Trace blocks

In some cases, you might need to perform some computations before you decide whether to output certain trace data. To perform computations for a tracepoint, define a trace block.

A trace block initially compares a specified threshold with the current trace level to determine whether to continue with the trace computations. Within the trace block, it can output a result in a trace message.

The DataBlade® API provides the following tracing functions for use in a trace block:
  • The tf() function acts as a threshold check that determines whether to execute a particular trace block.
    The syntax of the tf() function is as follows: 
    tf(trace_class, threshold)

    This function returns a Boolean result; it is TRUE if the current trace level of the trace_class class is greater than or equal to the threshold.

  • The tflev() function returns the current trace level of the specified trace class.

    The syntax of the tflev() function is as follows:

    tflev(trace_class)

    This function returns an integer result that is the current trace level of the trace_class class.

  • The tprintf() function outputs a trace message but does not require the threshold argument.
    The syntax of the tprintf() function is as follows: 
    tprintf(format [,arg]...)

    The format and arg arguments are the same as those in the DPRINTF macro.

The DataBlade API also provides the gl_tprintf() function for formatting internationalized trace messages within a trace block. For more information aboutgl_tprintf(), see the Informix® GLS User's Guide.

You can combine these trace-block functions with conventional C structures. The following example is typical: 
/* Compare current trace level of "chck_consist" class and
 * with a tracepoint threshold of 20. Continue execution of
 * trace block if trace level >= 20
 */
if( tf("chck_consist", 20) ) 
   {
   x = fastScan(aList, y);
   consFactor = checkRconsit(x, bList);

   /* Generate trace message (in US English) */
   tprintf("...in doWork: x = %f and consFactor = %f",
      x, consFactor);
   }