FirstKey

Find the first entry in an index file.

Short Name

FRSKEY()

Type

Low-level index file function

Declaration

LONG FirstKey(COUNT keyno, pVOID idxval)

Description

FirstKey() searches index file keyno for the first entry in the index. If successful, it copies the first index entry into the space pointed to by idxval.

Return

FirstKey() returns the data record position associated with the first entry in the index file. If the index is empty or an error is detected, FirstKey() returns zero. If FirstKey() returns zero, check uerr_cod to see if an error occurred: if uerr_cod is also zero, then the index is empty; otherwise, an error condition was detected. See “c-tree Plus Error Codes” in the c-tree Plus Programmer’s Reference Guide for a complete listing of valid c-tree Plus error values.

Example

TEXT         idxval[10];

COUNT        keyno;

if (FirstKey(keyno,idxval))

   printf("\nFirst index entry = %.10s", idxval);

else {

   printf("\nEither index is empty or an error occurred.");

   if (uerr_cod)

      printf("\Error = %d",uerr_cod);

   else

      printf("\Index is empty.);

Limitations

No check is made to determine if idxval points to a region sufficiently large to accept a key value from the index file. If the area is too small, either code or data will be clobbered. Use GetCtFileInfo to determine the key length.

The key value returned by this function will be a properly formatted key value (i.e., HIGH_LOW order, forced to upper case, etc.). The main issue is if binary key values will be displayed on a LOW_HIGH machine, it will be necessary to reverse any numeric segments. The “Key Segment Modes” in the c-tree Plus Programmer’s Reference Guide contains suggestions for manipulating the key value.