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Program Announcements / Coming Soon : CRC32

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MrTAToad
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Posted: 2nd Aug 2003 18:56 Edited at: 2nd Aug 2003 18:58
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This calculates a CRC-32 value from either a given file or from memory. This was mainly done has a half-way house for the security for the URLDownload (the idea being you calculate the CRC-32 value for all files to check that they are correct).

Its quite fast too - checking a 19Mb file takes around 4 seconds on a 2Ghz machine.


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UberTuba
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Posted: 2nd Aug 2003 21:35
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and the englsh translation is:

the artist formally known as darkfluff
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MrTAToad
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Posted: 2nd Aug 2003 22:54
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It calculates a large number.


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Shock
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Posted: 3rd Aug 2003 01:12
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lol, sounds fun

Sticking feathers up your butt doesn't make you a chicken.
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Rob K
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Posted: 3rd Aug 2003 01:39
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Explanation of CRC32 for those that don't know:

CRC is a special number which can be calculated based on the contents of any file. If you change just one byte in the file, the CRC number will completely change. Thus this number is useful with ZIP files for example, to check that files contained in the ZIP file have not been corrupted (check that the CRC written in the file = the CRC of the file extracted)

It is also used in copy protection to check whether or not a file has been tampered with.

@Toady

Tsk. tsk - Not bad speed - still room for improvement though


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MrTAToad
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Posted: 3rd Aug 2003 03:53 Edited at: 3rd Aug 2003 03:56
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Yes, got it down to two seconds - should have it around to less than 1 shortly (using a 1Mb file buffer).


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MrTAToad
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Posted: 3rd Aug 2003 04:07 Edited at: 3rd Aug 2003 04:12
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Good description of CRC by the way, although mine was shorter...

I think I know what was causing the WAIT KEY problem earlier - as I was using the DBPro window handle in a MFC program, to display a message box, MFC seems to block the first keypress afterwards. No idea why though, because by the time the DBPro continues, the message box has gone.


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Shadow Robert
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Posted: 3rd Aug 2003 06:35
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Critial Repair Code? ... something like that
would go well with that updater plugin, that downloads files bit-by-bit right?

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MrTAToad
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Posted: 3rd Aug 2003 12:59 Edited at: 3rd Aug 2003 13:00
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Thats it mainly for - after downloading, you check to see if all the files are correct.

Its actually Cyclic Redundency Check.


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Hell IVIonkey
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Posted: 3rd Aug 2003 13:53
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I've been wanting CRC support for ages, especially since I need extra security if I release my game commercially. I look forward to it!


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MrTAToad
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Posted: 3rd Aug 2003 14:12 Edited at: 3rd Aug 2003 14:23
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Well, the good news is its availiable for testing now.
If I remember correctly, your using DBC ? If so, you'll need DarkMatter to call DLL's.

The two functions are :

?calcCRC32FromMemory@@YAKKK@Z - Calculate CRC from memory
?calcCRC32@@YAKPAD@Z - Calculate CRC from file


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David T
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Posted: 21st Aug 2003 12:58
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This soudns really good. I'll be looking for this as soon as it's released.

Is the number generated a normal decimal number (123456) or is it hex?

How long are the numbers?

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OSX Using Happy Dude
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Posted: 21st Aug 2003 13:39
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Its been released for a while - generally when I say its coming soon in here, its ready but I haven't updated my web site (or its updating whilst I'm writing the message).

Its different from a coming soon message in the announcements, where generally I've finished it, but needs testing.

Its a normal 32-bit unsigned integer - I generally display it in hex, but its up to you.

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