binding.cc
+++ b/libdeno/binding.cc
@@ -316,14 +316,15 @@ void Shared(v8::Local<v8::Name> property,
   if (d->shared_.data_ptr == nullptr) {
     return;
   }
-  v8::Local<v8::ArrayBuffer> ab;
+  v8::Local<v8::SharedArrayBuffer> ab;
   if (d->shared_ab_.IsEmpty()) {
     // Lazily initialize the persistent external ArrayBuffer.
-    ab = v8::ArrayBuffer::New(isolate, d->shared_.data_ptr, d->shared_.data_len,
-                              v8::ArrayBufferCreationMode::kExternalized);
+    ab = v8::SharedArrayBuffer::New(isolate, d->shared_.data_ptr,
+                                    d->shared_.data_len,
+                                    v8::ArrayBufferCreationMode::kExternalized);
     d->shared_ab_.Reset(isolate, ab);
   }
-  info.GetReturnValue().Set(ab);
+  info.GetReturnValue().Set(d->shared_ab_);
 }
 
 void DenoIsolate::ClearModules() {
diff --git a/libdeno/internal.h b/libdeno/internal.h
index 14a9cd43f5..0cd50162c3 100644
--- a/libdeno/internal.h
+++ b/libdeno/internal.h
@@ -46,6 +46,7 @@ class DenoIsolate {
   }
 
   ~DenoIsolate() {
+    shared_ab_.Reset();
     if (snapshot_creator_) {
       delete snapshot_creator_;
     } else {
@@ -98,7 +99,7 @@ class DenoIsolate {
   v8::Persistent<v8::Function> recv_;
   v8::StartupData snapshot_;
   v8::Persistent<v8::ArrayBuffer> global_import_buf_;
-  v8::Persistent<v8::ArrayBuffer> shared_ab_;
+  v8::Persistent<v8::SharedArrayBuffer> shared_ab_;
 };
 
 class UserDataScope {
diff --git a/libdeno/libdeno_test.cc b/libdeno/libdeno_test.cc
index b14b4758bf..0936c53b42 100644
--- a/libdeno/libdeno_test.cc
+++ b/libdeno/libdeno_test.cc
@@ -289,3 +289,16 @@ TEST(LibDenoTest, Utf8Bug) {
   EXPECT_EQ(nullptr, deno_last_exception(d));
   deno_delete(d);
 }
+
+TEST(LibDenoTest, SharedAtomics) {
+  int32_t s[] = {0, 1, 2};
+  deno_buf shared = {nullptr, 0, reinterpret_cast<uint8_t*>(s), sizeof s};
+  Deno* d = deno_new(deno_config{0, empty, shared, nullptr});
+  deno_execute(d, nullptr, "a.js",
+               "Atomics.add(new Int32Array(libdeno.shared), 0, 1)");
+  EXPECT_EQ(nullptr, deno_last_exception(d));
+  EXPECT_EQ(s[0], 1);
+  EXPECT_EQ(s[1], 1);
+  EXPECT_EQ(s[2], 2);
+  deno_delete(d);
+}
diff --git a/libdeno/libdeno_test.js b/libdeno/libdeno_test.js
index 5e1430d9e2..50f5c03d4c 100644
--- a/libdeno/libdeno_test.js
+++ b/libdeno/libdeno_test.js
@@ -136,7 +136,8 @@ global.CheckPromiseErrors = () => {
 
 global.Shared = () => {
   const ab = libdeno.shared;
-  assert(ab instanceof ArrayBuffer);
+  assert(ab instanceof SharedArrayBuffer);
+  assert(libdeno.shared != undefined);
   assert(ab.byteLength === 3);
   const ui8 = new Uint8Array(ab);
   assert(ui8[0] === 0);