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Old 2005-12-21, 05:29   Link #36
Ledgem
Love Yourself
 
 
Join Date: Mar 2003
Location: Northeast USA
Age: 28
I would like to note that the instructions on how to use Zidrav posted by [Titan] are incorrect - while the program can be used that way, using that method requires that both files be the exact same size. This limits the program's usage to very few instances of patching corrupt files, when the program can actually be used exactly like BitTorrent.

Stepwise:
1. Have the person with the completed file make the checksum file (this will be a .cdt filetype). Send this file to the person with the corrupt/incomplete file.
2. Have the person with the damaged file use Make requests file - this will require both the checksum (.cdt) file from the person with the completed file, and the damaged file. Send the file created (.cdq filetype) back to the person with the completed file.
3. Have the person with the completed file use Fill requests file - this will require the .cdq file created by the person with the damaged/incomplete file, and the completed file. It will create a .cdp file, the size depending on how much data was missing from the corrupt file. Send this file back to the person with the damaged file.
4. Have the person with the damaged/incomplete file use Apply patch file. This will require the .cdp file from the person with the completed file, and the damaged/incomplete file.

Done. It requires more steps than simply having the person with the damaged file creating a checksum file, sending it to a person with the complete file, and having the person with the complete file sending a patch back. However, this will allow you to work around corruption/incompletions where the filesize does not match exactly.
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On a less related note, since this thread is dedicated to checking CRC values, I would like to suggest that people use HashCalc (http://slavasoft.com/hashcalc/overview.htm) for their checking needs. It's a very simple, free program that will also allow you to hash other algorithms. Note that while hashing, the program will act like it has frozen - the hashing process will take anywhere from a few seconds to a minute or two, depending on the speed of your hard drive and processor, and the size of the file you are hashing.

Want to calculate the CRC values of multiple files at once instead of one by one? No problem! Though it's made for checking over pre-made MD5 and SFV files, WXchecksums (http://sourceforge.net/projects/wxchecksums/) can be used to hash the CRC32 (and MD5) values of many files, all at once. The process is simple: open the program, and select to create a new SFV file. Then, drag and drop all of the files that you want to hash into the program. It will show you a progress bar regarding the hashing progress, which you can also pause/cancel at any time. When it is finished, you will see the list of files, as well as the CRC32 values. This makes for very easy checking of a downloaded series - simply align the name and data columns so that you can see the CRC32 tags in the filenames, and move the CRC32 column close to it. If you like, you can save this SFV file for fast future checking - so long as you keep the filenames the same and have the SFV file in the same directory, doubleclicking the SFV file will cause wxchecksums (or your SFV program of choice) to scan all files with those matching filenames and compare the CRC values on its own. If you don't care to save the SFV file, that's fine too. This makes checking for corruption among your episodes much more time efficient.

(originally posted 2005-06-25, 17:31, recovered 2005-12-21, 05:29)
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