Skip to main content
GameDev.net gamedev.net
🔒 Locked

Industrial Strength Hash Table

Started by Phil123 Mar 12, 2014 at 6:26 PM 15 replies 5.1k views
Original Post
Phil123
Phil123

I've been enjoying the coding horrors forum for a while, so I decided to post a snippet of code that I found in a large c++ project that I'm (unfortunately) a part of. Normally I wouldn't poke fun at code like this, but I couldn't resist this one.

Enjoy.


#pragma once

#include "Includes.h"



template<class T>

class Dictionary

{

private:

    std::vector<std::string> keys;

    std::vector<T> values;

public:

    Dictionary()

    {

        keys = new std::vector<std::string>{};

        values = new std::vector<T>{};

    }



    ~Dictionary()

    {

        delete[] keys;

        delete[] values;

    };



    std::vector* Values() { return &values };

    std::vector* Keys() { return &keys };



    size_t size() { return keys.size(); }



    void Add(std::string _key, T value)

    {

        keys.push_back(_key);

        values.push_back(value);

    };

    void Remove(std::string _key)

    {

        for (size_t i = 0; i < keys.size(); i++)

        {

            if (keys.at(i) == _key)

            {

                keys.erase(keys.begin() + i);

                values.erase(values.begin() + i);

                break;

            }

        }

    };

    T Get(std::string _key)

    {

        for (size_t i = 0; i < keys.size(); i++)

        {

            if (keys.at(i) == _key)

            {

                return values.at(i);

            }

        }

        return nullptr;

    };

};

TheComet
TheComet

So let's see what the WTFs basically are...

  • Assigning a pointer generated from new to a type that is not a pointer
  • Using delete[] on objects created with new and not new[]
  • Using braces instead of brackets for trying to call the constructor of an object
  • Returning a pointer pointing to what is supposed to be an array of pointers pointing to pointers (given the new[] and delete[]), even though the value being returned isn't of type pointer (which is a double-WTF because if it were to compile, that would still be retarded)
  • using a lookup method of complexity O(n)
  • Attempting to declare a return type without template arguments.
  • Returning a nullptr in the case of not finding an entry, implying that the templated type is always a pointer.
  • Method names begin with a capital letter
  • not using std::map
  • code doesn't even compile

Evaluation:

tumblr_mc2w7cEoiz1qmiwbe.png

"I would try to find halo source code by bungie best fps engine ever created, u see why call of duty loses speed due to its detail." -- GettingNifty
Rattrap
Rattrap

#include "Includes.h"

Got to love the all encompassing include.



Method names begin with a capital letter

This one is excusable, since that is just personal preference. I personally don't like camelCase.

"I can't believe I'm defending logic to a turing machine." - Kent Woolworth [Other Space]
ferrous
ferrous

Yeah, my favorite is that the person is using std::Vector, but didn't bother to look for existing hash table functionality. Or maybe they did but their google fu sucks.

And I agree with Rattrap, the capital letter on method names is actually the coding guideline here at my work.

Krohm
Krohm

One also wonders why they didn't made a pair to use a single vector.

Want to talk about exception safety?

Previously "Krohm"
Hodgman
Hodgman

Does that code even compile? In what compiler?

Mona2000
Mona2000

Does that code even compile? In what compiler?

In every compiler.

As long as you don't use that template.

Juliean
Juliean




So let's see what the WTFs basically are...

I would add:

- Creating the std::vectors with new, where they would better be created on the stack. Its not like one of the vectors benefits is that it takes away the memory management for dynamic arrays.

- Returning both vectors as non-const pointer, basically breaking every concept of encapsulation of that class. Especially hard since both vectors are meant to store dependant values for one entry, imagine someone deleting values out of only the Value-vector.

- Also, returning the vectors by pointer instead of reference when they can never be nullptr.

Datamancer
Datamancer

Method names begin with a capital letter

Hey! What's wrong with this? rolleyes.gif

I would like to add one. How about every line being spaced with the beginning of each function being double spaced. That might be "personal" preference, but it is a hell of an annoying one.

Does that code even compile? In what compiler?

In every compiler.

As long as you don't use that template.

Hehehehe.

EDIT: Or the fact that every function is terminated with a semicolon. Again, personal preference; hell of an annoying one.

"The code you write when you learn a new language is shit.
You either already know that and you are wise, or you don’t realize it for many years and you are an idiot. Either way, your learning code is ob
TheComet
TheComet

Does that code even compile? In what compiler?

In every compiler.

As long as you don't use that template.

Not instantiating a template doesn't prevent the first compilation pass, which will catch syntactical errors such as:


std::vector* Values() { return &values }; // invalid use of template-name "std::vector" without an argument list
"I would try to find halo source code by bungie best fps engine ever created, u see why call of duty loses speed due to its detail." -- GettingNifty
l0calh05t
l0calh05t




Using braces instead of brackets for trying to call the constructor of an object

That's actually valid in C++11 and called uniform initialization syntax.

TheComet
TheComet

Using braces instead of brackets for trying to call the constructor of an object

That's actually valid in C++11 and called uniform initialization syntax.

Thanks for the clarification. I learned something new today!

"I would try to find halo source code by bungie best fps engine ever created, u see why call of duty loses speed due to its detail." -- GettingNifty
HyperV
HyperV

i'm starting to have a trauma

TheComet
TheComet




EDIT: Or the fact that every function is terminated with a semicolon. Again, personal preference; hell of an annoying one.

WTF I didn't notice that at first.

"I would try to find halo source code by bungie best fps engine ever created, u see why call of duty loses speed due to its detail." -- GettingNifty
samoth
samoth
Using delete[] on objects created with new and not new[]

Relax, it is much worse than you think.laugh.png

delete[] is being called on objects which are not explicitly allocated via new at all. The vectors that are allocated on the heap are copied (if the compiler accepts this code at all!) and then leaked. I wonder how you can assign a pointer-to-vector to a vector though, since to my knowledge it only accepts const T& and T&& and std::initializer_list.

Both keys and values are objects, not pointers, and part of the Dictionary object. Which means that you call delete (with or without brackets, who cares) on an object that is either allocated on the stack or inside a larger heap-allocated object. In either case, this is very bad mojo.

The Dictionary class has no virtual functions and keys is the first member, so likely (void*) keys == (void*) dictionary_object

Which means if you somehow get the compiler to accept this code (I would be surprised, though), it would double-delete the Dictionary object, once explicitly and once from its own destructor via a type-punned std::vector pointer.

Phil123
Phil123




EDIT: Or the fact that every function is terminated with a semicolon. Again, personal preference; hell of an annoying one.

Haha, but get this, only some functions are terminated with a semicolon. Others aren't.

Oberon_Command
Oberon_Command

This looks like Java code that someone tried to port without an actual understanding of C++.

swiftcoder
swiftcoder

This looks like Java code that someone tried to port without an actual understanding of C++.

That reminds me of a joke which has become decidedly unfunny on my current project:

What's worse than C++ written by a Java developer?

[spoiler]Java written by a C++ developer.[/spoiler]

Tristam MacDonald. Ex-BigTech Software Engineer. Future farmer. [https://trist.am]

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.

Sign in to reply to this topic.