Re: converting pointer to value

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2021-03-04 20:38, Shark8 wrote:
> On Thursday, March 4, 2021 at 10:35:01 AM UTC-7, Dmitry A. Kazakov wrote:
>> On 2021-03-04 17:55, Shark8 wrote:
>>
>>>> type SQLPOINTER is private;
>>> ....
>>>> private
>>>> type SQLPOINTER is new System.Storage_Elements.Integer_Address;
>>>
>>> And here we have SQLPOINTER, which is private, but which is something of the same representation that Integer_Address has; let's assume that the ADDRESS type is implementation-defined, and a private type.
>> SQLPOINTER is System.Address.
> 
> Which is implementation-defined.

No, it defined this way

    typedef void * SQLPOINTER;

so for all purposes it is System.Address.

> None of that addresses the issue that he asked: "how to get the Pvalue as an SQLRETURN?"

OK, then the answer is you don't.

As the rule QDBC does not overlay different types. There are special 
pointer values though, like 1 etc. Integer_Address can be used to encode 
them. They are constants.

P.S. I think the OP refers to SQLParamData/SQLPutData mechanism. There 
is no overloading either. It works this way:

    prepare
    bind to special "address" value, 1, I believe

    execute
    if SQLParamData = need_data then
       loop
          SQLPutData (next chunk)
       end loop;
    end if;

I do not think it is worth using, unless the data are so big that they 
are not in the memory, or read from a stream chunk by chunk etc. Clearly 
it is a very expensive method. A normal bind would be a better choice 
for most applications.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de