problem with const objects in lazy parser

[joegen@pldtweroam.com]

Hi,

I am working on an o project that involves Lazy Parsing. To be more
specific, Its a SIP Message class that implements zero copy and lazy
parsing. Below is a sample function that is causing me problems.
Since my object is a lazy parser, it needs to evaluate the object to be
parsed during the time an accessor is called.

BOOL SIPMessage::Get Authorization(
Authorization & h
)
{
if( !ParseAuthoriza tion() )
return FALSE;

if( !HasAuthorizati on() )
return FALSE;

h = *m_Authorizatio n;

return TRUE;
}

Since this function is performing a none const action
"ParseAuthoriza tion()", I cannot declare this function as constant
which will eventually lead to making my object a perpetually none
constant object. Is there anyway to break this curse? I know I
could "mutate" my member objects ( probably a hundred of them ) but it
gives the shudder. Is there another technique to implement this
cleanly?

Joegen

[Karl Heinz Buchegger]

Re: problem with const objects in lazy parser

"joegen@pldtwer oam.com" wrote:[color=blue]
>
> Hi,
>
> I am working on an o project that involves Lazy Parsing. To be more
> specific, Its a SIP Message class that implements zero copy and lazy
> parsing. Below is a sample function that is causing me problems.
> Since my object is a lazy parser, it needs to evaluate the object to be
> parsed during the time an accessor is called.
>
> BOOL SIPMessage::Get Authorization(
> Authorization & h
> )
> {
> if( !ParseAuthoriza tion() )
> return FALSE;
>
> if( !HasAuthorizati on() )
> return FALSE;
>
> h = *m_Authorizatio n;
>
> return TRUE;
> }
>
> Since this function is performing a none const action
> "ParseAuthoriza tion()", I cannot declare this function as constant
> which will eventually lead to making my object a perpetually none
> constant object. Is there anyway to break this curse? I know I
> could "mutate" my member objects ( probably a hundred of them ) but it
> gives the shudder. Is there another technique to implement this
> cleanly?[/color]

Well.
It might be on of those cases where a const_cast is acceptable.

if( ! (<const_cast*>( this))->ParseAuthoriza tion() )


--
Karl Heinz Buchegger
kbuchegg@gascad .at

[joegen@pldtweroam.com]

Re: problem with const objects in lazy parser

Hi Karl,

Thanks for the tip. It should be the answer to my problem. By the
way i needed to rewrite it this way for it to compile

if( !(const_cast< SIPMessage * >( this ))->ParseAuthoriza tion() )

Thanks again!

Joegen