Function AlwaysNull

cpp/src/arrow/type.h:111–111

  static BufferSpec VariableWidth() { return BufferSpec{VARIABLE_WIDTH, -1}; }
  static BufferSpec Bitmap() { return BufferSpec{BITMAP, -1}; }
  static BufferSpec AlwaysNull() { return BufferSpec{ALWAYS_NULL, -1}; }

  /// A vector of buffer layout specifications, one for each expected buffer
  std::vector<BufferSpec> buffers;