import std.stdio;

import core.stdc.stdio  : puts;

import core.stdc.string : strlen;

​

void main()

{

    string s;

    s = "D string";

​

    auto c_string = toStringz( s );

​

    //

    writeln( "D string: ", s );

    write  ( "C string: " ); puts( c_string );writeln();

​

    //

    writeln( "D string length: ", s.length );

    writeln( "C string length: ", strlen( c_string ) );

}

​

​

immutable(char)* toStringz( ref string s )

{

    if ( s.capacity <= s.length )

        s.reserve( s.length + 1 );

​

    char* cptr = cast( char* ) s.ptr; // C ptr

    char* zptr = cptr + s.length;     // zero ptr

    *zptr = '\0';

​

    return cast( immutable(char)* ) cptr;

}

​