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Using iot_data_t


The iot_data_t type is a holder for various types of data, and it is used in the SDK API to hold reading values and name-value collections (maps keyed by string). This chapter describes how to use iot_data_t in interactions with the SDK. It is not a complete guide to either the type or to the IOT utilities package which includes it


The type of data held in an iot_data_t object is represented by the iot_data_type_t type. This can take the following values:

  • IOT_DATA_INT8 IOT_DATA_INT16 IOT_DATA_INT32 IOT_DATA_INT64 for signed integers
  • IOT_DATA_UINT8 IOT_DATA_UINT16 IOT_DATA_UINT32 IOT_DATA_UINT64 for unsigned integers
  • IOT_DATA_FLOAT32 IOT_DATA_FLOAT64 for floating point values
  • IOT_DATA_BOOL for booleans
  • IOT_DATA_STRING for strings
  • IOT_DATA_ARRAY for arrays
  • IOT_DATA_MAP for maps


Instances of iot_data_t are created with the iot_data_alloc_* functions

Primitive types

For primitive types, use

  • iot_data_alloc_i8 iot_data_alloc_i16 iot_data_alloc_i32 iot_data_alloc_i64 for signed integers
  • iot_data_alloc_ui8 iot_data_alloc_ui16 iot_data_alloc_ui32 iot_data_alloc_ui64 for unsigned integers
  • iot_data_alloc_f32 iot_data_alloc_f64 for floats
  • iot_data_alloc_bool for booleans

Each takes a single parameter which is the value to hold


Strings are allocated using iot_data_alloc_string. In addition to the const char* which specifies the string to hold, a further parameter of type iot_data_ownership_t must be provided. This sets the ownership semantics for the string, and can take the following values:

Ownership Meaning
IOT_DATA_REF The created object holds a pointer to the string, ownership remains the responsibility of the calling code. Useful in particular for string constants
IOT_DATA_TAKE The created object takes ownership of the string. It will be freed when the iot_data_t object is freed
IOT_DATA_COPY A copy will be made of the string. This copy will be freed when the iot_data_t object is freed, but the calling code remains responsible for the original

Arrays and Binary data

For array readings use iot_data_alloc_array

Parameter Type Description
data void* A C array of primitive types
length uint32_t The number of elements in the array
type iot_data_type_t The type of the data elements
ownership iot_data_ownership_t Ownership semantics for the data (see description in Strings section)

For binary data allocate an array of uint8_t / IOT_DATA_UINT8


Object-typed readings are represented by a map. Allocate it using

iot_data_alloc_map (IOT_DATA_STRING)

Values are added to the map using the iot_data_string_map_add function

Parameter Type Description
map iot_data_t* The map representing the Object
key char* The name of the field to add. This should be a string literal
val iot_data_t* The value of the field

Accessing values

Primitive types

The accessors for primitive types are

  • iot_data_i8 iot_data_i16 iot_data_i32 iot_data_i64
  • iot_data_ui8 iot_data_ui16 iot_data_ui32 iot_data_ui64
  • iot_data_f32 iot_data_f64
  • iot_data_bool

Each function takes an iot_data_t* as parameter and returns the value in the expected C type


The iot_data_string function returns the char* held in the data object

Arrays and Binary data

  • iot_data_array_length returns the length of an array
  • iot_data_address returns a pointer to the first element
  • iot_data_array_type returns the type of the elements (as iot_data_type_t)

Binary data is represented as an array of uint8_t (ie, IOT_DATA_UINT8)


Use iot_data_string_map_get to obtain the iot_data_t instance representing a field

Parameter Type Description
map iot_data_t* The map representing the Object
key char* The name of the field to retrieve


Instances of iot_data_t are freed using the iot_data_free function