[Gambas-user] [Fwd: Gambas3 Pointers example]

[Demosthenes Koptsis]

Thanks Jussi! 

It's nice to understand the language.
I didn't say that there was a bug, my mind just did not go to the
behavior of WRITE instruction, which it moved the stream pointer after
writing the data.

I remade the example to show this detail for better comprehension.

-------------------------------------
' Gambas module file

 Public Sub Main()

 Dim pPointer As Pointer
 Dim hMemory As Stream
 Dim iA As Integer

 pPointer = Alloc(SizeOf(gb.Integer))
 hMemory = Memory pPointer For Read Write

 Write #hMemory, 10 As Integer
 
 'get stream pointer position
 Print Seek(hMemory) '4
 
 'set stream pointer potition
 Seek #hMemory, 0

'get stream pointer position
 Print Seek(hMemory) '0
 
 'read from memory stream
 iA = Read #hMemory As Integer
 Print iA '10
 
 'read from address
 iA = Integer@(pPointer)
 Print iA '10

 Free(pPointer)
End
-------------------------------------

something else, as i read the docs i found a way to write to a pointer
by instructions

hMemory = Memory pPointer For Read Write
Write #hMemory, 10 As Integer

is there any other way that i did not notice?

there is also PRINT to stream but as i see it converts the expression to
string with Str$, so it is not a good option.

On Sat, 2011-01-08 at 20:43 +0200, Jussi Lahtinen wrote:
> Argh... of course:
> 
> This uses internal counter:
> iA = Read #hMemory As Integer
> 
> This uses pPointer as address:
> iA = Integer@(pPointer)
> 
> 
> Jussi
> 
> 
> On Sat, Jan 8, 2011 at 20:40, Jussi Lahtinen <jussi.lahtinen at ...626...>wrote:
> 
> > Behaviour confirmed with Gambas 3 rev 3447 @ Ubuntu 10.10 64bit.
> > Though I don't think this is bug, since stream pointer position moves after
> > write.
> > "Seek #hMemory, 0" will fix that, in this case. See more from documentation
> > of Seek.
> >
> > However I don't know how Interger@ gets correct position...
> >
> > Jussi
> >
> >
> >
> >
> >
> > On Sat, Jan 8, 2011 at 18:09, Demosthenes Koptsis <demosthenesk at ...626...>wrote:
> >
> >>
> >> But if i write,
> >>
> >> iA = Integer@(pPointer)
> >> Print iA
> >>
> >> then iA gets the value 10.
> >>
> >> why is that?
> >>
> >> what's the difference between
> >> iA = Read #hMemory As Integer
> >> iA = Integer@(pPointer)
> >>
> >> ?
> >> --
> >> Regards,
> >> Demosthenes Koptsis.
> >>
> >>
> >> ---------- Forwarded message ----------
> >> From: Demosthenes Koptsis <demosthenesk at ...626...>
> >> To: Gambas User List <gambas-user at lists.sourceforge.net>
> >> Date: Sat, 08 Jan 2011 10:32:12 +0200
> >> Subject: Gambas3 Pointers example
> >> Hello,
> >> i remake an example for pointers in Gambas3-svn3432, ubuntu 10.04 LTS,
> >> AMD64
> >>
> >> The example is the next:
> >>
> >> -------------------------
> >> ' Gambas module file
> >>
> >> Public Sub Main()
> >>
> >> Dim pPointer As Pointer
> >> Dim hMemory As Stream
> >> Dim iA As Integer
> >>
> >> pPointer = Alloc(SizeOf(gb.Integer))
> >> hMemory = Memory pPointer For Read Write
> >>
> >> Write #hMemory, 10 As Integer
> >> iA = Read #hMemory As Integer
> >>
> >> Print iA
> >>
> >> Free(pPointer)
> >>
> >> End
> >> -------------------------
> >>
> >> the iA var when it prints is not 10 but something else like 0 or 32621
> >> or similar.
> >>
> >> What am i doing wrong?
> >>
> >>
> >>
> >> --
> >> Regards,
> >> Demosthenes Koptsis.
> >>
> >>
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> that requires sensitive data to be transmitted over the Web.   Learn how to 
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> and instills the confidence they need to proceed with transactions.
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-- 
Regards,
Demosthenes