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hash_page.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *    Sleepycat Software.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994
 *    Margo Seltzer.  All rights reserved.
 */
/*
 * 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.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)hash_page.c   10.55 (Sleepycat) 1/3/99";
#endif /* not lint */

/*
 * PACKAGE:  hashing
 *
 * DESCRIPTION:
 *      Page manipulation for hashing package.
 *
 * ROUTINES:
 *
 * External
 *      __get_page
 *      __add_ovflpage
 *      __overflow_page
 * Internal
 *      open_temp
 */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <string.h>
#endif

#include "db_int.h"
#include "db_page.h"
#include "hash.h"

static int __ham_lock_bucket __P((DBC *, db_lockmode_t));

#ifdef DEBUG_SLOW
static void  __account_page(DB *, db_pgno_t, int);
#endif

/*
 * PUBLIC: int __ham_item __P((DBC *, db_lockmode_t));
 */
int
__ham_item(dbc, mode)
      DBC *dbc;
      db_lockmode_t mode;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      db_pgno_t next_pgno;
      int ret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;

      if (F_ISSET(hcp, H_DELETED))
            return (EINVAL);
      F_CLR(hcp, H_OK | H_NOMORE);

      /* Check if we need to get a page for this cursor. */
      if ((ret = __ham_get_cpage(dbc, mode)) != 0)
            return (ret);

      /* Check if we are looking for space in which to insert an item. */
      if (hcp->seek_size && hcp->seek_found_page == PGNO_INVALID
          && hcp->seek_size < P_FREESPACE(hcp->pagep))
            hcp->seek_found_page = hcp->pgno;

      /* Check if we need to go on to the next page. */
      if (F_ISSET(hcp, H_ISDUP) && hcp->dpgno == PGNO_INVALID)
            /*
             * ISDUP is set, and offset is at the beginning of the datum.
             * We need to grab the length of the datum, then set the datum
             * pointer to be the beginning of the datum.
             */
            memcpy(&hcp->dup_len,
                HKEYDATA_DATA(H_PAIRDATA(hcp->pagep, hcp->bndx)) +
                hcp->dup_off, sizeof(db_indx_t));
      else if (F_ISSET(hcp, H_ISDUP)) {
            /* Make sure we're not about to run off the page. */
            if (hcp->dpagep == NULL && (ret = __ham_get_page(dbp,
                hcp->dpgno, &hcp->dpagep)) != 0)
                  return (ret);

            if (hcp->dndx >= NUM_ENT(hcp->dpagep)) {
                  if (NEXT_PGNO(hcp->dpagep) == PGNO_INVALID) {
                        if (F_ISSET(hcp, H_DUPONLY)) {
                              F_CLR(hcp, H_OK);
                              F_SET(hcp, H_NOMORE);
                              return (0);
                        }
                        if ((ret = __ham_put_page(dbp,
                            hcp->dpagep, 0)) != 0)
                              return (ret);
                        F_CLR(hcp, H_ISDUP);
                        hcp->dpagep = NULL;
                        hcp->dpgno = PGNO_INVALID;
                        hcp->dndx = NDX_INVALID;
                        hcp->bndx++;
                  } else if ((ret = __ham_next_cpage(dbc,
                      NEXT_PGNO(hcp->dpagep), 0, H_ISDUP)) != 0)
                        return (ret);
            }
      }

      if (hcp->bndx >= (db_indx_t)H_NUMPAIRS(hcp->pagep)) {
            /* Fetch next page. */
            if (NEXT_PGNO(hcp->pagep) == PGNO_INVALID) {
                  F_SET(hcp, H_NOMORE);
                  if (hcp->dpagep != NULL &&
                      (ret = __ham_put_page(dbp, hcp->dpagep, 0)) != 0)
                        return (ret);
                  hcp->dpgno = PGNO_INVALID;
                  return (DB_NOTFOUND);
            }
            next_pgno = NEXT_PGNO(hcp->pagep);
            hcp->bndx = 0;
            if ((ret = __ham_next_cpage(dbc, next_pgno, 0, 0)) != 0)
                  return (ret);
      }

      F_SET(hcp, H_OK);
      return (0);
}

/*
 * PUBLIC: int __ham_item_reset __P((DBC *));
 */
int
__ham_item_reset(dbc)
      DBC *dbc;
{
      HASH_CURSOR *hcp;
      DB *dbp;
      int ret;

      ret = 0;
      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      if (hcp->pagep != NULL)
            ret = __ham_put_page(dbp, hcp->pagep, 0);
      if (ret == 0 && hcp->dpagep != NULL)
            ret = __ham_put_page(dbp, hcp->dpagep, 0);

      __ham_item_init(hcp);
      return (ret);
}

/*
 * PUBLIC: void __ham_item_init __P((HASH_CURSOR *));
 */
void
__ham_item_init(hcp)
      HASH_CURSOR *hcp;
{
      /*
       * If this cursor still holds any locks, we must
       * release them if we are not running with transactions.
       */
      if (hcp->lock && hcp->dbc->txn == NULL)
          (void)lock_put(hcp->dbc->dbp->dbenv->lk_info, hcp->lock);

      /*
       * The following fields must *not* be initialized here
       * because they may have meaning across inits.
       *    hlock, hdr, split_buf, stats
       */
      hcp->bucket = BUCKET_INVALID;
      hcp->lbucket = BUCKET_INVALID;
      hcp->lock = 0;
      hcp->pagep = NULL;
      hcp->pgno = PGNO_INVALID;
      hcp->bndx = NDX_INVALID;
      hcp->dpagep = NULL;
      hcp->dpgno = PGNO_INVALID;
      hcp->dndx = NDX_INVALID;
      hcp->dup_off = 0;
      hcp->dup_len = 0;
      hcp->dup_tlen = 0;
      hcp->seek_size = 0;
      hcp->seek_found_page = PGNO_INVALID;
      hcp->flags = 0;
}

/*
 * PUBLIC: int __ham_item_done __P((DBC *, int));
 */
int
__ham_item_done(dbc, dirty)
      DBC *dbc;
      int dirty;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      int ret, t_ret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      t_ret = ret = 0;

      if (hcp->pagep)
            ret = __ham_put_page(dbp, hcp->pagep,
                dirty && hcp->dpagep == NULL);
      hcp->pagep = NULL;

      if (hcp->dpagep)
            t_ret = __ham_put_page(dbp, hcp->dpagep, dirty);
      hcp->dpagep = NULL;

      if (ret == 0 && t_ret != 0)
            ret = t_ret;

      /*
       * We don't throw out the page number since we might want to
       * continue getting on this page.
       */
      return (ret != 0 ? ret : t_ret);
}

/*
 * Returns the last item in a bucket.
 *
 * PUBLIC: int __ham_item_last __P((DBC *, db_lockmode_t));
 */
int
__ham_item_last(dbc, mode)
      DBC *dbc;
      db_lockmode_t mode;
{
      HASH_CURSOR *hcp;
      int ret;

      hcp = (HASH_CURSOR *)dbc->internal;
      if ((ret = __ham_item_reset(dbc)) != 0)
            return (ret);

      hcp->bucket = hcp->hdr->max_bucket;
      F_SET(hcp, H_OK);
      return (__ham_item_prev(dbc, mode));
}

/*
 * PUBLIC: int __ham_item_first __P((DBC *, db_lockmode_t));
 */
int
__ham_item_first(dbc, mode)
      DBC *dbc;
      db_lockmode_t mode;
{
      HASH_CURSOR *hcp;
      int ret;

      hcp = (HASH_CURSOR *)dbc->internal;
      if ((ret = __ham_item_reset(dbc)) != 0)
            return (ret);
      F_SET(hcp, H_OK);
      hcp->bucket = 0;
      return (__ham_item_next(dbc, mode));
}

/*
 * __ham_item_prev --
 *    Returns a pointer to key/data pair on a page.  In the case of
 *    bigkeys, just returns the page number and index of the bigkey
 *    pointer pair.
 *
 * PUBLIC: int __ham_item_prev __P((DBC *, db_lockmode_t));
 */
int
__ham_item_prev(dbc, mode)
      DBC *dbc;
      db_lockmode_t mode;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      db_pgno_t next_pgno;
      int ret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      /*
       * There are N cases for backing up in a hash file.
       * Case 1: In the middle of a page, no duplicates, just dec the index.
       * Case 2: In the middle of a duplicate set, back up one.
       * Case 3: At the beginning of a duplicate set, get out of set and
       *    back up to next key.
       * Case 4: At the beginning of a page; go to previous page.
       * Case 5: At the beginning of a bucket; go to prev bucket.
       */
      F_CLR(hcp, H_OK | H_NOMORE | H_DELETED);

      /*
       * First handle the duplicates.  Either you'll get the key here
       * or you'll exit the duplicate set and drop into the code below
       * to handle backing up through keys.
       */
      if (F_ISSET(hcp, H_ISDUP)) {
            if (hcp->dpgno == PGNO_INVALID) {
                  /* Duplicates are on-page. */
                  if (hcp->dup_off != 0)
                        if ((ret = __ham_get_cpage(dbc, mode)) != 0)
                              return (ret);
                        else {
                              HASH_CURSOR *h;
                              h = hcp;
                              memcpy(&h->dup_len, HKEYDATA_DATA(
                                  H_PAIRDATA(h->pagep, h->bndx))
                                  + h->dup_off - sizeof(db_indx_t),
                                  sizeof(db_indx_t));
                              hcp->dup_off -=
                                  DUP_SIZE(hcp->dup_len);
                              hcp->dndx--;
                              return (__ham_item(dbc, mode));
                        }
            } else if (hcp->dndx > 0) {   /* Duplicates are off-page. */
                  hcp->dndx--;
                  return (__ham_item(dbc, mode));
            } else if ((ret = __ham_get_cpage(dbc, mode)) != 0)
                  return (ret);
            else if (PREV_PGNO(hcp->dpagep) == PGNO_INVALID) {
                  if (F_ISSET(hcp, H_DUPONLY)) {
                        F_CLR(hcp, H_OK);
                        F_SET(hcp, H_NOMORE);
                        return (0);
                  } else {
                        F_CLR(hcp, H_ISDUP); /* End of dups */
                        hcp->dpgno = PGNO_INVALID;
                        if (hcp->dpagep != NULL)
                              (void)__ham_put_page(dbp,
                                  hcp->dpagep, 0);
                        hcp->dpagep = NULL;
                  }
            } else if ((ret = __ham_next_cpage(dbc,
                PREV_PGNO(hcp->dpagep), 0, H_ISDUP)) != 0)
                  return (ret);
            else {
                  hcp->dndx = NUM_ENT(hcp->pagep) - 1;
                  return (__ham_item(dbc, mode));
            }
      }

      /*
       * If we get here, we are not in a duplicate set, and just need
       * to back up the cursor.  There are still three cases:
       * midpage, beginning of page, beginning of bucket.
       */

      if (F_ISSET(hcp, H_DUPONLY)) {
            F_CLR(hcp, H_OK);
            F_SET(hcp, H_NOMORE);
            return (0);
      }

      if (hcp->bndx == 0) {         /* Beginning of page. */
            if ((ret = __ham_get_cpage(dbc, mode)) != 0)
                  return (ret);
            hcp->pgno = PREV_PGNO(hcp->pagep);
            if (hcp->pgno == PGNO_INVALID) {
                  /* Beginning of bucket. */
                  F_SET(hcp, H_NOMORE);
                  return (DB_NOTFOUND);
            } else if ((ret =
                __ham_next_cpage(dbc, hcp->pgno, 0, 0)) != 0)
                  return (ret);
            else
                  hcp->bndx = H_NUMPAIRS(hcp->pagep);
      }

      /*
       * Either we've got the cursor set up to be decremented, or we
       * have to find the end of a bucket.
       */
      if (hcp->bndx == NDX_INVALID) {
            if (hcp->pagep == NULL)
                  next_pgno = BUCKET_TO_PAGE(hcp, hcp->bucket);
            else
                  goto got_page;

            do {
                  if ((ret = __ham_next_cpage(dbc, next_pgno, 0, 0)) != 0)
                        return (ret);
got_page:         next_pgno = NEXT_PGNO(hcp->pagep);
                  hcp->bndx = H_NUMPAIRS(hcp->pagep);
            } while (next_pgno != PGNO_INVALID);

            if (hcp->bndx == 0) {
                  /* Bucket was empty. */
                  F_SET(hcp, H_NOMORE);
                  return (DB_NOTFOUND);
            }
      }

      hcp->bndx--;

      return (__ham_item(dbc, mode));
}

/*
 * Sets the cursor to the next key/data pair on a page.
 *
 * PUBLIC: int __ham_item_next __P((DBC *, db_lockmode_t));
 */
int
__ham_item_next(dbc, mode)
      DBC *dbc;
      db_lockmode_t mode;
{
      HASH_CURSOR *hcp;

      hcp = (HASH_CURSOR *)dbc->internal;
      /*
       * Deleted on-page duplicates are a weird case. If we delete the last
       * one, then our cursor is at the very end of a duplicate set and
       * we actually need to go on to the next key.
       */
      if (F_ISSET(hcp, H_DELETED)) {
            if (hcp->bndx != NDX_INVALID &&
                F_ISSET(hcp, H_ISDUP) &&
                hcp->dpgno == PGNO_INVALID &&
                hcp->dup_tlen == hcp->dup_off) {
                  if (F_ISSET(hcp, H_DUPONLY)) {
                        F_CLR(hcp, H_OK);
                        F_SET(hcp, H_NOMORE);
                        return (0);
                  } else {
                        F_CLR(hcp, H_ISDUP);
                        hcp->dpgno = PGNO_INVALID;
                        hcp->bndx++;
                  }
            } else if (!F_ISSET(hcp, H_ISDUP) &&
                F_ISSET(hcp, H_DUPONLY)) {
                  F_CLR(hcp, H_OK);
                  F_SET(hcp, H_NOMORE);
                  return (0);
            }
            F_CLR(hcp, H_DELETED);
      } else if (hcp->bndx == NDX_INVALID) {
            hcp->bndx = 0;
            hcp->dpgno = PGNO_INVALID;
            F_CLR(hcp, H_ISDUP);
      } else if (F_ISSET(hcp, H_ISDUP) && hcp->dpgno != PGNO_INVALID)
            hcp->dndx++;
      else if (F_ISSET(hcp, H_ISDUP)) {
            if (hcp->dup_off + DUP_SIZE(hcp->dup_len) >=
                hcp->dup_tlen && F_ISSET(hcp, H_DUPONLY)) {
                  F_CLR(hcp, H_OK);
                  F_SET(hcp, H_NOMORE);
                  return (0);
            }
            hcp->dndx++;
            hcp->dup_off += DUP_SIZE(hcp->dup_len);
            if (hcp->dup_off >= hcp->dup_tlen) {
                  F_CLR(hcp, H_ISDUP);
                  hcp->dpgno = PGNO_INVALID;
                  hcp->bndx++;
            }
      } else if (F_ISSET(hcp, H_DUPONLY)) {
            F_CLR(hcp, H_OK);
            F_SET(hcp, H_NOMORE);
            return (0);
      } else
            hcp->bndx++;

      return (__ham_item(dbc, mode));
}

/*
 * PUBLIC: void __ham_putitem __P((PAGE *p, const DBT *, int));
 *
 * This is a little bit sleazy in that we're overloading the meaning
 * of the H_OFFPAGE type here.  When we recover deletes, we have the
 * entire entry instead of having only the DBT, so we'll pass type
 * H_OFFPAGE to mean, "copy the whole entry" as opposed to constructing
 * an H_KEYDATA around it.
 */
void
__ham_putitem(p, dbt, type)
      PAGE *p;
      const DBT *dbt;
      int type;
{
      u_int16_t n, off;

      n = NUM_ENT(p);

      /* Put the item element on the page. */
      if (type == H_OFFPAGE) {
            off = HOFFSET(p) - dbt->size;
            HOFFSET(p) = p->inp[n] = off;
            memcpy(P_ENTRY(p, n), dbt->data, dbt->size);
      } else {
            off = HOFFSET(p) - HKEYDATA_SIZE(dbt->size);
            HOFFSET(p) = p->inp[n] = off;
            PUT_HKEYDATA(P_ENTRY(p, n), dbt->data, dbt->size, type);
      }

      /* Adjust page info. */
      NUM_ENT(p) += 1;
}

/*
 * PUBLIC: void __ham_reputpair
 * PUBLIC:    __P((PAGE *p, u_int32_t, u_int32_t, const DBT *, const DBT *));
 *
 * This is a special case to restore a key/data pair to its original
 * location during recovery.  We are guaranteed that the pair fits
 * on the page and is not the last pair on the page (because if it's
 * the last pair, the normal insert works).
 */
void
__ham_reputpair(p, psize, ndx, key, data)
      PAGE *p;
      u_int32_t psize, ndx;
      const DBT *key, *data;
{
      db_indx_t i, movebytes, newbytes;
      u_int8_t *from;

      /* First shuffle the existing items up on the page.  */
      movebytes =
          (ndx == 0 ? psize : p->inp[H_DATAINDEX(ndx - 1)]) - HOFFSET(p);
      newbytes = key->size + data->size;
      from = (u_int8_t *)p + HOFFSET(p);
      memmove(from - newbytes, from, movebytes);

      /*
       * Adjust the indices and move them up 2 spaces. Note that we
       * have to check the exit condition inside the loop just in case
       * we are dealing with index 0 (db_indx_t's are unsigned).
       */
      for (i = NUM_ENT(p) - 1; ; i-- ) {
            p->inp[i + 2] = p->inp[i] - newbytes;
            if (i == H_KEYINDEX(ndx))
                  break;
      }

      /* Put the key and data on the page. */
      p->inp[H_KEYINDEX(ndx)] =
          (ndx == 0 ? psize : p->inp[H_DATAINDEX(ndx - 1)]) - key->size;
      p->inp[H_DATAINDEX(ndx)] = p->inp[H_KEYINDEX(ndx)] - data->size;
      memcpy(P_ENTRY(p, H_KEYINDEX(ndx)), key->data, key->size);
      memcpy(P_ENTRY(p, H_DATAINDEX(ndx)), data->data, data->size);

      /* Adjust page info. */
      HOFFSET(p) -= newbytes;
      NUM_ENT(p) += 2;
}


/*
 * PUBLIC: int __ham_del_pair __P((DBC *, int));
 */
int
__ham_del_pair(dbc, reclaim_page)
      DBC *dbc;
      int reclaim_page;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      DBT data_dbt, key_dbt;
      DB_ENV *dbenv;
      DB_LSN new_lsn, *n_lsn, tmp_lsn;
      PAGE *p;
      db_indx_t ndx;
      db_pgno_t chg_pgno, pgno;
      int ret, tret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;

      dbenv = dbp->dbenv;
      ndx = hcp->bndx;
      if (hcp->pagep == NULL &&
          (ret = __ham_get_page(dbp, hcp->pgno, &hcp->pagep)) != 0)
            return (ret);

      p = hcp->pagep;

      /*
       * We optimize for the normal case which is when neither the key nor
       * the data are large.  In this case, we write a single log record
       * and do the delete.  If either is large, we'll call __big_delete
       * to remove the big item and then update the page to remove the
       * entry referring to the big item.
       */
      ret = 0;
      if (HPAGE_PTYPE(H_PAIRKEY(p, ndx)) == H_OFFPAGE) {
            memcpy(&pgno, HOFFPAGE_PGNO(P_ENTRY(p, H_KEYINDEX(ndx))),
                sizeof(db_pgno_t));
            ret = __db_doff(dbc, pgno, __ham_del_page);
      }

      if (ret == 0)
            switch (HPAGE_PTYPE(H_PAIRDATA(p, ndx))) {
            case H_OFFPAGE:
                  memcpy(&pgno,
                      HOFFPAGE_PGNO(P_ENTRY(p, H_DATAINDEX(ndx))),
                      sizeof(db_pgno_t));
                  ret = __db_doff(dbc, pgno, __ham_del_page);
                  break;
            case H_OFFDUP:
                  memcpy(&pgno,
                      HOFFDUP_PGNO(P_ENTRY(p, H_DATAINDEX(ndx))),
                      sizeof(db_pgno_t));
                  ret = __db_ddup(dbc, pgno, __ham_del_page);
                  F_CLR(hcp, H_ISDUP);
                  break;
            case H_DUPLICATE:
                  /*
                   * If we delete a pair that is/was a duplicate, then
                   * we had better clear the flag so that we update the
                   * cursor appropriately.
                   */
                  F_CLR(hcp, H_ISDUP);
                  break;
            }

      if (ret)
            return (ret);

      /* Now log the delete off this page. */
      if (DB_LOGGING(dbc)) {
            key_dbt.data = P_ENTRY(p, H_KEYINDEX(ndx));
            key_dbt.size =
                LEN_HITEM(p, hcp->hdr->pagesize, H_KEYINDEX(ndx));
            data_dbt.data = P_ENTRY(p, H_DATAINDEX(ndx));
            data_dbt.size =
                LEN_HITEM(p, hcp->hdr->pagesize, H_DATAINDEX(ndx));

            if ((ret = __ham_insdel_log(dbenv->lg_info,
                dbc->txn, &new_lsn, 0, DELPAIR,
                dbp->log_fileid, PGNO(p), (u_int32_t)ndx,
                &LSN(p), &key_dbt, &data_dbt)) != 0)
                  return (ret);

            /* Move lsn onto page. */
            LSN(p) = new_lsn;
      }

      __ham_dpair(dbp, p, ndx);

      /*
       * If we are locking, we will not maintain this, because it is
       * a hot spot.
       * XXX perhaps we can retain incremental numbers and apply them
       * later.
       */
      if (!F_ISSET(dbp, DB_AM_LOCKING))
            --hcp->hdr->nelem;

      /*
       * If we need to reclaim the page, then check if the page is empty.
       * There are two cases.  If it's empty and it's not the first page
       * in the bucket (i.e., the bucket page) then we can simply remove
       * it. If it is the first chain in the bucket, then we need to copy
       * the second page into it and remove the second page.
       */
      if (reclaim_page && NUM_ENT(p) == 0 && PREV_PGNO(p) == PGNO_INVALID &&
          NEXT_PGNO(p) != PGNO_INVALID) {
            PAGE *n_pagep, *nn_pagep;
            db_pgno_t tmp_pgno;

            /*
             * First page in chain is empty and we know that there
             * are more pages in the chain.
             */
            if ((ret =
                __ham_get_page(dbp, NEXT_PGNO(p), &n_pagep)) != 0)
                  return (ret);

            if (NEXT_PGNO(n_pagep) != PGNO_INVALID) {
                  if ((ret =
                      __ham_get_page(dbp, NEXT_PGNO(n_pagep),
                      &nn_pagep)) != 0) {
                        (void) __ham_put_page(dbp, n_pagep, 0);
                        return (ret);
                  }
            }

            if (DB_LOGGING(dbc)) {
                  key_dbt.data = n_pagep;
                  key_dbt.size = hcp->hdr->pagesize;
                  if ((ret = __ham_copypage_log(dbenv->lg_info,
                      dbc->txn, &new_lsn, 0, dbp->log_fileid, PGNO(p),
                      &LSN(p), PGNO(n_pagep), &LSN(n_pagep),
                      NEXT_PGNO(n_pagep),
                      NEXT_PGNO(n_pagep) == PGNO_INVALID ? NULL :
                      &LSN(nn_pagep), &key_dbt)) != 0)
                        return (ret);

                  /* Move lsn onto page. */
                  LSN(p) = new_lsn; /* Structure assignment. */
                  LSN(n_pagep) = new_lsn;
                  if (NEXT_PGNO(n_pagep) != PGNO_INVALID)
                        LSN(nn_pagep) = new_lsn;
            }
            if (NEXT_PGNO(n_pagep) != PGNO_INVALID) {
                  PREV_PGNO(nn_pagep) = PGNO(p);
                  (void)__ham_put_page(dbp, nn_pagep, 1);
            }

            tmp_pgno = PGNO(p);
            tmp_lsn = LSN(p);
            memcpy(p, n_pagep, hcp->hdr->pagesize);
            PGNO(p) = tmp_pgno;
            LSN(p) = tmp_lsn;
            PREV_PGNO(p) = PGNO_INVALID;

            /*
             * Cursor is advanced to the beginning of the next page.
             */
            hcp->bndx = 0;
            hcp->pgno = PGNO(p);
            F_SET(hcp, H_DELETED);
            chg_pgno = PGNO(p);
            if ((ret = __ham_dirty_page(dbp, p)) != 0 ||
                (ret = __ham_del_page(dbc, n_pagep)) != 0)
                  return (ret);
      } else if (reclaim_page &&
          NUM_ENT(p) == 0 && PREV_PGNO(p) != PGNO_INVALID) {
            PAGE *n_pagep, *p_pagep;

            if ((ret =
                __ham_get_page(dbp, PREV_PGNO(p), &p_pagep)) != 0)
                  return (ret);

            if (NEXT_PGNO(p) != PGNO_INVALID) {
                  if ((ret = __ham_get_page(dbp,
                      NEXT_PGNO(p), &n_pagep)) != 0) {
                        (void)__ham_put_page(dbp, p_pagep, 0);
                        return (ret);
                  }
                  n_lsn = &LSN(n_pagep);
            } else {
                  n_pagep = NULL;
                  n_lsn = NULL;
            }

            NEXT_PGNO(p_pagep) = NEXT_PGNO(p);
            if (n_pagep != NULL)
                  PREV_PGNO(n_pagep) = PGNO(p_pagep);

            if (DB_LOGGING(dbc)) {
                  if ((ret = __ham_newpage_log(dbenv->lg_info,
                      dbc->txn, &new_lsn, 0, DELOVFL,
                      dbp->log_fileid, PREV_PGNO(p), &LSN(p_pagep),
                      PGNO(p), &LSN(p), NEXT_PGNO(p), n_lsn)) != 0)
                        return (ret);

                  /* Move lsn onto page. */
                  LSN(p_pagep) = new_lsn; /* Structure assignment. */
                  if (n_pagep)
                        LSN(n_pagep) = new_lsn;
                  LSN(p) = new_lsn;
            }
            hcp->pgno = NEXT_PGNO(p);
            hcp->bndx = 0;
            /*
             * Since we are about to delete the cursor page and we have
             * just moved the cursor, we need to make sure that the
             * old page pointer isn't left hanging around in the cursor.
             */
            hcp->pagep = NULL;
            chg_pgno = PGNO(p);
            ret = __ham_del_page(dbc, p);
            if ((tret = __ham_put_page(dbp, p_pagep, 1)) != 0 &&
                ret == 0)
                  ret = tret;
            if (n_pagep != NULL &&
                (tret = __ham_put_page(dbp, n_pagep, 1)) != 0 &&
                ret == 0)
                  ret = tret;
            if (ret != 0)
                  return (ret);
      } else {
            /*
             * Mark item deleted so that we don't try to return it, and
             * so that we update the cursor correctly on the next call
             * to next.
             */
            F_SET(hcp, H_DELETED);
            chg_pgno = hcp->pgno;
            ret = __ham_dirty_page(dbp, p);
      }
      __ham_c_update(hcp, chg_pgno, 0, 0, 0);

      /*
       * Since we just deleted a pair from the master page, anything
       * in hcp->dpgno should be cleared.
       */
      hcp->dpgno = PGNO_INVALID;

      F_CLR(hcp, H_OK);
      return (ret);
}

/*
 * __ham_replpair --
 *    Given the key data indicated by the cursor, replace part/all of it
 *    according to the fields in the dbt.
 *
 * PUBLIC: int __ham_replpair __P((DBC *, DBT *, u_int32_t));
 */
int
__ham_replpair(dbc, dbt, make_dup)
      DBC *dbc;
      DBT *dbt;
      u_int32_t make_dup;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      DBT old_dbt, tdata, tmp;
      DB_LSN      new_lsn;
      int32_t change;               /* XXX: Possible overflow. */
      u_int32_t len;
      int is_big, ret, type;
      u_int8_t *beg, *dest, *end, *hk, *src;

      /*
       * Big item replacements are handled in generic code.
       * Items that fit on the current page fall into 4 classes.
       * 1. On-page element, same size
       * 2. On-page element, new is bigger (fits)
       * 3. On-page element, new is bigger (does not fit)
       * 4. On-page element, old is bigger
       * Numbers 1, 2, and 4 are essentially the same (and should
       * be the common case).  We handle case 3 as a delete and
       * add.
       */
      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;

      /*
       * We need to compute the number of bytes that we are adding or
       * removing from the entry.  Normally, we can simply substract
       * the number of bytes we are replacing (dbt->dlen) from the
       * number of bytes we are inserting (dbt->size).  However, if
       * we are doing a partial put off the end of a record, then this
       * formula doesn't work, because we are essentially adding
       * new bytes.
       */
      change = dbt->size - dbt->dlen;

      hk = H_PAIRDATA(hcp->pagep, hcp->bndx);
      is_big = HPAGE_PTYPE(hk) == H_OFFPAGE;

      if (is_big)
            memcpy(&len, HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
      else
            len = LEN_HKEYDATA(hcp->pagep,
                dbp->pgsize, H_DATAINDEX(hcp->bndx));

      if (dbt->doff + dbt->dlen > len)
            change += dbt->doff + dbt->dlen - len;


      if (change > (int32_t)P_FREESPACE(hcp->pagep) || is_big) {
            /*
             * Case 3 -- two subcases.
             * A. This is not really a partial operation, but an overwrite.
             *    Simple del and add works.
             * B. This is a partial and we need to construct the data that
             *    we are really inserting (yuck).
             * In both cases, we need to grab the key off the page (in
             * some cases we could do this outside of this routine; for
             * cleanliness we do it here.  If you happen to be on a big
             * key, this could be a performance hit).
             */
            tmp.flags = 0;
            F_SET(&tmp, DB_DBT_MALLOC | DB_DBT_INTERNAL);
            if ((ret =
                __db_ret(dbp, hcp->pagep, H_KEYINDEX(hcp->bndx),
                &tmp, &dbc->rkey.data, &dbc->rkey.size)) != 0)
                  return (ret);

            if (dbt->doff == 0 && dbt->dlen == len) {
                  ret = __ham_del_pair(dbc, 0);
                  if (ret == 0)
                      ret = __ham_add_el(dbc, &tmp, dbt, H_KEYDATA);
            } else {                            /* Case B */
                  type = HPAGE_PTYPE(hk) != H_OFFPAGE ?
                      HPAGE_PTYPE(hk) : H_KEYDATA;
                  tdata.flags = 0;
                  F_SET(&tdata, DB_DBT_MALLOC | DB_DBT_INTERNAL);

                  if ((ret = __db_ret(dbp, hcp->pagep,
                      H_DATAINDEX(hcp->bndx), &tdata, &dbc->rdata.data,
                      &dbc->rdata.size)) != 0)
                        goto err;

                  /* Now we can delete the item. */
                  if ((ret = __ham_del_pair(dbc, 0)) != 0) {
                        __os_free(tdata.data, tdata.size);
                        goto err;
                  }

                  /* Now shift old data around to make room for new. */
                  if (change > 0) {
                         if ((ret = __os_realloc(&tdata.data,
                             tdata.size + change)) != 0)
                              return (ret);
                        memset((u_int8_t *)tdata.data + tdata.size,
                            0, change);
                  }
                  end = (u_int8_t *)tdata.data + tdata.size;

                  src = (u_int8_t *)tdata.data + dbt->doff + dbt->dlen;
                  if (src < end && tdata.size > dbt->doff + dbt->dlen) {
                        len = tdata.size - dbt->doff - dbt->dlen;
                        dest = src + change;
                        memmove(dest, src, len);
                  }
                  memcpy((u_int8_t *)tdata.data + dbt->doff,
                      dbt->data, dbt->size);
                  tdata.size += change;

                  /* Now add the pair. */
                  ret = __ham_add_el(dbc, &tmp, &tdata, type);
                  __os_free(tdata.data, tdata.size);
            }
err:        __os_free(tmp.data, tmp.size);
            return (ret);
      }

      /*
       * Set up pointer into existing data. Do it before the log
       * message so we can use it inside of the log setup.
       */
      beg = HKEYDATA_DATA(H_PAIRDATA(hcp->pagep, hcp->bndx));
      beg += dbt->doff;

      /*
       * If we are going to have to move bytes at all, figure out
       * all the parameters here.  Then log the call before moving
       * anything around.
       */
      if (DB_LOGGING(dbc)) {
            old_dbt.data = beg;
            old_dbt.size = dbt->dlen;
            if ((ret = __ham_replace_log(dbp->dbenv->lg_info,
                dbc->txn, &new_lsn, 0, dbp->log_fileid, PGNO(hcp->pagep),
                (u_int32_t)H_DATAINDEX(hcp->bndx), &LSN(hcp->pagep),
                (u_int32_t)dbt->doff, &old_dbt, dbt, make_dup)) != 0)
                  return (ret);

            LSN(hcp->pagep) = new_lsn;    /* Structure assignment. */
      }

      __ham_onpage_replace(hcp->pagep, dbp->pgsize,
          (u_int32_t)H_DATAINDEX(hcp->bndx), (int32_t)dbt->doff, change, dbt);

      return (0);
}

/*
 * Replace data on a page with new data, possibly growing or shrinking what's
 * there.  This is called on two different occasions. On one (from replpair)
 * we are interested in changing only the data.  On the other (from recovery)
 * we are replacing the entire data (header and all) with a new element.  In
 * the latter case, the off argument is negative.
 * pagep: the page that we're changing
 * ndx: page index of the element that is growing/shrinking.
 * off: Offset at which we are beginning the replacement.
 * change: the number of bytes (+ or -) that the element is growing/shrinking.
 * dbt: the new data that gets written at beg.
 * PUBLIC: void __ham_onpage_replace __P((PAGE *, size_t, u_int32_t, int32_t,
 * PUBLIC:     int32_t,  DBT *));
 */
void
__ham_onpage_replace(pagep, pgsize, ndx, off, change, dbt)
      PAGE *pagep;
      size_t pgsize;
      u_int32_t ndx;
      int32_t off;
      int32_t change;
      DBT *dbt;
{
      db_indx_t i;
      int32_t len;
      u_int8_t *src, *dest;
      int zero_me;

      if (change != 0) {
            zero_me = 0;
            src = (u_int8_t *)(pagep) + HOFFSET(pagep);
            if (off < 0)
                  len = pagep->inp[ndx] - HOFFSET(pagep);
            else if ((u_int32_t)off >= LEN_HKEYDATA(pagep, pgsize, ndx)) {
                  len = HKEYDATA_DATA(P_ENTRY(pagep, ndx)) +
                      LEN_HKEYDATA(pagep, pgsize, ndx) - src;
                  zero_me = 1;
            } else
                  len = (HKEYDATA_DATA(P_ENTRY(pagep, ndx)) + off) - src;
            dest = src - change;
            memmove(dest, src, len);
            if (zero_me)
                  memset(dest + len, 0, change);

            /* Now update the indices. */
            for (i = ndx; i < NUM_ENT(pagep); i++)
                  pagep->inp[i] -= change;
            HOFFSET(pagep) -= change;
      }
      if (off >= 0)
            memcpy(HKEYDATA_DATA(P_ENTRY(pagep, ndx)) + off,
                dbt->data, dbt->size);
      else
            memcpy(P_ENTRY(pagep, ndx), dbt->data, dbt->size);
}

/*
 * PUBLIC: int __ham_split_page __P((DBC *, u_int32_t, u_int32_t));
 */
int
__ham_split_page(dbc, obucket, nbucket)
      DBC *dbc;
      u_int32_t obucket, nbucket;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      DBT key, page_dbt;
      DB_ENV *dbenv;
      DB_LSN new_lsn;
      PAGE **pp, *old_pagep, *temp_pagep, *new_pagep;
      db_indx_t n;
      db_pgno_t bucket_pgno, next_pgno;
      u_int32_t big_len, len;
      int ret, tret;
      void *big_buf;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      dbenv = dbp->dbenv;
      temp_pagep = old_pagep = new_pagep = NULL;

      bucket_pgno = BUCKET_TO_PAGE(hcp, obucket);
      if ((ret = __ham_get_page(dbp, bucket_pgno, &old_pagep)) != 0)
            return (ret);
      if ((ret = __ham_new_page(dbp, BUCKET_TO_PAGE(hcp, nbucket), P_HASH,
          &new_pagep)) != 0)
            goto err;

      temp_pagep = hcp->split_buf;
      memcpy(temp_pagep, old_pagep, hcp->hdr->pagesize);

      if (DB_LOGGING(dbc)) {
            page_dbt.size = hcp->hdr->pagesize;
            page_dbt.data = old_pagep;
            if ((ret = __ham_splitdata_log(dbenv->lg_info,
                dbc->txn, &new_lsn, 0, dbp->log_fileid, SPLITOLD,
                PGNO(old_pagep), &page_dbt, &LSN(old_pagep))) != 0)
                  goto err;
      }

      P_INIT(old_pagep, hcp->hdr->pagesize, PGNO(old_pagep), PGNO_INVALID,
          PGNO_INVALID, 0, P_HASH);

      if (DB_LOGGING(dbc))
            LSN(old_pagep) = new_lsn;     /* Structure assignment. */

      big_len = 0;
      big_buf = NULL;
      key.flags = 0;
      while (temp_pagep != NULL) {
            for (n = 0; n < (db_indx_t)H_NUMPAIRS(temp_pagep); n++) {
                  if ((ret =
                      __db_ret(dbp, temp_pagep, H_KEYINDEX(n),
                      &key, &big_buf, &big_len)) != 0)
                        goto err;

                  if (__ham_call_hash(hcp, key.data, key.size)
                      == obucket)
                        pp = &old_pagep;
                  else
                        pp = &new_pagep;

                  /*
                   * Figure out how many bytes we need on the new
                   * page to store the key/data pair.
                   */

                  len = LEN_HITEM(temp_pagep, hcp->hdr->pagesize,
                      H_DATAINDEX(n)) +
                      LEN_HITEM(temp_pagep, hcp->hdr->pagesize,
                      H_KEYINDEX(n)) +
                      2 * sizeof(db_indx_t);

                  if (P_FREESPACE(*pp) < len) {
                        if (DB_LOGGING(dbc)) {
                              page_dbt.size = hcp->hdr->pagesize;
                              page_dbt.data = *pp;
                              if ((ret = __ham_splitdata_log(
                                  dbenv->lg_info, dbc->txn,
                                  &new_lsn, 0, dbp->log_fileid,
                                  SPLITNEW, PGNO(*pp), &page_dbt,
                                  &LSN(*pp))) != 0)
                                    goto err;
                              LSN(*pp) = new_lsn;
                        }
                        if ((ret =
                            __ham_add_ovflpage(dbc, *pp, 1, pp)) != 0)
                              goto err;
                  }
                  __ham_copy_item(dbp->pgsize,
                      temp_pagep, H_KEYINDEX(n), *pp);
                  __ham_copy_item(dbp->pgsize,
                      temp_pagep, H_DATAINDEX(n), *pp);
            }
            next_pgno = NEXT_PGNO(temp_pagep);

            /* Clear temp_page; if it's a link overflow page, free it. */
            if (PGNO(temp_pagep) != bucket_pgno && (ret =
                __ham_del_page(dbc, temp_pagep)) != 0)
                  goto err;

            if (next_pgno == PGNO_INVALID)
                  temp_pagep = NULL;
            else if ((ret =
                __ham_get_page(dbp, next_pgno, &temp_pagep)) != 0)
                  goto err;

            if (temp_pagep != NULL && DB_LOGGING(dbc)) {
                  page_dbt.size = hcp->hdr->pagesize;
                  page_dbt.data = temp_pagep;
                  if ((ret = __ham_splitdata_log(dbenv->lg_info,
                      dbc->txn, &new_lsn, 0, dbp->log_fileid,
                      SPLITOLD, PGNO(temp_pagep),
                      &page_dbt, &LSN(temp_pagep))) != 0)
                        goto err;
                  LSN(temp_pagep) = new_lsn;
            }
      }
      if (big_buf != NULL)
            __os_free(big_buf, big_len);

      /*
       * If the original bucket spanned multiple pages, then we've got
       * a pointer to a page that used to be on the bucket chain.  It
       * should be deleted.
       */
      if (temp_pagep != NULL && PGNO(temp_pagep) != bucket_pgno &&
          (ret = __ham_del_page(dbc, temp_pagep)) != 0)
            goto err;

      /*
       * Write new buckets out.
       */
      if (DB_LOGGING(dbc)) {
            page_dbt.size = hcp->hdr->pagesize;
            page_dbt.data = old_pagep;
            if ((ret = __ham_splitdata_log(dbenv->lg_info,
               dbc->txn, &new_lsn, 0, dbp->log_fileid,
               SPLITNEW, PGNO(old_pagep),
                &page_dbt, &LSN(old_pagep))) != 0)
                  goto err;
            LSN(old_pagep) = new_lsn;

            page_dbt.data = new_pagep;
            if ((ret = __ham_splitdata_log(dbenv->lg_info,
                dbc->txn, &new_lsn, 0, dbp->log_fileid,
                SPLITNEW, PGNO(new_pagep), &page_dbt, &LSN(new_pagep))) != 0)
                  goto err;
            LSN(new_pagep) = new_lsn;
      }
      ret = __ham_put_page(dbp, old_pagep, 1);
      if ((tret = __ham_put_page(dbp, new_pagep, 1)) != 0 &&
          ret == 0)
            ret = tret;

      if (0) {
err:        if (old_pagep != NULL)
                  (void)__ham_put_page(dbp, old_pagep, 1);
            if (new_pagep != NULL)
                  (void)__ham_put_page(dbp, new_pagep, 1);
            if (temp_pagep != NULL && PGNO(temp_pagep) != bucket_pgno)
                  (void)__ham_put_page(dbp, temp_pagep, 1);
      }
      return (ret);
}

/*
 * Add the given pair to the page.  The page in question may already be
 * held (i.e. it was already gotten).  If it is, then the page is passed
 * in via the pagep parameter.  On return, pagep will contain the page
 * to which we just added something.  This allows us to link overflow
 * pages and return the new page having correctly put the last page.
 *
 * PUBLIC: int __ham_add_el __P((DBC *, const DBT *, const DBT *, int));
 */
int
__ham_add_el(dbc, key, val, type)
      DBC *dbc;
      const DBT *key, *val;
      int type;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      const DBT *pkey, *pdata;
      DBT key_dbt, data_dbt;
      DB_LSN new_lsn;
      HOFFPAGE doff, koff;
      db_pgno_t next_pgno;
      u_int32_t data_size, key_size, pairsize, rectype;
      int do_expand, is_keybig, is_databig, ret;
      int key_type, data_type;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      do_expand = 0;

      if (hcp->pagep == NULL && (ret = __ham_get_page(dbp,
          hcp->seek_found_page != PGNO_INVALID ?  hcp->seek_found_page :
          hcp->pgno, &hcp->pagep)) != 0)
            return (ret);

      key_size = HKEYDATA_PSIZE(key->size);
      data_size = HKEYDATA_PSIZE(val->size);
      is_keybig = ISBIG(hcp, key->size);
      is_databig = ISBIG(hcp, val->size);
      if (is_keybig)
            key_size = HOFFPAGE_PSIZE;
      if (is_databig)
            data_size = HOFFPAGE_PSIZE;

      pairsize = key_size + data_size;

      /* Advance to first page in chain with room for item. */
      while (H_NUMPAIRS(hcp->pagep) && NEXT_PGNO(hcp->pagep) !=
          PGNO_INVALID) {
            /*
             * This may not be the end of the chain, but the pair may fit
             * anyway.  Check if it's a bigpair that fits or a regular
             * pair that fits.
             */
            if (P_FREESPACE(hcp->pagep) >= pairsize)
                  break;
            next_pgno = NEXT_PGNO(hcp->pagep);
            if ((ret =
                __ham_next_cpage(dbc, next_pgno, 0, 0)) != 0)
                  return (ret);
      }

      /*
       * Check if we need to allocate a new page.
       */
      if (P_FREESPACE(hcp->pagep) < pairsize) {
            do_expand = 1;
            if ((ret = __ham_add_ovflpage(dbc,
                hcp->pagep, 1, &hcp->pagep)) !=  0)
                  return (ret);
            hcp->pgno = PGNO(hcp->pagep);
      }

      /*
       * Update cursor.
       */
      hcp->bndx = H_NUMPAIRS(hcp->pagep);
      F_CLR(hcp, H_DELETED);
      if (is_keybig) {
            koff.type = H_OFFPAGE;
            UMRW(koff.unused[0]);
            UMRW(koff.unused[1]);
            UMRW(koff.unused[2]);
            if ((ret = __db_poff(dbc,
                key, &koff.pgno, __ham_overflow_page)) != 0)
                  return (ret);
            koff.tlen = key->size;
            key_dbt.data = &koff;
            key_dbt.size = sizeof(koff);
            pkey = &key_dbt;
            key_type = H_OFFPAGE;
      } else {
            pkey = key;
            key_type = H_KEYDATA;
      }

      if (is_databig) {
            doff.type = H_OFFPAGE;
            UMRW(doff.unused[0]);
            UMRW(doff.unused[1]);
            UMRW(doff.unused[2]);
            if ((ret = __db_poff(dbc,
                val, &doff.pgno, __ham_overflow_page)) != 0)
                  return (ret);
            doff.tlen = val->size;
            data_dbt.data = &doff;
            data_dbt.size = sizeof(doff);
            pdata = &data_dbt;
            data_type = H_OFFPAGE;
      } else {
            pdata = val;
            data_type = type;
      }

      if (DB_LOGGING(dbc)) {
            rectype = PUTPAIR;
            if (is_databig)
                  rectype |= PAIR_DATAMASK;
            if (is_keybig)
                  rectype |= PAIR_KEYMASK;

            if ((ret = __ham_insdel_log(dbp->dbenv->lg_info,
                dbc->txn, &new_lsn, 0, rectype,
                dbp->log_fileid, PGNO(hcp->pagep),
                (u_int32_t)H_NUMPAIRS(hcp->pagep),
                &LSN(hcp->pagep), pkey, pdata)) != 0)
                  return (ret);

            /* Move lsn onto page. */
            LSN(hcp->pagep) = new_lsn;    /* Structure assignment. */
      }

      __ham_putitem(hcp->pagep, pkey, key_type);
      __ham_putitem(hcp->pagep, pdata, data_type);

      /*
       * For splits, we are going to update item_info's page number
       * field, so that we can easily return to the same page the
       * next time we come in here.  For other operations, this shouldn't
       * matter, since odds are this is the last thing that happens before
       * we return to the user program.
       */
      hcp->pgno = PGNO(hcp->pagep);

      /*
       * XXX Maybe keep incremental numbers here
       */
      if (!F_ISSET(dbp, DB_AM_LOCKING))
            hcp->hdr->nelem++;

      if (do_expand || (hcp->hdr->ffactor != 0 &&
          (u_int32_t)H_NUMPAIRS(hcp->pagep) > hcp->hdr->ffactor))
            F_SET(hcp, H_EXPAND);
      return (0);
}


/*
 * Special __putitem call used in splitting -- copies one entry to
 * another.  Works for all types of hash entries (H_OFFPAGE, H_KEYDATA,
 * H_DUPLICATE, H_OFFDUP).  Since we log splits at a high level, we
 * do not need to do any logging here.
 *
 * PUBLIC: void __ham_copy_item __P((size_t, PAGE *, u_int32_t, PAGE *));
 */
void
__ham_copy_item(pgsize, src_page, src_ndx, dest_page)
      size_t pgsize;
      PAGE *src_page;
      u_int32_t src_ndx;
      PAGE *dest_page;
{
      u_int32_t len;
      void *src, *dest;

      /*
       * Copy the key and data entries onto this new page.
       */
      src = P_ENTRY(src_page, src_ndx);

      /* Set up space on dest. */
      len = LEN_HITEM(src_page, pgsize, src_ndx);
      HOFFSET(dest_page) -= len;
      dest_page->inp[NUM_ENT(dest_page)] = HOFFSET(dest_page);
      dest = P_ENTRY(dest_page, NUM_ENT(dest_page));
      NUM_ENT(dest_page)++;

      memcpy(dest, src, len);
}

/*
 *
 * Returns:
 *      pointer on success
 *      NULL on error
 *
 * PUBLIC: int __ham_add_ovflpage __P((DBC *, PAGE *, int, PAGE **));
 */
int
__ham_add_ovflpage(dbc, pagep, release, pp)
      DBC *dbc;
      PAGE *pagep;
      int release;
      PAGE **pp;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      DB_LSN new_lsn;
      PAGE *new_pagep;
      int ret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;

      if ((ret = __ham_overflow_page(dbc, P_HASH, &new_pagep)) != 0)
            return (ret);

      if (DB_LOGGING(dbc)) {
            if ((ret = __ham_newpage_log(dbp->dbenv->lg_info,
                dbc->txn, &new_lsn, 0, PUTOVFL,
                dbp->log_fileid, PGNO(pagep), &LSN(pagep),
                PGNO(new_pagep), &LSN(new_pagep), PGNO_INVALID, NULL)) != 0)
                  return (ret);

            /* Move lsn onto page. */
            LSN(pagep) = LSN(new_pagep) = new_lsn;
      }
      NEXT_PGNO(pagep) = PGNO(new_pagep);
      PREV_PGNO(new_pagep) = PGNO(pagep);

      if (release)
            ret = __ham_put_page(dbp, pagep, 1);

      hcp->stats.hash_overflows++;
      *pp = new_pagep;
      return (ret);
}


/*
 * PUBLIC: int __ham_new_page __P((DB *, u_int32_t, u_int32_t, PAGE **));
 */
int
__ham_new_page(dbp, addr, type, pp)
      DB *dbp;
      u_int32_t addr, type;
      PAGE **pp;
{
      PAGE *pagep;
      int ret;

      if ((ret = memp_fget(dbp->mpf,
          &addr, DB_MPOOL_CREATE, &pagep)) != 0)
            return (ret);

      /* This should not be necessary because page-in should do it. */
      P_INIT(pagep, dbp->pgsize, addr, PGNO_INVALID, PGNO_INVALID, 0, type);

      *pp = pagep;
      return (0);
}

/*
 * PUBLIC: int __ham_del_page __P((DBC *, PAGE *));
 */
int
__ham_del_page(dbc, pagep)
      DBC *dbc;
      PAGE *pagep;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      DB_LSN new_lsn;
      int ret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      ret = 0;
      DIRTY_META(dbp, hcp, ret);
      if (ret != 0) {
            if (ret != EAGAIN)
                  __db_err(dbp->dbenv,
                      "free_ovflpage: unable to lock meta data page %s\n",
                      strerror(ret));
            /*
             * If we are going to return an error, then we should free
             * the page, so it doesn't stay pinned forever.
             */
            (void)__ham_put_page(dbp, pagep, 0);
            return (ret);
      }

      if (DB_LOGGING(dbc)) {
            if ((ret = __ham_newpgno_log(dbp->dbenv->lg_info,
                dbc->txn, &new_lsn, 0, DELPGNO,
                dbp->log_fileid, PGNO(pagep), hcp->hdr->last_freed,
                (u_int32_t)TYPE(pagep), NEXT_PGNO(pagep), P_INVALID,
                &LSN(pagep), &hcp->hdr->lsn)) != 0)
                  return (ret);

            hcp->hdr->lsn = new_lsn;
            LSN(pagep) = new_lsn;
      }

#ifdef DIAGNOSTIC
      {
            db_pgno_t __pgno;
            DB_LSN __lsn;
            __pgno = pagep->pgno;
            __lsn = pagep->lsn;
            memset(pagep, 0xdb, dbp->pgsize);
            pagep->pgno = __pgno;
            pagep->lsn = __lsn;
      }
#endif
      TYPE(pagep) = P_INVALID;
      NEXT_PGNO(pagep) = hcp->hdr->last_freed;
      hcp->hdr->last_freed = PGNO(pagep);

      return (__ham_put_page(dbp, pagep, 1));
}


/*
 * PUBLIC: int __ham_put_page __P((DB *, PAGE *, int32_t));
 */
int
__ham_put_page(dbp, pagep, is_dirty)
      DB *dbp;
      PAGE *pagep;
      int32_t is_dirty;
{
#ifdef DEBUG_SLOW
      __account_page(dbp, ((BKT *)((char *)pagep - sizeof(BKT)))->pgno, -1);
#endif
      return (memp_fput(dbp->mpf, pagep, (is_dirty ? DB_MPOOL_DIRTY : 0)));
}

/*
 * __ham_dirty_page --
 *    Mark a page dirty.
 *
 * PUBLIC: int __ham_dirty_page __P((DB *, PAGE *));
 */
int
__ham_dirty_page(dbp, pagep)
      DB *dbp;
      PAGE *pagep;
{
      return (memp_fset(dbp->mpf, pagep, DB_MPOOL_DIRTY));
}

/*
 * PUBLIC: int __ham_get_page __P((DB *, db_pgno_t, PAGE **));
 */
int
__ham_get_page(dbp, addr, pagep)
      DB *dbp;
      db_pgno_t addr;
      PAGE **pagep;
{
      int ret;

      ret = memp_fget(dbp->mpf, &addr, DB_MPOOL_CREATE, pagep);
#ifdef DEBUG_SLOW
      if (*pagep != NULL)
            __account_page(dbp, addr, 1);
#endif
      return (ret);
}

/*
 * PUBLIC: int __ham_overflow_page
 * PUBLIC:     __P((DBC *, u_int32_t, PAGE **));
 */
int
__ham_overflow_page(dbc, type, pp)
      DBC *dbc;
      u_int32_t type;
      PAGE **pp;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      DB_LSN *lsnp, new_lsn;
      PAGE *p;
      db_pgno_t new_addr, next_free, newalloc_flag;
      u_int32_t offset, splitnum;
      int ret;

      ret = 0;
      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      DIRTY_META(dbp, hcp, ret);
      if (ret != 0)
            return (ret);

      /*
       * This routine is split up into two parts.  First we have
       * to figure out the address of the new page that we are
       * allocating.  Then we have to log the allocation.  Only
       * after the log do we get to complete allocation of the
       * new page.
       */
      new_addr = hcp->hdr->last_freed;
      if (new_addr != PGNO_INVALID) {
            if ((ret = __ham_get_page(dbp, new_addr, &p)) != 0)
                  return (ret);
            next_free = NEXT_PGNO(p);
            lsnp = &LSN(p);
            newalloc_flag = 0;
      } else {
            splitnum = hcp->hdr->ovfl_point;
            hcp->hdr->spares[splitnum]++;
            offset = hcp->hdr->spares[splitnum] -
                (splitnum ? hcp->hdr->spares[splitnum - 1] : 0);
            new_addr = PGNO_OF(hcp, hcp->hdr->ovfl_point, offset);
            if (new_addr > MAX_PAGES(hcp)) {
                  __db_err(dbp->dbenv, "hash: out of file pages");
                  hcp->hdr->spares[splitnum]--;
                  return (ENOMEM);
            }
            next_free = PGNO_INVALID;
            p = NULL;
            lsnp = NULL;
            newalloc_flag = 1;
      }

      if (DB_LOGGING(dbc)) {
            if ((ret = __ham_newpgno_log(dbp->dbenv->lg_info,
                dbc->txn, &new_lsn, 0, ALLOCPGNO,
                dbp->log_fileid, new_addr, next_free,
                0, newalloc_flag, type, lsnp, &hcp->hdr->lsn)) != 0)
                  return (ret);

            hcp->hdr->lsn = new_lsn;
            if (lsnp != NULL)
                  *lsnp = new_lsn;
      }

      if (p != NULL) {
            /* We just took something off the free list, initialize it. */
            hcp->hdr->last_freed = next_free;
            P_INIT(p, hcp->hdr->pagesize, PGNO(p), PGNO_INVALID,
                PGNO_INVALID, 0, (u_int8_t)type);
      } else {
            /* Get the new page. */
            if ((ret = __ham_new_page(dbp, new_addr, type, &p)) != 0)
                  return (ret);
      }
      if (DB_LOGGING(dbc))
            LSN(p) = new_lsn;

      *pp = p;
      return (0);
}

#ifdef DEBUG
/*
 * PUBLIC: #ifdef DEBUG
 * PUBLIC: db_pgno_t __bucket_to_page __P((HASH_CURSOR *, db_pgno_t));
 * PUBLIC: #endif
 */
db_pgno_t
__bucket_to_page(hcp, n)
      HASH_CURSOR *hcp;
      db_pgno_t n;
{
      int ret_val;

      ret_val = n + 1;
      if (n != 0)
            ret_val += hcp->hdr->spares[__db_log2(n + 1) - 1];
      return (ret_val);
}
#endif

/*
 * Create a bunch of overflow pages at the current split point.
 * PUBLIC: void __ham_init_ovflpages __P((DBC *));
 */
void
__ham_init_ovflpages(dbc)
      DBC *dbc;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      DB_LSN new_lsn;
      PAGE *p;
      db_pgno_t last_pgno, new_pgno;
      u_int32_t i, curpages, numpages;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;

      curpages = hcp->hdr->spares[hcp->hdr->ovfl_point] -
          hcp->hdr->spares[hcp->hdr->ovfl_point - 1];
      numpages = hcp->hdr->ovfl_point + 1 - curpages;

      last_pgno = hcp->hdr->last_freed;
      new_pgno = PGNO_OF(hcp, hcp->hdr->ovfl_point, curpages + 1);
      if (DB_LOGGING(dbc)) {
            (void)__ham_ovfl_log(dbp->dbenv->lg_info,
                dbc->txn, &new_lsn, 0, dbp->log_fileid, new_pgno,
                numpages, last_pgno, hcp->hdr->ovfl_point, &hcp->hdr->lsn);
            hcp->hdr->lsn = new_lsn;
      } else
            ZERO_LSN(new_lsn);

      hcp->hdr->spares[hcp->hdr->ovfl_point] += numpages;
      for (i = numpages; i > 0; i--) {
            if (__ham_new_page(dbp,
                PGNO_OF(hcp, hcp->hdr->ovfl_point, curpages + i),
                P_INVALID, &p) != 0)
                  break;
            LSN(p) = new_lsn;
            NEXT_PGNO(p) = last_pgno;
            last_pgno = PGNO(p);
            (void)__ham_put_page(dbp, p, 1);
      }
      hcp->hdr->last_freed = last_pgno;
}

/*
 * PUBLIC: int __ham_get_cpage __P((DBC *, db_lockmode_t));
 */
int
__ham_get_cpage(dbc, mode)
      DBC *dbc;
      db_lockmode_t mode;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      int ret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;

      /*
       * There are three cases with respect to buckets and locks.  If there
       * is no lock held, then if we are locking, we should get the lock.
       * If there is a lock held and it's for the current bucket, we don't
       * need to do anything.  If there is a lock, but it's for a different
       * bucket, then we need to release and get.
       */
      if (F_ISSET(dbp, DB_AM_LOCKING)) {
            if (hcp->lock != 0 && hcp->lbucket != hcp->bucket) {
                  /*
                   * If this is the original lock, don't release it,
                   * because we may need to restore it upon exit.
                   */
                  if (dbc->txn == NULL &&
                      !F_ISSET(hcp, H_ORIGINAL) && (ret =
                      lock_put(dbp->dbenv->lk_info, hcp->lock)) != 0)
                        return (ret);
                  F_CLR(hcp, H_ORIGINAL);
                  hcp->lock = 0;
            }
            if (hcp->lock == 0 && (ret = __ham_lock_bucket(dbc, mode)) != 0)
                  return (ret);
            hcp->lbucket = hcp->bucket;
      }

      if (hcp->pagep == NULL) {
            if (hcp->pgno == PGNO_INVALID) {
                  hcp->pgno = BUCKET_TO_PAGE(hcp, hcp->bucket);
                  hcp->bndx = 0;
            }

            if ((ret =
                __ham_get_page(dbp, hcp->pgno, &hcp->pagep)) != 0)
                  return (ret);
      }

      if (hcp->dpgno != PGNO_INVALID && hcp->dpagep == NULL)
            if ((ret =
                __ham_get_page(dbp, hcp->dpgno, &hcp->dpagep)) != 0)
                  return (ret);
      return (0);
}

/*
 * Get a new page at the cursor, putting the last page if necessary.
 * If the flag is set to H_ISDUP, then we are talking about the
 * duplicate page, not the main page.
 *
 * PUBLIC: int __ham_next_cpage __P((DBC *, db_pgno_t, int, u_int32_t));
 */
int
__ham_next_cpage(dbc, pgno, dirty, flags)
      DBC *dbc;
      db_pgno_t pgno;
      int dirty;
      u_int32_t flags;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      PAGE *p;
      int ret;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      if (LF_ISSET(H_ISDUP) && hcp->dpagep != NULL &&
          (ret = __ham_put_page(dbp, hcp->dpagep, dirty)) != 0)
            return (ret);
      else if (!LF_ISSET(H_ISDUP) && hcp->pagep != NULL &&
          (ret = __ham_put_page(dbp, hcp->pagep, dirty)) != 0)
            return (ret);

      if ((ret = __ham_get_page(dbp, pgno, &p)) != 0)
            return (ret);

      if (LF_ISSET(H_ISDUP)) {
            hcp->dpagep = p;
            hcp->dpgno = pgno;
            hcp->dndx = 0;
      } else {
            hcp->pagep = p;
            hcp->pgno = pgno;
            hcp->bndx = 0;
      }

      return (0);
}

/*
 * __ham_lock_bucket --
 *    Get the lock on a particular bucket.
 */
static int
__ham_lock_bucket(dbc, mode)
      DBC *dbc;
      db_lockmode_t mode;
{
      HASH_CURSOR *hcp;
      int ret;

      hcp = (HASH_CURSOR *)dbc->internal;
      dbc->lock.pgno = (db_pgno_t)(hcp->bucket);
      if (dbc->txn == NULL)
            ret = lock_get(dbc->dbp->dbenv->lk_info, dbc->locker, 0,
                &dbc->lock_dbt, mode, &hcp->lock);
      else
            ret = lock_tget(dbc->dbp->dbenv->lk_info, dbc->txn, 0,
                &dbc->lock_dbt, mode, &hcp->lock);

      return (ret < 0 ? EAGAIN : ret);
}

/*
 * __ham_dpair --
 *    Delete a pair on a page, paying no attention to what the pair
 *    represents.  The caller is responsible for freeing up duplicates
 *    or offpage entries that might be referenced by this pair.
 *
 * PUBLIC: void __ham_dpair __P((DB *, PAGE *, u_int32_t));
 */
void
__ham_dpair(dbp, p, pndx)
      DB *dbp;
      PAGE *p;
      u_int32_t pndx;
{
      db_indx_t delta, n;
      u_int8_t *dest, *src;

      /*
       * Compute "delta", the amount we have to shift all of the
       * offsets.  To find the delta, we just need to calculate
       * the size of the pair of elements we are removing.
       */
      delta = H_PAIRSIZE(p, dbp->pgsize, pndx);

      /*
       * The hard case: we want to remove something other than
       * the last item on the page.  We need to shift data and
       * offsets down.
       */
      if ((db_indx_t)pndx != H_NUMPAIRS(p) - 1) {
            /*
             * Move the data: src is the first occupied byte on
             * the page. (Length is delta.)
             */
            src = (u_int8_t *)p + HOFFSET(p);

            /*
             * Destination is delta bytes beyond src.  This might
             * be an overlapping copy, so we have to use memmove.
             */
            dest = src + delta;
            memmove(dest, src, p->inp[H_DATAINDEX(pndx)] - HOFFSET(p));
      }

      /* Adjust the offsets. */
      for (n = (db_indx_t)pndx; n < (db_indx_t)(H_NUMPAIRS(p) - 1); n++) {
            p->inp[H_KEYINDEX(n)] = p->inp[H_KEYINDEX(n+1)] + delta;
            p->inp[H_DATAINDEX(n)] = p->inp[H_DATAINDEX(n+1)] + delta;
      }

      /* Adjust page metadata. */
      HOFFSET(p) = HOFFSET(p) + delta;
      NUM_ENT(p) = NUM_ENT(p) - 2;
}


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