Delete every x bytes?

[richietheprogrammer]

Hello,

I am trying to delete every 840 bytes from a file, and keep the rest. How would I do that? Thanks for any help

[trancexx]

Hello,

I am trying to delete every 840 bytes from a file, and keep the rest. How would I do that? Thanks for any help

But if you delete every 840 bytes then you'll delete all.

Or you mean every other?

[richietheprogrammer]

But if you delete every 840 bytes then you'll delete all.

Or you mean every other?

Haha good point. Well basically I want to delete "3A" bytes every 840 bytes. So start by deleting 3A bytes, then jump 840 bytes, delete 3A bytes, jump another 840 bytes... Thanks for requiring clarification!

[jchd]

Read your input as binary then repeatedly use BinaryMid to grab parts you need and rewrite that back to wherever you want.

[richietheprogrammer]

Read your input as binary then repeatedly use BinaryMid to grab parts you need and rewrite that back to wherever you want.

Thank you. Can you please provide a sample code? I'd appreciate it

[jchd]

Sorry for delay, had to taxi kids around, eat, etc.

If your input is a file, then this should work (no much time to test it really).

#include <Constants.au3)

Local $hInpf = FileOpen("myinpfile.bin", 16)
If $hInpf <> -1 Then
    Local $hOutf = FileOpen("myoutfile.bin", 2 + 16)
    If $hOutf <> -1 Then
        Local $ret, $data, $done
        Do
            $ret = FileSetPos($hInpf, 58, $FILE_CURRENT)
            If Not $ret Then ExitLoop
            $data = FileRead($hInpf, 840)
            $done = (@error = -1)       ; read incomplete (EOF reached) but maybe something to write anyway
            FileWrite($hOutf, $data)
            ; process write error
        until $done
        FileClose($hInpf)
        FileClose($hOutf)
    Else
        ; process error
    EndIf
    ; process error
EndIf

Edited April 7, 2011 by jchd

[richietheprogrammer]

Sorry for delay, had to taxi kids around, eat, etc.

If your input is a file, then this should work (no much time to test it really).

#include <Constants.au3)

Local $hInpf = FileOpen("myinpfile.bin", 16)
If $hInpf <> -1 Then
    Local $hOutf = FileOpen("myoutfile.bin", 2 + 16)
    If $hOutf <> -1 Then
        Local $ret, $data, $done
        Do
            $ret = FileSetPos($hInpf, 58, $FILE_CURRENT)
            If Not $ret Then ExitLoop
            $data = FileRead($hInpf, 840)
            $done = (@error = -1)       ; read incomplete (EOF reached) but maybe something to write anyway
            FileWrite($hOutf, $data)
            ; process write error
        until $done
        FileClose($hInpf)
        FileClose($hOutf)
    Else
        ; process error
    EndIf
    ; process error
EndIf

No worries, and thanks a lot for this! However, I cannot get it to function the way I want it to. It is deleting the first 58 bytes correctly, but then it is not jumping and deleting the rest correctly. it seems like it is miscounting. Also, the 840 is in hex, so really I want it 2112, assuming the script counts in dec? But anyways, maybe there is something wrong with counting 2112 every time, because if we remove the first 58, then shouldn't we count (2112 minus 58) from the new file so we can get to the next set? Thanks again for your help!!! (I think if we just add 2054 it will jump correctly.) Do you agree? Edited April 7, 2011 by richietheprogrammer

[jchd]

OK I misunderstood your "jump" offset. Try this working( for me) example:

#include <Constants.au3>

Local $htest = FileOpen(@ScriptDir & "\myinpfile.bin", 2 + 16)
Local $ch = Asc('a')
For $i = 1 To 10
    For $j = 1 To 58
        FileWrite($htest, Chr($ch))
    Next
    $ch += 1
    For $j = 1 To 2112 - 58
        FileWrite($htest, Chr($ch))
    Next
    $ch += 1
Next
FileClose($htest)

Local $hInpf = FileOpen(@ScriptDir & "\myinpfile.bin", 16)
If $hInpf <> -1 Then
    Local $hOutf = FileOpen(@ScriptDir & "\myoutfile.bin", 2 + 16)
    If $hOutf <> -1 Then
        Local $ret, $data, $done
        Do
            $ret = FileSetPos($hInpf, 58, $FILE_CURRENT)
            If Not $ret Then ExitLoop
            $data = FileRead($hInpf, 2112 - 58)
            $done = (@error = -1)       ; read incomplete (EOF reached) but maybe something to write anyway
            FileWrite($hOutf, $data)
            ; process write error
        until $done
        FileClose($hInpf)
        FileClose($hOutf)
    Else
        ; process error
    EndIf
    ; process error
EndIf

[richietheprogrammer]

Thanks a lot !