Function scanForUnloadedRanges

source/InfiniteLoader/InfiniteLoader.js:174–247

({
  isRowLoaded,
  minimumBatchSize,
  rowCount,
  startIndex,
  stopIndex,
})

 * Returns all of the ranges within a larger range that contain unloaded rows.
 */
export function scanForUnloadedRanges({
  isRowLoaded,
  minimumBatchSize,
  rowCount,
  startIndex,
  stopIndex,
}) {
  const unloadedRanges = [];

  let rangeStartIndex = null;
  let rangeStopIndex = null;

  for (let index = startIndex; index <= stopIndex; index++) {
    let loaded = isRowLoaded({index});

    if (!loaded) {
      rangeStopIndex = index;
      if (rangeStartIndex === null) {
        rangeStartIndex = index;
      }
    } else if (rangeStopIndex !== null) {
      unloadedRanges.push({
        startIndex: rangeStartIndex,
        stopIndex: rangeStopIndex,
      });

      rangeStartIndex = rangeStopIndex = null;
    }
  }

  // If :rangeStopIndex is not null it means we haven't ran out of unloaded rows.
  // Scan forward to try filling our :minimumBatchSize.
  if (rangeStopIndex !== null) {
    const potentialStopIndex = Math.min(
      Math.max(rangeStopIndex, rangeStartIndex + minimumBatchSize - 1),
      rowCount - 1,
    );

    for (let index = rangeStopIndex + 1; index <= potentialStopIndex; index++) {
      if (!isRowLoaded({index})) {
        rangeStopIndex = index;
      } else {
        break;
      }
    }

    unloadedRanges.push({
      startIndex: rangeStartIndex,
      stopIndex: rangeStopIndex,
    });
  }

  // Check to see if our first range ended prematurely.
  // In this case we should scan backwards to try filling our :minimumBatchSize.
  if (unloadedRanges.length) {
    const firstUnloadedRange = unloadedRanges[0];

    while (