modbus_mapping_new

Name

modbus_mapping_new - allocate four arrays of bits and registers

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

Description

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 ⟨modbus_mapping_new_start_address.md⟩ 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.

Errors

    •   ENOMEM, not enough memory.

Example
    /* 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",
            modbus_strerror(errno)
        );
        modbus_free(ctx);
        return -1;
    }

See also

    •   modbus_mapping_free ⟨modbus_mapping_free.md⟩

    •   modbus_mapping_new_start_address ⟨modbus_mapping_new_start_address.md⟩