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db_overflow.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *    Sleepycat Software.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994, 1995, 1996
 *    Keith Bostic.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994, 1995
 *    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.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)db_overflow.c 10.11 (Sleepycat) 5/7/98";
#endif /* not lint */

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

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

#include "db_int.h"
#include "db_page.h"
#include "db_am.h"

/*
 * Big key/data code.
 *
 * Big key and data entries are stored on linked lists of pages.  The initial
 * reference is a structure with the total length of the item and the page
 * number where it begins.  Each entry in the linked list contains a pointer
 * to the next page of data, and so on.
 */

/*
 * __db_goff --
 *    Get an offpage item.
 *
 * PUBLIC: int __db_goff __P((DB *, DBT *,
 * PUBLIC:     u_int32_t, db_pgno_t, void **, u_int32_t *));
 */
int
__db_goff(dbp, dbt, tlen, pgno, bpp, bpsz)
      DB *dbp;
      DBT *dbt;
      u_int32_t tlen;
      db_pgno_t pgno;
      void **bpp;
      u_int32_t *bpsz;
{
      PAGE *h;
      db_indx_t bytes;
      u_int32_t curoff, needed, start;
      u_int8_t *p, *src;
      int ret;

      /*
       * Check if the buffer is big enough; if it is not and we are
       * allowed to malloc space, then we'll malloc it.  If we are
       * not (DB_DBT_USERMEM), then we'll set the dbt and return
       * appropriately.
       */
      if (F_ISSET(dbt, DB_DBT_PARTIAL)) {
            start = dbt->doff;
            needed = dbt->dlen;
      } else {
            start = 0;
            needed = tlen;
      }

      /*
       * Allocate any necessary memory.
       *
       * XXX: Never allocate 0 bytes;
       */
      if (F_ISSET(dbt, DB_DBT_USERMEM)) {
            if (needed > dbt->ulen) {
                  dbt->size = needed;
                  return (ENOMEM);
            }
      } else if (F_ISSET(dbt, DB_DBT_MALLOC)) {
            dbt->data = dbp->db_malloc == NULL ?
                (void *)__db_malloc(needed + 1) :
                (void *)dbp->db_malloc(needed + 1);
            if (dbt->data == NULL)
                  return (ENOMEM);
      } else if (*bpsz == 0 || *bpsz < needed) {
            *bpp = (*bpp == NULL ?
                (void *)__db_malloc(needed + 1) :
                (void *)__db_realloc(*bpp, needed + 1));
            if (*bpp == NULL)
                  return (ENOMEM);
            *bpsz = needed + 1;
            dbt->data = *bpp;
      } else
            dbt->data = *bpp;

      /*
       * Step through the linked list of pages, copying the data on each
       * one into the buffer.  Never copy more than the total data length.
       */
      dbt->size = needed;
      for (curoff = 0, p = dbt->data; pgno != P_INVALID && needed > 0;) {
            if ((ret = memp_fget(dbp->mpf, &pgno, 0, &h)) != 0) {
                  (void)__db_pgerr(dbp, pgno);
                  return (ret);
            }
            /* Check if we need any bytes from this page. */
            if (curoff + OV_LEN(h) >= start) {
                  src = (u_int8_t *)h + P_OVERHEAD;
                  bytes = OV_LEN(h);
                  if (start > curoff) {
                        src += start - curoff;
                        bytes -= start - curoff;
                  }
                  if (bytes > needed)
                        bytes = needed;
                  memcpy(p, src, bytes);
                  p += bytes;
                  needed -= bytes;
            }
            curoff += OV_LEN(h);
            pgno = h->next_pgno;
            memp_fput(dbp->mpf, h, 0);
      }
      return (0);
}

/*
 * __db_poff --
 *    Put an offpage item.
 *
 * PUBLIC: int __db_poff __P((DB *, const DBT *, db_pgno_t *,
 * PUBLIC:     int (*)(DB *, u_int32_t, PAGE **)));
 */
int
__db_poff(dbp, dbt, pgnop, newfunc)
      DB *dbp;
      const DBT *dbt;
      db_pgno_t *pgnop;
      int (*newfunc) __P((DB *, u_int32_t, PAGE **));
{
      PAGE *pagep, *lastp;
      DB_LSN new_lsn, null_lsn;
      DBT tmp_dbt;
      db_indx_t pagespace;
      u_int32_t sz;
      u_int8_t *p;
      int ret;

      /*
       * Allocate pages and copy the key/data item into them.  Calculate the
       * number of bytes we get for pages we fill completely with a single
       * item.
       */
      pagespace = P_MAXSPACE(dbp->pgsize);

      lastp = NULL;
      for (p = dbt->data,
          sz = dbt->size; sz > 0; p += pagespace, sz -= pagespace) {
            /*
             * Reduce pagespace so we terminate the loop correctly and
             * don't copy too much data.
             */
            if (sz < pagespace)
                  pagespace = sz;

            /*
             * Allocate and initialize a new page and copy all or part of
             * the item onto the page.  If sz is less than pagespace, we
             * have a partial record.
             */
            if ((ret = newfunc(dbp, P_OVERFLOW, &pagep)) != 0)
                  return (ret);
            if (DB_LOGGING(dbp)) {
                  tmp_dbt.data = p;
                  tmp_dbt.size = pagespace;
                  ZERO_LSN(null_lsn);
                  if ((ret = __db_big_log(dbp->dbenv->lg_info, dbp->txn,
                      &new_lsn, 0, DB_ADD_BIG, dbp->log_fileid,
                      PGNO(pagep), lastp ? PGNO(lastp) : PGNO_INVALID,
                      PGNO_INVALID, &tmp_dbt, &LSN(pagep),
                      lastp == NULL ? &null_lsn : &LSN(lastp),
                      &null_lsn)) != 0)
                        return (ret);

                  /* Move lsn onto page. */
                  if (lastp)
                        LSN(lastp) = new_lsn;
                  LSN(pagep) = new_lsn;
            }

            P_INIT(pagep, dbp->pgsize,
                PGNO(pagep), PGNO_INVALID, PGNO_INVALID, 0, P_OVERFLOW);
            OV_LEN(pagep) = pagespace;
            OV_REF(pagep) = 1;
            memcpy((u_int8_t *)pagep + P_OVERHEAD, p, pagespace);

            /*
             * If this is the first entry, update the user's info.
             * Otherwise, update the entry on the last page filled
             * in and release that page.
             */
            if (lastp == NULL)
                  *pgnop = PGNO(pagep);
            else {
                  lastp->next_pgno = PGNO(pagep);
                  pagep->prev_pgno = PGNO(lastp);
                  (void)memp_fput(dbp->mpf, lastp, DB_MPOOL_DIRTY);
            }
            lastp = pagep;
      }
      (void)memp_fput(dbp->mpf, lastp, DB_MPOOL_DIRTY);
      return (0);
}

/*
 * __db_ovref --
 *    Increment/decrement the reference count on an overflow page.
 *
 * PUBLIC: int __db_ovref __P((DB *, db_pgno_t, int32_t));
 */
int
__db_ovref(dbp, pgno, adjust)
      DB *dbp;
      db_pgno_t pgno;
      int32_t adjust;
{
      PAGE *h;
      int ret;

      if ((ret = memp_fget(dbp->mpf, &pgno, 0, &h)) != 0) {
            (void)__db_pgerr(dbp, pgno);
            return (ret);
      }

      if (DB_LOGGING(dbp))
            if ((ret = __db_ovref_log(dbp->dbenv->lg_info, dbp->txn,
                &LSN(h), 0, dbp->log_fileid, h->pgno, adjust,
                &LSN(h))) != 0)
                  return (ret);
      OV_REF(h) += adjust;

      (void)memp_fput(dbp->mpf, h, DB_MPOOL_DIRTY);
      return (0);
}

/*
 * __db_doff --
 *    Delete an offpage chain of overflow pages.
 *
 * PUBLIC: int __db_doff __P((DB *, db_pgno_t, int (*)(DB *, PAGE *)));
 */
int
__db_doff(dbp, pgno, freefunc)
      DB *dbp;
      db_pgno_t pgno;
      int (*freefunc) __P((DB *, PAGE *));
{
      PAGE *pagep;
      DB_LSN null_lsn;
      DBT tmp_dbt;
      int ret;

      do {
            if ((ret = memp_fget(dbp->mpf, &pgno, 0, &pagep)) != 0) {
                  (void)__db_pgerr(dbp, pgno);
                  return (ret);
            }

            /*
             * If it's an overflow page and it's referenced by more than
             * one key/data item, decrement the reference count and return.
             */
            if (TYPE(pagep) == P_OVERFLOW && OV_REF(pagep) > 1) {
                  (void)memp_fput(dbp->mpf, pagep, 0);
                  return (__db_ovref(dbp, pgno, -1));
            }

            if (DB_LOGGING(dbp)) {
                  tmp_dbt.data = (u_int8_t *)pagep + P_OVERHEAD;
                  tmp_dbt.size = OV_LEN(pagep);
                  ZERO_LSN(null_lsn);
                  if ((ret = __db_big_log(dbp->dbenv->lg_info, dbp->txn,
                      &LSN(pagep), 0, DB_REM_BIG, dbp->log_fileid,
                      PGNO(pagep), PREV_PGNO(pagep), NEXT_PGNO(pagep),
                      &tmp_dbt, &LSN(pagep), &null_lsn, &null_lsn)) != 0)
                        return (ret);
            }
            pgno = pagep->next_pgno;
            if ((ret = freefunc(dbp, pagep)) != 0)
                  return (ret);
      } while (pgno != PGNO_INVALID);

      return (0);
}

/*
 * __db_moff --
 *    Match on overflow pages.
 *
 * Given a starting page number and a key, return <0, 0, >0 to indicate if the
 * key on the page is less than, equal to or greater than the key specified.
 *
 * PUBLIC: int __db_moff __P((DB *, const DBT *, db_pgno_t));
 */
int
__db_moff(dbp, dbt, pgno)
      DB *dbp;
      const DBT *dbt;
      db_pgno_t pgno;
{
      PAGE *pagep;
      u_int32_t cmp_bytes, key_left;
      u_int8_t *p1, *p2;
      int ret;

      /* While there are both keys to compare. */
      for (ret = 0, p1 = dbt->data,
          key_left = dbt->size; key_left > 0 && pgno != PGNO_INVALID;) {
            if (memp_fget(dbp->mpf, &pgno, 0, &pagep) != 0) {
                  (void)__db_pgerr(dbp, pgno);
                  return (0); /* No system error return. */
            }

            cmp_bytes = OV_LEN(pagep) < key_left ? OV_LEN(pagep) : key_left;
            key_left -= cmp_bytes;
            for (p2 =
                (u_int8_t *)pagep + P_OVERHEAD; cmp_bytes-- > 0; ++p1, ++p2)
                  if (*p1 != *p2) {
                        ret = (long)*p1 - (long)*p2;
                        break;
                  }
            pgno = NEXT_PGNO(pagep);
            (void)memp_fput(dbp->mpf, pagep, 0);
            if (ret != 0)
                  return (ret);
      }
      if (key_left > 0)       /* DBT is longer than page key. */
            return (-1);
      if (pgno != PGNO_INVALID)     /* DBT is shorter than page key. */
            return (1);
      return (0);
}

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