hash_page.c revision 8870
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) 38static char sccsid[] = "@(#)hash_page.c 8.4 (Berkeley) 2/21/94"; 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 75static u_long *fetch_bitmap __P((HTAB *, int)); 76static u_long first_free __P((u_long)); 77static int open_temp __P((HTAB *)); 78static u_short overflow_page __P((HTAB *)); 79static void putpair __P((char *, const DBT *, const DBT *)); 80static void squeeze_key __P((u_short *, const DBT *, const DBT *)); 81static int ugly_split 82 __P((HTAB *, u_int, BUFHEAD *, BUFHEAD *, int, int)); 83 84#define PAGE_INIT(P) { \ 85 ((u_short *)(P))[0] = 0; \ 86 ((u_short *)(P))[1] = hashp->BSIZE - 3 * sizeof(u_short); \ 87 ((u_short *)(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 */ 95static void 96putpair(p, key, val) 97 char *p; 98 const DBT *key, *val; 99{ 100 register u_short *bp, n, off; 101 102 bp = (u_short *)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_short)); 119 bp[n + 2] = off; 120} 121 122/* 123 * Returns: 124 * 0 OK 125 * -1 error 126 */ 127extern int 128__delpair(hashp, bufp, ndx) 129 HTAB *hashp; 130 BUFHEAD *bufp; 131 register int ndx; 132{ 133 register u_short *bp, newoff; 134 register int n; 135 u_short pairlen; 136 137 bp = (u_short *)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_short); 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 */ 180extern int 181__split_page(hashp, obucket, nbucket) 182 HTAB *hashp; 183 u_int obucket, nbucket; 184{ 185 register BUFHEAD *new_bufp, *old_bufp; 186 register u_short *ino; 187 register char *np; 188 DBT key, val; 189 int n, ndx, retval; 190 u_short copyto, diff, off, moved; 191 char *op; 192 193 copyto = (u_short)hashp->BSIZE; 194 off = (u_short)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_short *)(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_short) * (ino[0] + 3); 248 OFFSET(ino) = copyto; 249 250#ifdef DEBUG3 251 (void)fprintf(stderr, "split %d/%d\n", 252 ((u_short *)np)[0] / 2, 253 ((u_short *)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 */ 276static int 277ugly_split(hashp, obucket, old_bufp, new_bufp, copyto, moved) 278 HTAB *hashp; 279 u_int 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_short *ino; /* Page keys come off of */ 286 register u_short *np; /* New page */ 287 register u_short *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_short n, off, ov_addr, scopyto; 293 char *cino; /* Character value of ino */ 294 295 bufp = old_bufp; 296 ino = (u_short *)old_bufp->page; 297 np = (u_short *)new_bufp->page; 298 op = (u_short *)old_bufp->page; 299 last_bfp = NULL; 300 scopyto = (u_short)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_short *)old_bufp->page; 312 new_bufp = ret.newp; 313 if (!new_bufp) 314 return (-1); 315 np = (u_short *)new_bufp->page; 316 bufp = ret.nextp; 317 if (!bufp) 318 return (0); 319 cino = (char *)bufp->page; 320 ino = (u_short *)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_short) * (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_short *)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_short *)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_short *)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 */ 397extern int 398__addel(hashp, bufp, key, val) 399 HTAB *hashp; 400 BUFHEAD *bufp; 401 const DBT *key, *val; 402{ 403 register u_short *bp, *sop; 404 int do_expand; 405 406 bp = (u_short *)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_short *)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_short *)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_short *)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 */ 464extern BUFHEAD * 465__add_ovflpage(hashp, bufp) 466 HTAB *hashp; 467 BUFHEAD *bufp; 468{ 469 register u_short *sp; 470 u_short ndx, ovfl_num; 471#ifdef DEBUG1 472 int tmp1, tmp2; 473#endif 474 sp = (u_short *)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 */ 517extern int 518__get_page(hashp, p, bucket, is_bucket, is_disk, is_bitmap) 519 HTAB *hashp; 520 char *p; 521 u_int bucket; 522 int is_bucket, is_disk, is_bitmap; 523{ 524 register int fd, page, size; 525 int rsize; 526 u_short *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_short *)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(((long *)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 */ 577extern int 578__put_page(hashp, p, bucket, is_bucket, is_bitmap) 579 HTAB *hashp; 580 char *p; 581 u_int 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(((long *)p)[i]); 600 } else { 601 max = ((u_short *)p)[0] + 2; 602 for (i = 0; i <= max; i++) 603 M_16_SWAP(((u_short *)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 */ 626extern int 627__init_bitmap(hashp, pnum, nbits, ndx) 628 HTAB *hashp; 629 int pnum, nbits, ndx; 630{ 631 u_long *ip; 632 int clearbytes, clearints; 633 634 if ((ip = (u_long *)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_short)pnum; 645 hashp->mapp[ndx] = ip; 646 return (0); 647} 648 649static u_long 650first_free(map) 651 u_long map; 652{ 653 register u_long 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 664static u_short 665overflow_page(hashp) 666 HTAB *hashp; 667{ 668 register u_long *freep; 669 register int max_free, offset, splitnum; 670 u_short 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_long *)hashp->mapp[i]) && 685 !(freep = fetch_bitmap(hashp, i))) 686 return (NULL); 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 (NULL); 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 (NULL); 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 (__init_bitmap(hashp, (int)OADDR_OF(splitnum, offset), 743 1, free_page)) 744 return (NULL); 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 (NULL); 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 778found: 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 (NULL); /* 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 */ 812extern void 813__free_ovflpage(hashp, obufp) 814 HTAB *hashp; 815 BUFHEAD *obufp; 816{ 817 register u_short addr; 818 u_long *freep; 819 int bit_address, free_page, free_bit; 820 u_short ndx; 821 822 addr = obufp->addr; 823#ifdef DEBUG1 824 (void)fprintf(stderr, "Freeing %d\n", addr); 825#endif 826 ndx = (((u_short)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 */ 858static int 859open_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 */ 880static void 881squeeze_key(sp, key, val) 882 u_short *sp; 883 const DBT *key, *val; 884{ 885 register char *p; 886 u_short 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 907static u_long * 908fetch_bitmap(hashp, ndx) 909 HTAB *hashp; 910 int ndx; 911{ 912 if (ndx >= hashp->nmaps) 913 return (NULL); 914 if ((hashp->mapp[ndx] = (u_long *)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 925int 926print_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 945