net-snmp C语言API编程学习4--获取各个类型数据的返回值

通过net-snmp C语言API，得到agent端返回的数据，各种snmp类型的数据的解析方法

/* manipuate the information ourselves */
        for(vars = response->variables; vars; vars = vars->next_variable)     //pdu is a snmp_pdu style variable
        {
            printf("var type is %d\n", vars->type);
            if (vars->type == ASN_OCTET_STR)                                    //vars is a variable_list style variable
            {
                //判断是字符串还是Hex-STRING
                int hex = 0;
                int x;
                u_char * cp;
                int allow_realloc = 1;
                u_char *buf = NULL;
                size_t buf_len = 256, out_len = 0;

                for (cp = vars->val.string, x = 0; x < (int) vars->val_len; x++, cp++)
                {
                    if (!isprint(*cp) && !isspace(*cp))
                    {
                        hex = 1;
                    }
                }
                if(!hex)    //字符串
                {
                    char *sp = (char *)malloc(1 + vars->val_len);
                    memcpy(sp, vars->val.string, vars->val_len);                           //netsnmp_vardata is a netsnmp_vardata style variable
                    sp[vars->val_len] = '\0';
                    printf("value #%d is a string: %s\n", count++, sp);
                    free(sp);
                }
                else    //Hex-STRING
                {
                    buf = (u_char *) calloc(buf_len, 1);
                    snmp_cstrcat(&buf, &buf_len, &out_len, allow_realloc, "");
                    sprint_realloc_hexstring(&buf, &buf_len, &out_len, allow_realloc,vars->val.string, vars->val_len);
                    printf("value #%d is a hex-string: %s\n", count++, buf);
                    free(buf);
                }
            }
            else if(vars->type == ASN_TIMETICKS)
            {
                long timetick = *vars->val.integer;
                printf("value #%d is a timetick: %d\n", count++, timetick);
            }
            else if(vars->type == ASN_OBJECT_ID)
            {
                 printf("value #%d is a oid: ", count++);
                 for(i=0; i<vars->name_length; i++)
                 {
                     if(*(vars->name_loc+i) == 0)
                         break;
                     printf(".%d", *(vars->name_loc+i));
                 }
                 printf(" and value is ");
                 for(i=0; i<(vars->val_len/sizeof(int)); i++)
                 {
                     printf(".%d", *(vars->val.objid+i));
                 }
                 printf("\n");

            }
            else if(vars->type == ASN_INTEGER)
            {
                printf("value #%d is a integer: %d\n", count++, *(vars->val.integer));
            }
            else if(vars->type == ASN_COUNTER)
            {
                printf("value #%d is a count: %u\n", count++, (unsigned int)(*vars->val.integer & 0xffffffff));
            }
            else if(vars->type == ASN_GAUGE)
            {
                printf("value #%d is a gauge: %u\n", count++, *(vars->val.integer));
            }
            else if(vars->type == ASN_IPADDRESS)
            {
                u_char *ip = vars->val.string;
                printf("value #%d is a ipaddress: %d.%d.%d.%d\n", count++, ip[0], ip[1], ip[2], ip[3]);
            }
            else if(vars->type == ASN_NULL)
            {
                printf("value #%d is a null: \n", count++);
            }
            else
              printf("value #%d is NOT a string! Ack!\n", count++);
        }

    }