move _callbacks to an object to avoid empty slots

[humaidk2]

I noticed by logging sessions that _callbacks kept growing to [null,null,null,null...] for every smpp request
After investigation, I found the issue to be that the use of an array for _callbacks.
This pr changes it to an object to solve the issue.

Fixes #170

[coveralls]

Coverage remained the same at 75.62% when pulling 8253d77 on humaidk2:fix-callbacks-issue into fe53dcc on farhadi:master.

[coveralls]

Coverage remained the same at 75.62% when pulling 8253d77 on humaidk2:fix-callbacks-issue into fe53dcc on farhadi:master.

[juliangut]

@humaidk2 I'm ready to prepare next release ASAP and I'd like to add this if needed

I've tested your PR branch and the project keeps working all right

But I haven't been able to reproduce the problem you mention, I've tried this simple test directly in node 6, 8, 10, 12, and 14 and those nulls you mention

var _callbacks = [];
_callbacks['one'] = function(){};
_callbacks['two'] = function(){};
_callbacks['three'] = function(){};
_callbacks['four'] = function(){};
console.log(_callbacks);
delete _callbacks['two'];
console.log(_callbacks);

var _callbacks = {};
_callbacks['one'] = function(){};
_callbacks['two'] = function(){};
_callbacks['three'] = function(){};
_callbacks['four'] = function(){};
console.log(_callbacks);
delete _callbacks['two'];
console.log(_callbacks);
delete _callbacks.three;
console.log(_callbacks);

Can you tell me which node version are you using?

[humaidk2]

Hay Julian,

your example works fine, but try this out

var _callbacks = [];
_callbacks[1] = function(){};
_callbacks[2] = function(){};
_callbacks[3] = function(){};
_callbacks[4] = function(){};
console.log(_callbacks);
delete _callbacks[2];
console.log(_callbacks);

var _callbacks = {};
_callbacks[1] = function(){};
_callbacks[2] = function(){};
_callbacks[3] = function(){};
_callbacks[4] = function(){};
console.log(_callbacks);
delete _callbacks[2];
console.log(_callbacks);

Based on the code, it's definitely using numbers as the sequence number, not strings

[juliangut]

Great catch indeed

It's even worse if sequence_number does not start at 0 but at a higher number the array will have plenty of null values right from the start

Thanks for noticing and creating this PR, will merge