Olive.Random/README.md

# Free Pascal Random Bytes

This file is a part of Olive BBS.

This will only work with [Free Pascal](http://freepascal.org "Free Pascal") version 3+.

### Usage
Make sure to include ```{$mode objfpc}{$H+}``` in your header or compile with ```-S2 -Sh``` switches.

```pascal
Program RandomTest;
{$mode objfpc}{$H+}

uses
  Olive.Random,
  Classes;

var
  R : TRandom;
  S : AnsiString;
  T : TBytes;
begin
  R := TRandom.Init;
  S := R.GetString(22);
  T := R.GetBytes(22);
  R.Free;
```

You can also use a custom random generator.  It needs to implement Olive.Random.RandomInterface;
```pascal
Program RandomTest;
{$mode objfpc}{$H+}

uses
  Olive.Random,
  MyCustomGenerator,
  Classes;

var
  R : TRandom;
  S : AnsiString;
  T : TBytes;
begin
  R := TRandom.Init;
  R.RandomGenerator := MyCustomGenerator.Create;
  S := R.GetString(22);
  T := R.GetBytes(22);
  R.SetDefaultGenerator; // To get back to the default Generator.
  S := R.GetString(22);
  T := R.GetBytes(22);
  R.Free;
```


  * On Linux systems TRandom uses SYS_getrandom.
  * On Windows systems TRandom uses Windows built in [CryptGenRandom](https://msdn.microsoft.com/en-us/library/windows/desktop/aa379942(v=vs.85).aspx "CryptGenRandom") function.
  * On BSD systems TRandom uses [arc4random_buf](https://www.freebsd.org/cgi/man.cgi?query=arc4random_buf&sektion=3 "arc4random_buf") this is the same on Mac systems, because Mac = FreeBSD).

TRandom will fall back on reading from /dev/urandom, then /dev/random, and finally Free Pascal's [Random](http://www.freepascal.org/docs-html/rtl/system/random.html "Random") function which uses the [Mersenne Twister](https://en.wikipedia.org/wiki/Mersenne_Twister "Mersenne Twister") algorithm to get random bytes.