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Industrial Strength Hash Table

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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;

    };

};

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

Want to talk about exception safety?

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Does that code even compile? In what compiler?

 

In every compiler.

 

 

 

 

As long as you don't use that template.

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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.

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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.

Edited by ByteTroll

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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
Edited by TheComet

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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.

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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!

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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<T>.

 

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.

Edited by samoth

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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.

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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]

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