320 lines
6.5 KiB
C
320 lines
6.5 KiB
C
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/* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* sdbm - ndbm work-alike hashed database library
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* based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
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* author: oz@nexus.yorku.ca
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* status: ex-public domain.
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*
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* page-level routines
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*/
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#include "apr_sdbm.h"
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#include "sdbm_tune.h"
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#include "sdbm_pair.h"
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#include "sdbm_private.h"
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#include <string.h> /* for memset() */
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#define exhash(item) sdbm_hash((item).dptr, (item).dsize)
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/*
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* forward
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*/
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static int seepair(char *, int, char *, int);
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/*
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* page format:
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* +------------------------------+
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* ino | n | keyoff | datoff | keyoff |
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* +------------+--------+--------+
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* | datoff | - - - ----> |
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* +--------+---------------------+
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* | F R E E A R E A |
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* +--------------+---------------+
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* | <---- - - - | data |
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* +--------+-----+----+----------+
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* | key | data | key |
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* +--------+----------+----------+
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*
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* calculating the offsets for free area: if the number
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* of entries (ino[0]) is zero, the offset to the END of
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* the free area is the block size. Otherwise, it is the
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* nth (ino[ino[0]]) entry's offset.
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*/
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int
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fitpair(pag, need)
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char *pag;
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int need;
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{
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register int n;
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register int off;
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register int avail;
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register short *ino = (short *) pag;
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off = ((n = ino[0]) > 0) ? ino[n] : PBLKSIZ;
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avail = off - (n + 1) * sizeof(short);
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need += 2 * sizeof(short);
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debug(("avail %d need %d\n", avail, need));
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return need <= avail;
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}
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void
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putpair(pag, key, val)
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char *pag;
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apr_sdbm_datum_t key;
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apr_sdbm_datum_t val;
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{
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register int n;
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register int off;
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register short *ino = (short *) pag;
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off = ((n = ino[0]) > 0) ? ino[n] : PBLKSIZ;
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/*
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* enter the key first
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*/
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off -= key.dsize;
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(void) memcpy(pag + off, key.dptr, key.dsize);
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ino[n + 1] = off;
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/*
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* now the data
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*/
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off -= val.dsize;
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(void) memcpy(pag + off, val.dptr, val.dsize);
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ino[n + 2] = off;
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/*
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* adjust item count
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*/
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ino[0] += 2;
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}
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apr_sdbm_datum_t
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getpair(pag, key)
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char *pag;
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apr_sdbm_datum_t key;
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{
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register int i;
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register int n;
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apr_sdbm_datum_t val;
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register short *ino = (short *) pag;
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if ((n = ino[0]) == 0)
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return sdbm_nullitem;
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if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0)
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return sdbm_nullitem;
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val.dptr = pag + ino[i + 1];
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val.dsize = ino[i] - ino[i + 1];
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return val;
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}
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int
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duppair(pag, key)
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char *pag;
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apr_sdbm_datum_t key;
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{
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register short *ino = (short *) pag;
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return ino[0] > 0 && seepair(pag, ino[0], key.dptr, key.dsize) > 0;
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}
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apr_sdbm_datum_t
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getnkey(pag, num)
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char *pag;
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int num;
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{
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apr_sdbm_datum_t key;
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register int off;
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register short *ino = (short *) pag;
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num = num * 2 - 1;
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if (ino[0] == 0 || num > ino[0])
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return sdbm_nullitem;
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off = (num > 1) ? ino[num - 1] : PBLKSIZ;
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key.dptr = pag + ino[num];
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key.dsize = off - ino[num];
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return key;
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}
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int
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delpair(pag, key)
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char *pag;
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apr_sdbm_datum_t key;
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{
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register int n;
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register int i;
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register short *ino = (short *) pag;
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if ((n = ino[0]) == 0)
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return 0;
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if ((i = seepair(pag, n, key.dptr, key.dsize)) == 0)
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return 0;
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/*
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* found the key. if it is the last entry
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* [i.e. i == n - 1] we just adjust the entry count.
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* hard case: move all data down onto the deleted pair,
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* shift offsets onto deleted offsets, and adjust them.
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* [note: 0 < i < n]
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*/
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if (i < n - 1) {
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register int m;
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register char *dst = pag + (i == 1 ? PBLKSIZ : ino[i - 1]);
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register char *src = pag + ino[i + 1];
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register short zoo = (short) (dst - src);
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debug(("free-up %d ", zoo));
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/*
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* shift data/keys down
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*/
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m = ino[i + 1] - ino[n];
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#undef DUFF /* just use memmove. it should be plenty fast. */
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#ifdef DUFF
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#define MOVB *--dst = *--src
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if (m > 0) {
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register int loop = (m + 8 - 1) >> 3;
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switch (m & (8 - 1)) {
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case 0: do {
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MOVB; case 7: MOVB;
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case 6: MOVB; case 5: MOVB;
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case 4: MOVB; case 3: MOVB;
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case 2: MOVB; case 1: MOVB;
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} while (--loop);
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}
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}
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#else
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dst -= m;
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src -= m;
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memmove(dst, src, m);
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#endif
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/*
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* adjust offset index up
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*/
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while (i < n - 1) {
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ino[i] = ino[i + 2] + zoo;
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i++;
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}
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}
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ino[0] -= 2;
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return 1;
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}
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/*
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* search for the key in the page.
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* return offset index in the range 0 < i < n.
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* return 0 if not found.
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*/
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static int
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seepair(pag, n, key, siz)
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char *pag;
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register int n;
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register char *key;
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register int siz;
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{
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register int i;
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register int off = PBLKSIZ;
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register short *ino = (short *) pag;
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for (i = 1; i < n; i += 2) {
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if (siz == off - ino[i] &&
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memcmp(key, pag + ino[i], siz) == 0)
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return i;
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off = ino[i + 1];
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}
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return 0;
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}
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void
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splpage(pag, new, sbit)
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char *pag;
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char *new;
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long sbit;
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{
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apr_sdbm_datum_t key;
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apr_sdbm_datum_t val;
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register int n;
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register int off = PBLKSIZ;
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char cur[PBLKSIZ];
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register short *ino = (short *) cur;
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(void) memcpy(cur, pag, PBLKSIZ);
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(void) memset(pag, 0, PBLKSIZ);
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(void) memset(new, 0, PBLKSIZ);
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n = ino[0];
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for (ino++; n > 0; ino += 2) {
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key.dptr = cur + ino[0];
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key.dsize = off - ino[0];
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val.dptr = cur + ino[1];
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val.dsize = ino[0] - ino[1];
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/*
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* select the page pointer (by looking at sbit) and insert
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*/
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(void) putpair((exhash(key) & sbit) ? new : pag, key, val);
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off = ino[1];
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n -= 2;
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}
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debug(("%d split %d/%d\n", ((short *) cur)[0] / 2,
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((short *) new)[0] / 2,
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((short *) pag)[0] / 2));
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}
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/*
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* check page sanity:
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* number of entries should be something
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* reasonable, and all offsets in the index should be in order.
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* this could be made more rigorous.
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*/
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int
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chkpage(pag)
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char *pag;
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{
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register int n;
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register int off;
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register short *ino = (short *) pag;
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if ((n = ino[0]) < 0 || n > PBLKSIZ / sizeof(short))
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return 0;
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if (n > 0) {
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off = PBLKSIZ;
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for (ino++; n > 0; ino += 2) {
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if (ino[0] > off || ino[1] > off ||
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ino[1] > ino[0])
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return 0;
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off = ino[1];
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n -= 2;
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}
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}
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return 1;
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}
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