minix/lib/libvtreefs/sdbm.c

   1 /* VTreeFS - sdbm.c - sdbm hash function */
   2
   3 /*
   4  * sdbm - ndbm work-alike hashed database library
   5  * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
   6  * author: oz@nexus.yorku.ca
   7  * status: public domain. keep it that way.
   8  *
   9  * hashing routine
  10  */
  11
  12 #include "inc.h"
  13
  14 /*
  15  * polynomial conversion ignoring overflows
  16  * [this seems to work remarkably well, in fact better
  17  * than the ndbm hash function. Replace at your own risk]
  18  * use: 65599   nice.
  19  *      65587   even better.
  20  */
  21 long
  22 sdbm_hash(const char *str, int len)
  23 {
  24         unsigned long n = 0;
  25
  26         while (len--)
  27                 n = *str++ + (n << 6) + (n << 16) - n;
  28
  29         return n;
  30 }