Re: Search through a (large) binary file.

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On Thu, 10 Sep 2009 16:43:16 +0200, "Michelle"
<michelle@xxxxxxxxxxxxxxx> wrote:

I need some help to search through a (sometimes large) binary file.

I'd like to search within this binary file for a pattern containing a
particular hex value (e.g. FF56131A1B087B15610800151E).
When the pattern is found, i need to know the (start) offset, because then I'd
like to read the 4 previous bytes (need the hex values).
I suppose that i need to read the file in blocks (500 kb or 1 mb) because
it's a large file.

I 'am a rookie using C#, so if possible please share a piece of code.

Thanks in advance,

Michelle

This is essentially a string searching problem. Google for the
"Rabin-Karp Algorithm", the "Knuth-Morris-Pratt Algorithm" and the
"Boyer-Moore Algorithm". If there is more than one possible pattern
to search for then Rabin-Karp is the best as it can search for
multiple patterns in a single pass. If there is only a single pattern
to match then use one of the other two as they will be faster at
finding a single target.

Google will find example C# code for all three algorithms.

rossum

.

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