c-treeDB API for C++ - Developers Guide

CTDB_ON_RECORD_BEFORE_READ

A CTDB_ON_RECORD_BEFORE_READ callback is invoked just before a record is read by one of the FairCom DB record reading functions. This callback is useful to prepare a record buffer just before data is read.

The handle passed as parameter for this callback is a record handle and you can safely typecast the handle parameter to a pCTDBRECORD structure pointer.

The following CTDBRECORD structure members keep information regarding the record buffer kept by the record handle:

CTDBRECORD Structure Member	Explanation
pUTEXT recbuf	record buffer
VRLEN recbuf_size	size in bytes of memory allocated for record buffer
VRLEN recbuf_len	actual length of data in record buffer

c-treeDB C API Example

CTDBRET ctdbDECL OnRecordBeforeRead(CTHANDLE Handle)

{

CTDBRET Retval = CTDBRET_OK;

pCTDBRECORD pRecord = (pCTDBRECORD)Handle;

if (!pRecord)

Retval = CTDBRET_NOTRECORD;

else

{

/* swap the record buffer with the localTag */

pUTEXT ptr = pRecord->recbuf;

pRecord->recbuf = pRecord->localTag;

pRecord->localTag = ptr;

}

return Retval;

}