Re: Need a way to convert a constant to a variable

[Victor Porton <porton@narod.ru>]

Jeffrey R. Carter wrote:

> On 08/05/2017 03:41 PM, Victor Porton wrote:
>> 
>> Write a function with an "in" indefinite holder with a string, return
>> chars_ptr corresponding to the string.
> 
> Your requirements are for an indefinite holder with a string, but your
> attempted solution is for an indefinite holder with a char_array. I will
> assume you meant an indefinite holder with a char_array.

Yes, my typo. I am about an indefinite holder with a char_array.

>> It looks like there is no solution of this in Ada 2012 :-(
> 
> with Ada.Containers.Indefinite_Holders;
> with Interfaces.C.Strings;
> 
> package Conv is
>     package C_Str_Holders is new Ada.Containers.Indefinite_Holders
>        (Element_Type => Interfaces.C.Char_Array, "=" => Interfaces.C."=");
> 
>     function To_Chars_Ptr (Item : C_Str_Holders.Holder)
>                         return Interfaces.C.Strings.Chars_Ptr is
>        (Interfaces.C.Strings.New_Char_Array (Item.Element) );
> end Conv;
> 
> This compiles fine, so clearly there is a way to do this without a
> language change.

Your code allocates a new string which requires to be freed later.

I want a function, which would return a pointer to the (not necessarily nul-
terminated) string hold in the indefinite holder, so that deallocation would 
be not required and code would be more efficient (not requiring to copy the 
char_array).

-- 
Victor Porton - http://portonvictor.org