Fast File CRC-Checksum Tagging

Posted: 2002-06-01
By: ArchiveBot
Viewed: 80

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Visual Basic 6

Protect your EXEs/OCXs/DLLs by CRC checksum verification - and do it QUICKLY!
Several methods exist to detect file modification, and CRC checking is one of the best. However, CRC checksum generation in VB is slow. Until Fredrik Qvarfort came along, that is... His CRC generator code is amazingly fast. If you combine his CRC code with Detonate's CRC-check-the-whole-EXE idea, you get the code presented here: a file checker that can check a file faster than just about anything else out there and still detect single-byte changes. By fast, we're talking several megabytes a second kind of fast. So fast it takes longer to load a big file into memory in preparation for CRC verification than it does to do the actual verify.
Includes a ready-to-compile CRC-"tagging" tool for creating the CRC markers that are used to verify the file's integrity, as well as Fredrik Qvarfort's CRC class code (with his permission) and demo CRC-check project.
NOTE: I have not tested this code in VB 5, but it's so straightforward that it should work with little or no modifiations.

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