class BatchMemoryQueue

class BatchMemoryQueue extends MemoryQueue {

  /**
   * Overrides MemoryQueue::claimItem().
   *
   * Unlike MemoryQueue::claimItem(), this method provides a default lease
   * time of 0 (no expiration) instead of 30. This allows the item to be
   * claimed repeatedly until it is deleted.
   */
  public function claimItem($lease_time = 0) {
    if (!empty($this->queue)) {
      reset($this->queue);
      return current($this->queue);
    }
    return FALSE;
  }

  /**
   * Retrieves all remaining items in the queue.
   *
   * This is specific to Batch API and is not part of the DrupalQueueInterface.
   */
  public function getAllItems() {
    $result = array();
    foreach ($this->queue as $item) {
      $result[] = $item->data;
    }
    return $result;
  }
}

og-7.x-1.x.database.php in sites/all/modules/ulmus/og/tests/og-7.x-1.x.database.php

Filled installation of Drupal 7.0, for test purposes.

_batch_populate_queue in includes/form.inc

Populates a job queue with the operations of a batch set.