This commit introduces the `OffsetRange` class, which represents a
range of offsets within a `Message` or data buffer (i.e., a starting
offset and a length indicating the number of bytes in the range).
The class provides methods for common operations:
- Getting the start or end offset, or the remaining length.
- Checking if the range is empty or contains a certain number of
bytes.
- Advancing the start offset by a given amount, ensuring it never goes
beyond the end offset.
- Shrinking the range's length.
The new `OffsetRange` class simplifies methods that previously used
separate `aOffset` and `aLength` input parameters, improving code
readability and maintainability. It also facilitates reading and
processing content within a specified range.
For example, `Tlv::FindTlvValueOffsetRange()` now directly returns an
`OffsetRange` indicating the location of the TLV value. The `Message`
class is also updated with new `Read()` and `Append()` method variants
that accept `OffsetRange` arguments. These methods ensure that read
content is contained within the specified `OffsetRange`.
This commit moves the `instance` module to a newly added folder
`core/instance` (from `core/common`. Header file `extension.hpp`
and its example is also moved to the same folder.
This commit adds new private type `ParsedInfo` in `Tlv` class
which contains parsed TLV info such as TLV type, length, size,
value offset. This class provides `ParseFrom()` and `FindIn()`
methods to parse or find a TLV from a message.
This commit also adds a unit test `test_tlv` to validate the TLV
methods.
Abtin Keshavarzian