Function murmurhash

src/lib/murmurhash.ts:10–75

(key: string)

 */

export function murmurhash(key: string) {
  const remainder = key.length & 3
  const bytes = key.length - remainder
  const c1 = 0xcc9e2d51
  const c2 = 0x1b873593

  let h1 = 0
  let i = 0

  while (i < bytes) {
    let k1 =
      (key.charCodeAt(i) & 0xff) |
      ((key.charCodeAt(++i) & 0xff) << 8) |
      ((key.charCodeAt(++i) & 0xff) << 16) |
      ((key.charCodeAt(++i) & 0xff) << 24)
    ++i

    k1 =
      ((k1 & 0xffff) * c1 + ((((k1 >>> 16) * c1) & 0xffff) << 16)) & 0xffffffff
    k1 = (k1 << 15) | (k1 >>> 17)
    k1 =
      ((k1 & 0xffff) * c2 + ((((k1 >>> 16) * c2) & 0xffff) << 16)) & 0xffffffff

    h1 ^= k1
    h1 = (h1 << 13) | (h1 >>> 19)
    const h1b =
      ((h1 & 0xffff) * 5 + ((((h1 >>> 16) * 5) & 0xffff) << 16)) & 0xffffffff
    h1 = (h1b & 0xffff) + 0x6b64 + ((((h1b >>> 16) + 0xe654) & 0xffff) << 16)
  }

  let k2 = 0

  switch (remainder) {
    case 3:
      k2 ^= (key.charCodeAt(i + 2) & 0xff) << 16
    case 2:
      k2 ^= (key.charCodeAt(i + 1) & 0xff) << 8
    case 1:
      k2 ^= key.charCodeAt(i) & 0xff

      k2 =
        ((k2 & 0xffff) * c1 + ((((k2 >>> 16) * c1) & 0xffff) << 16)) &
        0xffffffff
      k2 = (k2 << 15) | (k2 >>> 17)
      k2 =
        ((k2 & 0xffff) * c2 + ((((k2 >>> 16) * c2) & 0xffff) << 16)) &
        0xffffffff
      h1 ^= k2
  }

  h1 ^= key.length

  h1 ^= h1 >>> 16
  h1 =
    ((h1 & 0xffff) * 0x85ebca6b +
      ((((h1 >>> 16) * 0x85ebca6b) & 0xffff) << 16)) &
    0xffffffff
  h1 ^= h1 >>> 13