hash_page.c revision 1.2
1 /*- 2 * Copyright (c) 1990, 1993 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[] = "from: @(#)hash_page.c 8.1 (Berkeley) 6/6/93";*/ 39 static char rcsid[] = "$Id: hash_page.c,v 1.2 1993/08/01 18:43:25 mycroft Exp $"; 40 #endif /* LIBC_SCCS and not lint */ 41 42 /* 43 * PACKAGE: hashing 44 * 45 * DESCRIPTION: 46 * Page manipulation for hashing package. 47 * 48 * ROUTINES: 49 * 50 * External 51 * __get_page 52 * __add_ovflpage 53 * Internal 54 * overflow_page 55 * open_temp 56 */ 57 58 #include <sys/types.h> 59 60 #include <errno.h> 61 #include <fcntl.h> 62 #include <signal.h> 63 #include <stdio.h> 64 #include <stdlib.h> 65 #include <string.h> 66 #include <unistd.h> 67 #ifdef DEBUG 68 #include <assert.h> 69 #endif 70 71 #include <db.h> 72 #include "hash.h" 73 #include "page.h" 74 #include "extern.h" 75 76 static u_long *fetch_bitmap __P((HTAB *, int)); 77 static u_long first_free __P((u_long)); 78 static int open_temp __P((HTAB *)); 79 static u_short overflow_page __P((HTAB *)); 80 static void putpair __P((char *, const DBT *, const DBT *)); 81 static void squeeze_key __P((u_short *, const DBT *, const DBT *)); 82 static int ugly_split 83 __P((HTAB *, u_int, BUFHEAD *, BUFHEAD *, int, int)); 84 85 #define PAGE_INIT(P) { \ 86 ((u_short *)(P))[0] = 0; \ 87 ((u_short *)(P))[1] = hashp->BSIZE - 3 * sizeof(u_short); \ 88 ((u_short *)(P))[2] = hashp->BSIZE; \ 89 } 90 91 /* 92 * This is called AFTER we have verified that there is room on the page for 93 * the pair (PAIRFITS has returned true) so we go right ahead and start moving 94 * stuff on. 95 */ 96 static void 97 putpair(p, key, val) 98 char *p; 99 const DBT *key, *val; 100 { 101 register u_short *bp, n, off; 102 103 bp = (u_short *)p; 104 105 /* Enter the key first. */ 106 n = bp[0]; 107 108 off = OFFSET(bp) - key->size; 109 memmove(p + off, key->data, key->size); 110 bp[++n] = off; 111 112 /* Now the data. */ 113 off -= val->size; 114 memmove(p + off, val->data, val->size); 115 bp[++n] = off; 116 117 /* Adjust page info. */ 118 bp[0] = n; 119 bp[n + 1] = off - ((n + 3) * sizeof(u_short)); 120 bp[n + 2] = off; 121 } 122 123 /* 124 * Returns: 125 * 0 OK 126 * -1 error 127 */ 128 extern int 129 __delpair(hashp, bufp, ndx) 130 HTAB *hashp; 131 BUFHEAD *bufp; 132 register int ndx; 133 { 134 register u_short *bp, newoff; 135 register int n; 136 u_short pairlen; 137 138 bp = (u_short *)bufp->page; 139 n = bp[0]; 140 141 if (bp[ndx + 1] < REAL_KEY) 142 return (__big_delete(hashp, bufp)); 143 if (ndx != 1) 144 newoff = bp[ndx - 1]; 145 else 146 newoff = hashp->BSIZE; 147 pairlen = newoff - bp[ndx + 1]; 148 149 if (ndx != (n - 1)) { 150 /* Hard Case -- need to shuffle keys */ 151 register int i; 152 register char *src = bufp->page + (int)OFFSET(bp); 153 register char *dst = src + (int)pairlen; 154 memmove(dst, src, bp[ndx + 1] - OFFSET(bp)); 155 156 /* Now adjust the pointers */ 157 for (i = ndx + 2; i <= n; i += 2) { 158 if (bp[i + 1] == OVFLPAGE) { 159 bp[i - 2] = bp[i]; 160 bp[i - 1] = bp[i + 1]; 161 } else { 162 bp[i - 2] = bp[i] + pairlen; 163 bp[i - 1] = bp[i + 1] + pairlen; 164 } 165 } 166 } 167 /* Finally adjust the page data */ 168 bp[n] = OFFSET(bp) + pairlen; 169 bp[n - 1] = bp[n + 1] + pairlen + 2 * sizeof(u_short); 170 bp[0] = n - 2; 171 hashp->NKEYS--; 172 173 bufp->flags |= BUF_MOD; 174 return (0); 175 } 176 /* 177 * Returns: 178 * 0 ==> OK 179 * -1 ==> Error 180 */ 181 extern int 182 __split_page(hashp, obucket, nbucket) 183 HTAB *hashp; 184 u_int obucket, nbucket; 185 { 186 register BUFHEAD *new_bufp, *old_bufp; 187 register u_short *ino; 188 register char *np; 189 DBT key, val; 190 int n, ndx, retval; 191 u_short copyto, diff, off, moved; 192 char *op; 193 194 copyto = (u_short)hashp->BSIZE; 195 off = (u_short)hashp->BSIZE; 196 old_bufp = __get_buf(hashp, obucket, NULL, 0); 197 if (old_bufp == NULL) 198 return (-1); 199 new_bufp = __get_buf(hashp, nbucket, NULL, 0); 200 if (new_bufp == NULL) 201 return (-1); 202 203 old_bufp->flags |= (BUF_MOD | BUF_PIN); 204 new_bufp->flags |= (BUF_MOD | BUF_PIN); 205 206 ino = (u_short *)(op = old_bufp->page); 207 np = new_bufp->page; 208 209 moved = 0; 210 211 for (n = 1, ndx = 1; n < ino[0]; n += 2) { 212 if (ino[n + 1] < REAL_KEY) { 213 retval = ugly_split(hashp, obucket, old_bufp, new_bufp, 214 (int)copyto, (int)moved); 215 old_bufp->flags &= ~BUF_PIN; 216 new_bufp->flags &= ~BUF_PIN; 217 return (retval); 218 219 } 220 key.data = (u_char *)op + ino[n]; 221 key.size = off - ino[n]; 222 223 if (__call_hash(hashp, key.data, key.size) == obucket) { 224 /* Don't switch page */ 225 diff = copyto - off; 226 if (diff) { 227 copyto = ino[n + 1] + diff; 228 memmove(op + copyto, op + ino[n + 1], 229 off - ino[n + 1]); 230 ino[ndx] = copyto + ino[n] - ino[n + 1]; 231 ino[ndx + 1] = copyto; 232 } else 233 copyto = ino[n + 1]; 234 ndx += 2; 235 } else { 236 /* Switch page */ 237 val.data = (u_char *)op + ino[n + 1]; 238 val.size = ino[n] - ino[n + 1]; 239 putpair(np, &key, &val); 240 moved += 2; 241 } 242 243 off = ino[n + 1]; 244 } 245 246 /* Now clean up the page */ 247 ino[0] -= moved; 248 FREESPACE(ino) = copyto - sizeof(u_short) * (ino[0] + 3); 249 OFFSET(ino) = copyto; 250 251 #ifdef DEBUG3 252 (void)fprintf(stderr, "split %d/%d\n", 253 ((u_short *)np)[0] / 2, 254 ((u_short *)op)[0] / 2); 255 #endif 256 /* unpin both pages */ 257 old_bufp->flags &= ~BUF_PIN; 258 new_bufp->flags &= ~BUF_PIN; 259 return (0); 260 } 261 262 /* 263 * Called when we encounter an overflow or big key/data page during split 264 * handling. This is special cased since we have to begin checking whether 265 * the key/data pairs fit on their respective pages and because we may need 266 * overflow pages for both the old and new pages. 267 * 268 * The first page might be a page with regular key/data pairs in which case 269 * we have a regular overflow condition and just need to go on to the next 270 * page or it might be a big key/data pair in which case we need to fix the 271 * big key/data pair. 272 * 273 * Returns: 274 * 0 ==> success 275 * -1 ==> failure 276 */ 277 static int 278 ugly_split(hashp, obucket, old_bufp, new_bufp, copyto, moved) 279 HTAB *hashp; 280 u_int obucket; /* Same as __split_page. */ 281 BUFHEAD *old_bufp, *new_bufp; 282 int copyto; /* First byte on page which contains key/data values. */ 283 int moved; /* Number of pairs moved to new page. */ 284 { 285 register BUFHEAD *bufp; /* Buffer header for ino */ 286 register u_short *ino; /* Page keys come off of */ 287 register u_short *np; /* New page */ 288 register u_short *op; /* Page keys go on to if they aren't moving */ 289 290 BUFHEAD *last_bfp; /* Last buf header OVFL needing to be freed */ 291 DBT key, val; 292 SPLIT_RETURN ret; 293 u_short n, off, ov_addr, scopyto; 294 char *cino; /* Character value of ino */ 295 296 bufp = old_bufp; 297 ino = (u_short *)old_bufp->page; 298 np = (u_short *)new_bufp->page; 299 op = (u_short *)old_bufp->page; 300 last_bfp = NULL; 301 scopyto = (u_short)copyto; /* ANSI */ 302 303 n = ino[0] - 1; 304 while (n < ino[0]) { 305 if (ino[2] < REAL_KEY && ino[2] != OVFLPAGE) { 306 /* 307 * Ov_addr gets set before reaching this point; there's 308 * always an overflow page before a big key/data page. 309 */ 310 if (__big_split(hashp, old_bufp, 311 new_bufp, bufp, ov_addr, obucket, &ret)) 312 return (-1); 313 old_bufp = ret.oldp; 314 if (!old_bufp) 315 return (-1); 316 op = (u_short *)old_bufp->page; 317 new_bufp = ret.newp; 318 if (!new_bufp) 319 return (-1); 320 np = (u_short *)new_bufp->page; 321 bufp = ret.nextp; 322 if (!bufp) 323 return (0); 324 cino = (char *)bufp->page; 325 ino = (u_short *)cino; 326 last_bfp = ret.nextp; 327 } else if (ino[n + 1] == OVFLPAGE) { 328 ov_addr = ino[n]; 329 /* 330 * Fix up the old page -- the extra 2 are the fields 331 * which contained the overflow information. 332 */ 333 ino[0] -= (moved + 2); 334 FREESPACE(ino) = 335 scopyto - sizeof(u_short) * (ino[0] + 3); 336 OFFSET(ino) = scopyto; 337 338 bufp = __get_buf(hashp, ov_addr, bufp, 0); 339 if (!bufp) 340 return (-1); 341 342 ino = (u_short *)bufp->page; 343 n = 1; 344 scopyto = hashp->BSIZE; 345 moved = 0; 346 347 if (last_bfp) 348 __free_ovflpage(hashp, last_bfp); 349 last_bfp = bufp; 350 } 351 /* Move regular sized pairs of there are any */ 352 off = hashp->BSIZE; 353 for (n = 1; (n < ino[0]) && (ino[n + 1] >= REAL_KEY); n += 2) { 354 cino = (char *)ino; 355 key.data = (u_char *)cino + ino[n]; 356 key.size = off - ino[n]; 357 val.data = (u_char *)cino + ino[n + 1]; 358 val.size = ino[n] - ino[n + 1]; 359 off = ino[n + 1]; 360 361 if (__call_hash(hashp, key.data, key.size) == obucket) { 362 /* Keep on old page */ 363 if (PAIRFITS(op, (&key), (&val))) 364 putpair((char *)op, &key, &val); 365 else { 366 old_bufp = 367 __add_ovflpage(hashp, old_bufp); 368 if (!old_bufp) 369 return (-1); 370 op = (u_short *)old_bufp->page; 371 putpair((char *)op, &key, &val); 372 } 373 old_bufp->flags |= BUF_MOD; 374 } else { 375 /* Move to new page */ 376 if (PAIRFITS(np, (&key), (&val))) 377 putpair((char *)np, &key, &val); 378 else { 379 new_bufp = 380 __add_ovflpage(hashp, new_bufp); 381 if (!new_bufp) 382 return (-1); 383 np = (u_short *)new_bufp->page; 384 putpair((char *)np, &key, &val); 385 } 386 new_bufp->flags |= BUF_MOD; 387 } 388 } 389 } 390 if (last_bfp) 391 __free_ovflpage(hashp, last_bfp); 392 return (0); 393 } 394 395 /* 396 * Add the given pair to the page 397 * 398 * Returns: 399 * 0 ==> OK 400 * 1 ==> failure 401 */ 402 extern int 403 __addel(hashp, bufp, key, val) 404 HTAB *hashp; 405 BUFHEAD *bufp; 406 const DBT *key, *val; 407 { 408 register u_short *bp, *sop; 409 int do_expand; 410 411 bp = (u_short *)bufp->page; 412 do_expand = 0; 413 while (bp[0] && (bp[bp[0]] < REAL_KEY)) 414 /* Exception case */ 415 if (bp[2] < REAL_KEY && bp[bp[0]] != OVFLPAGE) { 416 /* This is a big-keydata pair */ 417 bufp = __add_ovflpage(hashp, bufp); 418 if (!bufp) 419 return (-1); 420 bp = (u_short *)bufp->page; 421 } else 422 /* Try to squeeze key on this page */ 423 if (FREESPACE(bp) > PAIRSIZE(key, val)) { 424 squeeze_key(bp, key, val); 425 return (0); 426 } else { 427 bufp = __get_buf(hashp, bp[bp[0] - 1], bufp, 0); 428 if (!bufp) 429 return (-1); 430 bp = (u_short *)bufp->page; 431 } 432 433 if (PAIRFITS(bp, key, val)) 434 putpair(bufp->page, key, val); 435 else { 436 do_expand = 1; 437 bufp = __add_ovflpage(hashp, bufp); 438 if (!bufp) 439 return (-1); 440 sop = (u_short *)bufp->page; 441 442 if (PAIRFITS(sop, key, val)) 443 putpair((char *)sop, key, val); 444 else 445 if (__big_insert(hashp, bufp, key, val)) 446 return (-1); 447 } 448 bufp->flags |= BUF_MOD; 449 /* 450 * If the average number of keys per bucket exceeds the fill factor, 451 * expand the table. 452 */ 453 hashp->NKEYS++; 454 if (do_expand || 455 (hashp->NKEYS / (hashp->MAX_BUCKET + 1) > hashp->FFACTOR)) 456 return (__expand_table(hashp)); 457 return (0); 458 } 459 460 /* 461 * 462 * Returns: 463 * pointer on success 464 * NULL on error 465 */ 466 extern BUFHEAD * 467 __add_ovflpage(hashp, bufp) 468 HTAB *hashp; 469 BUFHEAD *bufp; 470 { 471 register u_short *sp; 472 u_short ndx, ovfl_num; 473 #ifdef DEBUG1 474 int tmp1, tmp2; 475 #endif 476 sp = (u_short *)bufp->page; 477 478 /* Check if we are dynamically determining the fill factor */ 479 if (hashp->FFACTOR == DEF_FFACTOR) { 480 hashp->FFACTOR = sp[0] >> 1; 481 if (hashp->FFACTOR < MIN_FFACTOR) 482 hashp->FFACTOR = MIN_FFACTOR; 483 } 484 bufp->flags |= BUF_MOD; 485 ovfl_num = overflow_page(hashp); 486 #ifdef DEBUG1 487 tmp1 = bufp->addr; 488 tmp2 = bufp->ovfl ? bufp->ovfl->addr : 0; 489 #endif 490 if (!ovfl_num || !(bufp->ovfl = __get_buf(hashp, ovfl_num, bufp, 1))) 491 return (NULL); 492 bufp->ovfl->flags |= BUF_MOD; 493 #ifdef DEBUG1 494 (void)fprintf(stderr, "ADDOVFLPAGE: %d->ovfl was %d is now %d\n", 495 tmp1, tmp2, bufp->ovfl->addr); 496 #endif 497 ndx = sp[0]; 498 /* 499 * Since a pair is allocated on a page only if there's room to add 500 * an overflow page, we know that the OVFL information will fit on 501 * the page. 502 */ 503 sp[ndx + 4] = OFFSET(sp); 504 sp[ndx + 3] = FREESPACE(sp) - OVFLSIZE; 505 sp[ndx + 1] = ovfl_num; 506 sp[ndx + 2] = OVFLPAGE; 507 sp[0] = ndx + 2; 508 #ifdef HASH_STATISTICS 509 hash_overflows++; 510 #endif 511 return (bufp->ovfl); 512 } 513 514 /* 515 * Returns: 516 * 0 indicates SUCCESS 517 * -1 indicates FAILURE 518 */ 519 extern int 520 __get_page(hashp, p, bucket, is_bucket, is_disk, is_bitmap) 521 HTAB *hashp; 522 char *p; 523 u_int bucket; 524 int is_bucket, is_disk, is_bitmap; 525 { 526 register int fd, page, size; 527 int rsize; 528 u_short *bp; 529 530 fd = hashp->fp; 531 size = hashp->BSIZE; 532 533 if ((fd == -1) || !is_disk) { 534 PAGE_INIT(p); 535 return (0); 536 } 537 if (is_bucket) 538 page = BUCKET_TO_PAGE(bucket); 539 else 540 page = OADDR_TO_PAGE(bucket); 541 if ((lseek(fd, (off_t)page << hashp->BSHIFT, SEEK_SET) == -1) || 542 ((rsize = read(fd, p, size)) == -1)) 543 return (-1); 544 bp = (u_short *)p; 545 if (!rsize) 546 bp[0] = 0; /* We hit the EOF, so initialize a new page */ 547 else 548 if (rsize != size) { 549 errno = EFTYPE; 550 return (-1); 551 } 552 if (!is_bitmap && !bp[0]) { 553 PAGE_INIT(p); 554 } else 555 if (hashp->LORDER != BYTE_ORDER) { 556 register int i, max; 557 558 if (is_bitmap) { 559 max = hashp->BSIZE >> 2; /* divide by 4 */ 560 for (i = 0; i < max; i++) 561 BLSWAP(((long *)p)[i]); 562 } else { 563 BSSWAP(bp[0]); 564 max = bp[0] + 2; 565 for (i = 1; i <= max; i++) 566 BSSWAP(bp[i]); 567 } 568 } 569 return (0); 570 } 571 572 /* 573 * Write page p to disk 574 * 575 * Returns: 576 * 0 ==> OK 577 * -1 ==>failure 578 */ 579 extern int 580 __put_page(hashp, p, bucket, is_bucket, is_bitmap) 581 HTAB *hashp; 582 char *p; 583 u_int bucket; 584 int is_bucket, is_bitmap; 585 { 586 register int fd, page, size; 587 int wsize; 588 589 size = hashp->BSIZE; 590 if ((hashp->fp == -1) && open_temp(hashp)) 591 return (-1); 592 fd = hashp->fp; 593 594 if (hashp->LORDER != BYTE_ORDER) { 595 register int i; 596 register int max; 597 598 if (is_bitmap) { 599 max = hashp->BSIZE >> 2; /* divide by 4 */ 600 for (i = 0; i < max; i++) 601 BLSWAP(((long *)p)[i]); 602 } else { 603 max = ((u_short *)p)[0] + 2; 604 for (i = 0; i <= max; i++) 605 BSSWAP(((u_short *)p)[i]); 606 } 607 } 608 if (is_bucket) 609 page = BUCKET_TO_PAGE(bucket); 610 else 611 page = OADDR_TO_PAGE(bucket); 612 if ((lseek(fd, (off_t)page << hashp->BSHIFT, SEEK_SET) == -1) || 613 ((wsize = write(fd, p, size)) == -1)) 614 /* Errno is set */ 615 return (-1); 616 if (wsize != size) { 617 errno = EFTYPE; 618 return (-1); 619 } 620 return (0); 621 } 622 623 #define BYTE_MASK ((1 << INT_BYTE_SHIFT) -1) 624 /* 625 * Initialize a new bitmap page. Bitmap pages are left in memory 626 * once they are read in. 627 */ 628 extern int 629 __init_bitmap(hashp, pnum, nbits, ndx) 630 HTAB *hashp; 631 int pnum, nbits, ndx; 632 { 633 u_long *ip; 634 int clearbytes, clearints; 635 636 if (!(ip = malloc(hashp->BSIZE))) 637 return (1); 638 hashp->nmaps++; 639 clearints = ((nbits - 1) >> INT_BYTE_SHIFT) + 1; 640 clearbytes = clearints << INT_TO_BYTE; 641 (void)memset((char *)ip, 0, clearbytes); 642 (void)memset(((char *)ip) + clearbytes, 0xFF, 643 hashp->BSIZE - clearbytes); 644 ip[clearints - 1] = ALL_SET << (nbits & BYTE_MASK); 645 SETBIT(ip, 0); 646 hashp->BITMAPS[ndx] = (u_short)pnum; 647 hashp->mapp[ndx] = ip; 648 return (0); 649 } 650 651 static u_long 652 first_free(map) 653 u_long map; 654 { 655 register u_long i, mask; 656 657 mask = 0x1; 658 for (i = 0; i < BITS_PER_MAP; i++) { 659 if (!(mask & map)) 660 return (i); 661 mask = mask << 1; 662 } 663 return (i); 664 } 665 666 static u_short 667 overflow_page(hashp) 668 HTAB *hashp; 669 { 670 register u_long *freep; 671 register int max_free, offset, splitnum; 672 u_short addr; 673 int bit, first_page, free_bit, free_page, i, in_use_bits, j; 674 #ifdef DEBUG2 675 int tmp1, tmp2; 676 #endif 677 splitnum = hashp->OVFL_POINT; 678 max_free = hashp->SPARES[splitnum]; 679 680 free_page = (max_free - 1) >> (hashp->BSHIFT + BYTE_SHIFT); 681 free_bit = (max_free - 1) & ((hashp->BSIZE << BYTE_SHIFT) - 1); 682 683 /* Look through all the free maps to find the first free block */ 684 first_page = hashp->LAST_FREED >>(hashp->BSHIFT + BYTE_SHIFT); 685 for ( i = first_page; i <= free_page; i++ ) { 686 if (!(freep = (u_long *)hashp->mapp[i]) && 687 !(freep = fetch_bitmap(hashp, i))) 688 return (NULL); 689 if (i == free_page) 690 in_use_bits = free_bit; 691 else 692 in_use_bits = (hashp->BSIZE << BYTE_SHIFT) - 1; 693 694 if (i == first_page) { 695 bit = hashp->LAST_FREED & 696 ((hashp->BSIZE << BYTE_SHIFT) - 1); 697 j = bit / BITS_PER_MAP; 698 bit = bit & ~(BITS_PER_MAP - 1); 699 } else { 700 bit = 0; 701 j = 0; 702 } 703 for (; bit <= in_use_bits; j++, bit += BITS_PER_MAP) 704 if (freep[j] != ALL_SET) 705 goto found; 706 } 707 708 /* No Free Page Found */ 709 hashp->LAST_FREED = hashp->SPARES[splitnum]; 710 hashp->SPARES[splitnum]++; 711 offset = hashp->SPARES[splitnum] - 712 (splitnum ? hashp->SPARES[splitnum - 1] : 0); 713 714 #define OVMSG "HASH: Out of overflow pages. Increase page size\n" 715 if (offset > SPLITMASK) { 716 if (++splitnum >= NCACHED) { 717 (void)write(STDERR_FILENO, OVMSG, sizeof(OVMSG) - 1); 718 return (NULL); 719 } 720 hashp->OVFL_POINT = splitnum; 721 hashp->SPARES[splitnum] = hashp->SPARES[splitnum-1]; 722 hashp->SPARES[splitnum-1]--; 723 offset = 1; 724 } 725 726 /* Check if we need to allocate a new bitmap page */ 727 if (free_bit == (hashp->BSIZE << BYTE_SHIFT) - 1) { 728 free_page++; 729 if (free_page >= NCACHED) { 730 (void)write(STDERR_FILENO, OVMSG, sizeof(OVMSG) - 1); 731 return (NULL); 732 } 733 /* 734 * This is tricky. The 1 indicates that you want the new page 735 * allocated with 1 clear bit. Actually, you are going to 736 * allocate 2 pages from this map. The first is going to be 737 * the map page, the second is the overflow page we were 738 * looking for. The init_bitmap routine automatically, sets 739 * the first bit of itself to indicate that the bitmap itself 740 * is in use. We would explicitly set the second bit, but 741 * don't have to if we tell init_bitmap not to leave it clear 742 * in the first place. 743 */ 744 if (__init_bitmap(hashp, (int)OADDR_OF(splitnum, offset), 745 1, free_page)) 746 return (NULL); 747 hashp->SPARES[splitnum]++; 748 #ifdef DEBUG2 749 free_bit = 2; 750 #endif 751 offset++; 752 if (offset > SPLITMASK) { 753 if (++splitnum >= NCACHED) { 754 (void)write(STDERR_FILENO, OVMSG, 755 sizeof(OVMSG) - 1); 756 return (NULL); 757 } 758 hashp->OVFL_POINT = splitnum; 759 hashp->SPARES[splitnum] = hashp->SPARES[splitnum-1]; 760 hashp->SPARES[splitnum-1]--; 761 offset = 0; 762 } 763 } else { 764 /* 765 * Free_bit addresses the last used bit. Bump it to address 766 * the first available bit. 767 */ 768 free_bit++; 769 SETBIT(freep, free_bit); 770 } 771 772 /* Calculate address of the new overflow page */ 773 addr = OADDR_OF(splitnum, offset); 774 #ifdef DEBUG2 775 (void)fprintf(stderr, "OVERFLOW_PAGE: ADDR: %d BIT: %d PAGE %d\n", 776 addr, free_bit, free_page); 777 #endif 778 return (addr); 779 780 found: 781 bit = bit + first_free(freep[j]); 782 SETBIT(freep, bit); 783 #ifdef DEBUG2 784 tmp1 = bit; 785 tmp2 = i; 786 #endif 787 /* 788 * Bits are addressed starting with 0, but overflow pages are addressed 789 * beginning at 1. Bit is a bit addressnumber, so we need to increment 790 * it to convert it to a page number. 791 */ 792 bit = 1 + bit + (i * (hashp->BSIZE << BYTE_SHIFT)); 793 if (bit >= hashp->LAST_FREED) 794 hashp->LAST_FREED = bit - 1; 795 796 /* Calculate the split number for this page */ 797 for (i = 0; (i < splitnum) && (bit > hashp->SPARES[i]); i++); 798 offset = (i ? bit - hashp->SPARES[i - 1] : bit); 799 if (offset >= SPLITMASK) 800 return (NULL); /* Out of overflow pages */ 801 addr = OADDR_OF(i, offset); 802 #ifdef DEBUG2 803 (void)fprintf(stderr, "OVERFLOW_PAGE: ADDR: %d BIT: %d PAGE %d\n", 804 addr, tmp1, tmp2); 805 #endif 806 807 /* Allocate and return the overflow page */ 808 return (addr); 809 } 810 811 /* 812 * Mark this overflow page as free. 813 */ 814 extern void 815 __free_ovflpage(hashp, obufp) 816 HTAB *hashp; 817 BUFHEAD *obufp; 818 { 819 register u_short addr; 820 u_long *freep; 821 int bit_address, free_page, free_bit; 822 u_short ndx; 823 824 addr = obufp->addr; 825 #ifdef DEBUG1 826 (void)fprintf(stderr, "Freeing %d\n", addr); 827 #endif 828 ndx = (((u_short)addr) >> SPLITSHIFT); 829 bit_address = 830 (ndx ? hashp->SPARES[ndx - 1] : 0) + (addr & SPLITMASK) - 1; 831 if (bit_address < hashp->LAST_FREED) 832 hashp->LAST_FREED = bit_address; 833 free_page = (bit_address >> (hashp->BSHIFT + BYTE_SHIFT)); 834 free_bit = bit_address & ((hashp->BSIZE << BYTE_SHIFT) - 1); 835 836 if (!(freep = hashp->mapp[free_page])) 837 freep = fetch_bitmap(hashp, free_page); 838 #ifdef DEBUG 839 /* 840 * This had better never happen. It means we tried to read a bitmap 841 * that has already had overflow pages allocated off it, and we 842 * failed to read it from the file. 843 */ 844 if (!freep) 845 assert(0); 846 #endif 847 CLRBIT(freep, free_bit); 848 #ifdef DEBUG2 849 (void)fprintf(stderr, "FREE_OVFLPAGE: ADDR: %d BIT: %d PAGE %d\n", 850 obufp->addr, free_bit, free_page); 851 #endif 852 __reclaim_buf(hashp, obufp); 853 } 854 855 /* 856 * Returns: 857 * 0 success 858 * -1 failure 859 */ 860 static int 861 open_temp(hashp) 862 HTAB *hashp; 863 { 864 sigset_t set, oset; 865 static char namestr[] = "_hashXXXXXX"; 866 867 /* Block signals; make sure file goes away at process exit. */ 868 (void)sigfillset(&set); 869 (void)sigprocmask(SIG_BLOCK, &set, &oset); 870 if ((hashp->fp = mkstemp(namestr)) != -1) { 871 (void)unlink(namestr); 872 (void)fcntl(hashp->fp, F_SETFD, 1); 873 } 874 (void)sigprocmask(SIG_SETMASK, &oset, (sigset_t *)NULL); 875 return (hashp->fp != -1 ? 0 : -1); 876 } 877 878 /* 879 * We have to know that the key will fit, but the last entry on the page is 880 * an overflow pair, so we need to shift things. 881 */ 882 static void 883 squeeze_key(sp, key, val) 884 u_short *sp; 885 const DBT *key, *val; 886 { 887 register char *p; 888 u_short free_space, n, off, pageno; 889 890 p = (char *)sp; 891 n = sp[0]; 892 free_space = FREESPACE(sp); 893 off = OFFSET(sp); 894 895 pageno = sp[n - 1]; 896 off -= key->size; 897 sp[n - 1] = off; 898 memmove(p + off, key->data, key->size); 899 off -= val->size; 900 sp[n] = off; 901 memmove(p + off, val->data, val->size); 902 sp[0] = n + 2; 903 sp[n + 1] = pageno; 904 sp[n + 2] = OVFLPAGE; 905 FREESPACE(sp) = free_space - PAIRSIZE(key, val); 906 OFFSET(sp) = off; 907 } 908 909 static u_long * 910 fetch_bitmap(hashp, ndx) 911 HTAB *hashp; 912 int ndx; 913 { 914 if (ndx >= hashp->nmaps || 915 !(hashp->mapp[ndx] = malloc(hashp->BSIZE)) || 916 __get_page(hashp, (char *)hashp->mapp[ndx], 917 hashp->BITMAPS[ndx], 0, 1, 1)) 918 return (NULL); 919 return (hashp->mapp[ndx]); 920 } 921 922 #ifdef DEBUG4 923 int 924 print_chain(addr) 925 int addr; 926 { 927 BUFHEAD *bufp; 928 short *bp, oaddr; 929 930 (void)fprintf(stderr, "%d ", addr); 931 bufp = __get_buf(hashp, addr, NULL, 0); 932 bp = (short *)bufp->page; 933 while (bp[0] && ((bp[bp[0]] == OVFLPAGE) || 934 ((bp[0] > 2) && bp[2] < REAL_KEY))) { 935 oaddr = bp[bp[0] - 1]; 936 (void)fprintf(stderr, "%d ", (int)oaddr); 937 bufp = __get_buf(hashp, (int)oaddr, bufp, 0); 938 bp = (short *)bufp->page; 939 } 940 (void)fprintf(stderr, "\n"); 941 } 942 #endif 943
Indexes created Wed Oct 22 06:10:02 GMT 2025