6. Optional parameters

The functions build_tlv( ... ) and destroy_tlv( ... ) allow to create and destroy elements linked in a list of variables called optional parameters. This parameters are in some data structures in the SMPP-3.4 protocol, and they are called optional parameters.

int build_tlv( tlv_t **dest, 
               tlv_t  *source );

int destroy_tlv( tlv_t *sourceList );
    
Where:

dest: This pointer is a reference to pointer of data type tlv_t. In an example, we'll see how use this function.

source: This pointer is a reference to tlv_t.

sourceList: This pointer is a reference to tlv_t. In destroy_tlv( ... ) the parameter is a list linked reference.

6.1. An example

The use of optional parameters is bounded to data type tlv_t that is not present in all data structures of SMPP-3.4 protocol We'll see an example of this function.

#define TEXTO "mensaje de texto numero 01"
:
{
    submit_sm_t pdu;
    tlv_t tlv;

    memset(&tlv, 0, sizeof(tlv_t));
    tlv.tag = TLVID_user_message_reference;   /* tag present in submit_sm */
    tlv.length = sizeof(uint16_t);
    tlv.value.val16 = 0x0024;                                    /* valor */
    build_tlv( &(pdu.tlv), &tlv );    /* value attached to main structure */

    memset(&tlv, 0, sizeof(tlv_t));
    tlv.tag = TLVID_more_messages_to_send;    /* tag present in submit_sm */
    tlv.length = sizeof(uint8_t);
    tlv.value.val8 = 0x24;                                       /* valor */
    build_tlv( &(pdu.tlv), &tlv );    /* value attached to main structure */

    memset(&tlv, 0, sizeof(tlv_t));
    tlv.tag = TLVID_message_payload;          /* tag present in submit_sm */
    tlv.length = strlen(TEXTO);
    memcpy(tlv.value.octet, TEXTO, tlv.length);                  /* valor */
    build_tlv( &(pdu.tlv), &tlv );    /* value attached to main structure */

    /* Pack and send data in pdu */

    destroy_tlv( pdu.tlv ); /* Free pdu list */
}