db/hash/hash_page.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_page.c 8.7 (Berkeley) 8/16/94";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 /*
  42  * PACKAGE:  hashing
  43  *
  44  * DESCRIPTION:
  45  *      Page manipulation for hashing package.
  46  *
  47  * ROUTINES:
  48  *
  49  * External
  50  *      __get_page
  51  *      __add_ovflpage
  52  * Internal
  53  *      overflow_page
  54  *      open_temp
  55  */
  56
  57 #include <sys/types.h>
  58
  59 #include <errno.h>
  60 #include <fcntl.h>
  61 #include <signal.h>
  62 #include <stdio.h>
  63 #include <stdlib.h>
  64 #include <string.h>
  65 #include <unistd.h>
  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 u_int32_t        *fetch_bitmap __P((HTAB *, int));
  76 static u_int32_t         first_free __P((u_int32_t));
  77 static int       open_temp __P((HTAB *));
  78 static u_int16_t         overflow_page __P((HTAB *));
  79 static void      putpair __P((char *, const DBT *, const DBT *));
  80 static void      squeeze_key __P((u_int16_t *, const DBT *, const DBT *));
  81 static int       ugly_split
  82                     __P((HTAB *, u_int32_t, BUFHEAD *, BUFHEAD *, int, int));
  83
  84 #define PAGE_INIT(P) { \
  85         ((u_int16_t *)(P))[0] = 0; \
  86         ((u_int16_t *)(P))[1] = hashp->BSIZE - 3 * sizeof(u_int16_t); \
  87         ((u_int16_t *)(P))[2] = hashp->BSIZE; \
  88 }
  89
  90 /*
  91  * This is called AFTER we have verified that there is room on the page for
  92  * the pair (PAIRFITS has returned true) so we go right ahead and start moving
  93  * stuff on.
  94  */
  95 static void
  96 putpair(p, key, val)
  97         char *p;
  98         const DBT *key, *val;
  99 {
 100         register u_int16_t *bp, n, off;
 101
 102         bp = (u_int16_t *)p;
 103
 104         /* Enter the key first. */
 105         n = bp[0];
 106
 107         off = OFFSET(bp) - key->size;
 108         memmove(p + off, key->data, key->size);
 109         bp[++n] = off;
 110
 111         /* Now the data. */
 112         off -= val->size;
 113         memmove(p + off, val->data, val->size);
 114         bp[++n] = off;
 115
 116         /* Adjust page info. */
 117         bp[0] = n;
 118         bp[n + 1] = off - ((n + 3) * sizeof(u_int16_t));
 119         bp[n + 2] = off;
 120 }
 121
 122 /*
 123  * Returns:
 124  *       0 OK
 125  *      -1 error
 126  */
 127 extern int
 128 __delpair(hashp, bufp, ndx)
 129         HTAB *hashp;
 130         BUFHEAD *bufp;
 131         register int ndx;
 132 {
 133         register u_int16_t *bp, newoff;
 134         register int n;
 135         u_int16_t pairlen;
 136
 137         bp = (u_int16_t *)bufp->page;
 138         n = bp[0];
 139
 140         if (bp[ndx + 1] < REAL_KEY)
 141                 return (__big_delete(hashp, bufp));
 142         if (ndx != 1)
 143                 newoff = bp[ndx - 1];
 144         else
 145                 newoff = hashp->BSIZE;
 146         pairlen = newoff - bp[ndx + 1];
 147
 148         if (ndx != (n - 1)) {
 149                 /* Hard Case -- need to shuffle keys */
 150                 register int i;
 151                 register char *src = bufp->page + (int)OFFSET(bp);
 152                 register char *dst = src + (int)pairlen;
 153                 memmove(dst, src, bp[ndx + 1] - OFFSET(bp));
 154
 155                 /* Now adjust the pointers */
 156                 for (i = ndx + 2; i <= n; i += 2) {
 157                         if (bp[i + 1] == OVFLPAGE) {
 158                                 bp[i - 2] = bp[i];
 159                                 bp[i - 1] = bp[i + 1];
 160                         } else {
 161                                 bp[i - 2] = bp[i] + pairlen;
 162                                 bp[i - 1] = bp[i + 1] + pairlen;
 163                         }
 164                 }
 165         }
 166         /* Finally adjust the page data */
 167         bp[n] = OFFSET(bp) + pairlen;
 168         bp[n - 1] = bp[n + 1] + pairlen + 2 * sizeof(u_int16_t);
 169         bp[0] = n - 2;
 170         hashp->NKEYS--;
 171
 172         bufp->flags |= BUF_MOD;
 173         return (0);
 174 }
 175 /*
 176  * Returns:
 177  *       0 ==> OK
 178  *      -1 ==> Error
 179  */
 180 extern int
 181 __split_page(hashp, obucket, nbucket)
 182         HTAB *hashp;
 183         u_int32_t obucket, nbucket;
 184 {
 185         register BUFHEAD *new_bufp, *old_bufp;
 186         register u_int16_t *ino;
 187         register char *np;
 188         DBT key, val;
 189         int n, ndx, retval;
 190         u_int16_t copyto, diff, off, moved;
 191         char *op;
 192
 193         copyto = (u_int16_t)hashp->BSIZE;
 194         off = (u_int16_t)hashp->BSIZE;
 195         old_bufp = __get_buf(hashp, obucket, NULL, 0);
 196         if (old_bufp == NULL)
 197                 return (-1);
 198         new_bufp = __get_buf(hashp, nbucket, NULL, 0);
 199         if (new_bufp == NULL)
 200                 return (-1);
 201
 202         old_bufp->flags |= (BUF_MOD | BUF_PIN);
 203         new_bufp->flags |= (BUF_MOD | BUF_PIN);
 204
 205         ino = (u_int16_t *)(op = old_bufp->page);
 206         np = new_bufp->page;
 207
 208         moved = 0;
 209
 210         for (n = 1, ndx = 1; n < ino[0]; n += 2) {
 211                 if (ino[n + 1] < REAL_KEY) {
 212                         retval = ugly_split(hashp, obucket, old_bufp, new_bufp,
 213                             (int)copyto, (int)moved);
 214                         old_bufp->flags &= ~BUF_PIN;
 215                         new_bufp->flags &= ~BUF_PIN;
 216                         return (retval);
 217
 218                 }
 219                 key.data = (u_char *)op + ino[n];
 220                 key.size = off - ino[n];
 221
 222                 if (__call_hash(hashp, key.data, key.size) == obucket) {
 223                         /* Don't switch page */
 224                         diff = copyto - off;
 225                         if (diff) {
 226                                 copyto = ino[n + 1] + diff;
 227                                 memmove(op + copyto, op + ino[n + 1],
 228                                     off - ino[n + 1]);
 229                                 ino[ndx] = copyto + ino[n] - ino[n + 1];
 230                                 ino[ndx + 1] = copyto;
 231                         } else
 232                                 copyto = ino[n + 1];
 233                         ndx += 2;
 234                 } else {
 235                         /* Switch page */
 236                         val.data = (u_char *)op + ino[n + 1];
 237                         val.size = ino[n] - ino[n + 1];
 238                         putpair(np, &key, &val);
 239                         moved += 2;
 240                 }
 241
 242                 off = ino[n + 1];
 243         }
 244
 245         /* Now clean up the page */
 246         ino[0] -= moved;
 247         FREESPACE(ino) = copyto - sizeof(u_int16_t) * (ino[0] + 3);
 248         OFFSET(ino) = copyto;
 249
 250 #ifdef DEBUG3
 251         (void)fprintf(stderr, "split %d/%d\n",
 252             ((u_int16_t *)np)[0] / 2,
 253             ((u_int16_t *)op)[0] / 2);
 254 #endif
 255         /* unpin both pages */
 256         old_bufp->flags &= ~BUF_PIN;
 257         new_bufp->flags &= ~BUF_PIN;
 258         return (0);
 259 }
 260
 261 /*
 262  * Called when we encounter an overflow or big key/data page during split
 263  * handling.  This is special cased since we have to begin checking whether
 264  * the key/data pairs fit on their respective pages and because we may need
 265  * overflow pages for both the old and new pages.
 266  *
 267  * The first page might be a page with regular key/data pairs in which case
 268  * we have a regular overflow condition and just need to go on to the next
 269  * page or it might be a big key/data pair in which case we need to fix the
 270  * big key/data pair.
 271  *
 272  * Returns:
 273  *       0 ==> success
 274  *      -1 ==> failure
 275  */
 276 static int
 277 ugly_split(hashp, obucket, old_bufp, new_bufp, copyto, moved)
 278         HTAB *hashp;
 279         u_int32_t obucket;      /* Same as __split_page. */
 280         BUFHEAD *old_bufp, *new_bufp;
 281         int copyto;     /* First byte on page which contains key/data values. */
 282         int moved;      /* Number of pairs moved to new page. */
 283 {
 284         register BUFHEAD *bufp; /* Buffer header for ino */
 285         register u_int16_t *ino;        /* Page keys come off of */
 286         register u_int16_t *np; /* New page */
 287         register u_int16_t *op; /* Page keys go on to if they aren't moving */
 288
 289         BUFHEAD *last_bfp;      /* Last buf header OVFL needing to be freed */
 290         DBT key, val;
 291         SPLIT_RETURN ret;
 292         u_int16_t n, off, ov_addr, scopyto;
 293         char *cino;             /* Character value of ino */
 294
 295         bufp = old_bufp;
 296         ino = (u_int16_t *)old_bufp->page;
 297         np = (u_int16_t *)new_bufp->page;
 298         op = (u_int16_t *)old_bufp->page;
 299         last_bfp = NULL;
 300         scopyto = (u_int16_t)copyto;    /* ANSI */
 301
 302         n = ino[0] - 1;
 303         while (n < ino[0]) {
 304                 if (ino[2] < REAL_KEY && ino[2] != OVFLPAGE) {
 305                         if (__big_split(hashp, old_bufp,
 306                             new_bufp, bufp, bufp->addr, obucket, &ret))
 307                                 return (-1);
 308                         old_bufp = ret.oldp;
 309                         if (!old_bufp)
 310                                 return (-1);
 311                         op = (u_int16_t *)old_bufp->page;
 312                         new_bufp = ret.newp;
 313                         if (!new_bufp)
 314                                 return (-1);
 315                         np = (u_int16_t *)new_bufp->page;
 316                         bufp = ret.nextp;
 317                         if (!bufp)
 318                                 return (0);
 319                         cino = (char *)bufp->page;
 320                         ino = (u_int16_t *)cino;
 321                         last_bfp = ret.nextp;
 322                 } else if (ino[n + 1] == OVFLPAGE) {
 323                         ov_addr = ino[n];
 324                         /*
 325                          * Fix up the old page -- the extra 2 are the fields
 326                          * which contained the overflow information.
 327                          */
 328                         ino[0] -= (moved + 2);
 329                         FREESPACE(ino) =
 330                             scopyto - sizeof(u_int16_t) * (ino[0] + 3);
 331                         OFFSET(ino) = scopyto;
 332
 333                         bufp = __get_buf(hashp, ov_addr, bufp, 0);
 334                         if (!bufp)
 335                                 return (-1);
 336
 337                         ino = (u_int16_t *)bufp->page;
 338                         n = 1;
 339                         scopyto = hashp->BSIZE;
 340                         moved = 0;
 341
 342                         if (last_bfp)
 343                                 __free_ovflpage(hashp, last_bfp);
 344                         last_bfp = bufp;
 345                 }
 346                 /* Move regular sized pairs of there are any */
 347                 off = hashp->BSIZE;
 348                 for (n = 1; (n < ino[0]) && (ino[n + 1] >= REAL_KEY); n += 2) {
 349                         cino = (char *)ino;
 350                         key.data = (u_char *)cino + ino[n];
 351                         key.size = off - ino[n];
 352                         val.data = (u_char *)cino + ino[n + 1];
 353                         val.size = ino[n] - ino[n + 1];
 354                         off = ino[n + 1];
 355
 356                         if (__call_hash(hashp, key.data, key.size) == obucket) {
 357                                 /* Keep on old page */
 358                                 if (PAIRFITS(op, (&key), (&val)))
 359                                         putpair((char *)op, &key, &val);
 360                                 else {
 361                                         old_bufp =
 362                                             __add_ovflpage(hashp, old_bufp);
 363                                         if (!old_bufp)
 364                                                 return (-1);
 365                                         op = (u_int16_t *)old_bufp->page;
 366                                         putpair((char *)op, &key, &val);
 367                                 }
 368                                 old_bufp->flags |= BUF_MOD;
 369                         } else {
 370                                 /* Move to new page */
 371                                 if (PAIRFITS(np, (&key), (&val)))
 372                                         putpair((char *)np, &key, &val);
 373                                 else {
 374                                         new_bufp =
 375                                             __add_ovflpage(hashp, new_bufp);
 376                                         if (!new_bufp)
 377                                                 return (-1);
 378                                         np = (u_int16_t *)new_bufp->page;
 379                                         putpair((char *)np, &key, &val);
 380                                 }
 381                                 new_bufp->flags |= BUF_MOD;
 382                         }
 383                 }
 384         }
 385         if (last_bfp)
 386                 __free_ovflpage(hashp, last_bfp);
 387         return (0);
 388 }
 389
 390 /*
 391  * Add the given pair to the page
 392  *
 393  * Returns:
 394  *      0 ==> OK
 395  *      1 ==> failure
 396  */
 397 extern int
 398 __addel(hashp, bufp, key, val)
 399         HTAB *hashp;
 400         BUFHEAD *bufp;
 401         const DBT *key, *val;
 402 {
 403         register u_int16_t *bp, *sop;
 404         int do_expand;
 405
 406         bp = (u_int16_t *)bufp->page;
 407         do_expand = 0;
 408         while (bp[0] && (bp[2] < REAL_KEY || bp[bp[0]] < REAL_KEY))
 409                 /* Exception case */
 410                 if (bp[2] == FULL_KEY_DATA && bp[0] == 2)
 411                         /* This is the last page of a big key/data pair
 412                            and we need to add another page */
 413                         break;
 414                 else if (bp[2] < REAL_KEY && bp[bp[0]] != OVFLPAGE) {
 415                         bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 416                         if (!bufp)
 417                                 return (-1);
 418                         bp = (u_int16_t *)bufp->page;
 419                 } else
 420                         /* Try to squeeze key on this page */
 421                         if (FREESPACE(bp) > PAIRSIZE(key, val)) {
 422                                 squeeze_key(bp, key, val);
 423                                 return (0);
 424                         } else {
 425                                 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0);
 426                                 if (!bufp)
 427                                         return (-1);
 428                                 bp = (u_int16_t *)bufp->page;
 429                         }
 430
 431         if (PAIRFITS(bp, key, val))
 432                 putpair(bufp->page, key, val);
 433         else {
 434                 do_expand = 1;
 435                 bufp = __add_ovflpage(hashp, bufp);
 436                 if (!bufp)
 437                         return (-1);
 438                 sop = (u_int16_t *)bufp->page;
 439
 440                 if (PAIRFITS(sop, key, val))
 441                         putpair((char *)sop, key, val);
 442                 else
 443                         if (__big_insert(hashp, bufp, key, val))
 444                                 return (-1);
 445         }
 446         bufp->flags |= BUF_MOD;
 447         /*
 448          * If the average number of keys per bucket exceeds the fill factor,
 449          * expand the table.
 450          */
 451         hashp->NKEYS++;
 452         if (do_expand ||
 453             (hashp->NKEYS / (hashp->MAX_BUCKET + 1) > hashp->FFACTOR))
 454                 return (__expand_table(hashp));
 455         return (0);
 456 }
 457
 458 /*
 459  *
 460  * Returns:
 461  *      pointer on success
 462  *      NULL on error
 463  */
 464 extern BUFHEAD *
 465 __add_ovflpage(hashp, bufp)
 466         HTAB *hashp;
 467         BUFHEAD *bufp;
 468 {
 469         register u_int16_t *sp;
 470         u_int16_t ndx, ovfl_num;
 471 #ifdef DEBUG1
 472         int tmp1, tmp2;
 473 #endif
 474         sp = (u_int16_t *)bufp->page;
 475
 476         /* Check if we are dynamically determining the fill factor */
 477         if (hashp->FFACTOR == DEF_FFACTOR) {
 478                 hashp->FFACTOR = sp[0] >> 1;
 479                 if (hashp->FFACTOR < MIN_FFACTOR)
 480                         hashp->FFACTOR = MIN_FFACTOR;
 481         }
 482         bufp->flags |= BUF_MOD;
 483         ovfl_num = overflow_page(hashp);
 484 #ifdef DEBUG1
 485         tmp1 = bufp->addr;
 486         tmp2 = bufp->ovfl ? bufp->ovfl->addr : 0;
 487 #endif
 488         if (!ovfl_num || !(bufp->ovfl = __get_buf(hashp, ovfl_num, bufp, 1)))
 489                 return (NULL);
 490         bufp->ovfl->flags |= BUF_MOD;
 491 #ifdef DEBUG1
 492         (void)fprintf(stderr, "ADDOVFLPAGE: %d->ovfl was %d is now %d\n",
 493             tmp1, tmp2, bufp->ovfl->addr);
 494 #endif
 495         ndx = sp[0];
 496         /*
 497          * Since a pair is allocated on a page only if there's room to add
 498          * an overflow page, we know that the OVFL information will fit on
 499          * the page.
 500          */
 501         sp[ndx + 4] = OFFSET(sp);
 502         sp[ndx + 3] = FREESPACE(sp) - OVFLSIZE;
 503         sp[ndx + 1] = ovfl_num;
 504         sp[ndx + 2] = OVFLPAGE;
 505         sp[0] = ndx + 2;
 506 #ifdef HASH_STATISTICS
 507         hash_overflows++;
 508 #endif
 509         return (bufp->ovfl);
 510 }
 511
 512 /*
 513  * Returns:
 514  *       0 indicates SUCCESS
 515  *      -1 indicates FAILURE
 516  */
 517 extern int
 518 __get_page(hashp, p, bucket, is_bucket, is_disk, is_bitmap)
 519         HTAB *hashp;
 520         char *p;
 521         u_int32_t bucket;
 522         int is_bucket, is_disk, is_bitmap;
 523 {
 524         register int fd, page, size;
 525         int rsize;
 526         u_int16_t *bp;
 527
 528         fd = hashp->fp;
 529         size = hashp->BSIZE;
 530
 531         if ((fd == -1) || !is_disk) {
 532                 PAGE_INIT(p);
 533                 return (0);
 534         }
 535         if (is_bucket)
 536                 page = BUCKET_TO_PAGE(bucket);
 537         else
 538                 page = OADDR_TO_PAGE(bucket);
 539         if ((lseek(fd, (off_t)page << hashp->BSHIFT, SEEK_SET) == -1) ||
 540             ((rsize = read(fd, p, size)) == -1))
 541                 return (-1);
 542         bp = (u_int16_t *)p;
 543         if (!rsize)
 544                 bp[0] = 0;      /* We hit the EOF, so initialize a new page */
 545         else
 546                 if (rsize != size) {
 547                         errno = EFTYPE;
 548                         return (-1);
 549                 }
 550         if (!is_bitmap && !bp[0]) {
 551                 PAGE_INIT(p);
 552         } else
 553                 if (hashp->LORDER != BYTE_ORDER) {
 554                         register int i, max;
 555
 556                         if (is_bitmap) {
 557                                 max = hashp->BSIZE >> 2; /* divide by 4 */
 558                                 for (i = 0; i < max; i++)
 559                                         M_32_SWAP(((int *)p)[i]);
 560                         } else {
 561                                 M_16_SWAP(bp[0]);
 562                                 max = bp[0] + 2;
 563                                 for (i = 1; i <= max; i++)
 564                                         M_16_SWAP(bp[i]);
 565                         }
 566                 }
 567         return (0);
 568 }
 569
 570 /*
 571  * Write page p to disk
 572  *
 573  * Returns:
 574  *       0 ==> OK
 575  *      -1 ==>failure
 576  */
 577 extern int
 578 __put_page(hashp, p, bucket, is_bucket, is_bitmap)
 579         HTAB *hashp;
 580         char *p;
 581         u_int32_t bucket;
 582         int is_bucket, is_bitmap;
 583 {
 584         register int fd, page, size;
 585         int wsize;
 586
 587         size = hashp->BSIZE;
 588         if ((hashp->fp == -1) && open_temp(hashp))
 589                 return (-1);
 590         fd = hashp->fp;
 591
 592         if (hashp->LORDER != BYTE_ORDER) {
 593                 register int i;
 594                 register int max;
 595
 596                 if (is_bitmap) {
 597                         max = hashp->BSIZE >> 2;        /* divide by 4 */
 598                         for (i = 0; i < max; i++)
 599                                 M_32_SWAP(((int *)p)[i]);
 600                 } else {
 601                         max = ((u_int16_t *)p)[0] + 2;
 602                         for (i = 0; i <= max; i++)
 603                                 M_16_SWAP(((u_int16_t *)p)[i]);
 604                 }
 605         }
 606         if (is_bucket)
 607                 page = BUCKET_TO_PAGE(bucket);
 608         else
 609                 page = OADDR_TO_PAGE(bucket);
 610         if ((lseek(fd, (off_t)page << hashp->BSHIFT, SEEK_SET) == -1) ||
 611             ((wsize = write(fd, p, size)) == -1))
 612                 /* Errno is set */
 613                 return (-1);
 614         if (wsize != size) {
 615                 errno = EFTYPE;
 616                 return (-1);
 617         }
 618         return (0);
 619 }
 620
 621 #define BYTE_MASK       ((1 << INT_BYTE_SHIFT) -1)
 622 /*
 623  * Initialize a new bitmap page.  Bitmap pages are left in memory
 624  * once they are read in.
 625  */
 626 extern int
 627 __ibitmap(hashp, pnum, nbits, ndx)
 628         HTAB *hashp;
 629         int pnum, nbits, ndx;
 630 {
 631         u_int32_t *ip;
 632         int clearbytes, clearints;
 633
 634         if ((ip = (u_int32_t *)malloc(hashp->BSIZE)) == NULL)
 635                 return (1);
 636         hashp->nmaps++;
 637         clearints = ((nbits - 1) >> INT_BYTE_SHIFT) + 1;
 638         clearbytes = clearints << INT_TO_BYTE;
 639         (void)memset((char *)ip, 0, clearbytes);
 640         (void)memset(((char *)ip) + clearbytes, 0xFF,
 641             hashp->BSIZE - clearbytes);
 642         ip[clearints - 1] = ALL_SET << (nbits & BYTE_MASK);
 643         SETBIT(ip, 0);
 644         hashp->BITMAPS[ndx] = (u_int16_t)pnum;
 645         hashp->mapp[ndx] = ip;
 646         return (0);
 647 }
 648
 649 static u_int32_t
 650 first_free(map)
 651         u_int32_t map;
 652 {
 653         register u_int32_t i, mask;
 654
 655         mask = 0x1;
 656         for (i = 0; i < BITS_PER_MAP; i++) {
 657                 if (!(mask & map))
 658                         return (i);
 659                 mask = mask << 1;
 660         }
 661         return (i);
 662 }
 663
 664 static u_int16_t
 665 overflow_page(hashp)
 666         HTAB *hashp;
 667 {
 668         register u_int32_t *freep;
 669         register int max_free, offset, splitnum;
 670         u_int16_t addr;
 671         int bit, first_page, free_bit, free_page, i, in_use_bits, j;
 672 #ifdef DEBUG2
 673         int tmp1, tmp2;
 674 #endif
 675         splitnum = hashp->OVFL_POINT;
 676         max_free = hashp->SPARES[splitnum];
 677
 678         free_page = (max_free - 1) >> (hashp->BSHIFT + BYTE_SHIFT);
 679         free_bit = (max_free - 1) & ((hashp->BSIZE << BYTE_SHIFT) - 1);
 680
 681         /* Look through all the free maps to find the first free block */
 682         first_page = hashp->LAST_FREED >>(hashp->BSHIFT + BYTE_SHIFT);
 683         for ( i = first_page; i <= free_page; i++ ) {
 684                 if (!(freep = (u_int32_t *)hashp->mapp[i]) &&
 685                     !(freep = fetch_bitmap(hashp, i)))
 686                         return (0);
 687                 if (i == free_page)
 688                         in_use_bits = free_bit;
 689                 else
 690                         in_use_bits = (hashp->BSIZE << BYTE_SHIFT) - 1;
 691
 692                 if (i == first_page) {
 693                         bit = hashp->LAST_FREED &
 694                             ((hashp->BSIZE << BYTE_SHIFT) - 1);
 695                         j = bit / BITS_PER_MAP;
 696                         bit = bit & ~(BITS_PER_MAP - 1);
 697                 } else {
 698                         bit = 0;
 699                         j = 0;
 700                 }
 701                 for (; bit <= in_use_bits; j++, bit += BITS_PER_MAP)
 702                         if (freep[j] != ALL_SET)
 703                                 goto found;
 704         }
 705
 706         /* No Free Page Found */
 707         hashp->LAST_FREED = hashp->SPARES[splitnum];
 708         hashp->SPARES[splitnum]++;
 709         offset = hashp->SPARES[splitnum] -
 710             (splitnum ? hashp->SPARES[splitnum - 1] : 0);
 711
 712 #define OVMSG   "HASH: Out of overflow pages.  Increase page size\n"
 713         if (offset > SPLITMASK) {
 714                 if (++splitnum >= NCACHED) {
 715                         (void)write(STDERR_FILENO, OVMSG, sizeof(OVMSG) - 1);
 716                         return (0);
 717                 }
 718                 hashp->OVFL_POINT = splitnum;
 719                 hashp->SPARES[splitnum] = hashp->SPARES[splitnum-1];
 720                 hashp->SPARES[splitnum-1]--;
 721                 offset = 1;
 722         }
 723
 724         /* Check if we need to allocate a new bitmap page */
 725         if (free_bit == (hashp->BSIZE << BYTE_SHIFT) - 1) {
 726                 free_page++;
 727                 if (free_page >= NCACHED) {
 728                         (void)write(STDERR_FILENO, OVMSG, sizeof(OVMSG) - 1);
 729                         return (0);
 730                 }
 731                 /*
 732                  * This is tricky.  The 1 indicates that you want the new page
 733                  * allocated with 1 clear bit.  Actually, you are going to
 734                  * allocate 2 pages from this map.  The first is going to be
 735                  * the map page, the second is the overflow page we were
 736                  * looking for.  The init_bitmap routine automatically, sets
 737                  * the first bit of itself to indicate that the bitmap itself
 738                  * is in use.  We would explicitly set the second bit, but
 739                  * don't have to if we tell init_bitmap not to leave it clear
 740                  * in the first place.
 741                  */
 742                 if (__ibitmap(hashp,
 743                     (int)OADDR_OF(splitnum, offset), 1, free_page))
 744                         return (0);
 745                 hashp->SPARES[splitnum]++;
 746 #ifdef DEBUG2
 747                 free_bit = 2;
 748 #endif
 749                 offset++;
 750                 if (offset > SPLITMASK) {
 751                         if (++splitnum >= NCACHED) {
 752                                 (void)write(STDERR_FILENO, OVMSG,
 753                                     sizeof(OVMSG) - 1);
 754                                 return (0);
 755                         }
 756                         hashp->OVFL_POINT = splitnum;
 757                         hashp->SPARES[splitnum] = hashp->SPARES[splitnum-1];
 758                         hashp->SPARES[splitnum-1]--;
 759                         offset = 0;
 760                 }
 761         } else {
 762                 /*
 763                  * Free_bit addresses the last used bit.  Bump it to address
 764                  * the first available bit.
 765                  */
 766                 free_bit++;
 767                 SETBIT(freep, free_bit);
 768         }
 769
 770         /* Calculate address of the new overflow page */
 771         addr = OADDR_OF(splitnum, offset);
 772 #ifdef DEBUG2
 773         (void)fprintf(stderr, "OVERFLOW_PAGE: ADDR: %d BIT: %d PAGE %d\n",
 774             addr, free_bit, free_page);
 775 #endif
 776         return (addr);
 777
 778 found:
 779         bit = bit + first_free(freep[j]);
 780         SETBIT(freep, bit);
 781 #ifdef DEBUG2
 782         tmp1 = bit;
 783         tmp2 = i;
 784 #endif
 785         /*
 786          * Bits are addressed starting with 0, but overflow pages are addressed
 787          * beginning at 1. Bit is a bit addressnumber, so we need to increment
 788          * it to convert it to a page number.
 789          */
 790         bit = 1 + bit + (i * (hashp->BSIZE << BYTE_SHIFT));
 791         if (bit >= hashp->LAST_FREED)
 792                 hashp->LAST_FREED = bit - 1;
 793
 794         /* Calculate the split number for this page */
 795         for (i = 0; (i < splitnum) && (bit > hashp->SPARES[i]); i++);
 796         offset = (i ? bit - hashp->SPARES[i - 1] : bit);
 797         if (offset >= SPLITMASK)
 798                 return (0);     /* Out of overflow pages */
 799         addr = OADDR_OF(i, offset);
 800 #ifdef DEBUG2
 801         (void)fprintf(stderr, "OVERFLOW_PAGE: ADDR: %d BIT: %d PAGE %d\n",
 802             addr, tmp1, tmp2);
 803 #endif
 804
 805         /* Allocate and return the overflow page */
 806         return (addr);
 807 }
 808
 809 /*
 810  * Mark this overflow page as free.
 811  */
 812 extern void
 813 __free_ovflpage(hashp, obufp)
 814         HTAB *hashp;
 815         BUFHEAD *obufp;
 816 {
 817         register u_int16_t addr;
 818         u_int32_t *freep;
 819         int bit_address, free_page, free_bit;
 820         u_int16_t ndx;
 821
 822         addr = obufp->addr;
 823 #ifdef DEBUG1
 824         (void)fprintf(stderr, "Freeing %d\n", addr);
 825 #endif
 826         ndx = (((u_int16_t)addr) >> SPLITSHIFT);
 827         bit_address =
 828             (ndx ? hashp->SPARES[ndx - 1] : 0) + (addr & SPLITMASK) - 1;
 829          if (bit_address < hashp->LAST_FREED)
 830                 hashp->LAST_FREED = bit_address;
 831         free_page = (bit_address >> (hashp->BSHIFT + BYTE_SHIFT));
 832         free_bit = bit_address & ((hashp->BSIZE << BYTE_SHIFT) - 1);
 833
 834         if (!(freep = hashp->mapp[free_page]))
 835                 freep = fetch_bitmap(hashp, free_page);
 836 #ifdef DEBUG
 837         /*
 838          * This had better never happen.  It means we tried to read a bitmap
 839          * that has already had overflow pages allocated off it, and we
 840          * failed to read it from the file.
 841          */
 842         if (!freep)
 843                 assert(0);
 844 #endif
 845         CLRBIT(freep, free_bit);
 846 #ifdef DEBUG2
 847         (void)fprintf(stderr, "FREE_OVFLPAGE: ADDR: %d BIT: %d PAGE %d\n",
 848             obufp->addr, free_bit, free_page);
 849 #endif
 850         __reclaim_buf(hashp, obufp);
 851 }
 852
 853 /*
 854  * Returns:
 855  *       0 success
 856  *      -1 failure
 857  */
 858 static int
 859 open_temp(hashp)
 860         HTAB *hashp;
 861 {
 862         sigset_t set, oset;
 863         static char namestr[] = "_hashXXXXXX";
 864
 865         /* Block signals; make sure file goes away at process exit. */
 866         (void)sigfillset(&set);
 867         (void)sigprocmask(SIG_BLOCK, &set, &oset);
 868         if ((hashp->fp = mkstemp(namestr)) != -1) {
 869                 (void)unlink(namestr);
 870                 (void)fcntl(hashp->fp, F_SETFD, 1);
 871         }
 872         (void)sigprocmask(SIG_SETMASK, &oset, (sigset_t *)NULL);
 873         return (hashp->fp != -1 ? 0 : -1);
 874 }
 875
 876 /*
 877  * We have to know that the key will fit, but the last entry on the page is
 878  * an overflow pair, so we need to shift things.
 879  */
 880 static void
 881 squeeze_key(sp, key, val)
 882         u_int16_t *sp;
 883         const DBT *key, *val;
 884 {
 885         register char *p;
 886         u_int16_t free_space, n, off, pageno;
 887
 888         p = (char *)sp;
 889         n = sp[0];
 890         free_space = FREESPACE(sp);
 891         off = OFFSET(sp);
 892
 893         pageno = sp[n - 1];
 894         off -= key->size;
 895         sp[n - 1] = off;
 896         memmove(p + off, key->data, key->size);
 897         off -= val->size;
 898         sp[n] = off;
 899         memmove(p + off, val->data, val->size);
 900         sp[0] = n + 2;
 901         sp[n + 1] = pageno;
 902         sp[n + 2] = OVFLPAGE;
 903         FREESPACE(sp) = free_space - PAIRSIZE(key, val);
 904         OFFSET(sp) = off;
 905 }
 906
 907 static u_int32_t *
 908 fetch_bitmap(hashp, ndx)
 909         HTAB *hashp;
 910         int ndx;
 911 {
 912         if (ndx >= hashp->nmaps)
 913                 return (NULL);
 914         if ((hashp->mapp[ndx] = (u_int32_t *)malloc(hashp->BSIZE)) == NULL)
 915                 return (NULL);
 916         if (__get_page(hashp,
 917             (char *)hashp->mapp[ndx], hashp->BITMAPS[ndx], 0, 1, 1)) {
 918                 free(hashp->mapp[ndx]);
 919                 return (NULL);
 920         }
 921         return (hashp->mapp[ndx]);
 922 }
 923
 924 #ifdef DEBUG4
 925 int
 926 print_chain(addr)
 927         int addr;
 928 {
 929         BUFHEAD *bufp;
 930         short *bp, oaddr;
 931
 932         (void)fprintf(stderr, "%d ", addr);
 933         bufp = __get_buf(hashp, addr, NULL, 0);
 934         bp = (short *)bufp->page;
 935         while (bp[0] && ((bp[bp[0]] == OVFLPAGE) ||
 936                 ((bp[0] > 2) && bp[2] < REAL_KEY))) {
 937                 oaddr = bp[bp[0] - 1];
 938                 (void)fprintf(stderr, "%d ", (int)oaddr);
 939                 bufp = __get_buf(hashp, (int)oaddr, bufp, 0);
 940                 bp = (short *)bufp->page;
 941         }
 942         (void)fprintf(stderr, "\n");
 943 }
 944 #endif