db.1.85/hash/hash_bigkey.c

   1 /*-
   2  * Copyright (c) 1990, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Margo Seltzer.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)hash_bigkey.c       8.3 (Berkeley) 5/31/94";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 /*
  42  * PACKAGE: hash
  43  * DESCRIPTION:
  44  *      Big key/data handling for the hashing package.
  45  *
  46  * ROUTINES:
  47  * External
  48  *      __big_keydata
  49  *      __big_split
  50  *      __big_insert
  51  *      __big_return
  52  *      __big_delete
  53  *      __find_last_page
  54  * Internal
  55  *      collect_key
  56  *      collect_data
  57  */
  58
  59 #include <sys/param.h>
  60
  61 #include <errno.h>
  62 #include <stdio.h>
  63 #include <stdlib.h>
  64 #include <string.h>
  65
  66 #ifdef DEBUG
  67 #include <assert.h>
  68 #endif
  69
  70 #include <db.h>
  71 #include "hash.h"
  72 #include "page.h"
  73 #include "extern.h"
  74
  75 static int collect_key __P((HTAB *, BUFHEAD *, int, DBT *, int));
  76 static int collect_data __P((HTAB *, BUFHEAD *, int, int));
  77
  78 /*
  79  * Big_insert
  80  *
  81  * You need to do an insert and the key/data pair is too big
  82  *
  83  * Returns:
  84  * 0 ==> OK
  85  *-1 ==> ERROR
  86  */
  87 extern int
  88 __big_insert(hashp, bufp, key, val)
  89         HTAB *hashp;
  90         BUFHEAD *bufp;
  91         const DBT *key, *val;
  92 {
  93         register u_int16_t *p;
  94         int key_size, n, val_size;
  95         u_int16_t space, move_bytes, off;
  96         char *cp, *key_data, *val_data;
  97
  98         cp = bufp->page;                /* Character pointer of p. */
  99         p = (u_int16_t *)cp;
 100
 101         key_data = (char *)key->data;
 102         key_size = key->size;
 103         val_data = (char *)val->data;
 104         val_size = val->size;
 105
 106         /* First move the Key */
 107         for (space = FREESPACE(p) - BIGOVERHEAD; key_size;
 108             space = FREESPACE(p) - BIGOVERHEAD) {
 109                 move_bytes = MIN(space, key_size);
 110                 off = OFFSET(p) - move_bytes;
 111                 memmove(cp + off, key_data, move_bytes);
 112                 key_size -= move_bytes;
 113                 key_data += move_bytes;
 114                 n = p[0];
 115                 p[++n] = off;
 116                 p[0] = ++n;
 117                 FREESPACE(p) = off - PAGE_META(n);
 118                 OFFSET(p) = off;
 119                 p[n] = PARTIAL_KEY;
 120                 bufp = __add_ovflpage(hashp, bufp);
 121                 if (!bufp)
 122                         return (-1);
 123                 n = p[0];
 124                 if (!key_size)
 125                         if (FREESPACE(p)) {
 126                                 move_bytes = MIN(FREESPACE(p), val_size);
 127                                 off = OFFSET(p) - move_bytes;
 128                                 p[n] = off;
 129                                 memmove(cp + off, val_data, move_bytes);
 130                                 val_data += move_bytes;
 131                                 val_size -= move_bytes;
 132                                 p[n - 2] = FULL_KEY_DATA;
 133                                 FREESPACE(p) = FREESPACE(p) - move_bytes;
 134                                 OFFSET(p) = off;
 135                         } else
 136                                 p[n - 2] = FULL_KEY;
 137                 p = (u_int16_t *)bufp->page;
 138                 cp = bufp->page;
 139                 bufp->flags |= BUF_MOD;
 140         }
 141
 142         /* Now move the data */
 143         for (space = FREESPACE(p) - BIGOVERHEAD; val_size;
 144             space = FREESPACE(p) - BIGOVERHEAD) {
 145                 move_bytes = MIN(space, val_size);
 146                 /*
 147                  * Here's the hack to make sure that if the data ends on the
 148                  * same page as the key ends, FREESPACE is at least one.
 149                  */
 150                 if (space == val_size && val_size == val->size)
 151                         move_bytes--;
 152                 off = OFFSET(p) - move_bytes;
 153                 memmove(cp + off, val_data, move_bytes);
 154                 val_size -= move_bytes;
 155                 val_data += move_bytes;
 156                 n = p[0];
 157                 p[++n] = off;
 158                 p[0] = ++n;
 159                 FREESPACE(p) = off - PAGE_META(n);
 160                 OFFSET(p) = off;
 161                 if (val_size) {
 162                         p[n] = FULL_KEY;
 163                         bufp = __add_ovflpage(hashp, bufp);
 164                         if (!bufp)
 165                                 return (-1);
 166                         cp = bufp->page;
 167                         p = (u_int16_t *)cp;
 168                 } else
 169                         p[n] = FULL_KEY_DATA;
 170                 bufp->flags |= BUF_MOD;
 171         }
 172         return (0);
 173 }
 174
 175 /*
 176  * Called when bufp's page  contains a partial key (index should be 1)
 177  *
 178  * All pages in the big key/data pair except bufp are freed.  We cannot
 179  * free bufp because the page pointing to it is lost and we can't get rid
 180  * of its pointer.
 181  *
 182  * Returns:
 183  * 0 => OK
 184  *-1 => ERROR
 185  */
 186 extern int
 187 __big_delete(hashp, bufp)
 188         HTAB *hashp;
 189         BUFHEAD *bufp;
 190 {
 191         register BUFHEAD *last_bfp, *rbufp;
 192         u_int16_t *bp, pageno;
 193         int key_done, n;
 194
 195         rbufp = bufp;
 196         last_bfp = NULL;
 197         bp = (u_int16_t *)bufp->page;
 198         pageno = 0;
 199         key_done = 0;
 200
 201         while (!key_done || (bp[2] != FULL_KEY_DATA)) {
 202                 if (bp[2] == FULL_KEY || bp[2] == FULL_KEY_DATA)
 203                         key_done = 1;
 204
 205                 /*
 206                  * If there is freespace left on a FULL_KEY_DATA page, then
 207                  * the data is short and fits entirely on this page, and this
 208                  * is the last page.
 209                  */
 210                 if (bp[2] == FULL_KEY_DATA && FREESPACE(bp))
 211                         break;
 212                 pageno = bp[bp[0] - 1];
 213                 rbufp->flags |= BUF_MOD;
 214                 rbufp = __get_buf(hashp, pageno, rbufp, 0);
 215                 if (last_bfp)
 216                         __free_ovflpage(hashp, last_bfp);
 217                 last_bfp = rbufp;
 218                 if (!rbufp)
 219                         return (-1);            /* Error. */
 220                 bp = (u_int16_t *)rbufp->page;
 221         }
 222
 223         /*
 224          * If we get here then rbufp points to the last page of the big
 225          * key/data pair.  Bufp points to the first one -- it should now be
 226          * empty pointing to the next page after this pair.  Can't free it
 227          * because we don't have the page pointing to it.
 228          */
 229
 230         /* This is information from the last page of the pair. */
 231         n = bp[0];
 232         pageno = bp[n - 1];
 233
 234         /* Now, bp is the first page of the pair. */
 235         bp = (u_int16_t *)bufp->page;
 236         if (n > 2) {
 237                 /* There is an overflow page. */
 238                 bp[1] = pageno;
 239                 bp[2] = OVFLPAGE;
 240                 bufp->ovfl = rbufp->ovfl;
 241         } else
 242                 /* This is the last page. */
 243                 bufp->ovfl = NULL;
 244         n -= 2;
 245         bp[0] = n;
 246         FREESPACE(bp) = hashp->BSIZE - PAGE_META(n);
 247         OFFSET(bp) = hashp->BSIZE - 1;
 248
 249         bufp->flags |= BUF_MOD;
 250         if (rbufp)
 251                 __free_ovflpage(hashp, rbufp);
 252         if (last_bfp != rbufp)
 253                 __free_ovflpage(hashp, last_bfp);
 254
 255         hashp->NKEYS--;
 256         return (0);
 257 }
 258 /*
 259  * Returns:
 260  *  0 = key not found
 261  * -1 = get next overflow page
 262  * -2 means key not found and this is big key/data
 263  * -3 error
 264  */
 265 extern int
 266 __find_bigpair(hashp, bufp, ndx, key, size)
 267         HTAB *hashp;
 268         BUFHEAD *bufp;
 269         int ndx;
 270         char *key;
 271         int size;
 272 {
 273         register u_int16_t *bp;
 274         register char *p;
 275         int ksize;
 276         u_int16_t bytes;
 277         char *kkey;
 278
 279         bp = (u_int16_t *)bufp->page;
 280         p = bufp->page;
 281         ksize = size;
 282         kkey = key;
 283
 284         for (bytes = hashp->BSIZE - bp[ndx];
 285             bytes <= size && bp[ndx + 1] == PARTIAL_KEY;
 286             bytes = hashp->BSIZE - bp[ndx]) {
 287                 if (memcmp(p + bp[ndx], kkey, bytes))
 288                         return (-2);
 289                 kkey += bytes;
 290                 ksize -= bytes;
 291                 bufp = __get_buf(hashp, bp[ndx + 2], bufp, 0);
 292                 if (!bufp)
 293                         return (-3);
 294                 p = bufp->page;
 295                 bp = (u_int16_t *)p;
 296                 ndx = 1;
 297         }
 298
 299         if (bytes != ksize || memcmp(p + bp[ndx], kkey, bytes)) {
 300 #ifdef HASH_STATISTICS
 301                 ++hash_collisions;
 302 #endif
 303                 return (-2);
 304         } else
 305                 return (ndx);
 306 }
 307
 308 /*
 309  * Given the buffer pointer of the first overflow page of a big pair,
 310  * find the end of the big pair
 311  *
 312  * This will set bpp to the buffer header of the last page of the big pair.
 313  * It will return the pageno of the overflow page following the last page
 314  * of the pair; 0 if there isn't any (i.e. big pair is the last key in the
 315  * bucket)
 316  */
 317 extern u_int16_t
 318 __find_last_page(hashp, bpp)
 319         HTAB *hashp;
 320         BUFHEAD **bpp;
 321 {
 322         BUFHEAD *bufp;
 323         u_int16_t *bp, pageno;
 324         int n;
 325
 326         bufp = *bpp;
 327         bp = (u_int16_t *)bufp->page;
 328         for (;;) {
 329                 n = bp[0];
 330
 331                 /*
 332                  * This is the last page if: the tag is FULL_KEY_DATA and
 333                  * either only 2 entries OVFLPAGE marker is explicit there
 334                  * is freespace on the page.
 335                  */
 336                 if (bp[2] == FULL_KEY_DATA &&
 337                     ((n == 2) || (bp[n] == OVFLPAGE) || (FREESPACE(bp))))
 338                         break;
 339
 340                 pageno = bp[n - 1];
 341                 bufp = __get_buf(hashp, pageno, bufp, 0);
 342                 if (!bufp)
 343                         return (0);     /* Need to indicate an error! */
 344                 bp = (u_int16_t *)bufp->page;
 345         }
 346
 347         *bpp = bufp;
 348         if (bp[0] > 2)
 349                 return (bp[3]);
 350         else
 351                 return (0);
 352 }
 353
 354 /*
 355  * Return the data for the key/data pair that begins on this page at this
 356  * index (index should always be 1).
 357  */
 358 extern int
 359 __big_return(hashp, bufp, ndx, val, set_current)
 360         HTAB *hashp;
 361         BUFHEAD *bufp;
 362         int ndx;
 363         DBT *val;
 364         int set_current;
 365 {
 366         BUFHEAD *save_p;
 367         u_int16_t *bp, len, off, save_addr;
 368         char *tp;
 369
 370         bp = (u_int16_t *)bufp->page;
 371         while (bp[ndx + 1] == PARTIAL_KEY) {
 372                 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 373                 if (!bufp)
 374                         return (-1);
 375                 bp = (u_int16_t *)bufp->page;
 376                 ndx = 1;
 377         }
 378
 379         if (bp[ndx + 1] == FULL_KEY) {
 380                 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 381                 if (!bufp)
 382                         return (-1);
 383                 bp = (u_int16_t *)bufp->page;
 384                 save_p = bufp;
 385                 save_addr = save_p->addr;
 386                 off = bp[1];
 387                 len = 0;
 388         } else
 389                 if (!FREESPACE(bp)) {
 390                         /*
 391                          * This is a hack.  We can't distinguish between
 392                          * FULL_KEY_DATA that contains complete data or
 393                          * incomplete data, so we require that if the data
 394                          * is complete, there is at least 1 byte of free
 395                          * space left.
 396                          */
 397                         off = bp[bp[0]];
 398                         len = bp[1] - off;
 399                         save_p = bufp;
 400                         save_addr = bufp->addr;
 401                         bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 402                         if (!bufp)
 403                                 return (-1);
 404                         bp = (u_int16_t *)bufp->page;
 405                 } else {
 406                         /* The data is all on one page. */
 407                         tp = (char *)bp;
 408                         off = bp[bp[0]];
 409                         val->data = (u_char *)tp + off;
 410                         val->size = bp[1] - off;
 411                         if (set_current) {
 412                                 if (bp[0] == 2) {       /* No more buckets in
 413                                                          * chain */
 414                                         hashp->cpage = NULL;
 415                                         hashp->cbucket++;
 416                                         hashp->cndx = 1;
 417                                 } else {
 418                                         hashp->cpage = __get_buf(hashp,
 419                                             bp[bp[0] - 1], bufp, 0);
 420                                         if (!hashp->cpage)
 421                                                 return (-1);
 422                                         hashp->cndx = 1;
 423                                         if (!((u_int16_t *)
 424                                             hashp->cpage->page)[0]) {
 425                                                 hashp->cbucket++;
 426                                                 hashp->cpage = NULL;
 427                                         }
 428                                 }
 429                         }
 430                         return (0);
 431                 }
 432
 433         val->size = collect_data(hashp, bufp, (int)len, set_current);
 434         if (val->size == -1)
 435                 return (-1);
 436         if (save_p->addr != save_addr) {
 437                 /* We are pretty short on buffers. */
 438                 errno = EINVAL;                 /* OUT OF BUFFERS */
 439                 return (-1);
 440         }
 441         memmove(hashp->tmp_buf, (save_p->page) + off, len);
 442         val->data = (u_char *)hashp->tmp_buf;
 443         return (0);
 444 }
 445 /*
 446  * Count how big the total datasize is by recursing through the pages.  Then
 447  * allocate a buffer and copy the data as you recurse up.
 448  */
 449 static int
 450 collect_data(hashp, bufp, len, set)
 451         HTAB *hashp;
 452         BUFHEAD *bufp;
 453         int len, set;
 454 {
 455         register u_int16_t *bp;
 456         register char *p;
 457         BUFHEAD *xbp;
 458         u_int16_t save_addr;
 459         int mylen, totlen;
 460
 461         p = bufp->page;
 462         bp = (u_int16_t *)p;
 463         mylen = hashp->BSIZE - bp[1];
 464         save_addr = bufp->addr;
 465
 466         if (bp[2] == FULL_KEY_DATA) {           /* End of Data */
 467                 totlen = len + mylen;
 468                 if (hashp->tmp_buf)
 469                         free(hashp->tmp_buf);
 470                 if ((hashp->tmp_buf = (char *)malloc(totlen)) == NULL)
 471                         return (-1);
 472                 if (set) {
 473                         hashp->cndx = 1;
 474                         if (bp[0] == 2) {       /* No more buckets in chain */
 475                                 hashp->cpage = NULL;
 476                                 hashp->cbucket++;
 477                         } else {
 478                                 hashp->cpage =
 479                                     __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 480                                 if (!hashp->cpage)
 481                                         return (-1);
 482                                 else if (!((u_int16_t *)hashp->cpage->page)[0]) {
 483                                         hashp->cbucket++;
 484                                         hashp->cpage = NULL;
 485                                 }
 486                         }
 487                 }
 488         } else {
 489                 xbp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 490                 if (!xbp || ((totlen =
 491                     collect_data(hashp, xbp, len + mylen, set)) < 1))
 492                         return (-1);
 493         }
 494         if (bufp->addr != save_addr) {
 495                 errno = EINVAL;                 /* Out of buffers. */
 496                 return (-1);
 497         }
 498         memmove(&hashp->tmp_buf[len], (bufp->page) + bp[1], mylen);
 499         return (totlen);
 500 }
 501
 502 /*
 503  * Fill in the key and data for this big pair.
 504  */
 505 extern int
 506 __big_keydata(hashp, bufp, key, val, set)
 507         HTAB *hashp;
 508         BUFHEAD *bufp;
 509         DBT *key, *val;
 510         int set;
 511 {
 512         key->size = collect_key(hashp, bufp, 0, val, set);
 513         if (key->size == -1)
 514                 return (-1);
 515         key->data = (u_char *)hashp->tmp_key;
 516         return (0);
 517 }
 518
 519 /*
 520  * Count how big the total key size is by recursing through the pages.  Then
 521  * collect the data, allocate a buffer and copy the key as you recurse up.
 522  */
 523 static int
 524 collect_key(hashp, bufp, len, val, set)
 525         HTAB *hashp;
 526         BUFHEAD *bufp;
 527         int len;
 528         DBT *val;
 529         int set;
 530 {
 531         BUFHEAD *xbp;
 532         char *p;
 533         int mylen, totlen;
 534         u_int16_t *bp, save_addr;
 535
 536         p = bufp->page;
 537         bp = (u_int16_t *)p;
 538         mylen = hashp->BSIZE - bp[1];
 539
 540         save_addr = bufp->addr;
 541         totlen = len + mylen;
 542         if (bp[2] == FULL_KEY || bp[2] == FULL_KEY_DATA) {    /* End of Key. */
 543                 if (hashp->tmp_key != NULL)
 544                         free(hashp->tmp_key);
 545                 if ((hashp->tmp_key = (char *)malloc(totlen)) == NULL)
 546                         return (-1);
 547                 if (__big_return(hashp, bufp, 1, val, set))
 548                         return (-1);
 549         } else {
 550                 xbp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 551                 if (!xbp || ((totlen =
 552                     collect_key(hashp, xbp, totlen, val, set)) < 1))
 553                         return (-1);
 554         }
 555         if (bufp->addr != save_addr) {
 556                 errno = EINVAL;         /* MIS -- OUT OF BUFFERS */
 557                 return (-1);
 558         }
 559         memmove(&hashp->tmp_key[len], (bufp->page) + bp[1], mylen);
 560         return (totlen);
 561 }
 562
 563 /*
 564  * Returns:
 565  *  0 => OK
 566  * -1 => error
 567  */
 568 extern int
 569 __big_split(hashp, op, np, big_keyp, addr, obucket, ret)
 570         HTAB *hashp;
 571         BUFHEAD *op;    /* Pointer to where to put keys that go in old bucket */
 572         BUFHEAD *np;    /* Pointer to new bucket page */
 573                         /* Pointer to first page containing the big key/data */
 574         BUFHEAD *big_keyp;
 575         int addr;       /* Address of big_keyp */
 576         u_int32_t   obucket;/* Old Bucket */
 577         SPLIT_RETURN *ret;
 578 {
 579         register BUFHEAD *tmpp;
 580         register u_int16_t *tp;
 581         BUFHEAD *bp;
 582         DBT key, val;
 583         u_int32_t change;
 584         u_int16_t free_space, n, off;
 585
 586         bp = big_keyp;
 587
 588         /* Now figure out where the big key/data goes */
 589         if (__big_keydata(hashp, big_keyp, &key, &val, 0))
 590                 return (-1);
 591         change = (__call_hash(hashp, key.data, key.size) != obucket);
 592
 593         if (ret->next_addr = __find_last_page(hashp, &big_keyp)) {
 594                 if (!(ret->nextp =
 595                     __get_buf(hashp, ret->next_addr, big_keyp, 0)))
 596                         return (-1);;
 597         } else
 598                 ret->nextp = NULL;
 599
 600         /* Now make one of np/op point to the big key/data pair */
 601 #ifdef DEBUG
 602         assert(np->ovfl == NULL);
 603 #endif
 604         if (change)
 605                 tmpp = np;
 606         else
 607                 tmpp = op;
 608
 609         tmpp->flags |= BUF_MOD;
 610 #ifdef DEBUG1
 611         (void)fprintf(stderr,
 612             "BIG_SPLIT: %d->ovfl was %d is now %d\n", tmpp->addr,
 613             (tmpp->ovfl ? tmpp->ovfl->addr : 0), (bp ? bp->addr : 0));
 614 #endif
 615         tmpp->ovfl = bp;        /* one of op/np point to big_keyp */
 616         tp = (u_int16_t *)tmpp->page;
 617 #ifdef DEBUG
 618         assert(FREESPACE(tp) >= OVFLSIZE);
 619 #endif
 620         n = tp[0];
 621         off = OFFSET(tp);
 622         free_space = FREESPACE(tp);
 623         tp[++n] = (u_int16_t)addr;
 624         tp[++n] = OVFLPAGE;
 625         tp[0] = n;
 626         OFFSET(tp) = off;
 627         FREESPACE(tp) = free_space - OVFLSIZE;
 628
 629         /*
 630          * Finally, set the new and old return values. BIG_KEYP contains a
 631          * pointer to the last page of the big key_data pair. Make sure that
 632          * big_keyp has no following page (2 elements) or create an empty
 633          * following page.
 634          */
 635
 636         ret->newp = np;
 637         ret->oldp = op;
 638
 639         tp = (u_int16_t *)big_keyp->page;
 640         big_keyp->flags |= BUF_MOD;
 641         if (tp[0] > 2) {
 642                 /*
 643                  * There may be either one or two offsets on this page.  If
 644                  * there is one, then the overflow page is linked on normally
 645                  * and tp[4] is OVFLPAGE.  If there are two, tp[4] contains
 646                  * the second offset and needs to get stuffed in after the
 647                  * next overflow page is added.
 648                  */
 649                 n = tp[4];
 650                 free_space = FREESPACE(tp);
 651                 off = OFFSET(tp);
 652                 tp[0] -= 2;
 653                 FREESPACE(tp) = free_space + OVFLSIZE;
 654                 OFFSET(tp) = off;
 655                 tmpp = __add_ovflpage(hashp, big_keyp);
 656                 if (!tmpp)
 657                         return (-1);
 658                 tp[4] = n;
 659         } else
 660                 tmpp = big_keyp;
 661
 662         if (change)
 663                 ret->newp = tmpp;
 664         else
 665                 ret->oldp = tmpp;
 666         return (0);
 667 }