Class TokenRange

lib/token.js:137–282

* Represents a range of tokens on a Cassandra ring. * * A range is start-exclusive and end-inclusive. It is empty when * start and end are the same token, except if that is the minimum * token, in which case the range covers the whole ring (this is * consistent with the behavior of CQL range q

 * in a range, see {@link unwrap}.
 */
class TokenRange {
  constructor(start, end, tokenizer) {
    this.start = start;
    this.end = end;
    Object.defineProperty(this, '_tokenizer', { value: tokenizer, enumerable: false});
  }

  /**
   * Splits this range into a number of smaller ranges of equal "size"
   * (referring to the number of tokens, not the actual amount of data).
   *
   * Splitting an empty range is not permitted.  But not that, in edge
   * cases, splitting a range might produce one or more empty ranges.
   *
   * @param {Number} numberOfSplits Number of splits to make.
   * @returns {TokenRange[]} Split ranges.
   * @throws {Error} If splitting an empty range.
   */
  splitEvenly(numberOfSplits) {
    if (numberOfSplits < 1) {
      throw new Error(util.format("numberOfSplits (%d) must be greater than 0.", numberOfSplits));
    }
    if (this.isEmpty()) {
      throw new Error("Can't split empty range " + this.toString());
    }

    const tokenRanges = [];
    const splitPoints = this._tokenizer.split(this.start, this.end, numberOfSplits);
    let splitStart = this.start;
    let splitEnd;
    for (let splitIndex = 0; splitIndex < splitPoints.length; splitIndex++) {
      splitEnd = splitPoints[splitIndex];
      tokenRanges.push(new TokenRange(splitStart, splitEnd, this._tokenizer));
      splitStart = splitEnd;
    }
    tokenRanges.push(new TokenRange(splitStart, this.end, this._tokenizer));
    return tokenRanges;
  }

  /**
   * A range is empty when start and end are the same token, except if
   * that is the minimum token, in which case the range covers the
   * whole ring.  This is consistent with the behavior of CQL range
   * queries.
   *
   * @returns {boolean} Whether this range is empty.
   */
  isEmpty() {
    return this.start.equals(this.end) && !this.start.equals(this._tokenizer.minToken());
  }

  /**
   * A range wraps around the end of the ring when the start token
   * is greater than the end token and the end token is not the 
   * minimum token.
   *
   * @returns {boolean} Whether this range wraps around.
   */