Because it can be memorized and works reasonably well:
unsigned long
hash(unsigned char *str)
{
unsigned long hash = 5381;
int c;
while (c = *str++)
hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
return hash;
}
All one needs to remember is a single line and a number. For years SuperFastHash had been my first choice but the Non-Cryptographic Hash Function Zoo analysis changed this.
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