src: use AliasedBuffer for TickInfo

Backport-PR-URL: #19006
PR-URL: #17881
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

lib/internal/process/next_tick.js

@@ -29,7 +29,7 @@ function setupNextTick() {
   ] = process._setupNextTick(_tickCallback);
 
   // *Must* match Environment::TickInfo::Fields in src/env.h.
-  const kScheduled = 0;
+  const kHasScheduled = 0;
 
   const nextTickQueue = {
     head: null,
@@ -40,7 +40,7 @@ function setupNextTick() {
         this.tail.next = entry;
       } else {
         this.head = entry;
-        tickInfo[kScheduled] = 1;
+        tickInfo[kHasScheduled] = 1;
       }
       this.tail = entry;
     },
@@ -50,7 +50,7 @@ function setupNextTick() {
       const ret = this.head.data;
       if (this.head === this.tail) {
         this.head = this.tail = null;
-        tickInfo[kScheduled] = 0;
+        tickInfo[kHasScheduled] = 0;
       } else {
         this.head = this.head.next;
       }

src/env-inl.h

@@ -217,21 +217,15 @@ inline bool Environment::AsyncCallbackScope::in_makecallback() const {
   return env_->makecallback_cntr_ > 1;
 }
 
-inline Environment::TickInfo::TickInfo() {
-  for (int i = 0; i < kFieldsCount; ++i)
-    fields_[i] = 0;
-}
+inline Environment::TickInfo::TickInfo(v8::Isolate* isolate)
+    : fields_(isolate, kFieldsCount) {}
 
-inline uint8_t* Environment::TickInfo::fields() {
+inline AliasedBuffer<uint8_t, v8::Uint8Array>& Environment::TickInfo::fields() {
   return fields_;
 }
 
-inline int Environment::TickInfo::fields_count() const {
-  return kFieldsCount;
-}
-
-inline uint8_t Environment::TickInfo::scheduled() const {
-  return fields_[kScheduled];
+inline bool Environment::TickInfo::has_scheduled() const {
+  return fields_[kHasScheduled] == 1;
 }
 
 inline void Environment::AssignToContext(v8::Local<v8::Context> context,
@@ -269,6 +263,7 @@ inline Environment::Environment(IsolateData* isolate_data,
                                 v8::Local<v8::Context> context)
     : isolate_(context->GetIsolate()),
       isolate_data_(isolate_data),
+      tick_info_(context->GetIsolate()),
       timer_base_(uv_now(isolate_data->event_loop())),
       printed_error_(false),
       trace_sync_io_(false),

src/env.h

@@ -453,20 +453,19 @@ class Environment {
 
   class TickInfo {
    public:
-    inline uint8_t* fields();
-    inline int fields_count() const;
-    inline uint8_t scheduled() const;
+    inline AliasedBuffer<uint8_t, v8::Uint8Array>& fields();
+    inline bool has_scheduled() const;
 
    private:
     friend class Environment;  // So we can call the constructor.
-    inline TickInfo();
+    inline explicit TickInfo(v8::Isolate* isolate);
 
     enum Fields {
-      kScheduled,
+      kHasScheduled,
       kFieldsCount
     };
 
-    uint8_t fields_[kFieldsCount];
+    AliasedBuffer<uint8_t, v8::Uint8Array> fields_;
 
     DISALLOW_COPY_AND_ASSIGN(TickInfo);
   };

src/node.cc

@@ -169,7 +169,6 @@ using v8::SealHandleScope;
 using v8::String;
 using v8::TryCatch;
 using v8::Uint32Array;
-using v8::Uint8Array;
 using v8::Undefined;
 using v8::V8;
 using v8::Value;
@@ -1152,13 +1151,6 @@ void SetupNextTick(const FunctionCallbackInfo<Value>& args) {
       env->context(),
       FIXED_ONE_BYTE_STRING(env->isolate(), "_setupNextTick")).FromJust();
 
-  // Values use to cross communicate with processNextTick.
-  uint8_t* const fields = env->tick_info()->fields();
-  uint8_t const fields_count = env->tick_info()->fields_count();
-
-  Local<ArrayBuffer> array_buffer =
-      ArrayBuffer::New(env->isolate(), fields, sizeof(*fields) * fields_count);
-
   v8::Local<v8::Function> run_microtasks_fn =
       env->NewFunctionTemplate(RunMicrotasks)->GetFunction(env->context())
           .ToLocalChecked();
@@ -1167,7 +1159,7 @@ void SetupNextTick(const FunctionCallbackInfo<Value>& args) {
 
   Local<Array> ret = Array::New(env->isolate(), 2);
   ret->Set(env->context(), 0,
-           Uint8Array::New(array_buffer, 0, fields_count)).FromJust();
+           env->tick_info()->fields().GetJSArray()).FromJust();
   ret->Set(env->context(), 1, run_microtasks_fn).FromJust();
 
   args.GetReturnValue().Set(ret);
@@ -1286,7 +1278,7 @@ void InternalCallbackScope::Close() {
 
   Environment::TickInfo* tick_info = env_->tick_info();
 
-  if (tick_info->scheduled() == 0) {
+  if (!tick_info->has_scheduled()) {
     env_->isolate()->RunMicrotasks();
   }
 
@@ -1297,7 +1289,7 @@ void InternalCallbackScope::Close() {
     CHECK_EQ(env_->trigger_async_id(), 0);
   }
 
-  if (tick_info->scheduled() == 0) {
+  if (!tick_info->has_scheduled()) {
     return;
   }