node_events.cc

// Copyright 2009 Ryan Dahl <ry@tinyclouds.org>
#include <node_events.h>
#include <node.h>

namespace node {

using namespace v8;


// EventSource

EventSource* EventSource::current_source;


template <class T>
Local<FunctionTemplate> EventSource::BuildTemplate(Handle<Object> target,
                                                   const char *name) {
  HandleScope scope;

  Local<FunctionTemplate> t = FunctionTemplate::New(EventSource::JSNew<T>);
  t->InstanceTemplate()->SetInternalFieldCount(1);
  t->SetClassName(String::NewSymbol(name));

  NODE_SET_PROTOTYPE_METHOD(t, "start", EventSource::JSStart);
  NODE_SET_PROTOTYPE_METHOD(t, "stop", EventSource::JSStop);

  target->Set(String::NewSymbol(name), t->GetFunction());

  return scope.Close(t);
}


Local<Value> EventSource::MakeCallback(int argc, Handle<Value> argv[]) {
  HandleScope scope;

  Local<Value> callback_v = handle_->Get(String::NewSymbol("callback"));
  if (!callback_v->IsFunction()) return Local<Value>();
  Local<Function> callback = Local<Function>::Cast(callback_v);

  // TODO DTrace probe here.

  TryCatch try_catch;

  assert(current_source == NULL);
  current_source = this;

  Local<Value> ret = callback->Call(handle_, argc, argv);

  current_source = NULL;

  if (try_catch.HasCaught()) {
    // Here we print the stack trace from try_catch
    ReportException(try_catch, true);
    // Then we print the stored stacktrace plus our ancestors stacks.
    PrintStack();
    // Stop whatever activity might have been going on.
    Stop();
  }

  return scope.Close(ret);
}


void EventSource::PrintStack(int count) {
  Local<Value> trace_v = handle_->GetHiddenValue(String::NewSymbol("stacktrace"));
  assert(trace_v->IsArray());
  Local<Array> trace = Local<Array>::Cast(trace_v);

  // Print from for this EventSource
  for (int i = 0; i < trace->Length(); i++) {
    Local<Value> frame = trace->Get(i);
    // how do you cast Value to StackFrame ?
    // print frame somehow...
    String::Utf8Value sv(frame->ToString());
    fprintf(stderr, "%s\n", *sv);
  }

  fprintf(stderr, "\n");

  // Recursively print up to kAncestorStackLimit ancestor traces...
  if (parent_source_.IsEmpty() == false && count < kAncestorStackLimit) {
    EventSource *parent = ObjectWrap::Unwrap<EventSource>(parent_source_);
    parent->PrintStack(count + 1);
  }
}


template <class T>
Handle<Value> EventSource::JSNew(const Arguments& args) {
  HandleScope scope;
  T *t = new T();
  t->Wrap(args.This());
  return args.This();
}


Handle<Value> EventSource::JSStart(const Arguments& args) {
  HandleScope scope;
  EventSource *s = ObjectWrap::Unwrap<EventSource>(args.Holder());
  if (!s->IsActive()) {
    s->Start();
    s->Ref();
    s->RecordStack();
    // TODO DTrace probe here.
  }
  return Undefined();
}


Handle<Value> EventSource::JSStop(const Arguments& args) {
  HandleScope scope;
  EventSource *s = ObjectWrap::Unwrap<EventSource>(args.Holder());
  if (s->IsActive()) {
    s->DeleteParent();
    s->Stop();
    s->Unref();
  }
  return Undefined();
}


void EventSource::RecordStack() {
  // Assume inside HandleScope
  Local<StackTrace> trace =
      StackTrace::CurrentStackTrace(kFrameLimit, StackTrace::kOverview);
  // Cast to Array for storage as hidden value.
  handle_->SetHiddenValue(String::NewSymbol("stacktrace"), trace->AsArray());
  // Set parent.
  parent_source_ = Persistent<Object>::New(current_source->handle_);
  parent_source_.MakeWeak(this, WeakParent);
}


void EventSource::WeakParent(Persistent<Value> object, void* data) {
  EventSource *s = static_cast<EventSource*>(data);
  assert(s->parent_source_->StrictEquals(object));
  s->DeleteParent();
}


void EventSource::DeleteParent() {
  parent_source_.ClearWeak();
  parent_source_.Dispose();
  parent_source_.Clear();
}


}  // namespace node

node_events.h

// Copyright 2009 Ryan Dahl <ry@tinyclouds.org>
#ifndef SRC_EVENTS_H_
#define SRC_EVENTS_H_

#include <node_object_wrap.h>
#include <v8.h>

namespace node {

// "hard emitter" base class
class EventSource : public ObjectWrap {
 public:
  // All subclasses must call this function to initialize their JavaScript
  // counterparts. Subclasses are free to decorate the template with additional
  // and such.
  template <class T>
  static v8::Local<v8::FunctionTemplate> BuildTemplate(v8::Handle<v8::Object> target,
                                                       const char *name);

  virtual void Start() = 0; // ev_io_start()

  virtual void Stop() = 0; // ev_io_stop()

  virtual bool IsActive() = 0; // ev_is_active()

  EventSource() : ObjectWrap() {
    //assert(!IsActive());
  }

  virtual ~EventSource() {
    //Stop();
    //assert(!IsActive());
  }

  // Subclasses call this when they get a event.
  v8::Local<v8::Value> MakeCallback(int argc, v8::Handle<v8::Value> argv[]);

 private:
  template <class T>
  static v8::Handle<v8::Value> JSNew(const v8::Arguments& args);

  static v8::Handle<v8::Value> JSStart(const v8::Arguments& args);

  static v8::Handle<v8::Value> JSStop(const v8::Arguments& args);

  static void WeakParent(v8::Persistent<v8::Value> object, void* data);

  void RecordStack();

  void DeleteParent();

  void PrintStack(int count = 0);

  v8::Persistent<v8::Object> parent_source_;

  static const int kFrameLimit = 10;
  static const int kAncestorStackLimit = 10;
  static EventSource* current_source;
};


}  // namespace node
#endif  // SRC_EVENTS_H_