(05-23-2024, 07:25 PM)Steffan-68 Wrote: I might have another thought.
I'm not particularly a fan of constantly writing to a file and deleting it again.
Since it looks like it's just a Windows program, how about writing stad to a file just using the clipboard?
It would all be in RAM and no HDD access.

(05-23-2024, 06:56 PM)DSMan195276 Wrote:

(05-23-2024, 05:45 PM)Kernelpanic Wrote: One could almost compare it with a traffic light at an intersection: If North - South is green, then West - East has to wait (red) until it itself is green. If all road users stick to it, there won't be crashed. 

Unfortunately Steve's approach can't prevent both programs from reading and writing at the same time, I don't think there's a way to do it with read/write file interactions alone.....

Open "temp.txt" For Output As #1: Close 'make certain file is blank/new to begin with

Open "temp.txt" For Binary As #1



Do

    Select Case checkFile

        Case 11

            Print "Program 1 has control, is reading file."

            readfile

        Case 12

            Print "Program 1 has control, is writing to file."

            writefile

        Case 21

            Print "Program 2 has control, is reading file."

        Case 22

            Print "Program 2 has control, is writing to file."

        Case Else

            Print "File is free for usage."

            x = Int(Rnd * 100)

            Select Case x

                Case 10: writefile 'generate a random write every so often to see if we have issues

            End Select

    End Select

    _Limit 10

Loop



Sub readfile

    Dim temp As _Unsigned _Byte

    Dim junkdata As Long

    temp = 11

    Put #1, 1, temp

    _Delay .1 'wait 1/10 second to make certian other file isn't also trying to take control

    Get #1, 1, temp

    If temp <> 11 Then Exit Sub 'other file took control first.  We had a race condition and avoided it.

    Print "Recieved Data:"

    Do Until EOF(1)

        Get #1, , junkdata

        Print junkdata; ",";

    Loop

    Print

    'finished reading, free up the file now

    temp = 0

    Put #1, 1, temp

End Sub



Sub writefile

    Dim temp As _Unsigned _Byte

    Dim junkdata As Long

    temp = 12

    Put #1, 1, temp

    _Delay .1 'wait 1/10 second to make certian other file isn't also trying to take control

    Get #1, 1, temp

    If temp <> 12 Then Exit Sub 'other file took control first.  We had a race condition and avoided it.

    Print "Writing Data:"

    For i = 1 To 10

        junkdata = Int(Rnd * 100) + 1

        Put #1, , junkdata

        Print junkdata; ",";

    Next

    Print

    'finished reading, free up the file now

    temp = 21 'tell the second program that it's now time to read the file!

    Put #1, 1, temp

End Sub





Function checkFile~%%

    Dim temp As _Unsigned _Byte

    Get #1, 1, temp

    checkFile = temp

End Function

Open "temp.txt" For Binary As #1



Do

    Select Case checkFile

        Case 21

            Print "Program 2 has control, is reading file."

            readfile

        Case 22

            Print "Program 2 has control, is writing to file."

            writefile

        Case 11

            Print "Program 1 has control, is reading file."

        Case 12

            Print "Program 1 has control, is writing to file."

        Case Else

            Print "File is free for usage."

            x = Int(Rnd * 100)

            Select Case x

                Case 10: writefile 'generate a random write every so often to see if we have issues

            End Select

    End Select

    _Limit 10

Loop



Sub readfile

    Dim temp As _Unsigned _Byte

    Dim junkdata As Long

    temp = 21

    Put #1, 1, temp

    _Delay .1 'wait 1/10 second to make certian other file isn't also trying to take control

    Get #1, 1, temp

    If temp <> 21 Then Exit Sub 'other file took control first.  We had a race condition and avoided it.

    Print "Recieved Data:"

    Do Until EOF(1)

        Get #1, , junkdata

        Print junkdata; ",";

    Loop

    Print

    'finished reading, free up the file now

    temp = 0

    Put #1, 1, temp

End Sub



Sub writefile

    Dim temp As _Unsigned _Byte

    Dim junkdata As Long

    temp = 22

    Put #1, 1, temp

    _Delay .1 'wait 1/10 second to make certian other file isn't also trying to take control

    Get #1, 1, temp

    If temp <> 22 Then Exit Sub 'other file took control first.  We had a race condition and avoided it.

    Print "Writing Data:"

    For i = 1 To 10

        junkdata = Int(Rnd * 100) + 1

        Put #1, , junkdata

        Print junkdata; ",";

    Next

    Print

    'finished reading, free up the file now

    temp = 11 'tell the second program that it's now time to read the file!

    Put #1, 1, temp

End Sub





Function checkFile~%%

    Dim temp As _Unsigned _Byte

    Get #1, 1, temp

    checkFile = temp

End Function

(05-23-2024, 08:30 PM)Kernelpanic Wrote: This now reminds me of MySQL and PostgreSQL; that I once had to do with. The file that is currently being written to must of course be locked for other write access. . . otherwise there would be breakage.

This is all very complicated. And therefore very error-prone.
@madscijr, check the design of your program again.

(05-23-2024, 08:09 PM)SMcNeill Wrote: They set the flag for who has control, and skip doing anything unless they have control...  Then when they're finished writing, they set the flag so the other program now has control to read.   

(05-23-2024, 10:05 PM)DSMan195276 Wrote:

(05-23-2024, 08:09 PM)SMcNeill Wrote: They set the flag for who has control, and skip doing anything unless they have control...  Then when they're finished writing, they set the flag so the other program now has control to read.   

I mean you didn't really solve the underlying problem, you simply avoided the race by adding a _Delay .1

That said, one-way commutation with three states like you're doing has some potential. I'd still be concerned about caching, especially on Linux and Mac OS where we make use of the C++ file streams, but overall I think it's ok.

(05-23-2024, 10:05 PM)DSMan195276 Wrote:

(05-23-2024, 08:09 PM)SMcNeill Wrote: They set the flag for who has control, and skip doing anything unless they have control...  Then when they're finished writing, they set the flag so the other program now has control to read.   

I mean you didn't really solve the underlying problem, you simply avoided the race by adding a _Delay .1

That said, one-way commutation with three states like you're doing has some potential. I'd still be concerned about caching, especially on Linux and Mac OS where we make use of the C++ file streams, but overall I think it's ok.

(05-24-2024, 12:56 AM)SMcNeill Wrote:

(05-23-2024, 10:05 PM)DSMan195276 Wrote:

(05-23-2024, 08:09 PM)SMcNeill Wrote: They set the flag for who has control, and skip doing anything unless they have control...  Then when they're finished writing, they set the flag so the other program now has control to read.   

I mean you didn't really solve the underlying problem, you simply avoided the race by adding a _Delay .1

That said, one-way commutation with three states like you're doing has some potential. I'd still be concerned about caching, especially on Linux and Mac OS where we make use of the C++ file streams, but overall I think it's ok.

You can skip that delay completely and the flag system will still work.  The programs just take turns working with the file.

Program 1 starts up.  Creates file.  Sets flag for "In use."  Writes to file.
Program 2 starts up.  File exists.  Checks flag.  It's in use... does nothing.
Program 1 finishes writing.  Sets flag for "Hey you, read this!"...  It now enters standby mode.
Program 2 sees flag.  Reads file..
Program 1...  File still flagged for program 2 use... wait...
Program 2 finishes reading file.   Now writes whatever data it needs to send back.
Program 1... File still flagged for program 2 use... wait....
Program 2 finishes writing to file.  Now sets flag to "Hey, Program 1, it's your turn!"
Program 1... Reads flag...  Takes control...

BINARY lets you read and write at the same time.  As long as the first byte in the file is set, you can toggle that back and forth to pass control to whichever program gets to use the file at any given time.  

May wear your drive out toggling that one byte over and over and over again, but it's quite doable.

Even with caching, it wouldn't matter, as the control remains with the other program until that cache catches up and updates...  though if your cache doesn't push to file for a while, you may end up with both program just being locked in a waiting state until that write finally occurs. 

---

And with that said, I still think the easiest way to do things would be to just OPEN "localhost" for TCP/IP and PUT/GET info back and forth like that between the two programs. 

(05-24-2024, 12:56 AM)SMcNeill Wrote: You can skip that delay completely and the flag system will still work.  The programs just take turns working with the file.

Even with caching, it wouldn't matter, as the control remains with the other program until that cache catches up and updates...  though if your cache doesn't push to file for a while, you may end up with both program just being locked in a waiting state until that write finally occurs.