hash_bigkey.c

asterisk 一个模拟IPPBX的源代码

/*-
 * 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.