hash_bigkey.c

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/*-
 * Copyright (c) 1990, 1993, 1994
 * The Regents of the University of California. All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * 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[] = "@(#)hash_bigkey.c 8.3 (Berkeley) 5/31/94";
#endif /* LIBC_SCCS and not lint */

/*
 * PACKAGE: hash
 * DESCRIPTION:
 * Big key/data handling for the hashing package.
 *
 * ROUTINES:
 * External
 * __big_keydata
 * __big_split
 * __big_insert
 * __big_return
 * __big_delete
 * __find_last_page
 * Internal
 * collect_key
 * collect_data
 */

#include <sys/param.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef DEBUG
#include <assert.h>
#endif

#include "../include/db.h"
#include "hash.h"
#include "page.h"
#include "extern.h"

static int collect_key __P((HTAB *, BUFHEAD *, int, DBT *, int));
static int collect_data __P((HTAB *, BUFHEAD *, int, int));

/*
 * Big_insert
 *
 * You need to do an insert and the key/data pair is too big
 *
 * Returns:
 * 0 ==> OK
 *-1 ==> ERROR
 */
extern int
__big_insert(hashp, bufp, key, val)
 HTAB *hashp;
 BUFHEAD *bufp;
 const DBT *key, *val;
{
 register u_int16_t *p;
 int key_size, n, val_size;
 u_int16_t space, move_bytes, off;
 char *cp, *key_data, *val_data;

 cp = bufp->page; /* Character pointer of p. */
 p = (u_int16_t *)cp;

 key_data = (char *)key->data;
 key_size = key->size;
 val_data = (char *)val->data;
 val_size = val->size;

 /* First move the Key */
 for (space = FREESPACE(p) - BIGOVERHEAD; key_size;
 space = FREESPACE(p) - BIGOVERHEAD) {
 move_bytes = MIN(space, key_size);
 off = OFFSET(p) - move_bytes;
 memmove(cp + off, key_data, move_bytes);
 key_size -= move_bytes;
 key_data += move_bytes;
 n = p[0];
 p[++n] = off;
 p[0] = ++n;
 FREESPACE(p) = off - PAGE_META(n);
 OFFSET(p) = off;
 p[n] = PARTIAL_KEY;
 bufp = __add_ovflpage(hashp, bufp);
 if (!bufp)
 return (-1);
 n = p[0];
 if (!key_size) {
 if (FREESPACE(p)) {
 move_bytes = MIN(FREESPACE(p), val_size);
 off = OFFSET(p) - move_bytes;
 p[n] = off;
 memmove(cp + off, val_data, move_bytes);
 val_data += move_bytes;
 val_size -= move_bytes;
 p[n - 2] = FULL_KEY_DATA;
 FREESPACE(p) = FREESPACE(p) - move_bytes;
 OFFSET(p) = off;
 } else
 p[n - 2] = FULL_KEY;
 }
 p = (u_int16_t *)bufp->page;
 cp = bufp->page;
 bufp->flags |= BUF_MOD;
 }

 /* Now move the data */
 for (space = FREESPACE(p) - BIGOVERHEAD; val_size;
 space = FREESPACE(p) - BIGOVERHEAD) {
 move_bytes = MIN(space, val_size);
 /*
 * Here's the hack to make sure that if the data ends on the
 * same page as the key ends, FREESPACE is at least one.
 */
 if ((int) space == val_size && (size_t) val_size == val->size)
 move_bytes--;
 off = OFFSET(p) - move_bytes;
 memmove(cp + off, val_data, move_bytes);
 val_size -= move_bytes;
 val_data += move_bytes;
 n = p[0];
 p[++n] = off;
 p[0] = ++n;
 FREESPACE(p) = off - PAGE_META(n);
 OFFSET(p) = off;
 if (val_size) {
 p[n] = FULL_KEY;
 bufp = __add_ovflpage(hashp, bufp);
 if (!bufp)
 return (-1);
 cp = bufp->page;
 p = (u_int16_t *)cp;
 } else
 p[n] = FULL_KEY_DATA;
 bufp->flags |= BUF_MOD;
 }
 return (0);
}

/*
 * Called when bufp's page contains a partial key (index should be 1)
 *
 * All pages in the big key/data pair except bufp are freed. We cannot
 * free bufp because the page pointing to it is lost and we can't get rid
 * of its pointer.
 *
 * Returns:
 * 0 => OK
 *-1 => ERROR
 */
extern int
__big_delete(hashp, bufp)
 HTAB *hashp;
 BUFHEAD *bufp;
{
 register BUFHEAD *last_bfp, *rbufp;
 u_int16_t *bp, pageno;
 int key_done, n;

 rbufp = bufp;
 last_bfp = NULL;
 bp = (u_int16_t *)bufp->page;
 pageno = 0;
 key_done = 0;

 while (!key_done || (bp[2] != FULL_KEY_DATA)) {
 if (bp[2] == FULL_KEY || bp[2] == FULL_KEY_DATA)
 key_done = 1;

 /*
 * If there is freespace left on a FULL_KEY_DATA page, then
 * the data is short and fits entirely on this page, and this
 * is the last page.
 */
 if (bp[2] == FULL_KEY_DATA && FREESPACE(bp))
 break;
 pageno = bp[bp[0] - 1];
 rbufp->flags |= BUF_MOD;
 rbufp = __get_buf(hashp, pageno, rbufp, 0);
 if (last_bfp)
 __free_ovflpage(hashp, last_bfp);
 last_bfp = rbufp;
 if (!rbufp)
 return (-1); /* Error. */
 bp = (u_int16_t *)rbufp->page;
 }

 /*
 * If we get here then rbufp points to the last page of the big
 * key/data pair. Bufp points to the first one -- it should now be
 * empty pointing to the next page after this pair. Can't free it
 * because we don't have the page pointing to it.
 */

 /* This is information from the last page of the pair. */
 n = bp[0];
 pageno = bp[n - 1];

 /* Now, bp is the first page of the pair. */
 bp = (u_int16_t *)bufp->page;
 if (n > 2) {
 /* There is an overflow page. */
 bp[1] = pageno;
 bp[2] = OVFLPAGE;
 bufp->ovfl = rbufp->ovfl;
 } else
 /* This is the last page. */
 bufp->ovfl = NULL;
 n -= 2;
 bp[0] = n;
 FREESPACE(bp) = hashp->BSIZE - PAGE_META(n);
 OFFSET(bp) = hashp->BSIZE - 1;

 bufp->flags |= BUF_MOD;
 if (rbufp)
 __free_ovflpage(hashp, rbufp);
 if (last_bfp && last_bfp != rbufp)
 __free_ovflpage(hashp, last_bfp);

 hashp->NKEYS--;
 return (0);
}
/*
 * Returns:
 * 0 = key not found
 * -1 = get next overflow page
 * -2 means key not found and this is big key/data
 * -3 error
 */
extern int
__find_bigpair(hashp, bufp, ndx, key, size)
 HTAB *hashp;
 BUFHEAD *bufp;
 int ndx;
 char *key;
 int size;
{
 register u_int16_t *bp;
 register char *p;
 int ksize;
 u_int16_t bytes;
 char *kkey;

 bp = (u_int16_t *)bufp->page;
 p = bufp->page;
 ksize = size;
 kkey = key;

 for (bytes = hashp->BSIZE - bp[ndx];
 bytes <= size && bp[ndx + 1] == PARTIAL_KEY;
 bytes = hashp->BSIZE - bp[ndx]) {
 if (memcmp(p + bp[ndx], kkey, bytes))
 return (-2);
 kkey += bytes;
 ksize -= bytes;
 bufp = __get_buf(hashp, bp[ndx + 2], bufp, 0);
 if (!bufp)
 return (-3);
 p = bufp->page;
 bp = (u_int16_t *)p;
 ndx = 1;
 }

 if (bytes != ksize || memcmp(p + bp[ndx], kkey, bytes)) {
#ifdef HASH_STATISTICS
 ++hash_collisions;
#endif
 return (-2);
 } else
 return (ndx);
}

/*
 * Given the buffer pointer of the first overflow page of a big pair,
 * find the end of the big pair
 *
 * This will set bpp to the buffer header of the last page of the big pair.
 * It will return the pageno of the overflow page following the last page
 * of the pair; 0 if there isn't any (i.e. big pair is the last key in the
 * bucket)
 */
extern u_int16_t
__find_last_page(hashp, bpp)
 HTAB *hashp;
 BUFHEAD **bpp;
{
 BUFHEAD *bufp;
 u_int16_t *bp, pageno;
 int n;

 bufp = *bpp;
 bp = (u_int16_t *)bufp->page;
 for (;;) {
 n = bp[0];

 /*
 * This is the last page if: the tag is FULL_KEY_DATA and
 * either only 2 entries OVFLPAGE marker is explicit there
 * is freespace on the page.
 */
 if (bp[2] == FULL_KEY_DATA &&
 ((n == 2) || (bp[n] == OVFLPAGE) || (FREESPACE(bp))))
 break;

 pageno = bp[n - 1];
 bufp = __get_buf(hashp, pageno, bufp, 0);
 if (!bufp)
 return (0); /* Need to indicate an error! */
 bp = (u_int16_t *)bufp->page;
 }

 *bpp = bufp;
 if (bp[0] > 2)
 return (bp[3]);
 else
 return (0);
}

/*
 * Return the data for the key/data pair that begins on this page at this
 * index (index should always be 1).
 */
extern int
__big_return(hashp, bufp, ndx, val, set_current)
 HTAB *hashp;
 BUFHEAD *bufp;
 int ndx;
 DBT *val;
 int set_current;
{
 BUFHEAD *save_p;
 u_int16_t *bp, len, off, save_addr;
 char *tp;

 bp = (u_int16_t *)bufp->page;
 while (bp[ndx + 1] == PARTIAL_KEY) {
 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 if (!bufp)
 return (-1);
 bp = (u_int16_t *)bufp->page;
 ndx = 1;
 }

 if (bp[ndx + 1] == FULL_KEY) {
 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 if (!bufp)
 return (-1);
 bp = (u_int16_t *)bufp->page;
 save_p = bufp;
 save_addr = save_p->addr;
 off = bp[1];
 len = 0;
 } else
 if (!FREESPACE(bp)) {
 /*
 * This is a hack. We can't distinguish between
 * FULL_KEY_DATA that contains complete data or
 * incomplete data, so we require that if the data
 * is complete, there is at least 1 byte of free
 * space left.
 */
 off = bp[bp[0]];
 len = bp[1] - off;
 save_p = bufp;
 save_addr = bufp->addr;
 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 if (!bufp)
 return (-1);
 bp = (u_int16_t *)bufp->page;
 } else {
 /* The data is all on one page. */
 tp = (char *)bp;
 off = bp[bp[0]];
 val->data = (u_char *)tp + off;
 val->size = bp[1] - off;
 if (set_current) {
 if (bp[0] == 2) { /* No more buckets in
 * chain */
 hashp->cpage = NULL;
 hashp->cbucket++;
 hashp->cndx = 1;
 } else {
 hashp->cpage = __get_buf(hashp,
 bp[bp[0] - 1], bufp, 0);
 if (!hashp->cpage)
 return (-1);
 hashp->cndx = 1;
 if (!((u_int16_t *)
 hashp->cpage->page)[0]) {
 hashp->cbucket++;
 hashp->cpage = NULL;
 }
 }
 }
 return (0);
 }

 val->size = collect_data(hashp, bufp, (int)len, set_current);
 if (val->size == (size_t) -1)
 return (-1);
 if (save_p->addr != save_addr) {
 /* We are pretty short on buffers. */
 errno = EINVAL; /* OUT OF BUFFERS */
 return (-1);
 }
 memmove(hashp->tmp_buf, (save_p->page) + off, len);
 val->data = (u_char *)hashp->tmp_buf;
 return (0);
}
/*
 * Count how big the total datasize is by recursing through the pages. Then
 * allocate a buffer and copy the data as you recurse up.
 */
static int
collect_data(hashp, bufp, len, set)
 HTAB *hashp;
 BUFHEAD *bufp;
 int len, set;
{
 register u_int16_t *bp;
 register char *p;
 BUFHEAD *xbp;
 u_int16_t save_addr;
 int mylen, totlen;

 p = bufp->page;
 bp = (u_int16_t *)p;
 mylen = hashp->BSIZE - bp[1];
 save_addr = bufp->addr;

 if (bp[2] == FULL_KEY_DATA) { /* End of Data */
 totlen = len + mylen;
 if (hashp->tmp_buf)
 free(hashp->tmp_buf);
 if ((hashp->tmp_buf = (char *)malloc(totlen)) == NULL)
 return (-1);
 if (set) {
 hashp->cndx = 1;
 if (bp[0] == 2) { /* No more buckets in chain */
 hashp->cpage = NULL;
 hashp->cbucket++;
 } else {
 hashp->cpage =
 __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 if (!hashp->cpage)
 return (-1);
 else if (!((u_int16_t *)hashp->cpage->page)[0]) {
 hashp->cbucket++;
 hashp->cpage = NULL;
 }
 }
 }
 } else {
 xbp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 if (!xbp || ((totlen =
 collect_data(hashp, xbp, len + mylen, set)) < 1))
 return (-1);
 }
 if (bufp->addr != save_addr) {
 errno = EINVAL; /* Out of buffers. */
 return (-1);
 }
 memmove(&hashp->tmp_buf[len], (bufp->page) + bp[1], mylen);
 return (totlen);
}

/*
 * Fill in the key and data for this big pair.
 */
extern int
__big_keydata(hashp, bufp, key, val, set)
 HTAB *hashp;
 BUFHEAD *bufp;
 DBT *key, *val;
 int set;
{
 key->size = collect_key(hashp, bufp, 0, val, set);
 if (key->size == (size_t) -1)
 return (-1);
 key->data = (u_char *)hashp->tmp_key;
 return (0);
}

/*
 * Count how big the total key size is by recursing through the pages. Then
 * collect the data, allocate a buffer and copy the key as you recurse up.
 */
static int
collect_key(hashp, bufp, len, val, set)
 HTAB *hashp;
 BUFHEAD *bufp;
 int len;
 DBT *val;
 int set;
{
 BUFHEAD *xbp;
 char *p;
 int mylen, totlen;
 u_int16_t *bp, save_addr;

 p = bufp->page;
 bp = (u_int16_t *)p;
 mylen = hashp->BSIZE - bp[1];

 save_addr = bufp->addr;
 totlen = len + mylen;
 if (bp[2] == FULL_KEY || bp[2] == FULL_KEY_DATA) { /* End of Key. */
 if (hashp->tmp_key != NULL)
 free(hashp->tmp_key);
 if ((hashp->tmp_key = (char *)malloc(totlen)) == NULL)
 return (-1);
 if (__big_return(hashp, bufp, 1, val, set))
 return (-1);
 } else {
 xbp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 if (!xbp || ((totlen =
 collect_key(hashp, xbp, totlen, val, set)) < 1))
 return (-1);
 }
 if (bufp->addr != save_addr) {
 errno = EINVAL; /* MIS -- OUT OF BUFFERS */
 return (-1);
 }
 memmove(&hashp->tmp_key[len], (bufp->page) + bp[1], mylen);
 return (totlen);
}

/*
 * Returns:
 * 0 => OK
 * -1 => error
 */
extern int
__big_split(hashp, op, np, big_keyp, addr, obucket, ret)
 HTAB *hashp;
 BUFHEAD *op; /* Pointer to where to put keys that go in old bucket */
 BUFHEAD *np; /* Pointer to new bucket page */
 /* Pointer to first page containing the big key/data */
 BUFHEAD *big_keyp;
 int addr; /* Address of big_keyp */
 u_int32_t obucket;/* Old Bucket */
 SPLIT_RETURN *ret;
{
 register BUFHEAD *tmpp;
 register u_int16_t *tp;
 BUFHEAD *bp;
 DBT key, val;
 u_int32_t change;
 u_int16_t free_space, n, off;

 bp = big_keyp;

 /* Now figure out where the big key/data goes */
 if (__big_keydata(hashp, big_keyp, &key, &val, 0))
 return (-1);
 change = (__call_hash(hashp, key.data, key.size) != obucket);

 if ((ret->next_addr = __find_last_page(hashp, &big_keyp))) {
 if (!(ret->nextp =
 __get_buf(hashp, ret->next_addr, big_keyp, 0)))
 return (-1);;
 } else
 ret->nextp = NULL;

 /* Now make one of np/op point to the big key/data pair */
#ifdef DEBUG
 assert(np->ovfl == NULL);
#endif
 if (change)
 tmpp = np;
 else
 tmpp = op;

 tmpp->flags |= BUF_MOD;
#ifdef DEBUG1
 (void)fprintf(stderr,
 "BIG_SPLIT: %d->ovfl was %d is now %d\n", tmpp->addr,
 (tmpp->ovfl ? tmpp->ovfl->addr : 0), (bp ? bp->addr : 0));
#endif
 tmpp->ovfl = bp; /* one of op/np point to big_keyp */
 tp = (u_int16_t *)tmpp->page;
#ifdef DEBUG
 assert(FREESPACE(tp) >= OVFLSIZE);
#endif
 n = tp[0];
 off = OFFSET(tp);
 free_space = FREESPACE(tp);
 tp[++n] = (u_int16_t)addr;
 tp[++n] = OVFLPAGE;
 tp[0] = n;
 OFFSET(tp) = off;
 FREESPACE(tp) = free_space - OVFLSIZE;

 /*
 * Finally, set the new and old return values. BIG_KEYP contains a
 * pointer to the last page of the big key_data pair. Make sure that
 * big_keyp has no following page (2 elements) or create an empty
 * following page.
 */

 ret->newp = np;
 ret->oldp = op;

 tp = (u_int16_t *)big_keyp->page;
 big_keyp->flags |= BUF_MOD;
 if (tp[0] > 2) {
 /*
 * There may be either one or two offsets on this page. If
 * there is one, then the overflow page is linked on normally
 * and tp[4] is OVFLPAGE. If there are two, tp[4] contains
 * the second offset and needs to get stuffed in after the
 * next overflow page is added.
 */
 n = tp[4];
 free_space = FREESPACE(tp);
 off = OFFSET(tp);
 tp[0] -= 2;
 FREESPACE(tp) = free_space + OVFLSIZE;
 OFFSET(tp) = off;
 tmpp = __add_ovflpage(hashp, big_keyp);
 if (!tmpp)
 return (-1);
 tp[4] = n;
 } else
 tmpp = big_keyp;

 if (change)
 ret->newp = tmpp;
 else
 ret->oldp = tmpp;
 return (0);
}