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);
}