static FrequentDirections heapify()

in src/main/java/org/apache/datasketches/vector/decomposition/FrequentDirections.java [115:148]

• 28 lines of code
• 4 McCabe index (conditional complexity)

  static FrequentDirections heapify(final Memory srcMem, final MatrixType type) {
    final int preLongs = getAndCheckPreLongs(srcMem);
    final int serVer = extractSerVer(srcMem);
    if (serVer != SER_VER) {
      throw new IllegalArgumentException("Invalid serialization version: " + serVer);
    }

    final int family = extractFamilyID(srcMem);
    if (family != MatrixFamily.FREQUENTDIRECTIONS.getID()) {
      throw new IllegalArgumentException("Possible corruption: Family id (" + family + ") "
              + "is not a FrequentDirections sketch");
    }

    final int k = extractK(srcMem);
    final int numRows = extractNumRows(srcMem);
    final int d = extractNumColumns(srcMem);
    final boolean empty = (extractFlags(srcMem) & EMPTY_FLAG_MASK) > 0;

    if (empty) {
      return new FrequentDirections(k, d);
    }

    final long offsetBytes = (long)preLongs * Long.BYTES;
    final long mtxBytes = srcMem.getCapacity() - offsetBytes;
    final Matrix B = Matrix.heapify(srcMem.region(offsetBytes, mtxBytes), type);
    assert B != null;

    final FrequentDirections fd = new FrequentDirections(k, d, B, B.getMatrixType());
    fd.n_ = extractN(srcMem);
    fd.nextZeroRow_ = numRows;
    fd.svAdjustment_ = extractSVAdjustment(srcMem);

    return fd;
  }