Allow datasection with fixed-length types

[Mistrel]

This is just a rudimentary example to demonstrate what I'm talking about:

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DataSection
  Object:
    Data.l[3] ;/ x, y, z
    Data.l[2] ;/ max length
    Data.l[5] ;/ local object data
  Object_string:
    Data.s[16],[26],[3] ;/ object name, description, 3-char code
EndDataSection

It would also be nice to be able to use structures here as well.

[Kaeru Gaman]

the length of the Datasection is clearly defined by the length of the Data you put into it.
what would be the use of defining it twice?

[Trond]

Maybe Mistrel hasn't noticed that DataSections are write-only? Apart from that I don't know.

[netmaestro]

...DataSections are write-only?

I don't quite understand this part, could you explain?

[Kaeru Gaman]

DataSections are not read only... you can read and write aswell.

but the DataSection gets a fixed size by the values you put in.

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Data.b 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

creates a Section of 16 byte length

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Data.l 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

creates a Section of 64 byte length

... so, I don't understand what he is requesting.

[#NULL]

for numbers it were usefull then if you could define less elements of such an data block, not having to pad the remaining elements with 0s. and for strings it would be usefull because your string elements would then have all the same length regardless how long the literals are:

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Data.s [16],[16] "abc", "qrstuvw" ; will be of same size

and for numbers and strings as well you can define offsets between your data easier, without having to pad 0s or ""s.


@trond
what about writing to datasection indirectly, by modifying an *.exe by another one for example?

[cxAlex]

Maybe Mistrel hasn't noticed that DataSections are write-only? Apart from that I don't know.

DataSections are writeable:

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Define *Val.Long, Val.l
*Val = ?MyData

Restore MyData
Read.l Val
Debug Val

; Now change the Data in the DataSection
*Val\l = 123

Restore MyData
Read.l Val
Debug Val

DataSection
  MyData:
  Data.l 10
EndDataSection

[Psychophanta]

Not sure, but i think datasections are read only sections, as it is part of the program body and it should not be writable.
The above example, which can be easely like this, is not safe, is it?

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PokeL(?MyData,123)
Read.l d.l
Debug d

DataSection 
  MyData:Data.l 10

Maybe Trond wanted to say read-only.

[Demivec]

Not sure, but i think datasections are read only sections, as it is part of the program body and it should not be writable.
The above example, which can be easely like this, is not safe, is it?

It is safe (in the right hands).

You can also change the code in the program body as well. This allows for self-modifying code.

It is normally best to avoid both practices for the sake of "safety". What is best though, depends on the circumstances and the skill of the programmer.

[Kaeru Gaman]

btw... It would be nice to have the possibility to assing a fully dimensionated Array to a DataSection.
I mean, Dim Array( #X, #Y ), and then bow the pointer to a DataSection
to use the Space in the Section with predefined values and don't waste space by allocating twice..

[netmaestro]

@KG:

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DataSection 
  lbl:
  Data.l 10,20,30,40,50,60
EndDataSection

Dim stuff.l(2,1)

stuff()=?lbl

Debug stuff(0,0)

stuff(0,0)=99

Debug stuff(0,0)

[Kaeru Gaman]

@netmaestro

butI think there still is the problem with the previous allocated space...

the old location of the Array isn't freed when I just bow the pointer that way, is it?
so, when I have a 512x512 Long-Array, I would waste (leak) a full MB of Memory...

[netmaestro]

So dim it at 0,0 then repoint it and redim.

[helpy]

btw... It would be nice to have the possibility to assing a fully dimensionated Array to a DataSection.
I mean, Dim Array( #X, #Y ), and then bow the pointer to a DataSection
to use the Space in the Section with predefined values and don't waste space by allocating twice..

Do you mean something like this:

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Structure MyArrayRow
  item.i[10]
EndStructure
Structure MyArray
  row.MyArrayRow[2]
EndStructure

*myArray.MyArray = ?MyArray

For row = 0 To 1
  For item = 0 To 9
    Debug *myArray\row[row]\item[item]
  Next
Next

; A bit easier to write with a macro
Macro ArrayItem(xArray,x,y)
  xArray\row[x]\item[y]
EndMacro

For row = 0 To 1
  For item = 0 To 9
    Debug ArrayItem(*myArray,row,item)
  Next
Next

DataSection
  MyArray:
    Data.i  1,  2,  3,  4,  5,  6,  7,  8,  9, 10
    Data.i 11, 12, 13, 14, 15, 16, 17, 18, 19, 20
EndDataSection

cu, helpy

[Trond]

I meant to say read-only.

But I do not understand why Fred would make DataSections writeable, as it means they are basically useless. If it was read-only the same datasection would be shared amongst all loaded copies of the executable. If it is writable, it is no different from the rest of the program, so why make it a separate section?