Thread: best container to hold a text buffer?

Hello all,

I've recently been writing a text input field with SDL, It is nearly complete now, but I was hoping I could have your opinion on this one particular aspect.

I am currently using a std::vector<string> to hold input data from the keyboard (text). Basically the way it works is that every index of the vector represents a singular line.

However the requirements for this container make it difficult to choose if another container for the strings would be more efficient. The function that is called when a lines wrap is needed, and also when the user presses enter/return, must use a vector::emplace() (which I understand is inefficient when you have many elements that come after).

Under these conditions, is a vector the best choice? I know a list would be more efficient for inserting elements into the middle of, but also most of the string elements added will probably be added to the end.

I know the general usages for the container types in the STL, but the requirements for this are such that it seems like I'm giving up something whichever way I go.

What do you think? Thanks ☺

Originally Posted by Salem

I suggest you start with

Code:

class paragraph {
  private:
    std::vector<string>  mLines;
  public:
    // methods
};

Where you add methods to add, insert, delete, split lines as necessary.

This separates the program logic from your internal data structure choices. If you later decide to change std::vector<string> to something else, the impact on the rest of the system will be minimal.

Thanks Salem. I was mostly curious to know if using a vector was ok for this task, so it's a relief seeing you recommend it. I've gotten the class written out and it has been a lot of fun figuring it all out (especially all the highlighting stuff!). I'm going to keep working on it but I've definitely got many things I can use.

@ Ocifer - Thanks for the advice, and especially the article. One of the favorite things about the book where I learned C++ was that the author took you through building a few custom containers (Thinking in C++), and I can tell it will be interesting to see how it's done using C++11.

I think a vector should suffice for what I'm currently using the text editor for, which is really just to display/edit XML elements where the size is fairly small. I'll take a look at it if I go to re-use it with something else though.

Thanks again, Alpo.

+1 for profiling first.

Just design your code in a way that makes swapping containers easy (like what Salem suggested), then pick a container and stick with it.

Then, if you run into performance problems, profile the code to see if it's in container operations. If so, now you can actually see what operations are most common, and pick a more appropriate container for it.

A lot of times programmers spend way too much time optimizing things that don't matter at all anyways, because it will only end up taking something like 0.1% of the total run time (I am guilty of this myself, all the time).

Always keep your code flexible so that future optimizations are possible, but don't actually spend effort optimizing until there is a performance problem and profiling showed that this is the bottleneck.

Originally Posted by iMalc

The ideal for a text editor is the rope data structure.

That does look really clever. It might take a little while to get the hang of it, but I'll definitely give it a shot. Thanks!