Generating Strings with Random Contents

["Nordlöw" via Digitalmars-d-learn]

On Monday, 14 July 2014 at 22:21:36 UTC, bearophile wrote:
> Nordlöw:
>
>> Is there a natural way of generating/filling a 
>> string/wstring/dstring of a specific length with random 
>> contents?
>
> Do you mean something like this?
>
>
> import std.stdio, std.random, std.ascii, std.range, std.conv;
>
> string genRandomString(in size_t len) {
>     return len
>            .iota
>            .map!(_ => lowercase[uniform(0, $)])
>            .text;
> }
>
> void main() {
>     import std.stdio;
>
>     10.genRandomString.writeln;
> }
>
>
> Bye,
> bearophile

I was specifically interested in something that exercises (random 
samples) potentially _all_ code points for string, wstring and 
dstring (all code units that is).