Removed event emitter from v8 debug api

Matt Loring · Matt Loring · commit 2ba5bbd48842 · 2016-01-15T09:46:44.000-08:00
We were able to shave off a few ms by storing and invoking callbacks directly as opposed to registering them as named events and going through the event emitter pipeline. Addresses #71
diff --git a/lib/v8debugapi.js b/lib/v8debugapi.js
@@ -20,7 +20,6 @@
 /** @const */ var path = require('path');
 /** @const */ //var util = require('util');
 
-/** @const */ var events = require('events');
 /** @const */ var state = require('./state.js');
 /** @const */ var logModule = require('@google/cloud-diagnostics-common').logger;
 /** @const */ var apiclasses = require('./apiclasses.js');
@@ -58,7 +57,6 @@ module.exports.create = function(logger_, config_, fileStats_) {
   var v8 = null;
   var logger = null;
   var config = null;
-  var emitter = null;
   var fileStats = null;
   var breakpoints = {};
   var listeners = {};
@@ -90,8 +88,6 @@ module.exports.create = function(logger_, config_, fileStats_) {
   logger = logger_;
   config = config_;
   fileStats = fileStats_;
-  emitter = new events.EventEmitter();
-  emitter.setMaxListeners(0);
 
   if (usePermanentListener) {
     logger.info('activating v8 breakpoint listener (permanent)');
@@ -181,7 +177,7 @@ module.exports.create = function(logger_, config_, fileStats_) {
 
       v8.clearBreakPoint(v8bp.number());
       delete breakpoints[breakpoint.id];
-      delete listeners[breakpoint.id];
+      delete listeners[v8bp.number()];
       numBreakpoints--;
       if (numBreakpoints === 0 && !usePermanentListener) {
         // removed last breakpoint
@@ -196,17 +192,14 @@ module.exports.create = function(logger_, config_, fileStats_) {
      * @param {Function} callback
      */
     wait: function(breakpoint, callback) {
-      var eventName = 'v8breakpoint-' + breakpoints[breakpoint.id].v8Breakpoint
-                                                                  .number();
+      var num = breakpoints[breakpoint.id].v8Breakpoint.number();
       var listener = onBreakpointHit.bind(
           null, breakpoint, function(err) {
-            emitter.removeListener(eventName, listener);
-            delete listeners[breakpoint.id];
+            delete listeners[num];
             callback(err);
           });
 
-      listeners[breakpoint.id] = listener;
-      emitter.on(eventName, listener);
+      listeners[num] = listener;
     },
 
     // The following are for testing:
@@ -462,8 +455,7 @@ module.exports.create = function(logger_, config_, fileStats_) {
         eventData.breakPointsHit().forEach(function(hit) {
           var num = hit.script_break_point().number();
           logger.info('>>>V8 breakpoint hit<<< number: ' + num);
-          var eventName = 'v8breakpoint-' + num;
-          emitter.emit(eventName, execState, eventData);
+          listeners[num](execState, eventData);
         });
         break;
     }
