string[] to char**

[simendsjo]

On Fri, 23 Mar 2012 17:09:18 +0100, bearophile <bearophileHUGS at lycos.com>  
wrote:

> On Friday, 23 March 2012 at 15:48:12 UTC, simendsjo wrote:
>> What's the best way to convert char** from string[]?
>
> This is one way to do it:
>
>
> import std.algorithm, std.array, std.string, core.stdc.stdio;
> void main() {
>      auto data = ["red", "yellow", "green"];
>      immutable(char)** p = array(map!toStringz(data)).ptr;
>      printf("%s %s %s\n", p[0], p[1], p[2]);
> }
>
>
> Note: the pointer array is managed by the D GC.
>
> With DMD 2.059:
>
> immutable(char)** p = data.map!toStringz().array().ptr;
>
> Bye,
> bearophile

Thanks. A lot shorter and safer than my current approach. I also expect  
toStringz doesn't make a copy if \0 is at the end.

For reference, my current approach was:

auto strings = ["a", "b"];
auto c_strings = cast(char**)malloc((char*).sizeof * strings.length);
for(int i; i < strings.length; i++)
   c_strings[i] = strings[i].ptr;