I found this mentioned in a old user comment (it might not be relevant now): "Some quick reverse engineering shows they're using the standard CRC32 parameters:
Polynomial 0x04C11DB7l Initial register value 0xFFFFFFFF Register is inverted at end of calculation Bytes are reflected as they come in, and the result is reflected before it is returned. The documentation says this function returns the CRC polynomial of the string - that's a little misleading IMHO. I'd say it simply returns the CRC of the string. The polynomial is a magic number in the calculation." and I've just downloaded the lastest source and found the crc32 function to be in crc32.c and crc32.h. In the comments it mentions that the polynomial is /* generated using the AUTODIN II polynomial * x^32 + x^26 + x^23 + x^22 + x^16 + * x^12 + x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x^1 + 1 */ and there is a big table of 256 number which you may find useful. Oh finally I also found mentioned in the NEWS file that: "- Added a crc32 checksum function - used by the UdmSearch search engine and currently run through a system call. This will speed up the UdmSearch php frontend significantly. (Rasmus)" Which seems to be called udm_crc32, and so far undocumented. I hope this information has been useful. Andrew ----- Original Message ----- From: "Methusula" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, August 22, 2003 1:01 PM Subject: [PHP] CRC and Polynomials > Hi, > > Can anyone tell me which 32-bit polynomial is used by PHP in the crc > function? I am trying to write a crc function from scratch, however, php > does not appear to use any of the most commonly used polynomial divisors. > > Methusula. > > > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > > -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
