I want to create a VBA function that can calculate the CRC32 checksum for a file.
I found this webpage which looks promising: http://www.vbaccelerator.com/home/VB...32/article.asp
The only catch is that the code provided is VB not VBA. How hard would it be to tweak this code to run in VBA?
Last edited by mc84excel; 10-14-2013 at 08:43 PM.
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HELP WANTED! (Links to Forum threads)
Trying to create reusable code for Custom Events at Workbook (not Application) level
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It's a very easy port with minor changes but these are probably in code you will not use.
Problems:
Userform (if to be used) needs to be rebuild.
References to APP object can be replaced with APPLICATION.
References to PRINTER object and SCREEN object have no direct equivalents in VBA but as they are part of supplementary code can probably be ignored.
Nothing else noticed on reading* the source, but the core of the calculation should be a simple copy/paste into a class module. There is at least 1 conditional compilation constants (fComponent), this seems to be a flag if the code is part of a system, or a stand alone project. It can be removed or left as is.
*Note: Code was read, not compiled or tested...
Hi cytop.
I see the userform as unnecessary for my purposes. A simple file picker will do to pick the file and a MsgBox will be sufficient to return the CRC32 result (see attached workbook)
I'm afraid that I have never learnt classes. :S I have copy/pasted the code into class modules but I get invalid outside procedure messages...
Tested on one text file ...
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Entia non sunt multiplicanda sine necessitate
Thanks shg +1, this code looks like what I was after.
Before I mark this as solved however, I am uncertain about the output produced.
I tried a random file and obtained the CRC32 checksum using your function. It returned a result of 3281A458. I then tested the same file again on an online CRC32 calculator (I googled for one and used this website: http://hash.online-convert.com/crc32-generator) The checksum that this site returned on the uploaded file was 74EF76B6.
Why the difference?
The file read probably needs to be changed to a straight binary input. Over to you.
Ah:
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I set a reference to Microsoft ActiveX Data Objects 2.0 Library and ended up with a "user defined type" error on the lineGoogle provided the solution. You need to use Microsoft ActiveX Data Objects 2.5 Library (or higher version) to prevent this happening.Please Login or Register to view this content.
I am posting this here in case anyone else runs into this.
Brilliant work shg.
This thread is solved. I am posting my final version of this code below.
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Last edited by mc84excel; 10-14-2013 at 07:47 PM. Reason: solved problem
This is illogical. I created a dummy test file to compare the CRC32 result against other online calculators. To my surprise, there were a wide variety of results from different systems! How can this be?!
My test file is attached and the results I received are below:
D5509719 = Excel function
3578828569 = Checksum Calculator http://www.checksumcalculator.com/
D959103E = http://hash.online-convert.com/crc32-generator
d959103e = online-domain-tools (can't provide URL link - the post crashes whenever I try)
D5509719 = http://crc32-checksum.waraxe.us/
UPDATE:
I realised that there are only two different results in the above, not three. (Checksum Calculator result of 3578828569 = D5509719 in Hex).
So three different tools are returning D5509719 and two others are returning D959103E
Last edited by mc84excel; 10-14-2013 at 09:56 PM.
To follow/contribute to the next stage of this project, see: http://www.excelforum.com/excel-prog...stage-2-a.html
The CRC32-Mpeg2 seems use different algorithm, the explanation as following:
http://www.lammertbies.nl/forum/viewtopic.php?t=1398
And it also calculate by website correcty:
http://www.sunshine2k.de/coding/java...rc/crc_js.html
Configuration:
CRC-32
CRC32_MPEG2
Fill Data(00 to FF):
"000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9fa0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff"
CRC32_MPEG2 result is "494a116a".
The algorithm for normal CRC32 as following:
For I = 0 To 255
dwCrc = I
For j = 8 To 1 Step -1
If (dwCrc And 1) Then
dwCrc = ((dwCrc And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
dwCrc = dwCrc Xor iPoly
Else
dwCrc = ((dwCrc And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
End If
Next j
aiCRC(I) = dwCrc
Next I
But it seems not suit for CRC32-MPEG2.
Does someone can help to implement this algorithm? Thanks!!
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