Octtools

int st_strhash(string, modulus)
     register char *string;
     int modulus;
{
  register long val = 0;
  register int c;

  while ((c = *string++) != '\0') {
    val = val*997 + c;
  }

  /* Shachindra Sharma writes:

       ".. will have a problem when the value variable "val" is equal
       to the maximum negative integer value (for the particular OS its being
       run on say if its 32 bit OS the value would be -2^31 = -2147483648)
       val < 0 ? -val : val will still be -val for such a case due to the
       property of maximum negative integer that -val == val.

       As an example if we have a input string to this function like
       the one given below:

       "TRDTOP_HIP_UHIF1_HPDMA_UHPDREG1_HPDRCH3E1MCUADDR[20]"

       the value of the variable "val" would be -2147483648 resulting
       in a negative value being returned by the function which could result
       in problems for the user is OS was 32 bit. The hash function otherwise
       for any values of "val" larger or smaller than this value would work
       fine so the probabilty of such a situation is rather low.
  */
  if (val == -val) {
    unsigned int newhash = -val;
    return (newhash%modulus);
  } else {
    return ((val < 0) ? -val : val)%modulus;
  }
}