This commit introduces a common `Preference` class which defines
constants and helper methods (e.g., to convert between an `int8_t`
preference and its 2-bit unsigned representation). This is used for
`RoutePreference` in Network Data entries and also for Parent
Priority in `ConnectivityTlv`.
This commit contains smaller enhancements in `RouteTlv`:
- `RouteTlv::IsValid()` checks that number of allocated IDs in
the Router ID Mask is less than max number of routers.
- It also checks that the TLV contains correct number of Route
Data entries matching the number of allocated router IDs.
- A new method `SetRouteData()` is added to set all the
data fields (link quality in/out and route cost) for a given
router index.
- These changes help ensure that messages containing invalid
`RouteTlv` are rejected (avoid situation where we may have
more allocated router IDs than max routers).
This commit updates the scaling of the link margin and RSSI metrics.
The metric values are scaled when appended in the message (in a
Report sub-TLV) or when they are read back from received message. The
stored value in `MetricsValues` are changed to be always the actual
metric value (not the scaled value). This ensures that the value are
stored in proper int type (e.g., RSSI is `int8` vs the scaled value
which is `[0,255]`). Methods are added to perform the scaling which
now rounds to closest integer ensuring the reverse scaling gives back
the original value. Unit test is added to validate the scaling
methods.
This commit adds generic helper functions:
- `Min()` to get the minimum of two values,
- `Max()` to get the maximum of two values, and
- `Clamp()` to clamp a value to a given closed range from a minimum
up to a maximum value. It also adds functions
- `ClampToUint8()` and `ClampToUint16()` to clamp a `uint` value to
a smaller bit-size (`uint8_t` or `uint16_t`) range.
This commit adds `SerialNumber` class which provides `static` methods
`IsGeater<UintType>()` and `IsLess<UintType()` to compare two serial
numbers, taking into account the wrapping of serial number values
(similar to RFC-1982). This is then used in `MleRouter` and other
modules. This helps us avoid casting of `uint` to `int` for the
comparison (such a casting is undefined behavior in C++11 though
toolchains often implement it as expected). This commit also adds a
unit test `test_serial_number` to validate the new methods.
Abtin Keshavarzian