Libcanard for UAVCAN/CAN v1 is released

Applications & Usage Libcanard
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Here is the migration guide from Libcanard v0.100 to the stable v1.0.0. It is super short:

  1. Update your subject-ID idenfiers by clearing the two most significant bits. The maximum subject-ID was 32767 (15 bits), it was contracted down to 8191 (13 bits) in the Specification v1.0-beta. For example, the subject-ID of 32085 (0x7d55) would become 7509 (0x1d55). Notice that in many cases, this change does not really affect wire compatiblity between v0.100 and v1.0.0 (unless low subject-ID values are used) because the two removed bits are set to 1 when transmitting and ignored when receiving. This is now stabilized in Specification.

  2. When creating new subscriptions, the parameter extent should contain the extent of the data type, not just the maximum size of the object. Here is the explanation from the docs:

    The “extent” refers to the minimum amount of memory required to hold any serialized representation of any compatible version of the data type; or, in other words, it is the maximum possible size of received objects. This parameter is determined by the data type author at the data type definition time. It is typically larger than the maximum object size in order to allow the data type author to introduce more fields in the future versions of the type; for example, MyMessage.1.0 may have the maximum size of 100 bytes and the extent 200 bytes; a revised version MyMessage.1.1 may have the maximum size anywhere between 0 and 200 bytes. It is always safe to pick a larger value if not sure. You will find a more rigorous description in the UAVCAN Specification.

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