mb.c

/**
 * @file mb.c
 * @author Taka Wang
 * @brief modbus common functions
*/

#include "mb.h"

extern int enable_syslog; // syslog flag

/* ==================================================
 *  public functions
================================================== */

char * set_modbus_success_resp_str_with_data (char *tid, cJSON *json_arr)
{
    BEGIN (enable_syslog);

    cJSON *resp_root;
    resp_root = cJSON_CreateObject ();
    cJSON_AddStringToObject (resp_root, "tid", tid);
    
    if (json_arr != NULL) 
    {
        cJSON_AddItemToObject (resp_root, "data", json_arr);
    }
    cJSON_AddStringToObject (resp_root, "status", "ok");
    
    char * resp_json_str = cJSON_PrintUnformatted (resp_root);
    LOG (enable_syslog, "resp: %s", resp_json_str);
    // clean up
    cJSON_Delete (resp_root);
    return resp_json_str;
}

char * set_modbus_success_resp_str (char *tid)
{
    return set_modbus_success_resp_str_with_data (tid, NULL);
}

char * set_modbus_fail_resp_str (char *tid, const char *reason)
{
    BEGIN (enable_syslog);

    ERR (enable_syslog, "Fail: %s", reason);

    cJSON *resp_root;
    resp_root = cJSON_CreateObject ();
    cJSON_AddStringToObject (resp_root, "tid", tid);
    cJSON_AddStringToObject (resp_root, "status", reason);

    char * resp_json_string = cJSON_PrintUnformatted (resp_root);
    LOG(enable_syslog, "resp: %s", resp_json_string);
    // clean up
    cJSON_Delete (resp_root);
    return resp_json_string;
}

char * set_modbus_fail_resp_str_with_errno (char *tid, mbtcp_handle_s *handle, int errnum)
{
    BEGIN (enable_syslog);

    // [TODO][enhance] reconnect proactively?
    // ... if the request interval is very large, 
    // we should try to reconnect automatically
    
    if (errnum == 104) // Connection reset by peer (i.e, tcp connection timeout)
    {
        handle->connected = false;
    }

    ERR (enable_syslog, "%s:%d", modbus_strerror (errnum), errnum);
    return set_modbus_fail_resp_str (tid, modbus_strerror (errnum));
}