5. Data format descriptor

The layout of the data structures described here are assumed to be little-endian for the purposes of data transfer, but may be implemented in the natural endianness of the platform for internal use.

The data format descriptor consists of a contiguous area of memory, divided into one or more descriptor blocks which are tagged by the type of descriptor that they contain. The size of the data format descriptor varies according to its content.

Table 7. Data Format Descriptor layout



Descriptor block

first descriptor

Descriptor block

second descriptor (optional) etc.

The total_size field, measured in bytes, allows the full format descriptor to be copied without need for details of the descriptor to be interpreted.

Table 8. Data format descriptor header and descriptor blocks


Descriptor block 1

Descriptor block 2