What are the parameters CanardOnTransferReception on_reception and CanardShouldAcceptTransfer should_accept in canardInit?

YGQ · April 16, 2019, 6:03am

How should these two parameters be understood?

pavel.kirienko · August 1, 2019, 10:08pm

Sorry that your question was looked over! These are pointers to callback handlers. on_reception is invoked when a new transfer is received (and validated for data integrity) by libcanard. should_accept is invoked when libcanard receives a new transfer and it needs to understand if the transfer is of interest to the application. This is actually explained in the docs:

github.com

UAVCAN/libcanard/blob/4244b8c0b303ac02a20fd603844179809bee59b3/canard.h#L164-L186


/**
* The application must implement this function and supply a pointer to it to the library during initialization.
* The library calls this function to determine whether the transfer should be received.
*
* If the application returns true, the value pointed to by 'out_data_type_signature' must be initialized with the
* correct data type signature, otherwise transfer reception will fail with CRC mismatch error. Please refer to the
* specification for more details about data type signatures. Signature for any data type can be obtained in many
* ways; for example, using the command line tool distributed with Libcanard (see the repository).
*/
typedef bool (* CanardShouldAcceptTransfer)(const CanardInstance* ins,          ///< Library instance
                                           uint64_t* out_data_type_signature,  ///< Must be set by the application!
                                           uint16_t data_type_id,              ///< Refer to the specification
                                           CanardTransferType transfer_type,   ///< Refer to CanardTransferType
                                           uint8_t source_node_id);            ///< Source node ID or Broadcast (0)


/**
* This function will be invoked by the library every time a transfer is successfully received.
* If the application needs to send another transfer from this callback, it is highly recommended
* to call canardReleaseRxTransferPayload() first, so that the memory that was used for the block
* buffer can be released and re-used by the TX queue.

This file has been truncated. show original