src: introduce internal C++ SetImmediate() mechanism

PR-URL: https://github.com/nodejs/node/pull/17117
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/src/env.cc b/src/env.cc
index 425333ed7a..df9f872705 100644
--- a/src/env.cc
+++ b/src/env.cc
@@ -277,6 +277,59 @@ void Environment::EnvPromiseHook(v8::PromiseHookType type,
   }
 }
 
+void Environment::RunAndClearNativeImmediates() {
+  size_t count = native_immediate_callbacks_.size();
+  if (count > 0) {
+    std::vector<NativeImmediateCallback> list;
+    native_immediate_callbacks_.swap(list);
+    for (const auto& cb : list) {
+      cb.cb_(this, cb.data_);
+    }
+
+#ifdef DEBUG
+    CHECK_GE(scheduled_immediate_count_[0], count);
+#endif
+    scheduled_immediate_count_[0] = scheduled_immediate_count_[0] - count;
+  }
+}
+
+static bool MaybeStopImmediate(Environment* env) {
+  if (env->scheduled_immediate_count()[0] == 0) {
+    uv_check_stop(env->immediate_check_handle());
+    uv_idle_stop(env->immediate_idle_handle());
+    return true;
+  }
+  return false;
+}
+
+
+void Environment::CheckImmediate(uv_check_t* handle) {
+  Environment* env = Environment::from_immediate_check_handle(handle);
+  HandleScope scope(env->isolate());
+  Context::Scope context_scope(env->context());
+
+  if (MaybeStopImmediate(env))
+    return;
+
+  env->RunAndClearNativeImmediates();
+
+  MakeCallback(env->isolate(),
+               env->process_object(),
+               env->immediate_callback_string(),
+               0,
+               nullptr,
+               {0, 0}).ToLocalChecked();
+
+  MaybeStopImmediate(env);
+}
+
+void Environment::ActivateImmediateCheck() {
+  uv_check_start(&immediate_check_handle_, CheckImmediate);
+  // Idle handle is needed only to stop the event loop from blocking in poll.
+  uv_idle_start(&immediate_idle_handle_, [](uv_idle_t*){ });
+}
+
+
 void CollectExceptionInfo(Environment* env,
                           v8::Local<v8::Object> obj,
                           int errorno,