CODEWITHSUNDEEP
c#arraysmicro-optimization
makerofthings7
makerofthings7

Reputation: 61433

What is the fastest way to scan a C# byte[] for two bytes on a 64 bit computer and return the location?

I have an in-memory byte[] and need to locate the offset where 13 and 10 are. I will then use the following to extract that line:

 String oneLine = Encoding.ASCII.GetString(bytes, 0, max);

What is the fastest way to search for the two bytes on a x64 bit computer? ..and convert it to a string?

Is there anything I can do other than iterating through each byte, scanning for 13 and then scan for 10? 

// Disclaimer: 
// This is just for my curiosity.  Perhaps I'll gain a better understanding of
// how .NET interfaces with RAM, the CPU instructions related to comparisons, etc.
//  
// I don't suspect a performance problem, but I do suspect a lack of understanding
// (on my part) on how C# does low-level operations.

Upvotes: 3

Views: 1587

Answers (2)

user957902
user957902

Reputation: 3060

Since you are looking for a two byte sequence, you don't have to scan every byte, just every other one. If the target index contains a 13, then look at the next byte for a 10. If the target index contatins a 10, look at the previous byte for a 13. That should cut your scan time approximatly in half over a linear search.

Upvotes: 1

Raghu
Raghu

Reputation: 2758

Not sure if it will be 'the fastest way' but you can look at Boyer-Moore algorithm to find the indexes of the required values.

Have a look at this SO thread Search longest pattern in byte array in C#

Boyer-Moore would be better than a linear array traversal because it can skip elements depending on the length of you 'needle' and it gets better as the 'haystack' gets bigger. HTH.

Upvotes: 1

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