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/*-
* Copyright (c) 1990, 1993
* 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[] = "@(#)bt_seq.c 8.2 (Berkeley) 9/7/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <db.h>
#include "btree.h"
static int bt_seqadv __P((BTREE *, EPG *, int));
static int bt_seqset __P((BTREE *, EPG *, DBT *, int));
/*
* Sequential scan support.
*
* The tree can be scanned sequentially, starting from either end of the tree
* or from any specific key. A scan request before any scanning is done is
* initialized as starting from the least node.
*
* Each tree has an EPGNO which has the current position of the cursor. The
* cursor has to survive deletions/insertions in the tree without losing its
* position. This is done by noting deletions without doing them, and then
* doing them when the cursor moves (or the tree is closed).
*/
/*
* __BT_SEQ -- Btree sequential scan interface.
*
* Parameters:
* dbp: pointer to access method
* key: key for positioning and return value
* data: data return value
* flags: R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV.
*
* Returns:
* RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
*/
int
__bt_seq(dbp, key, data, flags)
const DB *dbp;
DBT *key, *data;
u_int flags;
{
BTREE *t;
EPG e;
int status;
t = dbp->internal;
/* Toss any page pinned across calls. */
if (t->bt_pinned != NULL) {
mpool_put(t->bt_mp, t->bt_pinned, 0);
t->bt_pinned = NULL;
}
/*
* If scan unitialized as yet, or starting at a specific record, set
* the scan to a specific key. Both bt_seqset and bt_seqadv pin the
* page the cursor references if they're successful.
*/
switch(flags) {
case R_NEXT:
case R_PREV:
if (ISSET(t, B_SEQINIT)) {
status = bt_seqadv(t, &e, flags);
break;
}
/* FALLTHROUGH */
case R_CURSOR:
case R_FIRST:
case R_LAST:
status = bt_seqset(t, &e, key, flags);
break;
default:
errno = EINVAL;
return (RET_ERROR);
}
if (status == RET_SUCCESS) {
status = __bt_ret(t, &e, key, data);
/* Update the actual cursor. */
t->bt_bcursor.pgno = e.page->pgno;
t->bt_bcursor.index = e.index;
/*
* If the user is doing concurrent access, we copied the
* key/data, toss the page.
*/
if (ISSET(t, B_DB_LOCK))
mpool_put(t->bt_mp, e.page, 0);
else
t->bt_pinned = e.page;
SET(t, B_SEQINIT);
}
return (status);
}
/*
* BT_SEQSET -- Set the sequential scan to a specific key.
*
* Parameters:
* t: tree
* ep: storage for returned key
* key: key for initial scan position
* flags: R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV
*
* Side effects:
* Pins the page the cursor references.
*
* Returns:
* RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
*/
static int
bt_seqset(t, ep, key, flags)
BTREE *t;
EPG *ep;
DBT *key;
int flags;
{
EPG *e;
PAGE *h;
pgno_t pg;
int exact;
/*
* Delete any already deleted record that we've been saving because
* the cursor pointed to it. Since going to a specific key, should
* delete any logically deleted records so they aren't found.
*/
if (ISSET(t, B_DELCRSR) && __bt_crsrdel(t, &t->bt_bcursor))
return (RET_ERROR);
/*
* Find the first, last or specific key in the tree and point the cursor
* at it. The cursor may not be moved until a new key has been found.
*/
switch(flags) {
case R_CURSOR: /* Keyed scan. */
/*
* Find the first instance of the key or the smallest key which
* is greater than or equal to the specified key. If run out
* of keys, return RET_SPECIAL.
*/
if (key->data == NULL || key->size == 0) {
errno = EINVAL;
return (RET_ERROR);
}
e = __bt_first(t, key, &exact); /* Returns pinned page. */
if (e == NULL)
return (RET_ERROR);
/*
* If at the end of a page, skip any empty pages and find the
* next entry.
*/
if (e->index == NEXTINDEX(e->page)) {
h = e->page;
do {
pg = h->nextpg;
mpool_put(t->bt_mp, h, 0);
if (pg == P_INVALID)
return (RET_SPECIAL);
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
} while (NEXTINDEX(h) == 0);
e->index = 0;
e->page = h;
}
*ep = *e;
break;
case R_FIRST: /* First record. */
case R_NEXT:
/* Walk down the left-hand side of the tree. */
for (pg = P_ROOT;;) {
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
if (h->flags & (P_BLEAF | P_RLEAF))
break;
pg = GETBINTERNAL(h, 0)->pgno;
mpool_put(t->bt_mp, h, 0);
}
/* Skip any empty pages. */
while (NEXTINDEX(h) == 0 && h->nextpg != P_INVALID) {
pg = h->nextpg;
mpool_put(t->bt_mp, h, 0);
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
}
if (NEXTINDEX(h) == 0) {
mpool_put(t->bt_mp, h, 0);
return (RET_SPECIAL);
}
ep->page = h;
ep->index = 0;
break;
case R_LAST: /* Last record. */
case R_PREV:
/* Walk down the right-hand side of the tree. */
for (pg = P_ROOT;;) {
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
if (h->flags & (P_BLEAF | P_RLEAF))
break;
pg = GETBINTERNAL(h, NEXTINDEX(h) - 1)->pgno;
mpool_put(t->bt_mp, h, 0);
}
/* Skip any empty pages. */
while (NEXTINDEX(h) == 0 && h->prevpg != P_INVALID) {
pg = h->prevpg;
mpool_put(t->bt_mp, h, 0);
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
}
if (NEXTINDEX(h) == 0) {
mpool_put(t->bt_mp, h, 0);
return (RET_SPECIAL);
}
ep->page = h;
ep->index = NEXTINDEX(h) - 1;
break;
}
return (RET_SUCCESS);
}
/*
* BT_SEQADVANCE -- Advance the sequential scan.
*
* Parameters:
* t: tree
* flags: R_NEXT, R_PREV
*
* Side effects:
* Pins the page the new key/data record is on.
*
* Returns:
* RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
*/
static int
bt_seqadv(t, e, flags)
BTREE *t;
EPG *e;
int flags;
{
EPGNO *c, delc;
PAGE *h;
indx_t index;
pgno_t pg;
/* Save the current cursor if going to delete it. */
c = &t->bt_bcursor;
if (ISSET(t, B_DELCRSR))
delc = *c;
if ((h = mpool_get(t->bt_mp, c->pgno, 0)) == NULL)
return (RET_ERROR);
/*
* Find the next/previous record in the tree and point the cursor at it.
* The cursor may not be moved until a new key has been found.
*/
index = c->index;
switch(flags) {
case R_NEXT: /* Next record. */
if (++index == NEXTINDEX(h)) {
do {
pg = h->nextpg;
mpool_put(t->bt_mp, h, 0);
if (pg == P_INVALID)
return (RET_SPECIAL);
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
} while (NEXTINDEX(h) == 0);
index = 0;
}
break;
case R_PREV: /* Previous record. */
if (index-- == 0) {
do {
pg = h->prevpg;
mpool_put(t->bt_mp, h, 0);
if (pg == P_INVALID)
return (RET_SPECIAL);
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
} while (NEXTINDEX(h) == 0);
index = NEXTINDEX(h) - 1;
}
break;
}
e->page = h;
e->index = index;
/*
* Delete any already deleted record that we've been saving because the
* cursor pointed to it. This could cause the new index to be shifted
* down by one if the record we're deleting is on the same page and has
* a larger index.
*/
if (ISSET(t, B_DELCRSR)) {
CLR(t, B_DELCRSR); /* Don't try twice. */
if (c->pgno == delc.pgno && c->index > delc.index)
--c->index;
if (__bt_crsrdel(t, &delc))
return (RET_ERROR);
}
return (RET_SUCCESS);
}
/*
* __BT_CRSRDEL -- Delete the record referenced by the cursor.
*
* Parameters:
* t: tree
*
* Returns:
* RET_ERROR, RET_SUCCESS
*/
int
__bt_crsrdel(t, c)
BTREE *t;
EPGNO *c;
{
PAGE *h;
int status;
CLR(t, B_DELCRSR); /* Don't try twice. */
if ((h = mpool_get(t->bt_mp, c->pgno, 0)) == NULL)
return (RET_ERROR);
status = __bt_dleaf(t, h, c->index);
mpool_put(t->bt_mp, h, MPOOL_DIRTY);
return (status);
}
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