index.ts

// this algorithm was created for sdbm (a public-domain reimplementation of ndbm) database library. it was found to do
// well in scrambling bits, causing better distribution of the keys and fewer splits. it also happens to be a good
// general hashing function with good distribution. the actual function is hash(i) = hash(i - 1) * 65599 + str[i];
// what is included below is the faster version used in gawk. [there is even a faster, duff-device version] the
// magic constant 65599 was picked out of thin air while experimenting with different constants, and turns
// out to be a prime. this is one of the algorithms used in berkeley db (see sleepycat) and elsewhere.
export function sdbm(string: string) {
  let hash = 0;

  for (const c of string) {
    hash = c.charCodeAt(0) + (hash << 6) + (hash << 16) - hash;
  }

  // Unsigned shift right
  return hash >>> 1;
}