Function splitI64

src/parseTools.mjs:301–340

(value)

// value, represented by a low and high i32 pair.
// Will suffer from rounding and truncation.
function splitI64(value) {
  if (WASM_BIGINT) {
    // Nothing to do: just make sure it is a BigInt (as it must be of that
    // type, to be sent into wasm).
    return castToBigInt(value);
  }

  // general idea:
  //
  //  $1$0 = ~~$d >>> 0;
  //  $1$1 = Math.abs($d) >= 1 ? (
  //     $d > 0 ? Math.floor(($d)/ 4294967296.0) >>> 0
  //            : Math.ceil(Math.min(-4294967296.0, $d - $1$0)/ 4294967296.0)
  //  ) : 0;
  //
  // We need to min on positive values here, since our input might be a double,
  // and large values are rounded, so they can be slightly higher than expected.
  // And if we get 4294967296, that will turn into a 0 if put into a HEAP32 or
  // |0'd, etc.
  //
  // For negatives, we need to ensure a -1 if the value is overall negative,
  // even if not significant negative component

  const low = value + '>>>0';
  // prettier-ignore
  const high = makeInlineCalculation(
      asmCoercion('Math.abs(VALUE)', 'double') + ' >= ' + asmEnsureFloat('1', 'double') + ' ? ' +
        '(VALUE > ' + asmEnsureFloat('0', 'double') + ' ? ' +
        asmCoercion('Math.floor((VALUE)/' +
        asmEnsureFloat(4294967296, 'double') + ')', 'double') + '>>>0' +
        ' : ' +
        asmFloatToInt(asmCoercion('Math.ceil((VALUE - +((' + asmFloatToInt('VALUE') + ')>>>0))/' +
        asmEnsureFloat(4294967296, 'double') + ')', 'double')) + '>>>0' +
        ')' +
      ' : 0',
      value,
      'tempDouble',
  );
  return [low, high];
}

// Misc