added ping command sidorares#38

lib/commands/index.js

@@ -1,4 +1,4 @@
-"client_handshake server_handshake query execute".split(' ').forEach(function(name) {
+"client_handshake server_handshake query execute ping".split(' ').forEach(function(name) {
   var ctor = require('./' + name);
   module.exports[ctor.name] = ctor;
 });

lib/commands/ping.js

@@ -0,0 +1,30 @@
+var Command  = require('./command');
+var util    = require('util');
+var CommandCode = require('../constants/commands');
+var Packet = require('../packets/packet');
+
+// TODO: time statistics?
+// usefull for queue size and network latency monitoring
+// store created,sent,reply timestamps
+
+function Ping(callback)
+{
+  Command.call(this);
+  this.onResult = callback;
+}
+util.inherits(Ping, Command);
+
+Ping.prototype.start = function(packet, connection) {
+  var ping = new Packet(0, new Buffer([0, 0, 0, 0, CommandCode.PING]));
+  connection.writePacket(ping);
+  return Ping.prototype.pingResponse;
+};
+
+Ping.prototype.pingResponse = function(packet) {
+  // TODO: check it's OK packet. error check already done in caller
+  if (this.onResult)
+    this.onResult();
+  return null;
+};
+
+module.exports = Ping;

lib/connection.js

@@ -303,6 +303,10 @@ Connection.prototype.execute = function(sql, values, cb) {
   return this.addCommand(new Commands.Execute(options.sql, options.values, cb));
 };
 
+Connection.prototype.ping = function(cb) {
+  return this.addCommand(new Commands.Ping(cb));
+};
+
 Connection.prototype.connect = function(cb) {
   // TODO: call cb only after succesfull handshake response
   // on('connect') handler?