libmodbus/doc/modbus_mapping_offset_new.txt

modbus_mapping_offset_new(3)
============================


NAME
----
modbus_mapping_offset_new - allocate four arrays of bits and registers


SYNOPSIS
--------
*modbus_mapping_t* modbus_mapping_new(int 'nb_bits', int 'offset_bits',
                                      int 'nb_input_bits', int 'offset_input_bits',
                                      int 'nb_registers', int 'offset_registers',
                                      int 'nb_input_registers', int 'offset_input_registers');*


DESCRIPTION
-----------
The _modbus_mapping_offset_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.

The different offsets make it possible to place the mapping at any address in
each address space.

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 _modbus_mapping_offset_new()_ function shall return the new allocated structure if
successful. Otherwise it shall return NULL and set errno.


ERRORS
------
ENOMEM::
Not enough memory


EXAMPLE
-------
[source,c]
-------------------
/* The first value of each array is accessible at address 4. */
mb_mapping = modbus_mapping_offset_new(BITS_ADDRESS + BITS_NB, 4,
                                INPUT_BITS_ADDRESS + INPUT_BITS_NB, 4,
                                REGISTERS_ADDRESS + REGISTERS_NB, 4,
                                INPUT_REGISTERS_ADDRESS + INPUT_REGISTERS_NB, 4);
if (mb_mapping == NULL) {
    fprintf(stderr, "Failed to allocate the mapping: %s\n",
            modbus_strerror(errno));
    modbus_free(ctx);
    return -1;
}
-------------------

SEE ALSO
--------
linkmb:modbus_mapping_free[3]


AUTHORS
-------
The libmodbus documentation was written by Stéphane Raimbault
<stephane.raimbault@gmail.com>