How to place char* of stringZ to ubyte[]?

[denizzzka]

On Monday, 29 October 2012 at 18:50:58 UTC, bearophile wrote:
> denizzzka:
>
>> I am trying to send to remote host utf8 text with zero byte at 
>> end (required by protocol)
>
> What if your UTF8 string coming from D already contains several 
> zeros?

Incredible situation because it is text-based protocol

>
> toStringz(s) returns a pointer, so you can't cast a pointer 
> (that doesn't know the length the buffer it points to) to an 
> array. You have to tell it the length in some way. One way is 
> to slice the pointer, another solution is to append a '\0' and 
> then cast it to an immutable array. Two solutions:
>
>
> import std.stdio, std.string;
> void main() {
>    string s = "hello";
>    auto valueBin1 = cast(immutable ubyte[])(s ~ '\0');
>    writeln(valueBin1);
>    auto valueBin2 = cast(immutable ubyte[])(s.toStringz()[0 .. 
> s.length + 1]);
>    writeln(valueBin2);
> }
>

I am concerned about the extra allocations of temp arrays. here 
is it, or not? compiler optimizes it?

In my case it does not matter but for the future I would like to 
know how it can be implemented without overhead.

> If you have to do this more than two or three times it's better 
> to write a little function to do it, to avoid bugs.
>
> Even better is to define with strong typing the type of such 
> nil-terminated array of bytes, to avoid other mistakes. This 
> used to be possible in D with typedef. Now one a little clumsy 
> way to do it is to use a struct with "alias this". This is just 
> a sketch:
>

Yes, already implemented similar.

>
> struct BytesBuf {
>     this(string s) {
>         this.data = cast(typeof(data))(s ~ '\0');
>     }
>     byte[] data = [0];

Why not "byte[] data;" ?

>     alias this = data; // new syntax

What difference between this syntax and "alias Something this"?

> }
> void main() {
>    import std.stdio;
>    string s = "hello";
>    auto valueBin3 = BytesBuf(s);
>    writeln(valueBin3);
> }