How to read/extract binary data?

[kevinlaikf]

Pardonb my ignorance, I had a hard time extracting binary info from a binary datafile.

I am struggling reading 8-bytes of data, reading them in hexadecimal right to left.

Below is part of my working script, but i believe there is a much efficient approach using Binary and BinaryMid functions.

$file = FileOpen($binfile, 16)

If $file = -1 Then

MsgBox(0, "Error", "Unable to open file.")

Exit

EndIf

$size = FileGetSize($binfile)

$newdatasize = $size - 691280

$junkdata = FileRead($file, 691280)

$usefuldata = FileRead($file, $newdatasize)

$hex1 = StringMid($usefuldata, 3, 2)

$hex2 = StringMid($usefuldata, 5, 2)

$hex3 = StringMid($usefuldata, 7, 2)

$hex4 = StringMid($usefuldata, 9, 2)

$hexdata = "0x" & $hex4 & $hex3 & $hex2 & $hex1

$epochsec = Number ($hexdata)

MsgBox(0,"hexdata",$hexdata & "-"& $epochsec,10)

$creationdate = _DateAdd("s", $epochsec, "1970/01/01 00:00:00")

Anyone would direct me to a better design?

Apart from the above issue, i had yet to find a good solution to extract the data.

The situation is: I got few data files, I had managed to spool the useful data without the junk data. Now my new datafile had a data structure of 34 bytes of info header followed by a JPEG stream, and continue to the next 34 bytes, then JPEG data stream until EOF. Of the 34 bytes, the first 4 bytes contain the epoch seconds (seconds since 1970/1/1 00:00:00), the JPEG stream start with FF D8 FF and ends with FF D9. I need to spool the JPEG data(s) with with filename linked to the individual epoch seconds date/time.

Any help for this?

Thanks in advance..

Regards,

Kevin Lai.

[martin]

Pardonb my ignorance, I had a hard time extracting binary info from a binary datafile.

I am struggling reading 8-bytes of data, reading them in hexadecimal right to left.

Below is part of my working script, but i believe there is a much efficient approach using Binary and BinaryMid functions.

$file = FileOpen($binfile, 16)

If $file = -1 Then

MsgBox(0, "Error", "Unable to open file.")

Exit

EndIf

$size = FileGetSize($binfile)

$newdatasize = $size - 691280

$junkdata = FileRead($file, 691280)

$usefuldata = FileRead($file, $newdatasize)

$hex1 = StringMid($usefuldata, 3, 2)

$hex2 = StringMid($usefuldata, 5, 2)

$hex3 = StringMid($usefuldata, 7, 2)

$hex4 = StringMid($usefuldata, 9, 2)

$hexdata = "0x" & $hex4 & $hex3 & $hex2 & $hex1

$epochsec = Number ($hexdata)

MsgBox(0,"hexdata",$hexdata & "-"& $epochsec,10)

$creationdate = _DateAdd("s", $epochsec, "1970/01/01 00:00:00")

Anyone would direct me to a better design?

Apart from the above issue, i had yet to find a good solution to extract the data.

The situation is: I got few data files, I had managed to spool the useful data without the junk data. Now my new datafile had a data structure of 34 bytes of info header followed by a JPEG stream, and continue to the next 34 bytes, then JPEG data stream until EOF. Of the 34 bytes, the first 4 bytes contain the epoch seconds (seconds since 1970/1/1 00:00:00), the JPEG stream start with FF D8 FF and ends with FF D9. I need to spool the JPEG data(s) with with filename linked to the individual epoch seconds date/time.

Any help for this?

Thanks in advance..

Regards,

Kevin Lai.

Try BinaryMid instead of StringMid

[kevinlaikf]

Try BinaryMid instead of StringMid

Yes, I tried that before.

$hex1 = BinaryMid ($usefuldata,1,1)

$hex2 = BinaryMid ($usefuldata,2,1)

$hex3 = BinaryMid ($usefuldata,3,1)

$hex4 = BinaryMid ($usefuldata,4,1)

The problem is, I had failed trying to convert them back to integer/number using Int() or Number() to get the value into var $epochsec.

But i believe each $hex* var of the above value had an additional prefix of "0x", it is more efficient to get them into string value to merge into a 4 bytes strings in right to left hex value orientation.

Edited August 31, 2008 by kevinlaikf