AlliedModders - [Solved] Set pack position on end not working

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- - Solved Set pack position on end not working (https://forums.alliedmods.net/showthread.php?t=301390)

hh2	09-18-2017 20:36

Set pack position on end not working

What is wrong in this code?

PHP Code:


		
			
    // Create DataPack

    DataPack pack = CreateDataPack();

    

    // Write data to DataPack

    pack.WriteCell(client);

    pack.WriteString("test");

    pack.WriteCell(5);

    

    // Get DataPack end position for later

    DataPackPos pos = pack.Position;

    

    // Reset DataPack

    pack.Reset();

    

    // Read only client id

    int client2 = pack.ReadCell();

    

    // Set position to end 

    pack.Position = pos;       // Error here

    

    // Write new data to the end

    pack.WriteCell(6);

Logs:

Code:

[SM] Exception reported: Invalid DataPack position, 28 is out of bounds

[SM] Call stack trace:

[SM] [0] DataPack.Position.set

I'm trying also something like (pos - view_as<DataPackPos>(1)), but this gave me incorrect results.

headline

09-18-2017 21:57

Re: Set pack position on end not working

Quote:

Originally Posted by Peace-Maker (Post 2144341)

You shouldn't be using SetPackPosition. It's setting the position of the internal char* stream to some offset. You'd need to calculate the offset yourself which will likely break easily.

WritePackCell first "pushes" the size of a cell (4 bytes) on the stream then the cell itself (4 bytes again). So you'd need to set the pack position to 5*8=40. It gets trickier with strings in the pack.. You'd be better off with an adt_trie. SetPackPosition should be deprecated as it's of no practical use.

Neuro Toxin

09-19-2017 03:15

Re: Set pack position on end not working

You could try using Dynamic (linked in my signature) or a plan Trie.

Fyren

09-19-2017 03:19

Re: Set pack position on end not working

The quote from PM above is probably talking about is arbitrarily setting the position (e.g. writing four cells then setting the position to 2, which is wrong).

The short answer is you cannot set the pack position to the end. I think the intented way to use datapacks is create them, write all the data, then reset them and send them off to be read.

The longer answer is I guess you can save the position of the last thing you wrote, then later set the position to that, then read that again to end up with the position being at the end. It also looks like SM's tracking of the datapack size will be wrong if you rewrite earlier portions of the datapack and not at the very end.

hh2	09-19-2017 11:41

Re: Set pack position on end not working

Quote:

Originally Posted by Neuro Toxin (Post 2549622)

You could try using Dynamic (linked in my signature) or a plan Trie.

This library looking good, but i dont wanna use it only for 1 callback.

Quote:

Originally Posted by Fyren (Post 2549624)

The longer answer is I guess you can save the position of the last thing you wrote, then later set the position to that, then read that again to end up with the position being at the end. It also looks like SM's tracking of the datapack size will be wrong if you rewrite earlier portions of the datapack and not at the very end.

Probably use this method, but is there way to get rid of that warning: warning 204: symbol is assigned a value that is never used: "five"

PHP Code:


		
			
    // Create DataPack
    DataPack pack = CreateDataPack();
    
    // Write data to DataPack
    pack.WriteCell(client);
    pack.WriteString("test");
    DataPackPos pos = pack.Position;
    pack.WriteCell(5);
    
    // Reset DataPack
    pack.Reset();
    
    // Read only client id
    int client2 = pack.ReadCell();
    
    // Set position to end
    pack.Position = pos;
    int five = pack.ReadCell();
    
    // Write new data to the end
    pack.WriteCell(6);

asherkin

09-19-2017 15:07

Re: Set pack position on end not working

Just do

Code:

pack.ReadCell();

hh2	09-19-2017 16:08

Re: Set pack position on end not working

This is what i need, thanks for your help guys.

Fyren

09-19-2017 18:51

Re: Set pack position on end not working

In the latest dev snapshot, setting the position to the end is now allowed.

Dragokas

02-21-2019 08:07

Re: Set pack position on end not working

Quote:

Originally Posted by Peace-Maker (Post 2144341)

WritePackCell first "pushes" the size of a cell (4 bytes) on the stream then the cell itself (4 bytes again).

in such case, why:

Code:

    DataPack hPack = new DataPack();

    PrintToServer("Position: %i", hPack.Position);

    hPack.WriteCell(5);

    PrintToServer("Position: %i", hPack.Position);

Quote:

Position: 0
Position: 9

0 ... 8 == 9 bytes, not 8 (4 + 4).

Quote:

Originally Posted by Fyren (Post 2549624)

It also looks like SM's tracking of the datapack size will be wrong if you rewrite earlier portions of the datapack and not at the very end.

So, this code will be unsafe?

Code:

        DataPack hPack = new DataPack();

        hPack.WriteCell(5);

        hPack.WriteCell(6);

        

        // ...... some actions

        

        // overwrite first cell

        hPack.Reset();

        hPack.WriteCell(4);

Dragokas

02-21-2019 09:22

Re: Set pack position on end not working

off.
One more question, please:

Can I withdraw the TIMER_DATA_HNDL_CLOSE flag in timer callback?
Or it is safe to use CloneHandle there:

Spoiler

thanks.

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