I wrote a simple class to get repeatable random numbers out of an input seed. I’ll post it here in case someone else would find such a thing useful. It is based on SHA1 rounds. After a number of any kind is fetched, another round of SHA1 is applied.
Download it here: RepeatablePseudoRNG
The class has 3 different methods for retrieving random numbers.
Methods:
Constructor(seed [null])
Provide your initial seed when you instantiate a new object.
fetch_int(min, max)
Fetch an integer between min and max. This is inclusive and the max range is limited to 31 bits on most systems.
fetch_float(min,max)
Fetch a floating point number between min and max. Like, fetch_int, this is inclusive.
rand()
Fetch a floating point number between o and 1. Also inclusive, though getting exactly 0 or 1 should be rare.
perform_rounds(roundcount)
Update the seed a specific number of times, without actually generating any numbers.
Usage example:
require 'rprng.php';
$rng = new RepeatablePseudoRNG('Totori');
//Generate some random numbers.
for($i = 0; $i < 10; $i++)
{
echo $rng->fetch_int(1,10),"\n";
}
The above would output a list similar to the following each time it is run:
2 8 3 5 2 6 9 2 5 1
