modbus_mapping_new - Man Page

allocate four arrays of bits and registers


modbus_mapping_t modbus_mapping_new(int nb_bits, int nb_input_bits, int nb_registers, int nb_input_registers);*


The modbus_mapping_new() function shall allocate four arrays to store bits, input bits, registers and inputs registers. The pointers are stored in modbus_mapping_t structure. All values of the arrays are initialized to zero.

This function is equivalent to a call of the modbus_mapping_new_start_address(3) function with all start addresses to 0.

If it isn’t necessary to allocate an array for a specific type of data, you can pass the zero value in argument, the associated pointer will be NULL.

This function is convenient to handle requests in a Modbus server/slave.

Return Value

The function shall return the new allocated structure if successful. Otherwise it shall return NULL and set errno.



Not enough memory


/* The first value of each array is accessible from the 0 address. */
mb_mapping = modbus_mapping_new(BITS_ADDRESS + BITS_NB,
                                INPUT_BITS_ADDRESS + INPUT_BITS_NB,
                                REGISTERS_ADDRESS + REGISTERS_NB,
                                INPUT_REGISTERS_ADDRESS + INPUT_REGISTERS_NB);
if (mb_mapping == NULL) {
    fprintf(stderr, "Failed to allocate the mapping: %s\n",
    return -1;

See Also

modbus_mapping_free(3) modbus_mapping_new_start_address(3)


The libmodbus documentation was written by Stéphane Raimbault <>

Referenced By

libmodbus(7), modbus_mapping_free(3), modbus_mapping_new_start_address(3).

10/18/2021 libmodbus v3.1.6 libmodbus Manual