| isfd | isam file descriptor |
| data | image to replace the current record |
ISTRUE, or ISFALSE, in which case the error code is returned by isErrno, or found in isfd->iserrno
isRewNxt first sets the current pointer to the next record in the current index before updating the original current record.
it is useful in situations where the update would place the new record between the original current and next keys in the index.
on successful return the application can then read current to obtain the record that was next in the sequence before the update was performed.
the contents of the original current record in the data file will be replaced with the image passed, and all related indexes updated.
an error code of EENDFILE on an unsuccessful return indicates that the update was successful and isRewNxt has reached the end of the file. any other error code indicates a failure in the update operation.
the original data image can be found in isfd->data on return