Home » Pages » Visual Foxpro

Adler32 Checksum

By Sergey - Posted on January 1st, 2008
Tagged:

Adler32 is different from CRC32. It's much faster but a little bit less reliable.
The free ZLIB.DLL from http://www.zlib.net/ has a function to calculate Adler32.

This is sample code. Add error handling and adjust to your requirements as necessary.

DECLARE Long adler32 IN Zlib Long Adler32, String Buffer, Long BuffLen
 
&& Initialize Adler32 and calculate 1st checksum
lnAdler32 = adler32(0, Null, 0)
lcText = "Adler32 checksum"
lnAdler32 = adler32(lnAdler32, lcText, LEN(lcText))
? TRANSFORM(lnAdler32, "@0")
 
&& Initialize Adler32 again and calculate 2nd checksum
lnAdler32 = adler32(0, Null, 0)
lcText = "DECLARE Long adler32 IN Zlib Long Adler32, String Buffer, Long BuffLen"
lnAdler32 = adler32(lnAdler32, lcText, LEN(lcText))
? TRANSFORM(lnAdler32, "@0")