Interesting!

First, Jeff is right - trying to get a 4 byte value out of 1 byte of randomness is... flawed.

Second, I'd expand that - I would really suggest adding an argument and/or logic and/or building a set of modules for each different output type. Perhaps a tinyint is required - that takes only 1 byte of random numbers.

Third, the entire technique you're using has bias built in. If we had a range of 1..4 in our 4 byte randomness, and we want an output range of 1..3, then you'll see the following:

Random Range limited

1 1

2 2

3 3

4 1

You get a bias towards numbers at the low end because of the mod function. Now, going from a 4 byte random to a range of 1..10, you'll be hard pressed to notice the issue (though dieharder might very well find it). Ideally, you'll discard numbers that are in the end range that only partially fills the area of the desired range (in the above example, if you get a 4, just try again).

I'd also recommend generating a lot of values, and then testing them with a suite like dieharder (http://www.phy.duke.edu/~rgb/General/dieharder/dieharder.html), or a government test suite if you need to go to that level. Random data is _hard_.