demo-delete.c

This example demonstrates how to publish a derived symbol when a base symbol has a field value within a configured range. If the field value is outside of the range the symbol is deleted.

Note

This example has been written using the legacy API.

Sample configuration:

symbols    /DEMO/*

check-field     Bid

check-upper     10
check-lower     5

Source code:

/*
 *    Transformer - Sample Module
 *
 *    Copyright CAPLIN Systems Ltd 2000-2006
 *
 *    This module example demonstrates how to publish a derived symbol when the base
 *    symbol has a field value with certain criteria. When the field value is outside
 *    the configured ranges, the symbol is deleted.
 *
 *    The module will send out duplcate DELETEOBJECT messages if the field value is
 *    outside of the configured range for consecutive updates.
 *
 */


#include "transformer.h"



static char      **symbols       = NULL;
static int         symbols_num   = 0;

static char       *check_field  = "dBestBid";
static double      check_upper  = 2.0;
static double      check_lower  = 1.0;



static void        demo_recv_update(int feed, ds_data_t *pkt, time_t arr_tim, int id, void *data);



void mod_init(char *module_name)
{
    char         buf[FILENAME_MAX+1];
    int          i;


    /* Add config option for the symbols we want to receive */
    ds_config_add_array_option("symbols","Symbols to process",DS_CONFIG_STR_ARRAY,&symbols,&symbols_num);

    /* Add a config option for which field to check */
    ds_config_add_option(0,"check-field","Fieldname to modify",DS_CONFIG_STR,&check_field);

    /* Add a config option for the ranges */
    ds_config_add_option(0,"check-upper","Upper value for range",DS_CONFIG_FLOAT,&check_upper);
    ds_config_add_option(0,"check-lower","Lower value for range",DS_CONFIG_FLOAT,&check_lower);

    /* Load a config file based on the name of the module */
    snprintf(buf,sizeof(buf),"%s.conf",module_name);
    mod_config_parse_file(buf);

    /* Check whether any symbols are required, if not then log this condition to the main Transformer
       log file
    */
    if ( symbols_num == 0 ) {
        ds_printf_time(rtas_log,"(%s) No symbols required\n",module_name);
        return;
    }

  

    /* Now register an interest in the symbols */
    for ( i = 0; i < symbols_num; i++ ) {
        register_interest(symbols[i],demo_recv_update,0,NULL);
    }

    return;
}



void mod_exit()
{
    int         i;

    /* We have to loop over all known symbols */
    for ( i = 0; i < symbols_num; i++ ) {
        /* Deregister interests in these symbols */
        deregister_interest(symbols[i],demo_recv_update,0,NULL);
    }
 
    return;
}


static void demo_recv_update(int feed, ds_data_t *pkt, time_t arr_tim, int id, void *data)
{
    char         derived_subject[1024];
    ds_data_t   *dsdata;
    char        *value_str;
    double       value;


    /* Check to see if the update packet has a F_DELETEOBJECT flag on it, if so then
     *  we should perform no processing on it. Our interest is automatically deregistered
     * by the Transformer core
     */
    if ( pkt->flags & F_DELETEOBJECT ) {
        return;
    }


    /* Prepare the derived subject */
    snprintf(derived_subject,sizeof(derived_subject),"%s-DERIVED",pkt->subject);

    /* Pick out the required field within this update */
    if ( ( value_str = packet_get_field_byname(pkt,check_field) ) != NULL ) {
        value = atof(value_str);

        /* Check to see if the field value is out of range */
        if ( value < check_lower || value > check_upper ) {
            /* If it was out of range then send a delete object through. If the Transformer
             * is in active move then a F_DELETEOBJECT message will be sent to interested peers.
             */
            symbol_send_nodata(derived_subject,F_DELETEOBJECT);
            return;
        } else {
            /* We had the field within the update so, publish the entire update out under the
             * derived symbol name
             */

            /* Create a duplicate of the input packet */
            dsdata = packet_clone(pkt);

            /* And make the subject the derived name */
            free(dsdata->subject);
            dsdata->subject = strdup(derived_subject);

            /* Publish the derived update to Datasource and cache within the Transformer core
             * memory
             */
            packet_contrib(dsdata,NULL,PACKET_NOLISTEN|PACKET_PUBLISH|PACKET_STORE|PACKET_FREE);
        }
    }

    return;
}