How to compare two ByteArray sections

pol2095

Hello,

how to compare two sections of two ByteArray ?
For example section(4,10) of the first ByteArray is equal to section(10, 16) of the second ByteArray ?

Thanks

JohnBlackburne

I don't think there's any other way than read out the sections of each of them and compare them. Probably quickest is read them out as a String using readMultiByte, then compare them with ==.

I think that would work with all sorts of data, i.e. even if the underlying data is numeric, but you would have to test it yourself. Otherwise reading out the data byte by byte and comparing it would definitely work, if more slowly.

pol2095

It's just to compare the begin of a ByteArray, I will use byte by byte, thanks.

pol2095

I can use flascc too...

JohnBlackburne

If performance was a big concern I would suggest an ANE, to access native code performance. That only makes sense if the extra overhead of handing it off to an ANE is worth it, for the performance gain you will see.

It's only going to be an issue if you are processing a lot of each ByteArray. Starling uses ByteArrays internally, and they are a bottleneck. But that's as you might be updating thousands of bits of data in them every frame, to upload them to the GPU.

pol2095

finally byte by byte is fast enough

pol2095

I tried for 2 files of 400 Mo :
as3 byte by byte : 55 sec
flascc memcmp() : 2 sec

JohnBlackburne

I assumed you were just loading a couple of files or strings and checking a few bytes to see if they were the same. I cannot think of a use case for checking almost 1GB of data !

If you really have to deal with such large data another approach might be better. E.g. you could create a checksum for the data, and compare checksums. This doesn't really help much if the checksums have to be calculated at check time, but if pre-calculated and stored with the data it might save a lot of loading and checking.

pol2095

It's just for testing, thanks.