Storing multiple types in same object

Question

First I will give a little background info so this question isn't completely without context:

I am writing a program which needs to read in binary files of which I know the format/layout. The bulk of these files contain "structs", with the layout of each stored in the header of the file. Each struct contains fields which could be either structs or "base" types (which are not structs, and can be either value or reference types like float or String or Vector3 ).

I do not need to access most of the data in these files, so I would not have to define all possible structs for my current project, but there are enough that I would have to define that doing it manually would be tedious and time consuming.

My problem is that there are an extremely large number of these structs (2500+ different ones, though only the ones appearing in a file are defined in that file's header). I would like to be able to read them in, without having to manually define each one, in a way that makes all the data available in the same way. My current thinking is that I should create a class like this:

class Struct{
  StructDefinition _def;
  List < Field > _fields;
  ...
}

In the field class I would need to be able to store both structs AND base types (or more importantly reference and value types). Is there a way to do this without turning everything into an object then casting it to the correct type when I need it? Also, is this the best way to go about reading in these files, or is there a better method?

Answer 1

If you define an interface that contains all of the methods that you need to manipulate the fields, then you can create a small set of objects - one for reference and one for value types.
As long as each of these objects implement the same interface, you will be able to work with them generically.

Answer 2

dynamic (.NET 4.0) can do this at runtime, but you lose compile-time type safety and IntelliSense.

For your particular situation, I would recommend the new file mapping classes in .NET 4.0.

If you need a pre-.NET 4.0 solution, consider looking at the file as a series of offsets instead of structures, and use a FileStream , seeking to and reading in only the information you need. This is kind of like a poor-man's file mapping. Note that in this situation, it's more performant if you only move forward through the file.

Using either of these last two solutions, you don't have to waste time and memory reading in data you won't need anyway.