dbm/src/h_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. ***REMOVED*** - see
  17  *    ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
  18  * 4. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #if defined(LIBC_SCCS) && !defined(lint)
  36 static char sccsid[] = "@(#)hash_bigkey.c       8.3 (Berkeley) 5/31/94";
  37 #endif /* LIBC_SCCS and not lint */
  38
  39 #include "watcomfx.h"
  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 #if !defined(_WIN32) && !defined(_WINDOWS) && !defined(macintosh) && !defined(XP_OS2_VACPP)
  60 #include <sys/param.h>
  61 #endif
  62
  63 #include <errno.h>
  64 #include <stdio.h>
  65 #include <stdlib.h>
  66 #include <string.h>
  67
  68 #ifdef DEBUG
  69 #include <assert.h>
  70 #endif
  71
  72 #include "mcom_db.h"
  73 #include "hash.h"
  74 #include "page.h"
  75 /* #include "extern.h" */
  76
  77 static int collect_key __P((HTAB *, BUFHEAD *, int, DBT *, int));
  78 static int collect_data __P((HTAB *, BUFHEAD *, int, int));
  79
  80 /*
  81  * Big_insert
  82  *
  83  * You need to do an insert and the key/data pair is too big
  84  *
  85  * Returns:
  86  * 0 ==> OK
  87  *-1 ==> ERROR
  88  */
  89 extern int
  90 __big_insert(HTAB *hashp, BUFHEAD *bufp, const DBT *key, const DBT *val)
  91 {
  92         register uint16 *p;
  93         uint key_size, n, val_size;
  94         uint16 space, move_bytes, off;
  95         char *cp, *key_data, *val_data;
  96
  97         cp = bufp->page;                /* Character pointer of p. */
  98         p = (uint16 *)cp;
  99
 100         key_data = (char *)key->data;
 101         key_size = key->size;
 102         val_data = (char *)val->data;
 103         val_size = val->size;
 104
 105         /* First move the Key */
 106         for (space = FREESPACE(p) - BIGOVERHEAD; key_size;
 107             space = FREESPACE(p) - BIGOVERHEAD) {
 108                 move_bytes = PR_MIN(space, key_size);
 109                 off = OFFSET(p) - move_bytes;
 110                 memmove(cp + off, key_data, move_bytes);
 111                 key_size -= move_bytes;
 112                 key_data += move_bytes;
 113                 n = p[0];
 114                 p[++n] = off;
 115                 p[0] = ++n;
 116                 FREESPACE(p) = off - PAGE_META(n);
 117                 OFFSET(p) = off;
 118                 p[n] = PARTIAL_KEY;
 119                 bufp = __add_ovflpage(hashp, bufp);
 120                 if (!bufp)
 121                         return (-1);
 122                 n = p[0];
 123                 if (!key_size) {
 124                         if (FREESPACE(p)) {
 125                                 move_bytes = PR_MIN(FREESPACE(p), val_size);
 126                                 off = OFFSET(p) - move_bytes;
 127                                 p[n] = off;
 128                                 memmove(cp + off, val_data, move_bytes);
 129                                 val_data += move_bytes;
 130                                 val_size -= move_bytes;
 131                                 p[n - 2] = FULL_KEY_DATA;
 132                                 FREESPACE(p) = FREESPACE(p) - move_bytes;
 133                                 OFFSET(p) = off;
 134                         } else
 135                                 p[n - 2] = FULL_KEY;
 136                 }
 137                 p = (uint16 *)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 = PR_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 = (uint16 *)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(HTAB *hashp, BUFHEAD *bufp)
 188 {
 189         register BUFHEAD *last_bfp, *rbufp;
 190         uint16 *bp, pageno;
 191         int key_done, n;
 192
 193         rbufp = bufp;
 194         last_bfp = NULL;
 195         bp = (uint16 *)bufp->page;
 196         pageno = 0;
 197         key_done = 0;
 198
 199         while (!key_done || (bp[2] != FULL_KEY_DATA)) {
 200                 if (bp[2] == FULL_KEY || bp[2] == FULL_KEY_DATA)
 201                         key_done = 1;
 202
 203                 /*
 204                  * If there is freespace left on a FULL_KEY_DATA page, then
 205                  * the data is short and fits entirely on this page, and this
 206                  * is the last page.
 207                  */
 208                 if (bp[2] == FULL_KEY_DATA && FREESPACE(bp))
 209                         break;
 210                 pageno = bp[bp[0] - 1];
 211                 rbufp->flags |= BUF_MOD;
 212                 rbufp = __get_buf(hashp, pageno, rbufp, 0);
 213                 if (last_bfp)
 214                         __free_ovflpage(hashp, last_bfp);
 215                 last_bfp = rbufp;
 216                 if (!rbufp)
 217                         return (-1);            /* Error. */
 218                 bp = (uint16 *)rbufp->page;
 219         }
 220
 221         /*
 222          * If we get here then rbufp points to the last page of the big
 223          * key/data pair.  Bufp points to the first one -- it should now be
 224          * empty pointing to the next page after this pair.  Can't free it
 225          * because we don't have the page pointing to it.
 226          */
 227
 228         /* This is information from the last page of the pair. */
 229         n = bp[0];
 230         pageno = bp[n - 1];
 231
 232         /* Now, bp is the first page of the pair. */
 233         bp = (uint16 *)bufp->page;
 234         if (n > 2) {
 235                 /* There is an overflow page. */
 236                 bp[1] = pageno;
 237                 bp[2] = OVFLPAGE;
 238                 bufp->ovfl = rbufp->ovfl;
 239         } else
 240                 /* This is the last page. */
 241                 bufp->ovfl = NULL;
 242         n -= 2;
 243         bp[0] = n;
 244         FREESPACE(bp) = hashp->BSIZE - PAGE_META(n);
 245         OFFSET(bp) = hashp->BSIZE - 1;
 246
 247         bufp->flags |= BUF_MOD;
 248         if (rbufp)
 249                 __free_ovflpage(hashp, rbufp);
 250         if (last_bfp != rbufp)
 251                 __free_ovflpage(hashp, last_bfp);
 252
 253         hashp->NKEYS--;
 254         return (0);
 255 }
 256 /*
 257  * Returns:
 258  *  0 = key not found
 259  * -1 = get next overflow page
 260  * -2 means key not found and this is big key/data
 261  * -3 error
 262  */
 263 extern int
 264 __find_bigpair(HTAB *hashp, BUFHEAD *bufp, int ndx, char *key, int size)
 265 {
 266         register uint16 *bp;
 267         register char *p;
 268         int ksize;
 269         uint16 bytes;
 270         char *kkey;
 271
 272         bp = (uint16 *)bufp->page;
 273         p = bufp->page;
 274         ksize = size;
 275         kkey = key;
 276
 277         for (bytes = hashp->BSIZE - bp[ndx];
 278             bytes <= size && bp[ndx + 1] == PARTIAL_KEY;
 279             bytes = hashp->BSIZE - bp[ndx]) {
 280                 if (memcmp(p + bp[ndx], kkey, bytes))
 281                         return (-2);
 282                 kkey += bytes;
 283                 ksize -= bytes;
 284                 bufp = __get_buf(hashp, bp[ndx + 2], bufp, 0);
 285                 if (!bufp)
 286                         return (-3);
 287                 p = bufp->page;
 288                 bp = (uint16 *)p;
 289                 ndx = 1;
 290         }
 291
 292         if (bytes != ksize || memcmp(p + bp[ndx], kkey, bytes)) {
 293 #ifdef HASH_STATISTICS
 294                 ++hash_collisions;
 295 #endif
 296                 return (-2);
 297         } else
 298                 return (ndx);
 299 }
 300
 301 /*
 302  * Given the buffer pointer of the first overflow page of a big pair,
 303  * find the end of the big pair
 304  *
 305  * This will set bpp to the buffer header of the last page of the big pair.
 306  * It will return the pageno of the overflow page following the last page
 307  * of the pair; 0 if there isn't any (i.e. big pair is the last key in the
 308  * bucket)
 309  */
 310 extern uint16
 311 __find_last_page(HTAB *hashp, BUFHEAD **bpp)
 312 {
 313         BUFHEAD *bufp;
 314         uint16 *bp, pageno;
 315         uint n;
 316
 317         bufp = *bpp;
 318         bp = (uint16 *)bufp->page;
 319         for (;;) {
 320                 n = bp[0];
 321
 322                 /*
 323                  * This is the last page if: the tag is FULL_KEY_DATA and
 324                  * either only 2 entries OVFLPAGE marker is explicit there
 325                  * is freespace on the page.
 326                  */
 327                 if (bp[2] == FULL_KEY_DATA &&
 328                     ((n == 2) || (bp[n] == OVFLPAGE) || (FREESPACE(bp))))
 329                         break;
 330
 331                 /* LJM bound the size of n to reasonable limits
 332                  */
 333                 if(n > hashp->BSIZE/sizeof(uint16))
 334                         return(0);
 335
 336                 pageno = bp[n - 1];
 337                 bufp = __get_buf(hashp, pageno, bufp, 0);
 338                 if (!bufp)
 339                         return (0);     /* Need to indicate an error! */
 340                 bp = (uint16 *)bufp->page;
 341         }
 342
 343         *bpp = bufp;
 344         if (bp[0] > 2)
 345                 return (bp[3]);
 346         else
 347                 return (0);
 348 }
 349
 350 /*
 351  * Return the data for the key/data pair that begins on this page at this
 352  * index (index should always be 1).
 353  */
 354 extern int
 355 __big_return(
 356         HTAB *hashp,
 357         BUFHEAD *bufp,
 358         int ndx,
 359         DBT *val,
 360         int set_current)
 361 {
 362         BUFHEAD *save_p;
 363         uint16 *bp, len, off, save_addr;
 364         char *tp;
 365         int save_flags;
 366
 367         bp = (uint16 *)bufp->page;
 368         while (bp[ndx + 1] == PARTIAL_KEY) {
 369                 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 370                 if (!bufp)
 371                         return (-1);
 372                 bp = (uint16 *)bufp->page;
 373                 ndx = 1;
 374         }
 375
 376         if (bp[ndx + 1] == FULL_KEY) {
 377                 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 378                 if (!bufp)
 379                         return (-1);
 380                 bp = (uint16 *)bufp->page;
 381                 save_p = bufp;
 382                 save_addr = save_p->addr;
 383                 off = bp[1];
 384                 len = 0;
 385         } else
 386                 if (!FREESPACE(bp)) {
 387                         /*
 388                          * This is a hack.  We can't distinguish between
 389                          * FULL_KEY_DATA that contains complete data or
 390                          * incomplete data, so we require that if the data
 391                          * is complete, there is at least 1 byte of free
 392                          * space left.
 393                          */
 394                         off = bp[bp[0]];
 395                         len = bp[1] - off;
 396                         save_p = bufp;
 397                         save_addr = bufp->addr;
 398                         bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 399                         if (!bufp)
 400                                 return (-1);
 401                         bp = (uint16 *)bufp->page;
 402                 } else {
 403                         /* The data is all on one page. */
 404                         tp = (char *)bp;
 405                         off = bp[bp[0]];
 406                         val->data = (uint8 *)tp + off;
 407                         val->size = bp[1] - off;
 408                         if (set_current) {
 409                                 if (bp[0] == 2) {       /* No more buckets in
 410                                                          * chain */
 411                                         hashp->cpage = NULL;
 412                                         hashp->cbucket++;
 413                                         hashp->cndx = 1;
 414                                 } else {
 415                                         hashp->cpage = __get_buf(hashp,
 416                                             bp[bp[0] - 1], bufp, 0);
 417                                         if (!hashp->cpage)
 418                                                 return (-1);
 419                                         hashp->cndx = 1;
 420                                         if (!((uint16 *)
 421                                             hashp->cpage->page)[0]) {
 422                                                 hashp->cbucket++;
 423                                                 hashp->cpage = NULL;
 424                                         }
 425                                 }
 426                         }
 427                         return (0);
 428                 }
 429
 430         /* pin our saved buf so that we don't lose if
 431          * we run out of buffers */
 432         save_flags = save_p->flags;
 433         save_p->flags |= BUF_PIN;
 434         val->size = collect_data(hashp, bufp, (int)len, set_current);
 435         save_p->flags = save_flags;
 436         if (val->size == (size_t)-1)
 437                 return (-1);
 438         if (save_p->addr != save_addr) {
 439                 /* We are pretty short on buffers. */
 440                 errno = EINVAL;                 /* OUT OF BUFFERS */
 441                 return (-1);
 442         }
 443         memmove(hashp->tmp_buf, (save_p->page) + off, len);
 444         val->data = (uint8 *)hashp->tmp_buf;
 445         return (0);
 446 }
 447
 448
 449 /*
 450  * Count how big the total datasize is by looping through the pages.  Then
 451  * allocate a buffer and copy the data in the second loop. NOTE: Our caller
 452  * may already have a bp which it is holding onto. The caller is
 453  * responsible for copying that bp into our temp buffer. 'len' is how much
 454  * space to reserve for that buffer.
 455  */
 456 static int
 457 collect_data(
 458         HTAB *hashp,
 459         BUFHEAD *bufp,
 460         int len, int set)
 461 {
 462         register uint16 *bp;
 463         BUFHEAD *save_bufp;
 464         int save_flags;
 465         int mylen, totlen;
 466
 467         /*
 468          * save the input buf head because we need to walk the list twice.
 469          * pin it to make sure it doesn't leave the buffer pool.
 470          * This has the effect of growing the buffer pool if necessary.
 471          */
 472         save_bufp = bufp;
 473         save_flags = save_bufp->flags;
 474         save_bufp->flags |= BUF_PIN;
 475
 476         /* read the length of the buffer */
 477         for (totlen = len; bufp ; bufp = __get_buf(hashp, bp[bp[0]-1], bufp, 0)) {
 478                 bp = (uint16 *)bufp->page;
 479                 mylen = hashp->BSIZE - bp[1];
 480
 481                 /* if mylen ever goes negative it means that the
 482                  * page is screwed up.
 483                  */
 484                 if (mylen < 0) {
 485                         save_bufp->flags = save_flags;
 486                         return (-1);
 487                 }
 488                 totlen += mylen;
 489                 if (bp[2] == FULL_KEY_DATA) {           /* End of Data */
 490                         break;
 491                 }
 492         }
 493
 494         if (!bufp) {
 495                 save_bufp->flags = save_flags;
 496                 return (-1);
 497         }
 498
 499         /* allocate a temp buf */
 500         if (hashp->tmp_buf)
 501                 free(hashp->tmp_buf);
 502         if ((hashp->tmp_buf = (char *)malloc((size_t)totlen)) == NULL) {
 503                 save_bufp->flags = save_flags;
 504                 return (-1);
 505         }
 506
 507         /* copy the buffers back into temp buf */
 508         for (bufp = save_bufp; bufp ;
 509                                 bufp = __get_buf(hashp, bp[bp[0]-1], bufp, 0)) {
 510                 bp = (uint16 *)bufp->page;
 511                 mylen = hashp->BSIZE - bp[1];
 512                 memmove(&hashp->tmp_buf[len], (bufp->page) + bp[1], (size_t)mylen);
 513                 len += mylen;
 514                 if (bp[2] == FULL_KEY_DATA) {
 515                         break;
 516                 }
 517         }
 518
 519         /* 'clear' the pin flags */
 520         save_bufp->flags = save_flags;
 521
 522         /* update the database cursor */
 523         if (set) {
 524                 hashp->cndx = 1;
 525                 if (bp[0] == 2) {       /* No more buckets in chain */
 526                         hashp->cpage = NULL;
 527                         hashp->cbucket++;
 528                 } else {
 529                         hashp->cpage = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 530                         if (!hashp->cpage)
 531                                 return (-1);
 532                         else if (!((uint16 *)hashp->cpage->page)[0]) {
 533                                 hashp->cbucket++;
 534                                 hashp->cpage = NULL;
 535                         }
 536                 }
 537         }
 538         return (totlen);
 539 }
 540
 541 /*
 542  * Fill in the key and data for this big pair.
 543  */
 544 extern int
 545 __big_keydata(
 546         HTAB *hashp,
 547         BUFHEAD *bufp,
 548         DBT *key, DBT *val,
 549         int set)
 550 {
 551         key->size = collect_key(hashp, bufp, 0, val, set);
 552         if (key->size == (size_t)-1)
 553                 return (-1);
 554         key->data = (uint8 *)hashp->tmp_key;
 555         return (0);
 556 }
 557
 558 /*
 559  * Count how big the total key size is by recursing through the pages.  Then
 560  * collect the data, allocate a buffer and copy the key as you recurse up.
 561  */
 562 static int
 563 collect_key(
 564         HTAB *hashp,
 565         BUFHEAD *bufp,
 566         int len,
 567         DBT *val,
 568         int set)
 569 {
 570         BUFHEAD *xbp;
 571         char *p;
 572         int mylen, totlen;
 573         uint16 *bp, save_addr;
 574
 575         p = bufp->page;
 576         bp = (uint16 *)p;
 577         mylen = hashp->BSIZE - bp[1];
 578
 579         save_addr = bufp->addr;
 580         totlen = len + mylen;
 581         if (bp[2] == FULL_KEY || bp[2] == FULL_KEY_DATA) {    /* End of Key. */
 582                 if (hashp->tmp_key != NULL)
 583                         free(hashp->tmp_key);
 584                 if ((hashp->tmp_key = (char *)malloc((size_t)totlen)) == NULL)
 585                         return (-1);
 586                 if (__big_return(hashp, bufp, 1, val, set))
 587                         return (-1);
 588         } else {
 589                 xbp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 590                 if (!xbp || ((totlen =
 591                     collect_key(hashp, xbp, totlen, val, set)) < 1))
 592                         return (-1);
 593         }
 594         if (bufp->addr != save_addr) {
 595                 errno = EINVAL;         /* MIS -- OUT OF BUFFERS */
 596                 return (-1);
 597         }
 598         memmove(&hashp->tmp_key[len], (bufp->page) + bp[1], (size_t)mylen);
 599         return (totlen);
 600 }
 601
 602 /*
 603  * Returns:
 604  *  0 => OK
 605  * -1 => error
 606  */
 607 extern int
 608 __big_split(
 609         HTAB *hashp,
 610         BUFHEAD *op,    /* Pointer to where to put keys that go in old bucket */
 611         BUFHEAD *np,    /* Pointer to new bucket page */
 612                         /* Pointer to first page containing the big key/data */
 613         BUFHEAD *big_keyp,
 614         uint32 addr,    /* Address of big_keyp */
 615         uint32   obucket,/* Old Bucket */
 616         SPLIT_RETURN *ret)
 617 {
 618         register BUFHEAD *tmpp;
 619         register uint16 *tp;
 620         BUFHEAD *bp;
 621         DBT key, val;
 622         uint32 change;
 623         uint16 free_space, n, off;
 624
 625         bp = big_keyp;
 626
 627         /* Now figure out where the big key/data goes */
 628         if (__big_keydata(hashp, big_keyp, &key, &val, 0))
 629                 return (-1);
 630         change = (__call_hash(hashp,(char*) key.data, key.size) != obucket);
 631
 632         if ((ret->next_addr = __find_last_page(hashp, &big_keyp))) {
 633                 if (!(ret->nextp =
 634                     __get_buf(hashp, ret->next_addr, big_keyp, 0)))
 635                         return (-1);;
 636         } else
 637                 ret->nextp = NULL;
 638
 639         /* Now make one of np/op point to the big key/data pair */
 640 #ifdef DEBUG
 641         assert(np->ovfl == NULL);
 642 #endif
 643         if (change)
 644                 tmpp = np;
 645         else
 646                 tmpp = op;
 647
 648         tmpp->flags |= BUF_MOD;
 649 #ifdef DEBUG1
 650         (void)fprintf(stderr,
 651             "BIG_SPLIT: %d->ovfl was %d is now %d\n", tmpp->addr,
 652             (tmpp->ovfl ? tmpp->ovfl->addr : 0), (bp ? bp->addr : 0));
 653 #endif
 654         tmpp->ovfl = bp;        /* one of op/np point to big_keyp */
 655         tp = (uint16 *)tmpp->page;
 656
 657
 658 #if 0  /* this get's tripped on database corrupted error */
 659         assert(FREESPACE(tp) >= OVFLSIZE);
 660 #endif
 661         if(FREESPACE(tp) < OVFLSIZE)
 662                 return(DATABASE_CORRUPTED_ERROR);
 663
 664         n = tp[0];
 665         off = OFFSET(tp);
 666         free_space = FREESPACE(tp);
 667         tp[++n] = (uint16)addr;
 668         tp[++n] = OVFLPAGE;
 669         tp[0] = n;
 670         OFFSET(tp) = off;
 671         FREESPACE(tp) = free_space - OVFLSIZE;
 672
 673         /*
 674          * Finally, set the new and old return values. BIG_KEYP contains a
 675          * pointer to the last page of the big key_data pair. Make sure that
 676          * big_keyp has no following page (2 elements) or create an empty
 677          * following page.
 678          */
 679
 680         ret->newp = np;
 681         ret->oldp = op;
 682
 683         tp = (uint16 *)big_keyp->page;
 684         big_keyp->flags |= BUF_MOD;
 685         if (tp[0] > 2) {
 686                 /*
 687                  * There may be either one or two offsets on this page.  If
 688                  * there is one, then the overflow page is linked on normally
 689                  * and tp[4] is OVFLPAGE.  If there are two, tp[4] contains
 690                  * the second offset and needs to get stuffed in after the
 691                  * next overflow page is added.
 692                  */
 693                 n = tp[4];
 694                 free_space = FREESPACE(tp);
 695                 off = OFFSET(tp);
 696                 tp[0] -= 2;
 697                 FREESPACE(tp) = free_space + OVFLSIZE;
 698                 OFFSET(tp) = off;
 699                 tmpp = __add_ovflpage(hashp, big_keyp);
 700                 if (!tmpp)
 701                         return (-1);
 702                 tp[4] = n;
 703         } else
 704                 tmpp = big_keyp;
 705
 706         if (change)
 707                 ret->newp = tmpp;
 708         else
 709                 ret->oldp = tmpp;
 710         return (0);
 711 }