Properties

Identity

A property is identified by a 64-bit integer +made up of two 32-bit parts: the category and the key.

A property belongs +to a category, and a category is identified by a UID.

A key is a 32-bit +value that identifies a specific property within a category. The meaning applied +to the key depends on the kind of enumeration scheme set up for the category. +At its simplest, a key can be an index value. It can also be another UID, +if the category is designed to be generally extensible.

Type

A property can be:

a single 32-bit value
a contiguous set of +bytes, referred to as a byte-array, whose length can vary from 0 to 512 bytes
Unicode text.

From the viewpoint of the implementation, Unicode text is treated +as a byte-array; the detail is hidden by the API.

Once defined, a property +value can change, but the property type cannot. Byte-array type properties +can also change length provided the length does not exceed the value RProperty::KMaxPropertySize. +The limit on size of property ensures some limit on RAM usage.

+ limit on size of property ensures some limit on RAM usage.

The API +allows byte-array and Unicode text type properties to be pre-allocated when +they are defined. This means that the time taken to set the values is bounded. +However, if the length of these property types subsequently increases, then +memory allocation may take place, and no guarantees can be made on the time +taken to set them.

Note that theRProperty::ELargeByteArray property +type can never provide a real-time guarantee.

Properties and their values +are defined, set and retrieved using RProperty .