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/*-------------------------------------------------------------------------
*
* beard.c
* sample routines to use large objects
*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/tutorial/beard.c,v 1.12 2004/12/31 22:04:05 pgsql Exp $
*
*-------------------------------------------------------------------------
*/
typedef struct ImageHdr
{
int size;
} ImageHdr;
#define BUFSIZE 10
/*
* beard -
* clips lower 1/3 of picture and return as large object
*/
Oid
beard(Oid picture)
{
Oid beard;
int pic_fd,
beard_fd;
ImageHdr ihdr;
char buf[BUFSIZE];
int cc;
pic_fd = DatumGetInt32(DirectFunctionCall2(lo_open,
ObjectIdGetDatum(picture),
Int32GetDatum(INV_READ)));
if (pic_fd < 0)
elog(ERROR, "Cannot access picture large object");
if (lo_read(pic_fd, (char *) &ihdr, sizeof(ihdr)) != sizeof(ihdr))
elog(ERROR, "Picture large object corrupted");
beardOffset = (ihdr.size / 3) * 2;
/*
* new large object
*/
beard = DatumGetObjectId(DirectFunctionCall1(lo_creat,
Int32GetDatum(INV_MD)));
if (beard == InvalidOid)
elog(ERROR, "Cannot create new large object");
beard_fd = DatumGetInt32(DirectFunctionCall2(lo_open,
ObjectIdGetDatum(beard),
Int32GetDatum(INV_WRITE)));
if (beard_fd < 0)
elog(ERROR, "Cannot access beard large object");
if (DatumGetInt32(DirectFunctionCall3(lo_lseek,
Int32GetDatum(pic_fd),
Int32GetDatum(beardOffset),
Int32GetDatum(SEEK_SET))) < 0)
elog(ERROR, "Cannot seek in picture large object");
while ((cc = lo_read(pic_fd, buf, BUFSIZE)) > 0)
{
if (lo_write(beard_fd, buf, cc) != cc)
elog(ERROR, "error while writing large object");
}
DirectFunctionCall1(lo_close, Int32GetDatum(pic_fd));
DirectFunctionCall1(lo_close, Int32GetDatum(beard_fd));
return beard;
}
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