hash_bigkey.c

Go to the documentation of this file.

/*-
 * 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);
}