lr-core/src/utils/hashNumberPair.js

Line Rider core library

// http://stackoverflow.com/a/13871379
export function hashUIntPair (a, b) {
  return (a >= b) ? (a * a + a + b) : (b * b + a)
}

export function unhashUIntPair (n) {
  let x = Math.sqrt(n) | 0 // x = a < b ? b : a
  let r = n - x * x //        r = a < b ? a : a+b
  if (r < x) { // r = a, x = b, a < b
    return [r, x]
  } else { // r = a+b, x = a
    return [x, r - x]
  }
}

export function hashIntPair (a, b) {
  let A = a >= 0 ? 2 * a : -2 * a - 1
  let B = b >= 0 ? 2 * b : -2 * b - 1
  let C = (A >= B) ? (A * A + A + B) : (B * B + A)
  return (C & 1) ? -(C - 1) / 2 - 1 : C / 2
}

export function unhashIntPair (n) {
  let C = n >= 0 ? n * 2 : (-(n + 1) * 2 + 1)
  let [A, B] = unhashUIntPair(C)
  let a = (A & 1) ? -(A + 1) / 2 : A / 2
  let b = (B & 1) ? -(B + 1) / 2 : B / 2
  return [a, b]
}