Net2/usr/src/lib/libc/db/btree/big.c
/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Mike Olson.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)big.c 5.2 (Berkeley) 2/22/91";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <db.h>
#include <stdlib.h>
#include <string.h>
#include "btree.h"
/*
* _BT_GETBIG -- Get big data from indirect pages.
*
* This routine chases indirect blocks for the big object at the
* specified page to a buffer, and return the address of the buffer.
*
* Parameters:
* t -- btree with the indirect blocks
* pgno -- page number that starts the chain
* p -- (char **) to get the address of the buffer containing
* the key or datum.
* sz -- pointer to an int to get the size of the instantiated
* object.
*
* Returns:
* RET_SUCCESS, RET_ERROR.
*
* Side Effects:
* None.
*/
int
_bt_getbig(t, pgno, p, sz)
BTREE_P t;
pgno_t pgno;
char **p;
int *sz;
{
pgno_t save;
size_t nbytes;
size_t nhere;
BTHEADER *h;
char *top, *from, *where;
save = t->bt_curpage->h_pgno;
if (_bt_getpage(t, pgno) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
bcopy((char *) &(h->h_linp[0]),
(char *) &nbytes,
(size_t) sizeof(nbytes));
if ((*p = (char *) malloc(nbytes)) == (char *) NULL)
return (RET_ERROR);
*sz = nbytes;
from = ((char *) (&h->h_linp[0])) + sizeof(nbytes);
top = ((char *) h) + t->bt_psize;
/* need more space for data? */
where = *p;
while (nbytes > 0) {
nhere = (int) (top - from);
if (nhere > nbytes) {
(void) bcopy(from, where, (size_t) nbytes);
nbytes = 0;
} else {
(void) bcopy(from, where, nhere);
where += nhere;
nbytes -= nhere;
if (_bt_getpage(t, h->h_nextpg) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
top = ((char *) h) + t->bt_psize;
from = (char *) &(h->h_linp[0]);
}
}
if (_bt_getpage(t, save) == RET_ERROR)
return (RET_ERROR);
return (RET_SUCCESS);
}
/*
* _BT_DELINDIR -- Delete a chain of indirect blocks from the btree.
*
* When a large item is deleted from the tree, this routine puts the
* space that it occupied onto the free list for later reuse. The
* bt_free entry in the btree structure points at the head of this list.
* This value is also stored on disk in the btree's metadata.
*
* Parameters:
* t -- btree from which to delete pages
* chain -- page number that starts the chain.
*
* Returns:
* RET_SUCCESS, RET_ERROR.
*
* Side Effects:
* Invalidates the current on-disk version of the btree's
* metadata (if any), and updates the free list appropriately.
*/
int
_bt_delindir(t, chain)
BTREE_P t;
pgno_t chain;
{
BTHEADER *h;
pgno_t save;
pgno_t oldfree;
h = t->bt_curpage;
save = h->h_pgno;
if (_bt_getpage(t, chain) == RET_ERROR)
return (RET_ERROR);
/*
* If some internal node is pointing at this chain, don't
* delete it.
*/
if (t->bt_curpage->h_flags & F_PRESERVE) {
if (_bt_getpage(t, save) == RET_ERROR)
return (RET_ERROR);
return (RET_SUCCESS);
}
/* if there's nothing on the free list, this is easy... */
if (t->bt_free == P_NONE) {
t->bt_free = chain;
} else {
oldfree = t->bt_free;
/* find the end of the data chain for the deleted datum */
t->bt_free = chain;
do {
if (_bt_getpage(t, chain) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
if (h->h_nextpg != P_NONE)
chain = h->h_nextpg;
} while (h->h_nextpg != P_NONE);
/* link freed pages into free list */
h->h_nextpg = oldfree;
if (_bt_write(t, h, RELEASE) == RET_ERROR)
return (RET_ERROR);
if (_bt_getpage(t, oldfree) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
h->h_prevpg = chain;
if (_bt_write(t, h, RELEASE) == RET_ERROR)
return (RET_ERROR);
}
/* restore the tree's current page pointer */
if (_bt_getpage(t, save) == RET_ERROR)
return (RET_ERROR);
/* we have trashed the tree metadata; rewrite it later */
t->bt_flags &= ~BTF_METAOK;
return (RET_SUCCESS);
}
/*
* _BT_INDIRECT -- Write a series of indirect pages for big objects.
*
* A chain of indirect pages looks like
*
* +-------------------+ +---------------------+
* |hdr|size| | |hdr| |
* +---+----+ | +---+ |
* | ... data ... | | ... data ... | ...
* | | | |
* +-------------------+ +---------------------+
*
* where hdr is a standard btree page header (with the indirect bit
* set), size on the first page is the real size of the datum, and
* data are bytes of the datum, split across as many pages as necessary.
* Indirect pages are chained together with the h_prevpg and h_nextpg
* entries of the page header struct.
*
* A single DBT is written per chain, so space on the last page is
* wasted.
*
* We return the page number of the start of the chain.
*
* When a big object is deleted from a tree, the space that it occupied
* is placed on a free list for later reuse. This routine checks that
* free list before allocating new pages to the big datum being inserted.
*
* Parameters:
* t -- btree in which to store indirect blocks
* data -- DBT with the big datum in it
* pgno -- place to put the starting page number of the chain
*
* Returns:
* RET_SUCCESS, RET_ERROR.
*
* Side Effects:
* Current page is changed on return.
*/
int
_bt_indirect(t, data, pgno)
BTREE_P t;
DBT *data;
pgno_t *pgno;
{
pgno_t prev;
char *top;
char *where;
char *from;
size_t dsize;
pgno_t nextchn;
int ischain;
BTHEADER *cur;
/* get set for first page in chain */
prev = P_NONE;
dsize = data->size;
from = (char *) data->data;
/* if there are blocks on the free list, use them first */
if ((*pgno = t->bt_free) == P_NONE) {
if ((cur = _bt_allocpg(t)) == (BTHEADER *) NULL)
return (RET_ERROR);
ischain = 0;
*pgno = cur->h_pgno = ++(t->bt_npages);
} else {
if (_bt_getpage(t, *pgno) == RET_ERROR)
return (RET_ERROR);
ischain = 1;
cur = t->bt_curpage;
}
cur->h_flags = F_CONT|F_LEAF;
(void) bcopy((char *) &dsize, (char *) &cur->h_linp[0], sizeof(size_t));
where = ((char *) (&cur->h_linp[0])) + sizeof(size_t);
/* fill and write pages in the chain */
for (;;) {
int nhere;
top = ((char *) cur) + t->bt_psize;
cur->h_prevpg = prev;
nextchn = cur->h_nextpg;
nhere = (int) (top - where);
if (nhere >= dsize) {
(void) bcopy(from, where, (int) dsize);
cur->h_nextpg = P_NONE;
dsize = 0;
} else {
(void) bcopy(from, where, (int) nhere);
dsize -= nhere;
from += nhere;
if (nextchn == P_NONE)
cur->h_nextpg = t->bt_npages + 1;
prev = cur->h_pgno;
}
/* current page is ready to go; write it out */
if (_bt_write(t, cur, RELEASE) == RET_ERROR)
return (RET_ERROR);
/* free the current page, if appropriate */
if (ISDISK(t) && !ISCACHE(t) && !ischain) {
(void) free ((char *) cur);
}
/* done? */
if (dsize == 0)
break;
/* allocate another page */
if (nextchn == P_NONE) {
if ((cur = _bt_allocpg(t)) == (BTHEADER *) NULL)
return (RET_ERROR);
ischain = 0;
cur->h_pgno = ++(t->bt_npages);
} else {
if (_bt_getpage(t, nextchn) == RET_ERROR)
return (RET_ERROR);
ischain = 1;
cur = t->bt_curpage;
}
cur->h_flags = F_LEAF | F_CONT;
where = (char *) (&cur->h_linp[0]);
}
/* if we used pages from the free list, record changes to it */
if (*pgno == t->bt_free) {
t->bt_free = nextchn;
t->bt_flags &= ~BTF_METAOK;
}
return (RET_SUCCESS);
}
/*
* _BT_MARKCHAIN -- Mark a chain of pages as used by an internal node.
*
* Chains of indirect blocks pointed to by leaf nodes get reclaimed
* when the item that points to them gets deleted. Chains pointed
* to by internal nodes never get deleted. This routine marks a
* chain as pointed to by an internal node.
*
* Parameters:
* t -- tree in which to mark
* chain -- number of first page in chain
*
* Returns:
* RET_SUCCESS, RET_ERROR.
*
* Side Effects:
* None.
*/
int
_bt_markchain(t, chain)
BTREE_P t;
pgno_t chain;
{
pgno_t save;
save = t->bt_curpage->h_pgno;
if (_bt_getpage(t, chain) == RET_ERROR)
return (RET_ERROR);
t->bt_curpage->h_flags |= (F_DIRTY|F_PRESERVE);
if (_bt_getpage(t, save) == RET_ERROR)
return (RET_ERROR);
return (RET_SUCCESS);
}