rec_delete.c

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/*-
 * Copyright (c) 1990, 1993, 1994
 * The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Mike Olson.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 * This product includes software developed by the University of
 * California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)rec_delete.c  8.7 (Berkeley) 7/14/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>

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

#include "../include/db.h"
#include "recno.h"

static int rec_rdelete __P((BTREE *, recno_t));

/*
 * __REC_DELETE -- Delete the item(s) referenced by a key.
 *
 * Parameters:
 * dbp:  pointer to access method
 * key:  key to delete
 * flags:   R_CURSOR if deleting what the cursor references
 *
 * Returns:
 * RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
 */
int
__rec_delete(dbp, key, flags)
   const DB *dbp;
   const DBT *key;
   u_int flags;
{
   BTREE *t;
   recno_t nrec;
   int status;

   t = dbp->internal;

   /* Toss any page pinned across calls. */
   if (t->bt_pinned != NULL) {
      mpool_put(t->bt_mp, t->bt_pinned, 0);
      t->bt_pinned = NULL;
   }

   switch(flags) {
   case 0:
      if ((nrec = *(recno_t *)key->data) == 0)
         goto einval;
      if (nrec > t->bt_nrecs)
         return (RET_SPECIAL);
      --nrec;
      status = rec_rdelete(t, nrec);
      break;
   case R_CURSOR:
      if (!F_ISSET(&t->bt_cursor, CURS_INIT))
         goto einval;
      if (t->bt_nrecs == 0)
         return (RET_SPECIAL);
      status = rec_rdelete(t, t->bt_cursor.rcursor - 1);
      if (status == RET_SUCCESS)
         --t->bt_cursor.rcursor;
      break;
   default:
einval:     errno = EINVAL;
      return (RET_ERROR);
   }

   if (status == RET_SUCCESS)
      F_SET(t, B_MODIFIED | R_MODIFIED);
   return (status);
}

/*
 * REC_RDELETE -- Delete the data matching the specified key.
 *
 * Parameters:
 * tree: tree
 * nrec: record to delete
 *
 * Returns:
 * RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
 */
static int
rec_rdelete(t, nrec)
   BTREE *t;
   recno_t nrec;
{
   EPG *e;
   PAGE *h;
   int status;

   /* Find the record; __rec_search pins the page. */
   if ((e = __rec_search(t, nrec, SDELETE)) == NULL)
      return (RET_ERROR);

   /* Delete the record. */
   h = e->page;
   status = __rec_dleaf(t, h, e->index);
   if (status != RET_SUCCESS) {
      mpool_put(t->bt_mp, h, 0);
      return (status);
   }
   mpool_put(t->bt_mp, h, MPOOL_DIRTY);
   return (RET_SUCCESS);
}

/*
 * __REC_DLEAF -- Delete a single record from a recno leaf page.
 *
 * Parameters:
 * t: tree
 * index:   index on current page to delete
 *
 * Returns:
 * RET_SUCCESS, RET_ERROR.
 */
int
__rec_dleaf(t, h, idx)
   BTREE *t;
   PAGE *h;
   u_int32_t idx;
{
   RLEAF *rl;
   indx_t *ip, cnt, offset;
   u_int32_t nbytes;
   char *from;
   void *to;

   /*
    * Delete a record from a recno leaf page.  Internal records are never
    * deleted from internal pages, regardless of the records that caused
    * them to be added being deleted.  Pages made empty by deletion are
    * not reclaimed.  They are, however, made available for reuse.
    *
    * Pack the remaining entries at the end of the page, shift the indices
    * down, overwriting the deleted record and its index.  If the record
    * uses overflow pages, make them available for reuse.
    */
   to = rl = GETRLEAF(h, idx);
   if (rl->flags & P_BIGDATA && __ovfl_delete(t, rl->bytes) == RET_ERROR)
      return (RET_ERROR);
   nbytes = NRLEAF(rl);

   /*
    * Compress the key/data pairs.  Compress and adjust the [BR]LEAF
    * offsets.  Reset the headers.
    */
   from = (char *)h + h->upper;
   memmove(from + nbytes, from, (char *)to - from);
   h->upper += nbytes;

   offset = h->linp[idx];
   for (cnt = &h->linp[idx] - (ip = &h->linp[0]); cnt--; ++ip)
      if (ip[0] < offset)
         ip[0] += nbytes;
   for (cnt = &h->linp[NEXTINDEX(h)] - ip; --cnt; ++ip)
      ip[0] = ip[1] < offset ? ip[1] + nbytes : ip[1];
   h->lower -= sizeof(indx_t);
   --t->bt_nrecs;
   return (RET_SUCCESS);
}