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Date: Wed, 12 May 2021 19:34:55 +0300
Message-ID: <CAAwdEzBVuZLWDoPK18m4ThkTct7wZTJVXdLEpw5_mMC+TTb=XQ@mail.gmail.com>
To: Christian Schneider <cschneid@cschneid.com>
Cc: php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Discussion: Object-scoped RNG
From: drealecs@gmail.com (=?UTF-8?Q?Alexandru_P=C4=83tr=C4=83nescu?=)

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On Wed, May 12, 2021 at 6:43 PM Christian Schneider <cschneid@cschneid.com>
wrote:

> Am 11.05.2021 um 23:20 schrieb Larry Garfield <larry@garfieldtech.com>:
> > 3) Perhaps it should be named RandomSequence or similar?  It's not truly
> generating random numbers.  It's generating a repeatable but difficult to
> produce sequence off of a seed value.  That's not the same thing as
> random_int() et al.
> >
> > So, at first pass, an API could be as simple as (pseudocode):
> >
> > class RandomSequence {
> >  public function __construct(int $seed = time(), $algorithm =
> 'some_default') { ... }
> >
> >  public function next(): int { ... }
> > }
> >
> > And that's it.  That's nice and simple and predictable to use.
>
>
> Would the generated values fill the whole int range, i.e. 64 bit on modern
> systems?
>
> And would it make sense to add max and min for the generated values like
> we have with random_int()?
> Because mapping arbitrary int values to a specific range is error-prone:
> Just using modulo leads to bias in the resulting values.
>
>
What I initially proposed is an interface something like:

interface RandomSource {
    public function next($length): string;
}

where the string returned would be of the specified length and made up of
random bytes.
I understood that internally, an 32/64 bit int is equivalent to 4 or 8
bytes and that various internal implementations already use ints and not
bytes to provide other constructs like shuffle() and array_rand() with
random behavior.
So I can understand if the function would return an int or an array of
ints. Maybe you can contradict me if I understood this wrong.

But to fulfill all the need for random, one can further use a wrapper class
that can be called RandomGenerator that takes a RandomSource as parameter
and have all types of handy methods:

generateInt($min = 0, $max = PHP_INT_MAX)
generateBoolean()
generateNumber() // float between 0 and 1
generateString($length, $characters = '')


RandomGenerator would take care of the uniform distribution of  values
generated based on uniform distribution of source bytes/ints generated.
I think that keeping a simple way to generate random information is
important so that it can easily be reimplemented in various ways when
needed.
I like the byte approach more because generateString(4, 'abcd') could
consume only 1 byte from the random source.
Of course, in this picture, RandomSource implementations can be
serializable, if it makes sense.

BTW, this name proposal is inspired from this library:
https://github.com/paragonie/RandomLib as I'm not good with namings either.

Alex

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