FairCom ISAM for C

cndxeval

Evaluates an expression tree produced by cndxeval().

Declaration

COUNT cndxeval( PTREE Tree, pVOID Recptr, pConvMap Schema, VRLEN fixlen, VRLEN datlen )

Description

Where:

Tree - parse tree generated by cndxparse()
Recptr - pointer to a record handle
Schema - record schema
fixlen - Fixed record length
datlen - total record length

Evaluating your expression involves three steps:

Allocate a run-time stack for the expression analyzer (first time only).
Set up a buffer containing the field data used in the expression.
Evaluate the expression.

If you wish, you can repeat steps b) and c) multiple times. Sample code to perform these steps is shown below. It is assumed the Get_Buffer() routine allocates a record buffer and initializes it with data conforming to the field definitions specified in the DODA.

Return Values

Value	Symbolic Constant	Explanation
1	YES	Expression evaluated as true
0	NO	Expression evaluated as false

Example

COUNT retcidx; /* Result of expression evaluation. */

pTEXT recbuf; /* Record buffer. */

/* Allocate a run-time stack for the expression analyzer (first time only). */

if (!ctcidxStk) {

ctcidxStk = (pVOID) getcndxmem(CNDX_MAX_STACK * ctSIZE(PLEAF));

if (!ctcidxStk) {

printf("Unable to allocate memory for run-time stack.\n");

ctrt_exit(1);

}

/* Set up a buffer containing the field data used in the expression. */

Get_Buffer(&recbuf);

/* Evaluate the expression. */

retcidx = cndxeval(ptree, recbuf, (pConvMap)schema);

if (retcidx < 0)

printf("The expression cannot be evaluated for this record

- error %d.\n", uerr_cod);

else if (retcidx)

printf("The expression evaluates to TRUE for this record.\n");

else

printf("The expression evaluates to FALSE for this record.\n");