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