Compute Adler-32 (used by zlib, PNG zTXt, gzip trailer of RFC 1950) and Fletcher-16/32 checksums for text, hex bytes, or files. Fast, streaming-friendly alternatives to CRC with weaker error detection but simpler math.
Adler-32 (RFC 1950): two 16-bit sums modulo 65521 combined into a 32-bit value. Faster than CRC-32 in software but weaker for short inputs. Used by zlib / gzip.
Fletcher-16: two 8-bit running sums modulo 255; Fletcher-32 uses 16-bit sums modulo 65535. Designed by John G. Fletcher at LLNL as a lightweight alternative to CRC.
Standard check: the Adler-32 of "Wikipedia" is 0x11E60398.