Dealing with dynamic integer types in C?

Question

I'm developing a Python module in C that parses a very efficient protocol which uses dynamic integer sizes. Integers sent using this protocol can range in size from the equivalent of C's 'short' to a 'long long.'

The protocol has a byte that specifies the type of variable being sent (from short to long long), but I'm not sure how to deal with this in code. Right now, I'm setting up a void pointer and allocating memory in the size of the value being sent -- then using atoi, atol, and atoll to set that pointer. The problem is, I need to be able to access that value, and am unable to do so without it being cast later.

What are some good ways to handle this issue?

Ignacio Vazquez-Abrams · Accepted Answer · 2010-02-22 03:46:13Z

4

Either always store it in a long long locally, or put it in a struct composed of a flag for the size and a union of all the possible types.

answered Feb 22, 2010 at 3:46

Ignacio Vazquez-Abrams

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6 Comments

foxtrot Over a year ago

I'm a little confused about how to use a struct/union for that.. Have a quick example?

foxtrot Over a year ago

Then you'd just always cast the union as a long long when you're accessing it in code? Or do you have to switch off of that flag and cast accordingly?

Ignacio Vazquez-Abrams Over a year ago

You switch off .flag and read the appropriate member (.ubyte, .ulong, etc.).

foxtrot Over a year ago

Thanks a lot! Gonna stick with using long longs locally.

Roger Pate Over a year ago

The first part of this answer, always using a long long, is going to be easier for you without any loss, compared to the second part of using a union.

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