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Encoding Helpers

CoRE Link-Format and SenML-JSON encoding for LWM2M payloads.

This module provides serialization functions used internally by the LWM2M client and available for direct use by applications:

Functions​

Encode registered objects as CoRE Link-Format for registration payload.

int wb_lwm2m_encode_link_format(const wb_lwm2m_object_def_t *const *objects, size_t object_count, char *buf, size_t buf_size)

Parameters:

  • objects (const wb_lwm2m_object_def_t *const *): Array of object definitions
  • object_count (size_t): Number of objects
  • buf (char *): Output buffer
  • buf_size (size_t): Size of output buffer

Returns:

Number of bytes written (excluding NUL), or -1 on error

Produces a string like: </1/0>,</3/0>,</5/0>

wb_lwm2m_encode_senml_json​

Encode a single resource value as SenML-JSON.

int wb_lwm2m_encode_senml_json(uint16_t obj_id, uint16_t inst_id, uint16_t res_id, const wb_lwm2m_value_t *value, char *buf, size_t buf_size)

Parameters:

  • obj_id (uint16_t): Object ID
  • inst_id (uint16_t): Instance ID
  • res_id (uint16_t): Resource ID
  • value (const wb_lwm2m_value_t *): Resource value
  • buf (char *): Output buffer
  • buf_size (size_t): Size of output buffer

Returns:

Number of bytes written (excluding NUL), or -1 on error

Supports all LWM2M data types: String/CoreLnk -> "vs" (string value) Integer/Time -> "v" (numeric value, signed) UInteger -> "v" (numeric value, unsigned) Float -> "v" (numeric value) Boolean -> "vb" (boolean value) Opaque -> "vd" (base64-encoded data value) Objlink -> "vlo" (object link "objId:instId")

Produces: [{"bn":"/3/0/","n":"0","vs":"WhirlingBits"}]

wb_lwm2m_encode_senml_json_instance​

Encode all readable resources of an object instance as SenML-JSON.

int wb_lwm2m_encode_senml_json_instance(const wb_lwm2m_object_def_t *obj, uint16_t inst_id, char *buf, size_t buf_size)

Parameters:

  • obj (const wb_lwm2m_object_def_t *): Object definition
  • inst_id (uint16_t): Instance ID
  • buf (char *): Output buffer
  • buf_size (size_t): Size of output buffer

Returns:

Number of bytes written (excluding NUL), or -1 on error

Iterates all resources, calls each read callback, and produces a single SenML-JSON array with a shared base name.