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 HCL 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);
   }