FairCom ISAM for C

ReadVData

Read variable-length data record.

Short Name

RDVREC()

Type

Low-Level variable-length record function

Declaration

COUNT ReadVData(FILNO datno, LONG recbyt, pVOID recptr, VRLEN varlen)

Description

ReadVData() reads the variable-length data record at byte position recbyt for data file datno into the buffer area pointed to by recptr. If varlen, the size of the buffer pointed to by recptr, is not large enough for the variable-length record, ReadVData() returns an error.

To ensure varlen is large enough, call VDataLength() before calling ReadVData(). VDataLength() returns the actual length of the record. If the existing buffer is not large enough, a new, larger buffer must be allocated before calling ReadVData().

Note: No check is actually made to be sure that the region pointed to by recptr is in fact as large as varlen indicates. It is up to the application to ensure that varlen accurately specifies the size of the area pointed to by recptr.

Return

Value	Symbolic Constant	Explanation
0	NO_ERROR	Successful read.
29	ZREC_ERR	Attempt to read at byte offset zero.
33	DNUL_ERR	recptr is NULL.
35	SEEK_ERR	lseek() failed while preparing for read.
36	READ_ERR	Operating system could not execute read.
48	FMOD_ERR	datno is not assigned to a variable-length data file.
123	RVHD_ERR	Record is not preceded by a valid record mark.
153	VBSZ_ERR	varlen < actual record length.
154	VRCL_ERR	Variable-length record is zero bytes long.
158	VFLG_ERR	Variable-length record is not marked as active.
160	ITIM_ERR	Multi-user interference: key value changed between index search and subsequent data record read.

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

Example

FILNO datno, keyno;

VRLEN cur_bufsiz, varlen;

pTEXT recptr, calloc();

LONG part_number, pntr;

scanf("%ld",&part_number);

if ((pntr = GetKey(keyno,&part_number)) != DRNZERO) {

varlen = VDataLength(datno,pntr);

if (varlen > cur_bufsiz) {

free(recptr);

recptr = calloc(1,varlen));

cur_bufsiz = varlen;

}

if (ReadVData(datno,pntr,recptr,varlen))

printf>("\nError #%d reading at %ld", uerr_cod, pntr);

}

Limitations

The recbyt parameter in this function is a 4-byte value capable of addressing at most 4 gigabytes. If your application supports HUGE files (greater than 4 gigabytes), you must use the ctSETHGH() and ctGETHGH() functions to set or get the high-order 4 bytes of the file offset. See also Record Offsets Under Huge File Support.