more OO way to do hex string to bytes conversion

[Ralph Doncaster]

On Tuesday, 6 February 2018 at 18:33:02 UTC, Ralph Doncaster 
wrote:
> I've been reading std.conv and std.range, trying to figure out 
> a high-level way of converting a hex string to bytes.  The only 
> way I've been able to do it is through pointer access:
>
> import std.stdio;
> import std.string;
> import std.conv;
>
> void main()
> {
>     immutable char* hex = "deadbeef".toStringz;
>     for (auto i=0; hex[i]; i += 2)
>         writeln(to!byte(hex[i]));
> }
>
>
> While it works, I'm wondering if there is a more 
> object-oriented way of doing it in D.

After a bunch of searching, I came across hex string literals.  
They are mentioned but not documented as a literal.
https://dlang.org/spec/lex.html#string_literals

Combined with the toHexString function in std.digest, it is easy 
to convert between hex strings and byte arrays.

import std.stdio;
import std.digest;

void main() {
     auto data = cast(ubyte[]) x"deadbeef";
     writeln("data: 0x", toHexString(data));
}

p.s. the cast should probably be to immutable ubyte[].  I'm 
guessing without it, there is an automatic copy of the data being 
made.