FairCom ISAM for C

PreviousVRecord

Read the previous variable-length data record in the data file.

Short Name

PRVVREC()

Type

ISAM function

Declaration

COUNT PreviousVRecord(FILNO filno, pVOID recptr, pVRLEN plen)

Description

In V12 the file number typedef was formally changed from COUNT, a two-byte value to FILNO, a four-byte value. Refer to this link for compatibility details. Four Byte File Numbering

PreviousVRecord() is identical to it’s fixed-length counterpart, PreviousRecord(), except that it reads the previous variable-length data record. If successful, this record becomes the current ISAM record for the associated data file.

plen acts as both an input and output parameter:

On input, plen contains the length of the output buffer.
On output, the contents of plen is the actual data-record length. If the length of the output buffer is less than the actual record length, a partial read is performed. If an error occurs, plen is unspecified.

Read the function description for PreviousRecord() for additional important information.

As of c-tree V8.14, c-tree sets the current ISAM position after a record is added such that the next or previous record can be read without having to re-read the record just added. Prior to V8.14, the current ISAM position was not set to a newly-added record and an INOT_ERR (101) error would result if you tried to read either the next or previous record.

Return

Value	Symbolic Constant	Explanation
0	NO_ERROR	Successful retrieval of current ISAM record.
633	NPLN_ERR	plen is NULL.
634	NLEN_ERR	plen is negative on input.

See c-tree Error Codes for a complete listing of valid c-tree error values.