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hash.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2002
 *    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. 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 "db_config.h"

#ifndef lint
static const char revid[] = "$Id: hash.c,v 11.166 2002/08/06 06:11:25 bostic Exp $";
#endif /* not lint */

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

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

#include "db_int.h"
#include "dbinc/db_page.h"
#include "dbinc/db_shash.h"
#include "dbinc/btree.h"
#include "dbinc/hash.h"
#include "dbinc/lock.h"

static int  __ham_bulk __P((DBC *, DBT *, u_int32_t));
static int  __ham_c_close __P((DBC *, db_pgno_t, int *));
static int  __ham_c_del __P((DBC *));
static int  __ham_c_destroy __P((DBC *));
static int  __ham_c_get __P((DBC *, DBT *, DBT *, u_int32_t, db_pgno_t *));
static int  __ham_c_put __P((DBC *, DBT *, DBT *, u_int32_t, db_pgno_t *));
static int  __ham_c_writelock __P((DBC *));
static int  __ham_dup_return __P((DBC *, DBT *, u_int32_t));
static int  __ham_expand_table __P((DBC *));
static int  __ham_lookup __P((DBC *,
            const DBT *, u_int32_t, db_lockmode_t, db_pgno_t *));
static int  __ham_overwrite __P((DBC *, DBT *, u_int32_t));

/*
 * __ham_quick_delete --
 *    When performing a DB->del operation that does not involve secondary
 *    indices and is not removing an off-page duplicate tree, we can
 *    speed things up substantially by removing the entire duplicate
 *    set, if any is present, in one operation, rather than by conjuring
 *    up and deleting each of the items individually.  (All are stored
 *    in one big HKEYDATA structure.)  We don't bother to distinguish
 *    on-page duplicate sets from single, non-dup items;  they're deleted
 *    in exactly the same way.
 *
 *    This function is called by __db_delete when the appropriate
 *    conditions are met, and it performs the delete in the optimized way.
 *
 *    The cursor should be set to the first item in the duplicate
 *    set, or to the sole key/data pair when the key does not have a
 *    duplicate set, before the function is called.
 *
 * PUBLIC: int __ham_quick_delete __P((DBC *));
 */
int
__ham_quick_delete(dbc)
      DBC *dbc;
{
      int ret, t_ret;

      if ((ret = __ham_get_meta(dbc)) != 0)
            return (ret);

      /* Assert that we're not using secondary indices. */
      DB_ASSERT(!F_ISSET(dbc->dbp, DB_AM_SECONDARY));
      /*
       * We should assert that we're not a primary either, but that
       * would require grabbing the dbp's mutex, so we don't bother.
       */

      /* Assert that we're set, but not to an off-page duplicate. */
      DB_ASSERT(IS_INITIALIZED(dbc));
      DB_ASSERT(((HASH_CURSOR *)dbc->internal)->opd == NULL);

      ret = __ham_del_pair(dbc, 1);

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

      return (ret);
}

/* ****************** CURSORS ********************************** */
/*
 * __ham_c_init --
 *    Initialize the hash-specific portion of a cursor.
 *
 * PUBLIC: int __ham_c_init __P((DBC *));
 */
int
__ham_c_init(dbc)
      DBC *dbc;
{
      DB_ENV *dbenv;
      HASH_CURSOR *new_curs;
      int ret;

      dbenv = dbc->dbp->dbenv;
      if ((ret = __os_calloc(dbenv,
          1, sizeof(struct cursor_t), &new_curs)) != 0)
            return (ret);
      if ((ret = __os_malloc(dbenv,
          dbc->dbp->pgsize, &new_curs->split_buf)) != 0) {
            __os_free(dbenv, new_curs);
            return (ret);
      }

      dbc->internal = (DBC_INTERNAL *) new_curs;
      dbc->c_close = __db_c_close;
      dbc->c_count = __db_c_count;
      dbc->c_del = __db_c_del;
      dbc->c_dup = __db_c_dup;
      dbc->c_get = dbc->c_real_get = __db_c_get;
      dbc->c_pget = __db_c_pget;
      dbc->c_put = __db_c_put;
      dbc->c_am_bulk = __ham_bulk;
      dbc->c_am_close = __ham_c_close;
      dbc->c_am_del = __ham_c_del;
      dbc->c_am_destroy = __ham_c_destroy;
      dbc->c_am_get = __ham_c_get;
      dbc->c_am_put = __ham_c_put;
      dbc->c_am_writelock = __ham_c_writelock;

      __ham_item_init(dbc);

      return (0);
}

/*
 * __ham_c_close --
 *    Close down the cursor from a single use.
 */
static int
__ham_c_close(dbc, root_pgno, rmroot)
      DBC *dbc;
      db_pgno_t root_pgno;
      int *rmroot;
{
      DB_MPOOLFILE *mpf;
      HASH_CURSOR *hcp;
      HKEYDATA *dp;
      int doroot, gotmeta, ret, t_ret;
      u_int32_t dirty;

      COMPQUIET(rmroot, 0);
      mpf = dbc->dbp->mpf;
      dirty = 0;
      doroot = gotmeta = ret = 0;
      hcp = (HASH_CURSOR *) dbc->internal;

      /* Check for off page dups. */
      if (dbc->internal->opd != NULL) {
            if ((ret = __ham_get_meta(dbc)) != 0)
                  goto done;
            gotmeta = 1;
            if ((ret = __ham_get_cpage(dbc, DB_LOCK_READ)) != 0)
                  goto out;
            dp = (HKEYDATA *)H_PAIRDATA(dbc->dbp, hcp->page, hcp->indx);

            /* If its not a dup we aborted before we changed it. */
            if (HPAGE_PTYPE(dp) == H_OFFDUP)
                  memcpy(&root_pgno,
                      HOFFPAGE_PGNO(dp), sizeof(db_pgno_t));
            else
                  root_pgno = PGNO_INVALID;

            if ((ret =
                hcp->opd->c_am_close(hcp->opd, root_pgno, &doroot)) != 0)
                  goto out;
            if (doroot != 0) {
                  if ((ret = __ham_del_pair(dbc, 1)) != 0)
                        goto out;
                  dirty = DB_MPOOL_DIRTY;
            }
      }

out:  if (hcp->page != NULL && (t_ret =
          mpf->put(mpf, hcp->page, dirty)) != 0 && ret == 0)
            ret = t_ret;
      if (gotmeta != 0 && (t_ret = __ham_release_meta(dbc)) != 0 && ret == 0)
            ret = t_ret;

done:
      __ham_item_init(dbc);
      return (ret);
}

/*
 * __ham_c_destroy --
 *    Cleanup the access method private part of a cursor.
 */
static int
__ham_c_destroy(dbc)
      DBC *dbc;
{
      HASH_CURSOR *hcp;

      hcp = (HASH_CURSOR *)dbc->internal;
      if (hcp->split_buf != NULL)
            __os_free(dbc->dbp->dbenv, hcp->split_buf);
      __os_free(dbc->dbp->dbenv, hcp);

      return (0);
}

/*
 * __ham_c_count --
 *    Return a count of on-page duplicates.
 *
 * PUBLIC: int __ham_c_count __P((DBC *, db_recno_t *));
 */
int
__ham_c_count(dbc, recnop)
      DBC *dbc;
      db_recno_t *recnop;
{
      DB *dbp;
      DB_MPOOLFILE *mpf;
      HASH_CURSOR *hcp;
      db_indx_t len;
      db_recno_t recno;
      int ret, t_ret;
      u_int8_t *p, *pend;

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

      recno = 0;

      if ((ret = __ham_get_cpage(dbc, DB_LOCK_READ)) != 0)
            return (ret);

      switch (HPAGE_PTYPE(H_PAIRDATA(dbp, hcp->page, hcp->indx))) {
      case H_KEYDATA:
      case H_OFFPAGE:
            recno = 1;
            break;
      case H_DUPLICATE:
            p = HKEYDATA_DATA(H_PAIRDATA(dbp, hcp->page, hcp->indx));
            pend = p +
                LEN_HDATA(dbp, hcp->page, dbp->pgsize, hcp->indx);
            for (; p < pend; recno++) {
                  /* p may be odd, so copy rather than just dereffing */
                  memcpy(&len, p, sizeof(db_indx_t));
                  p += 2 * sizeof(db_indx_t) + len;
            }

            break;
      default:
            ret = __db_pgfmt(dbp->dbenv, hcp->pgno);
            goto err;
      }

      *recnop = recno;

err:  if ((t_ret = mpf->put(mpf, hcp->page, 0)) != 0 && ret == 0)
            ret = t_ret;
      hcp->page = NULL;
      return (ret);
}

static int
__ham_c_del(dbc)
      DBC *dbc;
{
      DB *dbp;
      DBT repldbt;
      DB_MPOOLFILE *mpf;
      HASH_CURSOR *hcp;
      int ret, t_ret;

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

      if (F_ISSET(hcp, H_DELETED))
            return (DB_NOTFOUND);

      if ((ret = __ham_get_meta(dbc)) != 0)
            goto out;

      if ((ret = __ham_get_cpage(dbc, DB_LOCK_WRITE)) != 0)
            goto out;

      /* Off-page duplicates. */
      if (HPAGE_TYPE(dbp, hcp->page, H_DATAINDEX(hcp->indx)) == H_OFFDUP)
            goto out;

      if (F_ISSET(hcp, H_ISDUP)) { /* On-page duplicate. */
            if (hcp->dup_off == 0 &&
                DUP_SIZE(hcp->dup_len) == LEN_HDATA(dbp, hcp->page,
                hcp->hdr->dbmeta.pagesize, hcp->indx))
                  ret = __ham_del_pair(dbc, 1);
            else {
                  repldbt.flags = 0;
                  F_SET(&repldbt, DB_DBT_PARTIAL);
                  repldbt.doff = hcp->dup_off;
                  repldbt.dlen = DUP_SIZE(hcp->dup_len);
                  repldbt.size = 0;
                  repldbt.data = HKEYDATA_DATA(H_PAIRDATA(dbp, hcp->page,
                      hcp->indx));
                  if ((ret = __ham_replpair(dbc, &repldbt, 0)) == 0) {
                        hcp->dup_tlen -= DUP_SIZE(hcp->dup_len);
                        F_SET(hcp, H_DELETED);
                        ret = __ham_c_update(dbc,
                            DUP_SIZE(hcp->dup_len), 0, 1);
                  }
            }

      } else /* Not a duplicate */
            ret = __ham_del_pair(dbc, 1);

out:  if (hcp->page != NULL) {
            if ((t_ret = mpf->put(mpf,
                hcp->page, ret == 0 ? DB_MPOOL_DIRTY : 0)) && ret == 0)
                  ret = t_ret;
            hcp->page = NULL;
      }
      if ((t_ret = __ham_release_meta(dbc)) != 0 && ret == 0)
            ret = t_ret;
      return (ret);
}

/*
 * __ham_c_dup --
 *    Duplicate a hash cursor, such that the new one holds appropriate
 *    locks for the position of the original.
 *
 * PUBLIC: int __ham_c_dup __P((DBC *, DBC *));
 */
int
__ham_c_dup(orig_dbc, new_dbc)
      DBC *orig_dbc, *new_dbc;
{
      HASH_CURSOR *orig, *new;

      orig = (HASH_CURSOR *)orig_dbc->internal;
      new = (HASH_CURSOR *)new_dbc->internal;

      new->bucket = orig->bucket;
      new->lbucket = orig->lbucket;
      new->dup_off = orig->dup_off;
      new->dup_len = orig->dup_len;
      new->dup_tlen = orig->dup_tlen;

      if (F_ISSET(orig, H_DELETED))
            F_SET(new, H_DELETED);
      if (F_ISSET(orig, H_ISDUP))
            F_SET(new, H_ISDUP);

      /*
       * If the old cursor held a lock and we're not in transactions, get one
       * for the new one.   The reason that we don't need a new lock if we're
       * in a transaction is because we already hold a lock and will continue
       * to do so until commit, so there is no point in reaquiring it. We
       * don't know if the old lock was a read or write lock, but it doesn't
       * matter. We'll get a read lock.  We know that this locker already
       * holds a lock of the correct type, so if we need a write lock and
       * request it, we know that we'll get it.
       */
      if (!LOCK_ISSET(orig->lock) || orig_dbc->txn != NULL)
            return (0);

      return (__ham_lock_bucket(new_dbc, DB_LOCK_READ));
}

static int
__ham_c_get(dbc, key, data, flags, pgnop)
      DBC *dbc;
      DBT *key;
      DBT *data;
      u_int32_t flags;
      db_pgno_t *pgnop;
{
      DB *dbp;
      DB_MPOOLFILE *mpf;
      HASH_CURSOR *hcp;
      db_lockmode_t lock_type;
      int get_key, ret, t_ret;

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

      /* Clear OR'd in additional bits so we can check for flag equality. */
      if (F_ISSET(dbc, DBC_RMW))
            lock_type = DB_LOCK_WRITE;
      else
            lock_type = DB_LOCK_READ;

      if ((ret = __ham_get_meta(dbc)) != 0)
            return (ret);
      hcp->seek_size = 0;

      ret = 0;
      get_key = 1;
      switch (flags) {
      case DB_PREV_NODUP:
            F_SET(hcp, H_NEXT_NODUP);
            /* FALLTHROUGH */
      case DB_PREV:
            if (IS_INITIALIZED(dbc)) {
                  ret = __ham_item_prev(dbc, lock_type, pgnop);
                  break;
            }
            /* FALLTHROUGH */
      case DB_LAST:
            ret = __ham_item_last(dbc, lock_type, pgnop);
            break;
      case DB_NEXT_NODUP:
            F_SET(hcp, H_NEXT_NODUP);
            /* FALLTHROUGH */
      case DB_NEXT:
            if (IS_INITIALIZED(dbc)) {
                  ret = __ham_item_next(dbc, lock_type, pgnop);
                  break;
            }
            /* FALLTHROUGH */
      case DB_FIRST:
            ret = __ham_item_first(dbc, lock_type, pgnop);
            break;
      case DB_NEXT_DUP:
            /* cgetchk has already determined that the cursor is set. */
            F_SET(hcp, H_DUPONLY);
            ret = __ham_item_next(dbc, lock_type, pgnop);
            break;
      case DB_SET:
      case DB_SET_RANGE:
      case DB_GET_BOTH:
      case DB_GET_BOTH_RANGE:
            ret = __ham_lookup(dbc, key, 0, lock_type, pgnop);
            get_key = 0;
            break;
      case DB_GET_BOTHC:
            F_SET(hcp, H_DUPONLY);

            ret = __ham_item_next(dbc, lock_type, pgnop);
            get_key = 0;
            break;
      case DB_CURRENT:
            /* cgetchk has already determined that the cursor is set. */
            if (F_ISSET(hcp, H_DELETED)) {
                  ret = DB_KEYEMPTY;
                  goto err;
            }

            ret = __ham_item(dbc, lock_type, pgnop);
            break;
      }

      /*
       * Must always enter this loop to do error handling and
       * check for big key/data pair.
       */
      for (;;) {
            if (ret != 0 && ret != DB_NOTFOUND)
                  goto err;
            else if (F_ISSET(hcp, H_OK)) {
                  if (*pgnop == PGNO_INVALID)
                        ret = __ham_dup_return(dbc, data, flags);
                  break;
            } else if (!F_ISSET(hcp, H_NOMORE)) {
                  __db_err(dbp->dbenv,
                      "H_NOMORE returned to __ham_c_get");
                  ret = EINVAL;
                  break;
            }

            /*
             * Ran out of entries in a bucket; change buckets.
             */
            switch (flags) {
                  case DB_LAST:
                  case DB_PREV:
                  case DB_PREV_NODUP:
                        ret = mpf->put(mpf, hcp->page, 0);
                        hcp->page = NULL;
                        if (hcp->bucket == 0) {
                              ret = DB_NOTFOUND;
                              hcp->pgno = PGNO_INVALID;
                              goto err;
                        }
                        F_CLR(hcp, H_ISDUP);
                        hcp->bucket--;
                        hcp->indx = NDX_INVALID;
                        hcp->pgno = BUCKET_TO_PAGE(hcp, hcp->bucket);
                        if (ret == 0)
                              ret = __ham_item_prev(dbc,
                                  lock_type, pgnop);
                        break;
                  case DB_FIRST:
                  case DB_NEXT:
                  case DB_NEXT_NODUP:
                        ret = mpf->put(mpf, hcp->page, 0);
                        hcp->page = NULL;
                        hcp->indx = NDX_INVALID;
                        hcp->bucket++;
                        F_CLR(hcp, H_ISDUP);
                        hcp->pgno = BUCKET_TO_PAGE(hcp, hcp->bucket);
                        if (hcp->bucket > hcp->hdr->max_bucket) {
                              ret = DB_NOTFOUND;
                              hcp->pgno = PGNO_INVALID;
                              goto err;
                        }
                        if (ret == 0)
                              ret = __ham_item_next(dbc,
                                  lock_type, pgnop);
                        break;
                  case DB_GET_BOTH:
                  case DB_GET_BOTHC:
                  case DB_GET_BOTH_RANGE:
                  case DB_NEXT_DUP:
                  case DB_SET:
                  case DB_SET_RANGE:
                        /* Key not found. */
                        ret = DB_NOTFOUND;
                        goto err;
                  case DB_CURRENT:
                        /*
                         * This should only happen if you are doing
                         * deletes and reading with concurrent threads
                         * and not doing proper locking.  We return
                         * the same error code as we would if the
                         * cursor were deleted.
                         */
                        ret = DB_KEYEMPTY;
                        goto err;
                  default:
                        DB_ASSERT(0);
            }
      }

      if (get_key == 0)
            F_SET(key, DB_DBT_ISSET);

err:  if ((t_ret = __ham_release_meta(dbc)) != 0 && ret == 0)
            ret = t_ret;

      F_CLR(hcp, H_DUPONLY);
      F_CLR(hcp, H_NEXT_NODUP);

      return (ret);
}

/*
 * __ham_bulk -- Return bulk data from a hash table.
 */
static int
__ham_bulk(dbc, data, flags)
      DBC *dbc;
      DBT *data;
      u_int32_t flags;
{
      DB *dbp;
      DB_MPOOLFILE *mpf;
      HASH_CURSOR *cp;
      PAGE *pg;
      db_indx_t dup_len, dup_off, dup_tlen, indx, *inp;
      db_lockmode_t lock_mode;
      db_pgno_t pgno;
      int32_t  *endp, key_off, *offp, *saveoff;
      u_int32_t key_size, size, space;
      u_int8_t *dbuf, *dp, *hk, *np, *tmp;
      int is_dup, is_key;
      int need_pg, next_key, no_dup, pagesize, ret, t_ret;

      ret = 0;
      key_off = 0;
      dup_len = dup_off = dup_tlen = 0;
      size = 0;
      dbp = dbc->dbp;
      pagesize = dbp->pgsize;
      mpf = dbp->mpf;
      cp = (HASH_CURSOR *)dbc->internal;
      is_key = LF_ISSET(DB_MULTIPLE_KEY) ? 1 : 0;
      next_key = is_key && LF_ISSET(DB_OPFLAGS_MASK) != DB_NEXT_DUP;
      no_dup = LF_ISSET(DB_OPFLAGS_MASK) == DB_NEXT_NODUP;
      dbuf = data->data;
      np = dp = dbuf;

      /* Keep track of space that is left.  There is an termination entry */
      space = data->ulen;
      space -= sizeof(*offp);

      /* Build the offset/size table from the end up. */
      endp = (int32_t *) ((u_int8_t *)dbuf + data->ulen);
      endp--;
      offp = endp;

      key_size = 0;
      lock_mode = F_ISSET(dbc, DBC_RMW) ? DB_LOCK_WRITE: DB_LOCK_READ;

next_pg:
      need_pg = 1;
      indx = cp->indx;
      pg = cp->page;
      inp = P_INP(dbp, pg);

      do {
            if (is_key) {
                  hk = H_PAIRKEY(dbp, pg, indx);
                  if (HPAGE_PTYPE(hk) == H_OFFPAGE) {
                        memcpy(&key_size,
                            HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
                        memcpy(&pgno,
                            HOFFPAGE_PGNO(hk), sizeof(db_pgno_t));
                        size = key_size;
                        if (key_size > space)
                              goto get_key_space;
                        if ((ret = __bam_bulk_overflow(
                            dbc, key_size, pgno, np)) != 0)
                              return (ret);
                        space -= key_size;
                        key_off = (int32_t)(np - dbuf);
                        np += key_size;
                  } else {
                        if (need_pg) {
                              dp = np;
                              size = pagesize - HOFFSET(pg);
                              if (space < size) {
get_key_space:
                                    if (offp == endp) {
                                          data->size =
                                              ALIGN(size +
                                              pagesize,
                                              sizeof(u_int32_t));
                                          return (ENOMEM);
                                    }
                                    goto back_up;
                              }
                              memcpy(dp,
                                 (u_int8_t *)pg + HOFFSET(pg), size);
                              need_pg = 0;
                              space -= size;
                              np += size;
                        }
                        key_size = LEN_HKEY(dbp, pg, pagesize, indx);
                        key_off = (int32_t)(inp[indx] - HOFFSET(pg)
                            + dp - dbuf + SSZA(HKEYDATA, data));
                  }
            }

            hk = H_PAIRDATA(dbp, pg, indx);
            switch (HPAGE_PTYPE(hk)) {
            case H_DUPLICATE:
            case H_KEYDATA:
                  if (need_pg) {
                        dp = np;
                        size = pagesize - HOFFSET(pg);
                        if (space < size) {
back_up:
                              if (indx != 0) {
                                    indx -= 2;
                                    /* XXX
                                     * It's not clear that this is
                                     * the right way to fix this,
                                     * but here goes.
                                     * If we are backing up onto a
                                     * duplicate, then we need to
                                     * position ourselves at the
                                     * end of the duplicate set.
                                     * We probably need to make
                                     * this work for H_OFFDUP too.
                                     * It might be worth making a
                                     * dummy cursor and calling
                                     * __ham_item_prev.
                                     */
                                    tmp = H_PAIRDATA(dbp, pg, indx);
                                    if (HPAGE_PTYPE(tmp) ==
                                        H_DUPLICATE) {
                                          dup_off = dup_tlen =
                                              LEN_HDATA(dbp, pg,
                                              pagesize, indx + 1);
                                          memcpy(&dup_len,
                                              HKEYDATA_DATA(tmp),
                                              sizeof(db_indx_t));
                                    }
                                    goto get_space;
                              }
                              /* indx == 0 */
                              if ((ret = __ham_item_prev(dbc,
                                  lock_mode, &pgno)) != 0) {
                                    if (ret != DB_NOTFOUND)
                                          return (ret);
                                    if ((ret = mpf->put(mpf,
                                        cp->page, 0)) != 0)
                                          return (ret);
                                    cp->page = NULL;
                                    if (cp->bucket == 0) {
                                          cp->indx = indx =
                                              NDX_INVALID;
                                          goto get_space;
                                    }
                                    if ((ret =
                                        __ham_get_meta(dbc)) != 0)
                                          return (ret);

                                    cp->bucket--;
                                    cp->pgno = BUCKET_TO_PAGE(cp,
                                        cp->bucket);
                                    cp->indx = NDX_INVALID;
                                    if ((ret = __ham_release_meta(
                                        dbc)) != 0)
                                          return (ret);
                                    if ((ret = __ham_item_prev(dbc,
                                        lock_mode, &pgno)) != 0)
                                          return (ret);
                              }
                              indx = cp->indx;
get_space:
                              /*
                               * See if we put any data in the buffer.
                               */
                              if (offp >= endp ||
                                  F_ISSET(dbc, DBC_TRANSIENT)) {
                                    data->size = ALIGN(size +
                                        data->ulen - space,
                                        sizeof(u_int32_t));
                                    return (ENOMEM);
                              }
                              /*
                               * Don't continue;  we're all out
                               * of space, even though we're
                               * returning success.
                               */
                              next_key = 0;
                              break;
                        }
                        memcpy(dp, (u_int8_t *)pg + HOFFSET(pg), size);
                        need_pg = 0;
                        space -= size;
                        np += size;
                  }

                  /*
                   * We're about to crack the offset(s) and length(s)
                   * out of an H_KEYDATA or H_DUPLICATE item.
                   * There are three cases:
                   *   1. We were moved into a duplicate set by
                   *    the standard hash cursor code.  Respect
                   *    the dup_off and dup_tlen we were given.
                   *   2. We stumbled upon a duplicate set while
                   *    walking the page on our own.  We need to
                   *    recognize it as a dup and set dup_off and
                   *    dup_tlen.
                   *   3. The current item is not a dup.
                   */
                  if (F_ISSET(cp, H_ISDUP)) {
                        /* Case 1 */
                        is_dup = 1;
                        dup_len = cp->dup_len;
                        dup_off = cp->dup_off;
                        dup_tlen = cp->dup_tlen;
                  } else if (HPAGE_PTYPE(hk) == H_DUPLICATE) {
                        /* Case 2 */
                        is_dup = 1;
                        /*
                         * If we run out of memory and bail,
                         * make sure the fact we're in a dup set
                         * isn't ignored later.
                         */
                        F_SET(cp, H_ISDUP);
                        dup_off = 0;
                        memcpy(&dup_len,
                            HKEYDATA_DATA(hk), sizeof(db_indx_t));
                        dup_tlen = LEN_HDATA(dbp, pg, pagesize, indx);
                  } else
                        /* Case 3 */
                        is_dup = dup_len = dup_off = dup_tlen = 0;

                  do {
                        space -= (is_key ? 4 : 2) * sizeof(*offp);
                        size += (is_key ? 4 : 2) * sizeof(*offp);
                        /*
                         * Since space is an unsigned, if we happen
                         * to wrap, then this comparison will turn out
                         * to be true.  XXX Wouldn't it be better to
                         * simply check above that space is greater than
                         * the value we're about to subtract???
                         */
                        if (space > data->ulen) {
                              if (!is_dup || dup_off == 0)
                                    goto back_up;
                              dup_off -= (db_indx_t)DUP_SIZE(offp[1]);
                              goto get_space;
                        }
                        if (is_key) {
                              *offp-- = key_off;
                              *offp-- = key_size;
                        }
                        if (is_dup) {
                              *offp-- = (int32_t)(
                                  inp[indx + 1] - HOFFSET(pg) +
                                  dp - dbuf + SSZA(HKEYDATA, data) +
                                  dup_off + sizeof(db_indx_t));
                              memcpy(&dup_len,
                                  HKEYDATA_DATA(hk) + dup_off,
                                  sizeof(db_indx_t));
                              dup_off += DUP_SIZE(dup_len);
                              *offp-- = dup_len;
                        } else {
                              *offp-- = (int32_t)(
                                  inp[indx + 1] - HOFFSET(pg) +
                                  dp - dbuf + SSZA(HKEYDATA, data));
                              *offp-- = LEN_HDATA(dbp, pg,
                                  pagesize, indx);
                        }
                  } while (is_dup && dup_off < dup_tlen && no_dup == 0);
                  F_CLR(cp, H_ISDUP);
                  break;
            case H_OFFDUP:
                  memcpy(&pgno, HOFFPAGE_PGNO(hk), sizeof(db_pgno_t));
                  space -= 2 * sizeof(*offp);
                  if (space > data->ulen)
                        goto back_up;

                  if (is_key) {
                        space -= 2 * sizeof(*offp);
                        if (space > data->ulen)
                              goto back_up;
                        *offp-- = key_off;
                        *offp-- = key_size;
                  }
                  saveoff = offp;
                  if ((ret = __bam_bulk_duplicates(dbc,
                      pgno, dbuf, is_key ? offp + 2 : NULL,
                      &offp, &np, &space, no_dup)) != 0) {
                        if (ret == ENOMEM) {
                              size = space;
                              if (is_key && saveoff == offp) {
                                    offp += 2;
                                    goto back_up;
                              }
                              goto get_space;
                        }
                        return (ret);
                  }
                  break;
            case H_OFFPAGE:
                  space -= (is_key ? 4 : 2) * sizeof(*offp);
                  if (space > data->ulen)
                        goto back_up;

                  memcpy(&size, HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
                  memcpy(&pgno, HOFFPAGE_PGNO(hk), sizeof(db_pgno_t));
                  if (size > space)
                        goto back_up;

                  if ((ret =
                      __bam_bulk_overflow(dbc, size, pgno, np)) != 0)
                        return (ret);

                  if (is_key) {
                        *offp-- = key_off;
                        *offp-- = key_size;
                  }

                  *offp-- = (int32_t)(np - dbuf);
                  *offp-- = size;

                  np += size;
                  space -= size;
                  break;
            }
      } while (next_key && (indx += 2) < NUM_ENT(pg));

      cp->indx = indx;
      cp->dup_len = dup_len;
      cp->dup_off = dup_off;
      cp->dup_tlen = dup_tlen;

      /* If we are off the page then try to the next page. */
      if (ret == 0 && next_key && indx >= NUM_ENT(pg)) {
            if ((ret = __ham_item_next(dbc, lock_mode, &pgno)) == 0)
                  goto next_pg;
            if (ret != DB_NOTFOUND)
                  return (ret);
            if ((ret = mpf->put(dbc->dbp->mpf, cp->page, 0)) != 0)
                  return (ret);
            cp->page = NULL;
            if ((ret = __ham_get_meta(dbc)) != 0)
                  return (ret);

            cp->bucket++;
            if (cp->bucket > cp->hdr->max_bucket) {
                  /*
                   * Restore cursor to its previous state.  We're past
                   * the last item in the last bucket, so the next
                   * DBC->c_get(DB_NEXT) will return DB_NOTFOUND.
                   */
                  cp->bucket--;
                  ret = DB_NOTFOUND;
            } else {
                  /*
                   * Start on the next bucket.
                   *
                   * Note that if this new bucket happens to be empty,
                   * but there's another non-empty bucket after it,
                   * we'll return early.  This is a rare case, and we
                   * don't guarantee any particular number of keys
                   * returned on each call, so just let the next call
                   * to bulk get move forward by yet another bucket.
                   */
                  cp->pgno = BUCKET_TO_PAGE(cp, cp->bucket);
                  cp->indx = NDX_INVALID;
                  F_CLR(cp, H_ISDUP);
                  ret = __ham_item_next(dbc, lock_mode, &pgno);
            }

            if ((t_ret = __ham_release_meta(dbc)) != 0)
                  return (t_ret);
            if (ret == 0)
                  goto next_pg;
            if (ret != DB_NOTFOUND)
                  return (ret);
      }
      *offp = (u_int32_t) -1;
      return (0);
}

static int
__ham_c_put(dbc, key, data, flags, pgnop)
      DBC *dbc;
      DBT *key;
      DBT *data;
      u_int32_t flags;
      db_pgno_t *pgnop;
{
      DB *dbp;
      DB_MPOOLFILE *mpf;
      DBT tmp_val, *myval;
      HASH_CURSOR *hcp;
      u_int32_t nbytes;
      int ret, t_ret;

      /*
       * The compiler doesn't realize that we only use this when ret is
       * equal to 0 and that if ret is equal to 0, that we must have set
       * myval.  So, we initialize it here to shut the compiler up.
       */
      COMPQUIET(myval, NULL);

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

      if (F_ISSET(hcp, H_DELETED) &&
          flags != DB_KEYFIRST && flags != DB_KEYLAST)
            return (DB_NOTFOUND);

      if ((ret = __ham_get_meta(dbc)) != 0)
            goto err1;

      switch (flags) {
      case DB_KEYLAST:
      case DB_KEYFIRST:
      case DB_NODUPDATA:
            nbytes = (ISBIG(hcp, key->size) ? HOFFPAGE_PSIZE :
                HKEYDATA_PSIZE(key->size)) +
                (ISBIG(hcp, data->size) ? HOFFPAGE_PSIZE :
                HKEYDATA_PSIZE(data->size));
            if ((ret = __ham_lookup(dbc,
                key, nbytes, DB_LOCK_WRITE, pgnop)) == DB_NOTFOUND) {
                  ret = 0;
                  if (hcp->seek_found_page != PGNO_INVALID &&
                      hcp->seek_found_page != hcp->pgno) {
                        if ((ret = mpf->put(mpf, hcp->page, 0)) != 0)
                              goto err2;
                        hcp->page = NULL;
                        hcp->pgno = hcp->seek_found_page;
                        hcp->indx = NDX_INVALID;
                  }

                  if (F_ISSET(data, DB_DBT_PARTIAL) && data->doff != 0) {
                        /*
                         * A partial put, but the key does not exist
                         * and we are not beginning the write at 0.
                         * We must create a data item padded up to doff
                         * and then write the new bytes represented by
                         * val.
                         */
                        if ((ret = __ham_init_dbt(dbp->dbenv, &tmp_val,
                            data->size + data->doff,
                            &dbc->my_rdata.data,
                            &dbc->my_rdata.ulen)) == 0) {
                              memset(tmp_val.data, 0, data->doff);
                              memcpy((u_int8_t *)tmp_val.data +
                                  data->doff, data->data, data->size);
                              myval = &tmp_val;
                        }
                  } else
                        myval = (DBT *)data;

                  if (ret == 0)
                        ret = __ham_add_el(dbc, key, myval, H_KEYDATA);
                  goto done;
            }
            break;
      case DB_BEFORE:
      case DB_AFTER:
      case DB_CURRENT:
            ret = __ham_item(dbc, DB_LOCK_WRITE, pgnop);
            break;
      }

      if (*pgnop == PGNO_INVALID && ret == 0) {
            if (flags == DB_CURRENT ||
                ((flags == DB_KEYFIRST ||
                flags == DB_KEYLAST || flags == DB_NODUPDATA) &&
                !(F_ISSET(dbp, DB_AM_DUP) || F_ISSET(key, DB_DBT_DUPOK))))
                  ret = __ham_overwrite(dbc, data, flags);
            else
                  ret = __ham_add_dup(dbc, data, flags, pgnop);
      }

done: if (ret == 0 && F_ISSET(hcp, H_EXPAND)) {
            ret = __ham_expand_table(dbc);
            F_CLR(hcp, H_EXPAND);
      }

      if (hcp->page != NULL &&
          (t_ret = mpf->set(mpf, hcp->page, DB_MPOOL_DIRTY)) != 0 && ret == 0)
            ret = t_ret;

err2: if ((t_ret = __ham_release_meta(dbc)) != 0 && ret == 0)
            ret = t_ret;

err1: return (ret);
}

/********************************* UTILITIES ************************/

/*
 * __ham_expand_table --
 */
static int
__ham_expand_table(dbc)
      DBC *dbc;
{
      DB *dbp;
      DB_LOCK metalock;
      DB_LSN lsn;
      DB_MPOOLFILE *mpf;
      DBMETA *mmeta;
      HASH_CURSOR *hcp;
      PAGE *h;
      db_pgno_t pgno, mpgno;
      u_int32_t newalloc, new_bucket, old_bucket;
      int dirty_meta, got_meta, logn, new_double, ret;

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

      LOCK_INIT(metalock);
      mmeta = (DBMETA *) hcp->hdr;
      mpgno = mmeta->pgno;
      h = NULL;
      dirty_meta = 0;
      got_meta = 0;
      newalloc = 0;

      /*
       * If the split point is about to increase, make sure that we
       * have enough extra pages.  The calculation here is weird.
       * We'd like to do this after we've upped max_bucket, but it's
       * too late then because we've logged the meta-data split.  What
       * we'll do between then and now is increment max bucket and then
       * see what the log of one greater than that is; here we have to
       * look at the log of max + 2.  VERY NASTY STUFF.
       *
       * We figure out what we need to do, then we log it, then request
       * the pages from mpool.  We don't want to fail after extending
       * the file.
       *
       * If the page we are about to split into has already been allocated,
       * then we simply need to get it to get its LSN.  If it hasn't yet
       * been allocated, then we know it's LSN (0,0).
       */

      new_bucket = hcp->hdr->max_bucket + 1;
      old_bucket = new_bucket & hcp->hdr->low_mask;

      new_double = hcp->hdr->max_bucket == hcp->hdr->high_mask;
      logn = __db_log2(new_bucket);

      if (!new_double || hcp->hdr->spares[logn + 1] != PGNO_INVALID) {
            /* Page exists; get it so we can get its LSN */
            pgno = BUCKET_TO_PAGE(hcp, new_bucket);
            if ((ret =
                mpf->get(mpf, &pgno, DB_MPOOL_CREATE, &h)) != 0)
                  goto err;
            lsn = h->lsn;
      } else {
            /* Get the master meta-data page to do allocation. */
            if (F_ISSET(dbp, DB_AM_SUBDB)) {
                  mpgno = PGNO_BASE_MD;
                  if ((ret = __db_lget(dbc,
                     0, mpgno, DB_LOCK_WRITE, 0, &metalock)) != 0)
                        goto err;
                  if ((ret =
                      mpf->get(mpf, &mpgno, 0, (PAGE **)&mmeta)) != 0)
                        goto err;
                  got_meta = 1;
            }
            pgno = mmeta->last_pgno + 1;
            ZERO_LSN(lsn);
            newalloc = 1;
      }

      /* Log the meta-data split first. */
      if (DBC_LOGGING(dbc)) {
            /*
             * We always log the page number of the first page of
             * the allocation group.  However, the LSN that we log
             * is either the LSN on the first page (if we did not
             * do the actual allocation here) or the LSN on the last
             * page of the unit (if we did do the allocation here).
             */
            if ((ret = __ham_metagroup_log(dbp, dbc->txn,
                &lsn, 0, hcp->hdr->max_bucket, mpgno, &mmeta->lsn,
                hcp->hdr->dbmeta.pgno, &hcp->hdr->dbmeta.lsn,
                pgno, &lsn, newalloc)) != 0)
                  goto err;
      } else
            LSN_NOT_LOGGED(lsn);

      hcp->hdr->dbmeta.lsn = lsn;

      if (new_double && hcp->hdr->spares[logn + 1] == PGNO_INVALID) {
            /*
             * We need to begin a new doubling and we have not allocated
             * any pages yet.  Read the last page in and initialize it to
             * make the allocation contiguous.  The pgno we calculated
             * above is the first page allocated. The entry in spares is
             * that page number minus any buckets already allocated (it
             * simplifies bucket to page transaction).  After we've set
             * that, we calculate the last pgno.
             */

            hcp->hdr->spares[logn + 1] = pgno - new_bucket;
            pgno += hcp->hdr->max_bucket;
            mmeta->last_pgno = pgno;
            mmeta->lsn = lsn;
            dirty_meta = DB_MPOOL_DIRTY;

            if ((ret = mpf->get(mpf, &pgno, DB_MPOOL_CREATE, &h)) != 0)
                  goto err;

            P_INIT(h, dbp->pgsize,
                pgno, PGNO_INVALID, PGNO_INVALID, 0, P_HASH);
      }

      /* Write out whatever page we ended up modifying. */
      h->lsn = lsn;
      if ((ret = mpf->put(mpf, h, DB_MPOOL_DIRTY)) != 0)
            goto err;
      h = NULL;

      /*
       * Update the meta-data page of this hash database.
       */
      hcp->hdr->max_bucket = new_bucket;
      if (new_double) {
            hcp->hdr->low_mask = hcp->hdr->high_mask;
            hcp->hdr->high_mask = new_bucket | hcp->hdr->low_mask;
      }

      /* Relocate records to the new bucket */
      ret = __ham_split_page(dbc, old_bucket, new_bucket);

err:  if (got_meta)
            (void)mpf->put(mpf, mmeta, dirty_meta);

      if (LOCK_ISSET(metalock))
            (void)__TLPUT(dbc, metalock);

      if (h != NULL)
            (void)mpf->put(mpf, h, 0);

      return (ret);
}

/*
 * PUBLIC: u_int32_t __ham_call_hash __P((DBC *, u_int8_t *, int32_t));
 */
u_int32_t
__ham_call_hash(dbc, k, len)
      DBC *dbc;
      u_int8_t *k;
      int32_t len;
{
      DB *dbp;
      u_int32_t n, bucket;
      HASH_CURSOR *hcp;
      HASH *hashp;

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

      n = (u_int32_t)(hashp->h_hash(dbp, k, len));

      bucket = n & hcp->hdr->high_mask;
      if (bucket > hcp->hdr->max_bucket)
            bucket = bucket & hcp->hdr->low_mask;
      return (bucket);
}

/*
 * Check for duplicates, and call __db_ret appropriately.  Release
 * everything held by the cursor.
 */
static int
__ham_dup_return(dbc, val, flags)
      DBC *dbc;
      DBT *val;
      u_int32_t flags;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      PAGE *pp;
      DBT *myval, tmp_val;
      db_indx_t ndx;
      db_pgno_t pgno;
      u_int32_t off, tlen;
      u_int8_t *hk, type;
      int cmp, ret;
      db_indx_t len;

      /* Check for duplicate and return the first one. */
      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      ndx = H_DATAINDEX(hcp->indx);
      type = HPAGE_TYPE(dbp, hcp->page, ndx);
      pp = hcp->page;
      myval = val;

      /*
       * There are 4 cases:
       * 1. We are not in duplicate, simply return; the upper layer
       *    will do the right thing.
       * 2. We are looking at keys and stumbled onto a duplicate.
       * 3. We are in the middle of a duplicate set. (ISDUP set)
       * 4. We need to check for particular data match.
       */

      /* We should never get here with off-page dups. */
      DB_ASSERT(type != H_OFFDUP);

      /* Case 1 */
      if (type != H_DUPLICATE && flags != DB_GET_BOTH &&
          flags != DB_GET_BOTHC && flags != DB_GET_BOTH_RANGE)
            return (0);

      /*
       * Here we check for the case where we just stumbled onto a
       * duplicate.  In this case, we do initialization and then
       * let the normal duplicate code handle it. (Case 2)
       */
      if (!F_ISSET(hcp, H_ISDUP) && type == H_DUPLICATE) {
            F_SET(hcp, H_ISDUP);
            hcp->dup_tlen = LEN_HDATA(dbp, hcp->page,
                hcp->hdr->dbmeta.pagesize, hcp->indx);
            hk = H_PAIRDATA(dbp, hcp->page, hcp->indx);
            if (flags == DB_LAST ||
                flags == DB_PREV || flags == DB_PREV_NODUP) {
                  hcp->dup_off = 0;
                  do {
                        memcpy(&len,
                            HKEYDATA_DATA(hk) + hcp->dup_off,
                            sizeof(db_indx_t));
                        hcp->dup_off += DUP_SIZE(len);
                  } while (hcp->dup_off < hcp->dup_tlen);
                  hcp->dup_off -= DUP_SIZE(len);
            } else {
                  memcpy(&len,
                      HKEYDATA_DATA(hk), sizeof(db_indx_t));
                  hcp->dup_off = 0;
            }
            hcp->dup_len = len;
      }

      /*
       * If we are retrieving a specific key/data pair, then we
       * may need to adjust the cursor before returning data.
       * Case 4
       */
      if (flags == DB_GET_BOTH ||
          flags == DB_GET_BOTHC || flags == DB_GET_BOTH_RANGE) {
            if (F_ISSET(hcp, H_ISDUP)) {
                  /*
                   * If we're doing a join, search forward from the
                   * current position, not the beginning of the dup set.
                   */
                  if (flags == DB_GET_BOTHC)
                        F_SET(hcp, H_CONTINUE);

                  __ham_dsearch(dbc, val, &off, &cmp, flags);

                  /*
                   * This flag is set nowhere else and is safe to
                   * clear unconditionally.
                   */
                  F_CLR(hcp, H_CONTINUE);
                  hcp->dup_off = off;
            } else {
                  hk = H_PAIRDATA(dbp, hcp->page, hcp->indx);
                  if (((HKEYDATA *)hk)->type == H_OFFPAGE) {
                        memcpy(&tlen,
                            HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
                        memcpy(&pgno,
                            HOFFPAGE_PGNO(hk), sizeof(db_pgno_t));
                        if ((ret = __db_moff(dbp, val,
                            pgno, tlen, dbp->dup_compare, &cmp)) != 0)
                              return (ret);
                  } else {
                        /*
                         * We do not zero tmp_val since the comparison
                         * routines may only look at data and size.
                         */
                        tmp_val.data = HKEYDATA_DATA(hk);
                        tmp_val.size = LEN_HDATA(dbp, hcp->page,
                            dbp->pgsize, hcp->indx);
                        cmp = dbp->dup_compare == NULL ?
                            __bam_defcmp(dbp, &tmp_val, val) :
                            dbp->dup_compare(dbp, &tmp_val, val);
                  }
            }

            if (cmp != 0)
                  return (DB_NOTFOUND);
      }

      /*
       * If we're doing a bulk get, we don't want to actually return
       * the data:  __ham_bulk will take care of cracking out the
       * duplicates appropriately.
       *
       * The rest of this function calculates partial offsets and
       * handles the actual __db_ret, so just return if
       * DB_MULTIPLE(_KEY) is set.
       */
      if (F_ISSET(dbc, DBC_MULTIPLE | DBC_MULTIPLE_KEY))
            return (0);

      /*
       * Now, everything is initialized, grab a duplicate if
       * necessary.
       */
      if (F_ISSET(hcp, H_ISDUP)) {  /* Case 3 */
            /*
             * Copy the DBT in case we are retrieving into user
             * memory and we need the parameters for it.  If the
             * user requested a partial, then we need to adjust
             * the user's parameters to get the partial of the
             * duplicate which is itself a partial.
             */
            memcpy(&tmp_val, val, sizeof(*val));
            if (F_ISSET(&tmp_val, DB_DBT_PARTIAL)) {
                  /*
                   * Take the user's length unless it would go
                   * beyond the end of the duplicate.
                   */
                  if (tmp_val.doff + hcp->dup_off > hcp->dup_len)
                        tmp_val.dlen = 0;
                  else if (tmp_val.dlen + tmp_val.doff >
                      hcp->dup_len)
                        tmp_val.dlen =
                            hcp->dup_len - tmp_val.doff;

                  /*
                   * Calculate the new offset.
                   */
                  tmp_val.doff += hcp->dup_off;
            } else {
                  F_SET(&tmp_val, DB_DBT_PARTIAL);
                  tmp_val.dlen = hcp->dup_len;
                  tmp_val.doff = hcp->dup_off + sizeof(db_indx_t);
            }
            myval = &tmp_val;
      }

      /*
       * Finally, if we had a duplicate, pp, ndx, and myval should be
       * set appropriately.
       */
      if ((ret = __db_ret(dbp, pp, ndx, myval, &dbc->rdata->data,
          &dbc->rdata->ulen)) != 0)
            return (ret);

      /*
       * In case we sent a temporary off to db_ret, set the real
       * return values.
       */
      val->data = myval->data;
      val->size = myval->size;

      F_SET(val, DB_DBT_ISSET);

      return (0);
}

static int
__ham_overwrite(dbc, nval, flags)
      DBC *dbc;
      DBT *nval;
      u_int32_t flags;
{
      DB *dbp;
      DB_ENV *dbenv;
      HASH_CURSOR *hcp;
      DBT *myval, tmp_val, tmp_val2;
      void *newrec;
      u_int8_t *hk, *p;
      u_int32_t len, nondup_size;
      db_indx_t newsize;
      int ret;

      dbp = dbc->dbp;
      dbenv = dbp->dbenv;
      hcp = (HASH_CURSOR *)dbc->internal;
      if (F_ISSET(hcp, H_ISDUP)) {
            /*
             * This is an overwrite of a duplicate. We should never
             * be off-page at this point.
             */
            DB_ASSERT(hcp->opd == NULL);
            /* On page dups */
            if (F_ISSET(nval, DB_DBT_PARTIAL)) {
                  /*
                   * We're going to have to get the current item, then
                   * construct the record, do any padding and do a
                   * replace.
                   */
                  memset(&tmp_val, 0, sizeof(tmp_val));
                  if ((ret =
                      __ham_dup_return(dbc, &tmp_val, DB_CURRENT)) != 0)
                        return (ret);

                  /* Figure out new size. */
                  nondup_size = tmp_val.size;
                  newsize = nondup_size;

                  /*
                   * Three cases:
                   * 1. strictly append (may need to allocate space
                   *    for pad bytes; really gross).
                   * 2. overwrite some and append.
                   * 3. strictly overwrite.
                   */
                  if (nval->doff > nondup_size)
                        newsize +=
                            (nval->doff - nondup_size + nval->size);
                  else if (nval->doff + nval->dlen > nondup_size)
                        newsize += nval->size -
                            (nondup_size - nval->doff);
                  else
                        newsize += nval->size - nval->dlen;

                  /*
                   * Make sure that the new size doesn't put us over
                   * the onpage duplicate size in which case we need
                   * to convert to off-page duplicates.
                   */
                  if (ISBIG(hcp, hcp->dup_tlen - nondup_size + newsize)) {
                        if ((ret = __ham_dup_convert(dbc)) != 0)
                              return (ret);
                        return (hcp->opd->c_am_put(hcp->opd,
                            NULL, nval, flags, NULL));
                  }

                  if ((ret = __os_malloc(dbp->dbenv,
                      DUP_SIZE(newsize), &newrec)) != 0)
                        return (ret);
                  memset(&tmp_val2, 0, sizeof(tmp_val2));
                  F_SET(&tmp_val2, DB_DBT_PARTIAL);

                  /* Construct the record. */
                  p = newrec;
                  /* Initial size. */
                  memcpy(p, &newsize, sizeof(db_indx_t));
                  p += sizeof(db_indx_t);

                  /* First part of original record. */
                  len = nval->doff > tmp_val.size
                      ? tmp_val.size : nval->doff;
                  memcpy(p, tmp_val.data, len);
                  p += len;

                  if (nval->doff > tmp_val.size) {
                        /* Padding */
                        memset(p, 0, nval->doff - tmp_val.size);
                        p += nval->doff - tmp_val.size;
                  }

                  /* New bytes */
                  memcpy(p, nval->data, nval->size);
                  p += nval->size;

                  /* End of original record (if there is any) */
                  if (nval->doff + nval->dlen < tmp_val.size) {
                        len = tmp_val.size - nval->doff - nval->dlen;
                        memcpy(p, (u_int8_t *)tmp_val.data +
                            nval->doff + nval->dlen, len);
                        p += len;
                  }

                  /* Final size. */
                  memcpy(p, &newsize, sizeof(db_indx_t));

                  /*
                   * Make sure that the caller isn't corrupting
                   * the sort order.
                   */
                  if (dbp->dup_compare != NULL) {
                        tmp_val2.data =
                            (u_int8_t *)newrec + sizeof(db_indx_t);
                        tmp_val2.size = newsize;
                        if (dbp->dup_compare(
                            dbp, &tmp_val, &tmp_val2) != 0) {
                              (void)__os_free(dbenv, newrec);
                              return (__db_duperr(dbp, flags));
                        }
                  }

                  tmp_val2.data = newrec;
                  tmp_val2.size = DUP_SIZE(newsize);
                  tmp_val2.doff = hcp->dup_off;
                  tmp_val2.dlen = DUP_SIZE(hcp->dup_len);

                  ret = __ham_replpair(dbc, &tmp_val2, 0);
                  (void)__os_free(dbenv, newrec);

                  /* Update cursor */
                  if (ret != 0)
                        return (ret);

                  if (newsize > nondup_size)
                        hcp->dup_tlen += (newsize - nondup_size);
                  else
                        hcp->dup_tlen -= (nondup_size - newsize);
                  hcp->dup_len = DUP_SIZE(newsize);
                  return (0);
            } else {
                  /* Check whether we need to convert to off page. */
                  if (ISBIG(hcp,
                      hcp->dup_tlen - hcp->dup_len + nval->size)) {
                        if ((ret = __ham_dup_convert(dbc)) != 0)
                              return (ret);
                        return (hcp->opd->c_am_put(hcp->opd,
                            NULL, nval, flags, NULL));
                  }

                  /* Make sure we maintain sort order. */
                  if (dbp->dup_compare != NULL) {
                        tmp_val2.data =
                            HKEYDATA_DATA(H_PAIRDATA(dbp, hcp->page,
                            hcp->indx)) + hcp->dup_off +
                            sizeof(db_indx_t);
                        tmp_val2.size = hcp->dup_len;
                        if (dbp->dup_compare(dbp, nval, &tmp_val2) != 0)
                              return (EINVAL);
                  }
                  /* Overwriting a complete duplicate. */
                  if ((ret =
                      __ham_make_dup(dbp->dbenv, nval, &tmp_val,
                      &dbc->my_rdata.data, &dbc->my_rdata.ulen)) != 0)
                        return (ret);
                  /* Now fix what we are replacing. */
                  tmp_val.doff = hcp->dup_off;
                  tmp_val.dlen = DUP_SIZE(hcp->dup_len);

                  /* Update cursor */
                  if (nval->size > hcp->dup_len)
                        hcp->dup_tlen += (nval->size - hcp->dup_len);
                  else
                        hcp->dup_tlen -= (hcp->dup_len - nval->size);
                  hcp->dup_len = (db_indx_t)DUP_SIZE(nval->size);
            }
            myval = &tmp_val;
      } else if (!F_ISSET(nval, DB_DBT_PARTIAL)) {
            /* Put/overwrite */
            memcpy(&tmp_val, nval, sizeof(*nval));
            F_SET(&tmp_val, DB_DBT_PARTIAL);
            tmp_val.doff = 0;
            hk = H_PAIRDATA(dbp, hcp->page, hcp->indx);
            if (HPAGE_PTYPE(hk) == H_OFFPAGE)
                  memcpy(&tmp_val.dlen,
                      HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
            else
                  tmp_val.dlen = LEN_HDATA(dbp, hcp->page,
                      hcp->hdr->dbmeta.pagesize, hcp->indx);
            myval = &tmp_val;
      } else
            /* Regular partial put */
            myval = nval;

      return (__ham_replpair(dbc, myval, 0));
}

/*
 * Given a key and a cursor, sets the cursor to the page/ndx on which
 * the key resides.  If the key is found, the cursor H_OK flag is set
 * and the pagep, bndx, pgno (dpagep, dndx, dpgno) fields are set.
 * If the key is not found, the H_OK flag is not set.  If the sought
 * field is non-0, the pagep, bndx, pgno (dpagep, dndx, dpgno) fields
 * are set indicating where an add might take place.  If it is 0,
 * non of the cursor pointer field are valid.
 */
static int
__ham_lookup(dbc, key, sought, mode, pgnop)
      DBC *dbc;
      const DBT *key;
      u_int32_t sought;
      db_lockmode_t mode;
      db_pgno_t *pgnop;
{
      DB *dbp;
      HASH_CURSOR *hcp;
      db_pgno_t pgno;
      u_int32_t tlen;
      int match, ret;
      u_int8_t *hk, *dk;

      dbp = dbc->dbp;
      hcp = (HASH_CURSOR *)dbc->internal;
      /*
       * Set up cursor so that we're looking for space to add an item
       * as we cycle through the pages looking for the key.
       */
      if ((ret = __ham_item_reset(dbc)) != 0)
            return (ret);
      hcp->seek_size = sought;

      hcp->bucket = __ham_call_hash(dbc, (u_int8_t *)key->data, key->size);
      hcp->pgno = BUCKET_TO_PAGE(hcp, hcp->bucket);

      for (;;) {
            *pgnop = PGNO_INVALID;
            if ((ret = __ham_item_next(dbc, mode, pgnop)) != 0)
                  return (ret);

            if (F_ISSET(hcp, H_NOMORE))
                  break;

            hk = H_PAIRKEY(dbp, hcp->page, hcp->indx);
            switch (HPAGE_PTYPE(hk)) {
            case H_OFFPAGE:
                  memcpy(&tlen, HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
                  if (tlen == key->size) {
                        memcpy(&pgno,
                            HOFFPAGE_PGNO(hk), sizeof(db_pgno_t));
                        if ((ret = __db_moff(dbp,
                            key, pgno, tlen, NULL, &match)) != 0)
                              return (ret);
                        if (match == 0)
                              goto found_key;
                  }
                  break;
            case H_KEYDATA:
                  if (key->size ==
                      LEN_HKEY(dbp, hcp->page, dbp->pgsize, hcp->indx) &&
                      memcmp(key->data,
                      HKEYDATA_DATA(hk), key->size) == 0) {
                        /* Found the key, check for data type. */
found_key:              F_SET(hcp, H_OK);
                        dk = H_PAIRDATA(dbp, hcp->page, hcp->indx);
                        if (HPAGE_PTYPE(dk) == H_OFFDUP)
                              memcpy(pgnop, HOFFDUP_PGNO(dk),
                                  sizeof(db_pgno_t));
                        return (0);
                  }
                  break;
            case H_DUPLICATE:
            case H_OFFDUP:
                  /*
                   * These are errors because keys are never
                   * duplicated, only data items are.
                   */
                  return (__db_pgfmt(dbp->dbenv, PGNO(hcp->page)));
            }
      }

      /*
       * Item was not found.
       */

      if (sought != 0)
            return (ret);

      return (ret);
}

/*
 * __ham_init_dbt --
 *    Initialize a dbt using some possibly already allocated storage
 *    for items.
 *
 * PUBLIC: int __ham_init_dbt __P((DB_ENV *,
 * PUBLIC:     DBT *, u_int32_t, void **, u_int32_t *));
 */
int
__ham_init_dbt(dbenv, dbt, size, bufp, sizep)
      DB_ENV *dbenv;
      DBT *dbt;
      u_int32_t size;
      void **bufp;
      u_int32_t *sizep;
{
      int ret;

      memset(dbt, 0, sizeof(*dbt));
      if (*sizep < size) {
            if ((ret = __os_realloc(dbenv, size, bufp)) != 0) {
                  *sizep = 0;
                  return (ret);
            }
            *sizep = size;
      }
      dbt->data = *bufp;
      dbt->size = size;
      return (0);
}

/*
 * Adjust the cursor after an insert or delete.  The cursor passed is
 * the one that was operated upon; we just need to check any of the
 * others.
 *
 * len indicates the length of the item added/deleted
 * add indicates if the item indicated by the cursor has just been
 * added (add == 1) or deleted (add == 0).
 * dup indicates if the addition occurred into a duplicate set.
 *
 * PUBLIC: int __ham_c_update
 * PUBLIC:    __P((DBC *, u_int32_t, int, int));
 */
int
__ham_c_update(dbc, len, add, is_dup)
      DBC *dbc;
      u_int32_t len;
      int add, is_dup;
{
      DB *dbp, *ldbp;
      DBC *cp;
      DB_ENV *dbenv;
      DB_LSN lsn;
      DB_TXN *my_txn;
      HASH_CURSOR *hcp, *lcp;
      int found, ret;
      u_int32_t order;

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

      /*
       * Adjustment will only be logged if this is a subtransaction.
       * Only subtransactions can abort and effect their parent
       * transactions cursors.
       */

      my_txn = IS_SUBTRANSACTION(dbc->txn) ? dbc->txn : NULL;
      found = 0;

      MUTEX_THREAD_LOCK(dbenv, dbenv->dblist_mutexp);

      /*
       * Calculate the order of this deleted record.
       * This will be one greater than any cursor that is pointing
       * at this record and already marked as deleted.
       */
      order = 0;
      if (!add) {
            order = 1;
            for (ldbp = __dblist_get(dbenv, dbp->adj_fileid);
                ldbp != NULL && ldbp->adj_fileid == dbp->adj_fileid;
                ldbp = LIST_NEXT(ldbp, dblistlinks)) {
                  MUTEX_THREAD_LOCK(dbenv, dbp->mutexp);
                  for (cp = TAILQ_FIRST(&ldbp->active_queue); cp != NULL;
                      cp = TAILQ_NEXT(cp, links)) {
                        if (cp == dbc || cp->dbtype != DB_HASH)
                              continue;
                        lcp = (HASH_CURSOR *)cp->internal;
                        if (F_ISSET(lcp, H_DELETED) &&
                            hcp->pgno == lcp->pgno &&
                            hcp->indx == lcp->indx &&
                            order <= lcp->order &&
                            (!is_dup || hcp->dup_off == lcp->dup_off))
                              order = lcp->order + 1;
                  }
                  MUTEX_THREAD_UNLOCK(dbenv, dbp->mutexp);
            }
            hcp->order = order;
      }

      for (ldbp = __dblist_get(dbenv, dbp->adj_fileid);
          ldbp != NULL && ldbp->adj_fileid == dbp->adj_fileid;
          ldbp = LIST_NEXT(ldbp, dblistlinks)) {
            MUTEX_THREAD_LOCK(dbenv, dbp->mutexp);
            for (cp = TAILQ_FIRST(&ldbp->active_queue); cp != NULL;
                cp = TAILQ_NEXT(cp, links)) {
                  if (cp == dbc || cp->dbtype != DB_HASH)
                        continue;

                  lcp = (HASH_CURSOR *)cp->internal;

                  if (lcp->pgno != hcp->pgno || lcp->indx == NDX_INVALID)
                        continue;

                  if (my_txn != NULL && cp->txn != my_txn)
                        found = 1;

                  if (!is_dup) {
                        if (add) {
                              /*
                               * This routine is not called to add
                               * non-dup records which are always put
                               * at the end.  It is only called from
                               * recovery in this case and the
                               * cursor will be marked deleted.
                               * We are "undeleting" so unmark all
                               * cursors with the same order.
                               */
                              if (lcp->indx == hcp->indx &&
                                  F_ISSET(lcp, H_DELETED)) {
                                    if (lcp->order == hcp->order)
                                          F_CLR(lcp, H_DELETED);
                                    else if (lcp->order >
                                        hcp->order) {

                                    /*
                                     * If we've moved this cursor's
                                     * index, split its order
                                     * number--i.e., decrement it by
                                     * enough so that the lowest
                                     * cursor moved has order 1.
                                     * cp_arg->order is the split
                                     * point, so decrement by one
                                     * less than that.
                                     */
                                          lcp->order -=
                                              (hcp->order - 1);
                                          lcp->indx += 2;
                                    }
                              } else if (lcp->indx >= hcp->indx)
                                    lcp->indx += 2;

                        } else {
                              if (lcp->indx > hcp->indx) {
                                    lcp->indx -= 2;
                                    if (lcp->indx == hcp->indx &&
                                        F_ISSET(lcp, H_DELETED))
                                          lcp->order += order;
                              } else if (lcp->indx == hcp->indx &&
                                  !F_ISSET(lcp, H_DELETED)) {
                                    F_SET(lcp, H_DELETED);
                                    F_CLR(lcp, H_ISDUP);
                                    lcp->order = order;
                              }
                        }
                  } else if (lcp->indx == hcp->indx) {
                        /*
                         * Handle duplicates.  This routine is
                         * only called for on page dups.
                         * Off page dups are handled by btree/rtree
                         * code.
                         */
                        if (add) {
                              lcp->dup_tlen += len;
                              if (lcp->dup_off == hcp->dup_off &&
                                  F_ISSET(hcp, H_DELETED) &&
                                  F_ISSET(lcp, H_DELETED)) {
                                    /* Abort of a delete. */
                                    if (lcp->order == hcp->order)
                                          F_CLR(lcp, H_DELETED);
                                    else if (lcp->order >
                                        hcp->order) {
                                          lcp->order -=
                                              (hcp->order -1);
                                          lcp->dup_off += len;
                                    }
                              } else if (lcp->dup_off >= hcp->dup_off)
                                    lcp->dup_off += len;
                        } else {
                              lcp->dup_tlen -= len;
                              if (lcp->dup_off > hcp->dup_off) {
                                    lcp->dup_off -= len;
                                    if (lcp->dup_off ==
                                        hcp->dup_off &&
                                        F_ISSET(lcp, H_DELETED))
                                          lcp->order += order;
                              } else if (lcp->dup_off ==
                                  hcp->dup_off &&
                                  !F_ISSET(lcp, H_DELETED)) {
                                    F_SET(lcp, H_DELETED);
                                    lcp->order = order;
                              }
                        }
                  }
            }
            MUTEX_THREAD_UNLOCK(dbenv, dbp->mutexp);
      }
      MUTEX_THREAD_UNLOCK(dbenv, dbenv->dblist_mutexp);

      if (found != 0 && DBC_LOGGING(dbc)) {
            if ((ret = __ham_curadj_log(dbp, my_txn, &lsn, 0, hcp->pgno,
                hcp->indx, len, hcp->dup_off, add, is_dup, order)) != 0)
                  return (ret);
      }

      return (0);
}

/*
 * __ham_get_clist --
 *
 * Get a list of cursors either on a particular bucket or on a particular
 * page and index combination.  The former is so that we can update
 * cursors on a split.  The latter is so we can update cursors when we
 * move items off page.
 *
 * PUBLIC: int __ham_get_clist __P((DB *, db_pgno_t, u_int32_t, DBC ***));
 */
int
__ham_get_clist(dbp, pgno, indx, listp)
      DB *dbp;
      db_pgno_t pgno;
      u_int32_t indx;
      DBC ***listp;
{
      DB *ldbp;
      DBC *cp;
      DB_ENV *dbenv;
      int nalloc, nused, ret;

      /*
       * Assume that finding anything is the exception, so optimize for
       * the case where there aren't any.
       */
      nalloc = nused = 0;
      *listp = NULL;
      dbenv = dbp->dbenv;

      MUTEX_THREAD_LOCK(dbenv, dbenv->dblist_mutexp);
      for (ldbp = __dblist_get(dbenv, dbp->adj_fileid);
          ldbp != NULL && ldbp->adj_fileid == dbp->adj_fileid;
          ldbp = LIST_NEXT(ldbp, dblistlinks)) {
            MUTEX_THREAD_LOCK(dbenv, dbp->mutexp);
            for (cp = TAILQ_FIRST(&ldbp->active_queue); cp != NULL;
                cp = TAILQ_NEXT(cp, links))
                  /*
                   * We match if cp->pgno matches the specified
                   * pgno, and if either the cp->indx matches
                   * or we weren't given an index.
                   */
                  if (cp->internal->pgno == pgno &&
                      (indx == NDX_INVALID ||
                      cp->internal->indx == indx)) {
                        if (nused >= nalloc) {
                              nalloc += 10;
                              if ((ret = __os_realloc(dbp->dbenv,
                                  nalloc * sizeof(HASH_CURSOR *),
                                  listp)) != 0)
                                    goto err;
                        }
                        (*listp)[nused++] = cp;
                  }

            MUTEX_THREAD_UNLOCK(dbp->dbenv, dbp->mutexp);
      }
      MUTEX_THREAD_UNLOCK(dbenv, dbenv->dblist_mutexp);

      if (listp != NULL) {
            if (nused >= nalloc) {
                  nalloc++;
                  if ((ret = __os_realloc(dbp->dbenv,
                      nalloc * sizeof(HASH_CURSOR *), listp)) != 0)
                        return (ret);
            }
            (*listp)[nused] = NULL;
      }
      return (0);
err:
      MUTEX_THREAD_UNLOCK(dbp->dbenv, dbp->mutexp);
      MUTEX_THREAD_UNLOCK(dbenv, dbenv->dblist_mutexp);
      return (ret);
}

static int
__ham_c_writelock(dbc)
      DBC *dbc;
{
      DB_ENV *dbenv;
      DB_LOCK tmp_lock;
      HASH_CURSOR *hcp;
      int ret;

      /*
       * All we need do is acquire the lock and let the off-page
       * dup tree do its thing.
       */
      if (!STD_LOCKING(dbc))
            return (0);

      hcp = (HASH_CURSOR *)dbc->internal;
      if ((!LOCK_ISSET(hcp->lock) || hcp->lock_mode == DB_LOCK_READ)) {
            tmp_lock = hcp->lock;
            if ((ret = __ham_lock_bucket(dbc, DB_LOCK_WRITE)) != 0)
                  return (ret);
            dbenv = dbc->dbp->dbenv;
            if (LOCK_ISSET(tmp_lock) &&
                (ret = dbenv->lock_put(dbenv, &tmp_lock)) != 0)
                  return (ret);
      }
      return (0);
}

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