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/*-------------------------------------------------------------------------
*
* large_object.h
* file of info for Postgres large objects. POSTGRES 4.2 supports
* zillions of large objects (internal, external, jaquith, inversion).
* Now we only support inversion.
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: large_object.h,v 1.20 2001/01/24 19:43:27 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef LARGE_OBJECT_H
#define LARGE_OBJECT_H
#include "utils/rel.h"
/*----------
* Data about a currently-open large object.
*
* id is the logical OID of the large object
* offset is the current seek offset within the LO
* heap_r holds an open-relation reference to pg_largeobject
* index_r holds an open-relation reference to pg_largeobject_loid_pn_index
*
* NOTE: before 7.1, heap_r and index_r held references to the separate
* table and index of a specific large object. Now they all live in one rel.
*----------
*/
typedef struct LargeObjectDesc {
Oid id;
uint32 offset; /* current seek pointer */
int flags; /* locking info, etc */
/* flag bits: */
#define IFS_RDLOCK (1 << 0)
#define IFS_WRLOCK (1 << 1)
Relation heap_r;
Relation index_r;
} LargeObjectDesc;
/*
* Each "page" (tuple) of a large object can hold this much data
*
* We could set this as high as BLCKSZ less some overhead, but it seems
* better to make it a smaller value, so that not as much space is used
* up when a page-tuple is updated. Note that the value is deliberately
* chosen large enough to trigger the tuple toaster, so that we will
* attempt to compress page tuples in-line. (But they won't be moved off
* unless the user creates a toast-table for pg_largeobject...)
*
* Also, it seems to be a smart move to make the page size be a power of 2,
* since clients will often be written to send data in power-of-2 blocks.
* This avoids unnecessary tuple updates caused by partial-page writes.
*/
#define LOBLKSIZE (BLCKSZ / 4)
/*
* Function definitions...
*/
/* inversion stuff in inv_api.c */
extern LargeObjectDesc *inv_create(int flags);
extern LargeObjectDesc *inv_open(Oid lobjId, int flags);
extern void inv_close(LargeObjectDesc *obj_desc);
extern int inv_drop(Oid lobjId);
extern int inv_seek(LargeObjectDesc *obj_desc, int offset, int whence);
extern int inv_tell(LargeObjectDesc *obj_desc);
extern int inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes);
extern int inv_write(LargeObjectDesc *obj_desc, char *buf, int nbytes);
#endif /* LARGE_OBJECT_H */
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