3.2 Object Model and Data Types

SDDS++ represents the header separately from page data and uses typed C++ values instead of untyped allocation routines. The principal types are:

• Layout — The complete immutable description of parameters, arrays, columns, associates, data mode, byte order, major order, and protocol version.
• LayoutBuilder — A validating fluent builder for a new layout.
• LayoutEditor — A fluent editor for copying, renaming, replacing, adding, and dropping definitions in an existing layout.
• Scalar — A std::variant containing one parameter or cell value of any supported SDDS type.
• Values — A std::variant containing a homogeneous std::vector of any supported SDDS type.
• ArrayData — Array dimensions together with flattened values in SDDS storage order.
• Page — Parameter, array, and column values for one data page, together with its complete layout and field-loading state.
• Reader and Writer — Move-only streaming objects for input, output, append, and update operations.

The relationship between SDDS types and exact C++ value types is shown below.

typeOf returns the SDDS type represented by a Scalar or Values object, and typeName returns its protocol name. Exact typed access is available through methods such as parameterAs<T>, columnAs<T>, and arrayAs<T>. The corresponding parameterConverted<T>, columnConverted<T>, and arrayConverted<T> methods perform checked numeric conversion. Overflow or invalid narrowing throws TypeError; floating-point-to-integer conversion requires an explicit RoundingMode unless the value is already integral.