node-v0.x-archive/src/timer_wrap.cc

#include <v8.h>
#include <uv.h>
#include <node.h>

// Rules:
//
// - Do not throw from handle methods. Set errno.
//
// - MakeCallback may only be made directly off the event loop.
//   That is there can be no JavaScript stack frames underneith it.
//   (Is there anyway to assert that?)
//
// - No use of v8::WeakReferenceCallback. The close callback signifies that
//   we're done with a handle - external resources can be freed.
//
// - Reusable?
//
// - The uv_close_cb is used to free the c++ object. The close callback
//   is not made into javascript land.
//
// - uv_ref, uv_unref counts are managed at this layer to avoid needless
//   js/c++ boundary crossing. At the javascript layer that should all be
//   taken care of.


#define UNWRAP \
  assert(!args.Holder().IsEmpty()); \
  assert(args.Holder()->InternalFieldCount() > 0); \
  TimerWrap* wrap =  \
      static_cast<TimerWrap*>(args.Holder()->GetPointerFromInternalField(0)); \
  if (!wrap) { \
    SetErrno(UV_EBADF); \
    return scope.Close(Integer::New(-1)); \
  }

namespace node {

using v8::Object;
using v8::Handle;
using v8::Local;
using v8::Persistent;
using v8::Value;
using v8::HandleScope;
using v8::FunctionTemplate;
using v8::String;
using v8::Function;
using v8::TryCatch;
using v8::Context;
using v8::Arguments;
using v8::Integer;


class TimerWrap {
 public:
  static void Initialize(Handle<Object> target) {
    HandleScope scope;

    Local<FunctionTemplate> constructor = FunctionTemplate::New(New);
    constructor->InstanceTemplate()->SetInternalFieldCount(1);
    constructor->SetClassName(String::NewSymbol("Timer"));

    NODE_SET_PROTOTYPE_METHOD(constructor, "start", Start);
    NODE_SET_PROTOTYPE_METHOD(constructor, "stop", Stop);
    NODE_SET_PROTOTYPE_METHOD(constructor, "setRepeat", SetRepeat);
    NODE_SET_PROTOTYPE_METHOD(constructor, "getRepeat", GetRepeat);
    NODE_SET_PROTOTYPE_METHOD(constructor, "again", Again);
    NODE_SET_PROTOTYPE_METHOD(constructor, "close", Close);

    target->Set(String::NewSymbol("Timer"), constructor->GetFunction());
  }

 private:
  static Handle<Value> New(const Arguments& args) {
    // This constructor should not be exposed to public javascript.
    // Therefore we assert that we are not trying to call this as a
    // normal function.
    assert(args.IsConstructCall());

    HandleScope scope;
    TimerWrap *wrap = new TimerWrap(args.This());
    assert(wrap);

    return scope.Close(args.This());
  }

  TimerWrap(Handle<Object> object) {
    active_ = false;
    int r = uv_timer_init(&handle_);
    handle_.data = this;
    assert(r == 0); // How do we proxy this error up to javascript?
                    // Suggestion: uv_timer_init() returns void.
    assert(object_.IsEmpty());
    assert(object->InternalFieldCount() > 0);
    object_ = v8::Persistent<v8::Object>::New(object);
    object_->SetPointerInInternalField(0, this);

    // uv_timer_init adds a loop reference. (That is, it calls uv_ref.) This
    // is not the behavior we want in Node. Timers should not increase the
    // ref count of the loop except when active.
    uv_unref();
  }

  ~TimerWrap() {
    if (!active_) uv_ref();
    assert(!object_.IsEmpty());
    object_->SetPointerInInternalField(0, NULL);
    object_.Dispose();
  }

  void StateChange() {
    bool was_active = active_;
    active_ = uv_is_active((uv_handle_t*) &handle_);

    if (!was_active && active_) {
      // If our state is changing from inactive to active, we
      // increase the loop's reference count.
      uv_ref();
    } else if (was_active && !active_) {
      // If our state is changing from active to inactive, we
      // decrease the loop's reference count.
      uv_unref();
    }
  }

  // Free the C++ object on the close callback.
  static void OnClose(uv_handle_t* handle) {
    TimerWrap* wrap = static_cast<TimerWrap*>(handle->data);
    delete wrap;
  }

  static Handle<Value> Start(const Arguments& args) {
    HandleScope scope;

    UNWRAP

    int64_t timeout = args[0]->IntegerValue();
    int64_t repeat = args[1]->IntegerValue();

    int r = uv_timer_start(&wrap->handle_, OnTimeout, timeout, repeat);

    // Error starting the timer.
    if (r) SetErrno(uv_last_error().code);

    wrap->StateChange();

    return scope.Close(Integer::New(r));
  }

  static Handle<Value> Stop(const Arguments& args) {
    HandleScope scope;

    UNWRAP

    int r = uv_timer_stop(&wrap->handle_);

    if (r) SetErrno(uv_last_error().code);

    wrap->StateChange();

    return scope.Close(Integer::New(r));
  }

  static Handle<Value> Again(const Arguments& args) {
    HandleScope scope;

    UNWRAP

    int r = uv_timer_again(&wrap->handle_);

    if (r) SetErrno(uv_last_error().code);

    wrap->StateChange();

    return scope.Close(Integer::New(r));
  }

  static Handle<Value> SetRepeat(const Arguments& args) {
    HandleScope scope;

    UNWRAP

    int64_t repeat = args[0]->IntegerValue();

    uv_timer_set_repeat(&wrap->handle_, repeat);

    return scope.Close(Integer::New(0));
  }

  static Handle<Value> GetRepeat(const Arguments& args) {
    HandleScope scope;

    UNWRAP

    int64_t repeat = uv_timer_get_repeat(&wrap->handle_);

    if (repeat < 0) SetErrno(uv_last_error().code);

    return scope.Close(Integer::New(repeat));
  }

  // TODO: share me?
  static Handle<Value> Close(const Arguments& args) {
    HandleScope scope;

    UNWRAP

    int r = uv_close((uv_handle_t*) &wrap->handle_, OnClose);

    if (r) SetErrno(uv_last_error().code);

    wrap->StateChange();

    return scope.Close(Integer::New(r));
  }

  static void OnTimeout(uv_handle_t* handle, int status) {
    HandleScope scope;

    TimerWrap* wrap = static_cast<TimerWrap*>(handle->data);
    assert(wrap);

    wrap->StateChange();

    Local<Value> argv[1] = { Integer::New(status) };
    MakeCallback(wrap->object_, "ontimeout", 1, argv);
  }

  uv_timer_t handle_;
  Persistent<Object> object_;
  // This member is set false initially. When the timer is turned
  // on uv_ref is called. When the timer is turned off uv_unref is
  // called. Used to mirror libev semantics.
  bool active_;
};


}  // namespace node

NODE_MODULE(node_timer_wrap, node::TimerWrap::Initialize);