PureBasic Forums - English

Posted: **Thu Sep 30, 2004 3:19 pm**

Hi all,

I have a procedure that 'creates' and returns a pointer to a structure. I've already tested that and it works fine on its own.

However, I'm having problems using this pointer within another structure. This will come back with syntax errors..(extraneous code snipped):

Code: Select all

Structure HTTP_Connection
    
    *next.HTTP_Connection
    *prev.HTTP_Connection
    
    ;............
    
    *NetBank.Bank
    *url.URL
    
    ;............
    
EndStructure

Procedure.l HTTP_Create()
    Protected *hc.HTTP_Connection
    
    *hc = AddElement(HTTP_GlobalList())
    *hc\*url.URL = URL_Create()                                       ;<= syntax error
    *hc\*NetBank.Bank = Bank_Create(#HTTP_NetBankSize);<= syntax error
     
    ;...................
     
    ProcedureReturn *hc
EndProcedure

So what am I doin wrong here? Or is this type of thing just not possible in pure?

Thanks ahead of time.

Posted: **Thu Sep 30, 2004 3:30 pm**

Your error is that 'Addelement(MyList())' doesn't return the address to the structure. You should do it like this:

Code: Select all

If AddElement(HTTP_GlobalList())
  *hc = @HTTP_GlobalList()
  ; ... etc
Else
  Debug "Run out of memory?"
EndIf

Posted: **Thu Sep 30, 2004 4:02 pm**

I've converted the above procedure to your method, but I still get the same syntax error...

Code: Select all

Procedure.l HTTP_Create()
    Protected *hc.HTTP_Connection
    
    ;*hc = AddElement(HTTP_GlobalList())
    
    If AddElement(HTTP_GlobalList()) 
        *hc = @HTTP_GlobalList() 
        ; ... etc 
    Else 
        Debug "Run out of memory?" 
    EndIf
    
    ;*hc\*url.URL = URL_Create()
    
    If AddElement(URL_GlobalList()) 
        *hc\*url = @URL_GlobalList();<== syntax error still
        ; ... etc 
    Else 
        Debug "Run out of memory?" 
    EndIf
  
    ProcedureReturn *hc
EndProcedure

I'm not really clear as to why this:

Code: Select all

If AddElement(HTTP_GlobalList()) 
        *hc = @HTTP_GlobalList()

is different than:

Code: Select all

*hc = AddElement(HTTP_GlobalList())

Either way gives me a valid pointer...

Posted: **Thu Sep 30, 2004 4:53 pm**

POedBoy wrote: I'm not really clear as to why this:
Code: Select all
If AddElement(HTTP_GlobalList()) 
        *hc = @HTTP_GlobalList() 
is different than:
Code: Select all
*hc = AddElement(HTTP_GlobalList())
Either way gives me a valid pointer...

They're different pointers. This is explained in the linked list manual. One is a pointer to the user data and the other is the (address of the user data - 8).

Posted: **Thu Sep 30, 2004 7:33 pm**

Hmm, i didn't read trough your post thouroughly enough, and what i wrote in my first post was what i saw was wrong by just glancing through your code. Now i've experimented a bit and realized that you need to remove the '*' from the structure path or you'll get a syntax error.

Small example:

Code: Select all

Structure a1
  a.l
EndStructure

Structure a2
  *a.a1
  *b.a1
EndStructure

a.a2\a = @b.l
*p.a2 = @a

b = 1
Debug *p\a\a

Posted: **Thu Sep 30, 2004 8:13 pm**

Thanks for the help guys..

Posted: **Fri Oct 01, 2004 8:44 am**

re. pointer naming in structures:

http://www.xs4all.nl/~bluez/datatalk/pu ... structures

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Structures containing pointers to Structures

Structures containing pointers to Structures