crc_fast: inefficiency

From: Vladimir Prus (ghost_at_[hidden])
Date: 2001-03-06 09:17:03

crc_fast, despite its name, has a significant performance problem. Namely, if 
input is reversed, the code call a routine to reverse each byte. That 
bit-tossing routine is slow, and as far as I can tell, all practical 
implementation avoid reversing byte, but instread reverse everything else.

I compared performance of current crc_fast with implementation that uses 
optimization mentioned above. On 1Meg buffer with random data crc_fast is 
10 times slower. Without bytes reversing, it's only 2 times slower. So, 
changing code seems worthwhile.

-- 
Regards,	
Vladimir