Function Returning Array Of Pointers Concept

[Baker]

I have a rough concept of being able to return a variable length array of pointers (allocated by calloc) with the data (also allocated by calloc) where the pointer list ends with NULL.

So a <do .. while> could traverse the data and stop when it hits null, just like a string.

But I'm not 100% on how to dealloc the array of data (yet), dealloc on the array of pointers (+1 with last member) = NULL seems easy enough.

I guess maybe I could calloc each member of the array of data and use the pointer array to pass the right memory address to free. Then write a function to possible conveniently wrap this using type (void *) and passing size_t. Then possibly wrapping the entire calloc bit into a similar type void function to easy the actual return of data.

This seems obvious enough that I feel it has been done before. This is just a morph of the concept of returning a malloc allocated null-terminated string.

The reason I want to do this is to be able to possibly return a set of matching points for geometry functions, where the number of points (vertices) maybe be anything from 0 matches to N matches.

(Will have to write and test this, but I'm rather sure I can make this work. I do not like the idea I cannot return an array of unknown size in C.)

/End rant ...

[DolphinsOfCydonia]

Why not a linked list? Traversal time is going to be the same O(n), unless you already know the size of the array at access time.

[Baker]

That would require a struct. And you'd still have to make the final match unlinked. Still you could dynamically allocate each return result on the fly. I don't know. I would prefer a pure data type, but maybe that isn't the best way.

[mh]

[DolphinsOfCydonia]

[Baker]

It makes the implementation really ugly looking. Yet apparently, this is what I am going to do as I worked through the planning.

I wasn't really looking to make a custom return type just for this. But it solves some other issues.

[Baker]

[Baker]

[Baker]

[Baker]

[Baker]

[Jay Dolan]

I started using glib for collections management in Quake2World. It provides single and double linked lists, hash tables, and pointer arrays, all with a very complete API for allocating, extending, removing and freeing elements. Glib's memory allocator also uses slice management by default, which can rival the performance of Quake's "gimme a big heap and I'll take it from here" approach. Basically, my code is a lot smaller and tighter now, and I don't waste any time implementing or debugging ad-hoc collections (unless it's truly warranted for performance, like particles lists).

There are a dozen or so other great uses for glib in a Quake engine, too. Look at all the stuff you get for free:
https://developer.gnome.org/glib/2.37/