1/* Caching facts about regions of the buffer, for optimization. 2 Copyright (C) 1985, 1986, 1987, 1988, 1989, 1993, 1995, 2001, 2002, 2003, 3 2004, 2005, 2006, 2007 Free Software Foundation, Inc. 4 5This file is part of GNU Emacs. 6 7GNU Emacs is free software; you can redistribute it and/or modify 8it under the terms of the GNU General Public License as published by 9the Free Software Foundation; either version 2, or (at your option) 10any later version. 11 12GNU Emacs is distributed in the hope that it will be useful, 13but WITHOUT ANY WARRANTY; without even the implied warranty of 14MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15GNU General Public License for more details. 16 17You should have received a copy of the GNU General Public License 18along with GNU Emacs; see the file COPYING. If not, write to 19the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 20Boston, MA 02110-1301, USA. */ 21 22 23#include <config.h> 24#include <stdio.h> 25 26#include "lisp.h" 27#include "buffer.h" 28#include "region-cache.h" 29 30 31/* Data structures. */ 32 33/* The region cache. 34 35 We want something that maps character positions in a buffer onto 36 values. The representation should deal well with long runs of 37 characters with the same value. 38 39 The tricky part: the representation should be very cheap to 40 maintain in the presence of many insertions and deletions. If the 41 overhead of maintaining the cache is too high, the speedups it 42 offers will be worthless. 43 44 45 We represent the region cache as a sorted array of struct 46 boundary's, each of which contains a buffer position and a value; 47 the value applies to all the characters after the buffer position, 48 until the position of the next boundary, or the end of the buffer. 49 50 The cache always has a boundary whose position is BUF_BEG, so 51 there's always a value associated with every character in the 52 buffer. Since the cache is sorted, this is always the first 53 element of the cache. 54 55 To facilitate the insertion and deletion of boundaries in the 56 cache, the cache has a gap, just like Emacs's text buffers do. 57 58 To help boundary positions float along with insertions and 59 deletions, all boundary positions before the cache gap are stored 60 relative to BUF_BEG (buf) (thus they're >= 0), and all boundary 61 positions after the gap are stored relative to BUF_Z (buf) (thus 62 they're <= 0). Look at BOUNDARY_POS to see this in action. See 63 revalidate_region_cache to see how this helps. */ 64 65struct boundary { 66 int pos; 67 int value; 68}; 69 70struct region_cache { 71 /* A sorted array of locations where the known-ness of the buffer 72 changes. */ 73 struct boundary *boundaries; 74 75 /* boundaries[gap_start ... gap_start + gap_len - 1] is the gap. */ 76 int gap_start, gap_len; 77 78 /* The number of elements allocated to boundaries, not including the 79 gap. */ 80 int cache_len; 81 82 /* The areas that haven't changed since the last time we cleaned out 83 invalid entries from the cache. These overlap when the buffer is 84 entirely unchanged. */ 85 int beg_unchanged, end_unchanged; 86 87 /* The first and last positions in the buffer. Because boundaries 88 store their positions relative to the start (BEG) and end (Z) of 89 the buffer, knowing these positions allows us to accurately 90 interpret positions without having to pass the buffer structure 91 or its endpoints around all the time. 92 93 Yes, buffer_beg is always 1. It's there for symmetry with 94 buffer_end and the BEG and BUF_BEG macros. */ 95 int buffer_beg, buffer_end; 96}; 97 98/* Return the position of boundary i in cache c. */ 99#define BOUNDARY_POS(c, i) \ 100 ((i) < (c)->gap_start \ 101 ? (c)->buffer_beg + (c)->boundaries[(i)].pos \ 102 : (c)->buffer_end + (c)->boundaries[(c)->gap_len + (i)].pos) 103 104/* Return the value for text after boundary i in cache c. */ 105#define BOUNDARY_VALUE(c, i) \ 106 ((i) < (c)->gap_start \ 107 ? (c)->boundaries[(i)].value \ 108 : (c)->boundaries[(c)->gap_len + (i)].value) 109 110/* Set the value for text after boundary i in cache c to v. */ 111#define SET_BOUNDARY_VALUE(c, i, v) \ 112 ((i) < (c)->gap_start \ 113 ? ((c)->boundaries[(i)].value = (v))\ 114 : ((c)->boundaries[(c)->gap_len + (i)].value = (v))) 115 116 117/* How many elements to add to the gap when we resize the buffer. */ 118#define NEW_CACHE_GAP (40) 119 120/* See invalidate_region_cache; if an invalidation would throw away 121 information about this many characters, call 122 revalidate_region_cache before doing the new invalidation, to 123 preserve that information, instead of throwing it away. */ 124#define PRESERVE_THRESHOLD (500) 125 126static void revalidate_region_cache (); 127 128 129/* Interface: Allocating, initializing, and disposing of region caches. */ 130 131struct region_cache * 132new_region_cache () 133{ 134 struct region_cache *c 135 = (struct region_cache *) xmalloc (sizeof (struct region_cache)); 136 137 c->gap_start = 0; 138 c->gap_len = NEW_CACHE_GAP; 139 c->cache_len = 0; 140 c->boundaries = 141 (struct boundary *) xmalloc ((c->gap_len + c->cache_len) 142 * sizeof (*c->boundaries)); 143 144 c->beg_unchanged = 0; 145 c->end_unchanged = 0; 146 c->buffer_beg = BEG; 147 c->buffer_end = BEG; 148 149 /* Insert the boundary for the buffer start. */ 150 c->cache_len++; 151 c->gap_len--; 152 c->gap_start++; 153 c->boundaries[0].pos = 0; /* from buffer_beg */ 154 c->boundaries[0].value = 0; 155 156 return c; 157} 158 159void 160free_region_cache (c) 161 struct region_cache *c; 162{ 163 xfree (c->boundaries); 164 xfree (c); 165} 166 167 168/* Finding positions in the cache. */ 169 170/* Return the index of the last boundary in cache C at or before POS. 171 In other words, return the boundary that specifies the value for 172 the region POS..(POS + 1). 173 174 This operation should be logarithmic in the number of cache 175 entries. It would be nice if it took advantage of locality of 176 reference, too, by searching entries near the last entry found. */ 177static int 178find_cache_boundary (c, pos) 179 struct region_cache *c; 180 int pos; 181{ 182 int low = 0, high = c->cache_len; 183 184 while (low + 1 < high) 185 { 186 /* mid is always a valid index, because low < high and ">> 1" 187 rounds down. */ 188 int mid = (low + high) >> 1; 189 int boundary = BOUNDARY_POS (c, mid); 190 191 if (pos < boundary) 192 high = mid; 193 else 194 low = mid; 195 } 196 197 /* Some testing. */ 198 if (BOUNDARY_POS (c, low) > pos 199 || (low + 1 < c->cache_len 200 && BOUNDARY_POS (c, low + 1) <= pos)) 201 abort (); 202 203 return low; 204} 205 206 207 208/* Moving the cache gap around, inserting, and deleting. */ 209 210 211/* Move the gap of cache C to index POS, and make sure it has space 212 for at least MIN_SIZE boundaries. */ 213static void 214move_cache_gap (c, pos, min_size) 215 struct region_cache *c; 216 int pos; 217 int min_size; 218{ 219 /* Copy these out of the cache and into registers. */ 220 int gap_start = c->gap_start; 221 int gap_len = c->gap_len; 222 int buffer_beg = c->buffer_beg; 223 int buffer_end = c->buffer_end; 224 225 if (pos < 0 226 || pos > c->cache_len) 227 abort (); 228 229 /* We mustn't ever try to put the gap before the dummy start 230 boundary. That must always be start-relative. */ 231 if (pos == 0) 232 abort (); 233 234 /* Need we move the gap right? */ 235 while (gap_start < pos) 236 { 237 /* Copy one boundary from after to before the gap, and 238 convert its position to start-relative. */ 239 c->boundaries[gap_start].pos 240 = (buffer_end 241 + c->boundaries[gap_start + gap_len].pos 242 - buffer_beg); 243 c->boundaries[gap_start].value 244 = c->boundaries[gap_start + gap_len].value; 245 gap_start++; 246 } 247 248 /* To enlarge the gap, we need to re-allocate the boundary array, and 249 then shift the area after the gap to the new end. Since the cost 250 is proportional to the amount of stuff after the gap, we do the 251 enlargement here, after a right shift but before a left shift, 252 when the portion after the gap is smallest. */ 253 if (gap_len < min_size) 254 { 255 int i; 256 257 /* Always make at least NEW_CACHE_GAP elements, as long as we're 258 expanding anyway. */ 259 if (min_size < NEW_CACHE_GAP) 260 min_size = NEW_CACHE_GAP; 261 262 c->boundaries = 263 (struct boundary *) xrealloc (c->boundaries, 264 ((min_size + c->cache_len) 265 * sizeof (*c->boundaries))); 266 267 /* Some systems don't provide a version of the copy routine that 268 can be trusted to shift memory upward into an overlapping 269 region. memmove isn't widely available. */ 270 min_size -= gap_len; 271 for (i = c->cache_len - 1; i >= gap_start; i--) 272 { 273 c->boundaries[i + min_size].pos = c->boundaries[i + gap_len].pos; 274 c->boundaries[i + min_size].value = c->boundaries[i + gap_len].value; 275 } 276 277 gap_len = min_size; 278 } 279 280 /* Need we move the gap left? */ 281 while (pos < gap_start) 282 { 283 gap_start--; 284 285 /* Copy one region from before to after the gap, and 286 convert its position to end-relative. */ 287 c->boundaries[gap_start + gap_len].pos 288 = c->boundaries[gap_start].pos + buffer_beg - buffer_end; 289 c->boundaries[gap_start + gap_len].value 290 = c->boundaries[gap_start].value; 291 } 292 293 /* Assign these back into the cache. */ 294 c->gap_start = gap_start; 295 c->gap_len = gap_len; 296} 297 298 299/* Insert a new boundary in cache C; it will have cache index INDEX, 300 and have the specified POS and VALUE. */ 301static void 302insert_cache_boundary (c, index, pos, value) 303 struct region_cache *c; 304 int index; 305 int pos, value; 306{ 307 /* index must be a valid cache index. */ 308 if (index < 0 || index > c->cache_len) 309 abort (); 310 311 /* We must never want to insert something before the dummy first 312 boundary. */ 313 if (index == 0) 314 abort (); 315 316 /* We must only be inserting things in order. */ 317 if (! (BOUNDARY_POS (c, index-1) < pos 318 && (index == c->cache_len 319 || pos < BOUNDARY_POS (c, index)))) 320 abort (); 321 322 /* The value must be different from the ones around it. However, we 323 temporarily create boundaries that establish the same value as 324 the subsequent boundary, so we're not going to flag that case. */ 325 if (BOUNDARY_VALUE (c, index-1) == value) 326 abort (); 327 328 move_cache_gap (c, index, 1); 329 330 c->boundaries[index].pos = pos - c->buffer_beg; 331 c->boundaries[index].value = value; 332 c->gap_start++; 333 c->gap_len--; 334 c->cache_len++; 335} 336 337 338/* Delete the i'th entry from cache C if START <= i < END. */ 339 340static void 341delete_cache_boundaries (c, start, end) 342 struct region_cache *c; 343 int start, end; 344{ 345 int len = end - start; 346 347 /* Gotta be in range. */ 348 if (start < 0 349 || end > c->cache_len) 350 abort (); 351 352 /* Gotta be in order. */ 353 if (start > end) 354 abort (); 355 356 /* Can't delete the dummy entry. */ 357 if (start == 0 358 && end >= 1) 359 abort (); 360 361 /* Minimize gap motion. If we're deleting nothing, do nothing. */ 362 if (len == 0) 363 ; 364 /* If the gap is before the region to delete, delete from the start 365 forward. */ 366 else if (c->gap_start <= start) 367 { 368 move_cache_gap (c, start, 0); 369 c->gap_len += len; 370 } 371 /* If the gap is after the region to delete, delete from the end 372 backward. */ 373 else if (end <= c->gap_start) 374 { 375 move_cache_gap (c, end, 0); 376 c->gap_start -= len; 377 c->gap_len += len; 378 } 379 /* If the gap is in the region to delete, just expand it. */ 380 else 381 { 382 c->gap_start = start; 383 c->gap_len += len; 384 } 385 386 c->cache_len -= len; 387} 388 389 390 391/* Set the value for a region. */ 392 393/* Set the value in cache C for the region START..END to VALUE. */ 394static void 395set_cache_region (c, start, end, value) 396 struct region_cache *c; 397 int start, end; 398 int value; 399{ 400 if (start > end) 401 abort (); 402 if (start < c->buffer_beg 403 || end > c->buffer_end) 404 abort (); 405 406 /* Eliminate this case; then we can assume that start and end-1 are 407 both the locations of real characters in the buffer. */ 408 if (start == end) 409 return; 410 411 { 412 /* We need to make sure that there are no boundaries in the area 413 between start to end; the whole area will have the same value, 414 so those boundaries will not be necessary. 415 416 Let start_ix be the cache index of the boundary governing the 417 first character of start..end, and let end_ix be the cache 418 index of the earliest boundary after the last character in 419 start..end. (This tortured terminology is intended to answer 420 all the "< or <=?" sort of questions.) */ 421 int start_ix = find_cache_boundary (c, start); 422 int end_ix = find_cache_boundary (c, end - 1) + 1; 423 424 /* We must remember the value established by the last boundary 425 before end; if that boundary's domain stretches beyond end, 426 we'll need to create a new boundary at end, and that boundary 427 must have that remembered value. */ 428 int value_at_end = BOUNDARY_VALUE (c, end_ix - 1); 429 430 /* Delete all boundaries strictly within start..end; this means 431 those whose indices are between start_ix (exclusive) and end_ix 432 (exclusive). */ 433 delete_cache_boundaries (c, start_ix + 1, end_ix); 434 435 /* Make sure we have the right value established going in to 436 start..end from the left, and no unnecessary boundaries. */ 437 if (BOUNDARY_POS (c, start_ix) == start) 438 { 439 /* Is this boundary necessary? If no, remove it; if yes, set 440 its value. */ 441 if (start_ix > 0 442 && BOUNDARY_VALUE (c, start_ix - 1) == value) 443 { 444 delete_cache_boundaries (c, start_ix, start_ix + 1); 445 start_ix--; 446 } 447 else 448 SET_BOUNDARY_VALUE (c, start_ix, value); 449 } 450 else 451 { 452 /* Do we need to add a new boundary here? */ 453 if (BOUNDARY_VALUE (c, start_ix) != value) 454 { 455 insert_cache_boundary (c, start_ix + 1, start, value); 456 start_ix++; 457 } 458 } 459 460 /* This is equivalent to letting end_ix float (like a buffer 461 marker does) with the insertions and deletions we may have 462 done. */ 463 end_ix = start_ix + 1; 464 465 /* Make sure we have the correct value established as we leave 466 start..end to the right. */ 467 if (end == c->buffer_end) 468 /* There is no text after start..end; nothing to do. */ 469 ; 470 else if (end_ix >= c->cache_len 471 || end < BOUNDARY_POS (c, end_ix)) 472 { 473 /* There is no boundary at end, but we may need one. */ 474 if (value_at_end != value) 475 insert_cache_boundary (c, end_ix, end, value_at_end); 476 } 477 else 478 { 479 /* There is a boundary at end; should it be there? */ 480 if (value == BOUNDARY_VALUE (c, end_ix)) 481 delete_cache_boundaries (c, end_ix, end_ix + 1); 482 } 483 } 484} 485 486 487 488/* Interface: Invalidating the cache. Private: Re-validating the cache. */ 489 490/* Indicate that a section of BUF has changed, to invalidate CACHE. 491 HEAD is the number of chars unchanged at the beginning of the buffer. 492 TAIL is the number of chars unchanged at the end of the buffer. 493 NOTE: this is *not* the same as the ending position of modified 494 region. 495 (This way of specifying regions makes more sense than absolute 496 buffer positions in the presence of insertions and deletions; the 497 args to pass are the same before and after such an operation.) */ 498void 499invalidate_region_cache (buf, c, head, tail) 500 struct buffer *buf; 501 struct region_cache *c; 502 int head, tail; 503{ 504 /* Let chead = c->beg_unchanged, and 505 ctail = c->end_unchanged. 506 If z-tail < beg+chead by a large amount, or 507 z-ctail < beg+head by a large amount, 508 509 then cutting back chead and ctail to head and tail would lose a 510 lot of information that we could preserve by revalidating the 511 cache before processing this invalidation. Losing that 512 information may be more costly than revalidating the cache now. 513 So go ahead and call revalidate_region_cache if it seems that it 514 might be worthwhile. */ 515 if (((BUF_BEG (buf) + c->beg_unchanged) - (BUF_Z (buf) - tail) 516 > PRESERVE_THRESHOLD) 517 || ((BUF_BEG (buf) + head) - (BUF_Z (buf) - c->end_unchanged) 518 > PRESERVE_THRESHOLD)) 519 revalidate_region_cache (buf, c); 520 521 522 if (head < c->beg_unchanged) 523 c->beg_unchanged = head; 524 if (tail < c->end_unchanged) 525 c->end_unchanged = tail; 526 527 /* We now know nothing about the region between the unchanged head 528 and the unchanged tail (call it the "modified region"), not even 529 its length. 530 531 If the modified region has shrunk in size (deletions do this), 532 then the cache may now contain boundaries originally located in 533 text that doesn't exist any more. 534 535 If the modified region has increased in size (insertions do 536 this), then there may now be boundaries in the modified region 537 whose positions are wrong. 538 539 Even calling BOUNDARY_POS on boundaries still in the unchanged 540 head or tail may well give incorrect answers now, since 541 c->buffer_beg and c->buffer_end may well be wrong now. (Well, 542 okay, c->buffer_beg never changes, so boundaries in the unchanged 543 head will still be okay. But it's the principle of the thing.) 544 545 So things are generally a mess. 546 547 But we don't clean up this mess here; that would be expensive, 548 and this function gets called every time any buffer modification 549 occurs. Rather, we can clean up everything in one swell foop, 550 accounting for all the modifications at once, by calling 551 revalidate_region_cache before we try to consult the cache the 552 next time. */ 553} 554 555 556/* Clean out any cache entries applying to the modified region, and 557 make the positions of the remaining entries accurate again. 558 559 After calling this function, the mess described in the comment in 560 invalidate_region_cache is cleaned up. 561 562 This function operates by simply throwing away everything it knows 563 about the modified region. It doesn't care exactly which 564 insertions and deletions took place; it just tosses it all. 565 566 For example, if you insert a single character at the beginning of 567 the buffer, and a single character at the end of the buffer (for 568 example), without calling this function in between the two 569 insertions, then the entire cache will be freed of useful 570 information. On the other hand, if you do manage to call this 571 function in between the two insertions, then the modified regions 572 will be small in both cases, no information will be tossed, and the 573 cache will know that it doesn't have knowledge of the first and 574 last characters any more. 575 576 Calling this function may be expensive; it does binary searches in 577 the cache, and causes cache gap motion. */ 578 579static void 580revalidate_region_cache (buf, c) 581 struct buffer *buf; 582 struct region_cache *c; 583{ 584 /* The boundaries now in the cache are expressed relative to the 585 buffer_beg and buffer_end values stored in the cache. Now, 586 buffer_beg and buffer_end may not be the same as BUF_BEG (buf) 587 and BUF_Z (buf), so we have two different "bases" to deal with 588 --- the cache's, and the buffer's. */ 589 590 /* If the entire buffer is still valid, don't waste time. Yes, this 591 should be a >, not a >=; think about what beg_unchanged and 592 end_unchanged get set to when the only change has been an 593 insertion. */ 594 if (c->buffer_beg + c->beg_unchanged 595 > c->buffer_end - c->end_unchanged) 596 return; 597 598 /* If all the text we knew about as of the last cache revalidation 599 is still there, then all of the information in the cache is still 600 valid. Because c->buffer_beg and c->buffer_end are out-of-date, 601 the modified region appears from the cache's point of view to be 602 a null region located someplace in the buffer. 603 604 Now, invalidating that empty string will have no actual affect on 605 the cache; instead, we need to update the cache's basis first 606 (which will give the modified region the same size in the cache 607 as it has in the buffer), and then invalidate the modified 608 region. */ 609 if (c->buffer_beg + c->beg_unchanged 610 == c->buffer_end - c->end_unchanged) 611 { 612 /* Move the gap so that all the boundaries in the unchanged head 613 are expressed beg-relative, and all the boundaries in the 614 unchanged tail are expressed end-relative. That done, we can 615 plug in the new buffer beg and end, and all the positions 616 will be accurate. 617 618 The boundary which has jurisdiction over the modified region 619 should be left before the gap. */ 620 move_cache_gap (c, 621 (find_cache_boundary (c, (c->buffer_beg 622 + c->beg_unchanged)) 623 + 1), 624 0); 625 626 c->buffer_beg = BUF_BEG (buf); 627 c->buffer_end = BUF_Z (buf); 628 629 /* Now that the cache's basis has been changed, the modified 630 region actually takes up some space in the cache, so we can 631 invalidate it. */ 632 set_cache_region (c, 633 c->buffer_beg + c->beg_unchanged, 634 c->buffer_end - c->end_unchanged, 635 0); 636 } 637 638 /* Otherwise, there is a non-empty region in the cache which 639 corresponds to the modified region of the buffer. */ 640 else 641 { 642 int modified_ix; 643 644 /* These positions are correct, relative to both the cache basis 645 and the buffer basis. */ 646 set_cache_region (c, 647 c->buffer_beg + c->beg_unchanged, 648 c->buffer_end - c->end_unchanged, 649 0); 650 651 /* Now the cache contains only boundaries that are in the 652 unchanged head and tail; we've disposed of any boundaries 653 whose positions we can't be sure of given the information 654 we've saved. 655 656 If we put the cache gap between the unchanged head and the 657 unchanged tail, we can adjust all the boundary positions at 658 once, simply by setting buffer_beg and buffer_end. 659 660 The boundary which has jurisdiction over the modified region 661 should be left before the gap. */ 662 modified_ix = 663 find_cache_boundary (c, (c->buffer_beg + c->beg_unchanged)) + 1; 664 move_cache_gap (c, modified_ix, 0); 665 666 c->buffer_beg = BUF_BEG (buf); 667 c->buffer_end = BUF_Z (buf); 668 669 /* Now, we may have shrunk the buffer when we changed the basis, 670 and brought the boundaries we created for the start and end 671 of the modified region together, giving them the same 672 position. If that's the case, we should collapse them into 673 one boundary. Or we may even delete them both, if the values 674 before and after them are the same. */ 675 if (modified_ix < c->cache_len 676 && (BOUNDARY_POS (c, modified_ix - 1) 677 == BOUNDARY_POS (c, modified_ix))) 678 { 679 int value_after = BOUNDARY_VALUE (c, modified_ix); 680 681 /* Should we remove both of the boundaries? Yes, if the 682 latter boundary is now establishing the same value that 683 the former boundary's predecessor does. */ 684 if (modified_ix - 1 > 0 685 && value_after == BOUNDARY_VALUE (c, modified_ix - 2)) 686 delete_cache_boundaries (c, modified_ix - 1, modified_ix + 1); 687 else 688 { 689 /* We do need a boundary here; collapse the two 690 boundaries into one. */ 691 SET_BOUNDARY_VALUE (c, modified_ix - 1, value_after); 692 delete_cache_boundaries (c, modified_ix, modified_ix + 1); 693 } 694 } 695 } 696 697 /* Now the entire cache is valid. */ 698 c->beg_unchanged 699 = c->end_unchanged 700 = c->buffer_end - c->buffer_beg; 701} 702 703 704/* Interface: Adding information to the cache. */ 705 706/* Assert that the region of BUF between START and END (absolute 707 buffer positions) is "known," for the purposes of CACHE (e.g. "has 708 no newlines", in the case of the line cache). */ 709void 710know_region_cache (buf, c, start, end) 711 struct buffer *buf; 712 struct region_cache *c; 713 int start, end; 714{ 715 revalidate_region_cache (buf, c); 716 717 set_cache_region (c, start, end, 1); 718} 719 720 721/* Interface: using the cache. */ 722 723/* Return true if the text immediately after POS in BUF is known, for 724 the purposes of CACHE. If NEXT is non-zero, set *NEXT to the nearest 725 position after POS where the knownness changes. */ 726int 727region_cache_forward (buf, c, pos, next) 728 struct buffer *buf; 729 struct region_cache *c; 730 int pos; 731 int *next; 732{ 733 revalidate_region_cache (buf, c); 734 735 { 736 int i = find_cache_boundary (c, pos); 737 int i_value = BOUNDARY_VALUE (c, i); 738 int j; 739 740 /* Beyond the end of the buffer is unknown, by definition. */ 741 if (pos >= BUF_Z (buf)) 742 { 743 if (next) *next = BUF_Z (buf); 744 i_value = 0; 745 } 746 else if (next) 747 { 748 /* Scan forward from i to find the next differing position. */ 749 for (j = i + 1; j < c->cache_len; j++) 750 if (BOUNDARY_VALUE (c, j) != i_value) 751 break; 752 753 if (j < c->cache_len) 754 *next = BOUNDARY_POS (c, j); 755 else 756 *next = BUF_Z (buf); 757 } 758 759 return i_value; 760 } 761} 762 763/* Return true if the text immediately before POS in BUF is known, for 764 the purposes of CACHE. If NEXT is non-zero, set *NEXT to the nearest 765 position before POS where the knownness changes. */ 766int region_cache_backward (buf, c, pos, next) 767 struct buffer *buf; 768 struct region_cache *c; 769 int pos; 770 int *next; 771{ 772 revalidate_region_cache (buf, c); 773 774 /* Before the beginning of the buffer is unknown, by 775 definition. */ 776 if (pos <= BUF_BEG (buf)) 777 { 778 if (next) *next = BUF_BEG (buf); 779 return 0; 780 } 781 782 { 783 int i = find_cache_boundary (c, pos - 1); 784 int i_value = BOUNDARY_VALUE (c, i); 785 int j; 786 787 if (next) 788 { 789 /* Scan backward from i to find the next differing position. */ 790 for (j = i - 1; j >= 0; j--) 791 if (BOUNDARY_VALUE (c, j) != i_value) 792 break; 793 794 if (j >= 0) 795 *next = BOUNDARY_POS (c, j + 1); 796 else 797 *next = BUF_BEG (buf); 798 } 799 800 return i_value; 801 } 802} 803 804 805/* Debugging: pretty-print a cache to the standard error output. */ 806 807void 808pp_cache (c) 809 struct region_cache *c; 810{ 811 int i; 812 int beg_u = c->buffer_beg + c->beg_unchanged; 813 int end_u = c->buffer_end - c->end_unchanged; 814 815 fprintf (stderr, 816 "basis: %d..%d modified: %d..%d\n", 817 c->buffer_beg, c->buffer_end, 818 beg_u, end_u); 819 820 for (i = 0; i < c->cache_len; i++) 821 { 822 int pos = BOUNDARY_POS (c, i); 823 824 putc (((pos < beg_u) ? 'v' 825 : (pos == beg_u) ? '-' 826 : ' '), 827 stderr); 828 putc (((pos > end_u) ? '^' 829 : (pos == end_u) ? '-' 830 : ' '), 831 stderr); 832 fprintf (stderr, "%d : %d\n", pos, BOUNDARY_VALUE (c, i)); 833 } 834} 835 836/* arch-tag: 98c29f3f-2ca2-4e3a-92f0-f2249200a17d 837 (do not change this comment) */ 838