Compare contents by hash from context menu

[grindax]

From outside BC, if I choose two binary files that are large (e.g. 4GB iso files), and choose from the context menu to compare them using Beyond Compare, it seems that this launches a byte-by-byte comparison in the Quick Compare.

After several minutes of hearing my hard drive grinding away trying to compare these huge files in this manner, I gave up and cancelled the operation. I pointed a hash-checking program at the 2 files and was given a result within a few seconds.

Is there a way to make BC do a hash check by default instead when it's launched from the context menu?

[Aaron]

Hello,

You can configure if the Quick compare performs a Binary or Rules-based compare on startup. In the Tools menu -> Options, Startup section, is it set to Binary or Rules-based? You would want to use Binary, which, if the file sizes are different should return results quickly. Otherwise, we would need to scan the file until a difference is found.

A Rules-based scan would scan larger parts of the file, and would likely fail on a file that large (4 gigs is larger than our Hex Compare generally supports).

[grindax]

Hi Aaron

I've already got that option set to 'Binary quick compare'.

The files I'm comparing are exactly the same size. I want to confirm that they're exact matches.

So my question is: is there a way to make it hash the files rather than compare byte-by-byte? BC takes ages to compare these files byte-by-byte, and works the disk drive very hard. I would much rather have BC check the hashes which could be completed in just a few seconds.

[Aaron]

Hashing can be faster because it will scan one file then the other, but needs to scan through the whole file to generate the hash. The binary compare will scan both files simultaneously, and stop as soon as a difference is found, but if both files are on the same disk this can lower the performance.

If you go to the Tweaks dialog (Ctrl+Shift+T), File Views tab, and increase the buffer (16 MB), this should help. There is no way to force a CRC comparison from the quick compare; you would need to align the files and use the Folder Compare's interface for a CRC scan.

[grindax]

Thanks Aaron, setting the buffer size to 16777216 bytes made it a lot faster. Question #1: Is 16MB the largest size the buffer can be set to?

Question #2: For future versions, can it please be made possible to choose CRC comparison for quick compare on binary files?

Question #3: Out of interest, what hash algorithm is used for CRC comparisons (e.g. MD5, CRC32, SHA1, etc) ?

[Aaron]

Hello,

1. It isn't the largest but you'll see diminishing returns if it is set too large. 16 seems to be a good number for most people.

2. It is not likely we would add CRC to the Quick Compare. If we were to enhance this behavior, we would try to improve the performance of the Binary Compare, as this does not need to scan the entire file.

3. CRC32, which helps when working with archive files and the xCRC FTP command.