linenum.c revision 170257
1189251Ssam/* 2189251Ssam * Copyright (C) 1984-2007 Mark Nudelman 3189251Ssam * 4189251Ssam * You may distribute under the terms of either the GNU General Public 5189251Ssam * License or the Less License, as specified in the README file. 6189251Ssam * 7189251Ssam * For more information about less, or for information on how to 8189251Ssam * contact the author, see the README file. 9189251Ssam */ 10189251Ssam 11189251Ssam 12189251Ssam/* 13189251Ssam * Code to handle displaying line numbers. 14214734Srpaulo * 15214734Srpaulo * Finding the line number of a given file position is rather tricky. 16214734Srpaulo * We don't want to just start at the beginning of the file and 17189251Ssam * count newlines, because that is slow for large files (and also 18189251Ssam * wouldn't work if we couldn't get to the start of the file; e.g. 19189251Ssam * if input is a long pipe). 20189251Ssam * 21189251Ssam * So we use the function add_lnum to cache line numbers. 22189251Ssam * We try to be very clever and keep only the more interesting 23189251Ssam * line numbers when we run out of space in our table. A line 24189251Ssam * number is more interesting than another when it is far from 25189251Ssam * other line numbers. For example, we'd rather keep lines 26189251Ssam * 100,200,300 than 100,101,300. 200 is more interesting than 27189251Ssam * 101 because 101 can be derived very cheaply from 100, while 28189251Ssam * 200 is more expensive to derive from 100. 29189251Ssam * 30189251Ssam * The function currline() returns the line number of a given 31214734Srpaulo * position in the file. As a side effect, it calls add_lnum 32189251Ssam * to cache the line number. Therefore currline is occasionally 33214734Srpaulo * called to make sure we cache line numbers often enough. 34189251Ssam */ 35214734Srpaulo 36189251Ssam#include "less.h" 37189251Ssam 38189251Ssam/* 39189251Ssam * Structure to keep track of a line number and the associated file position. 40189251Ssam * A doubly-linked circular list of line numbers is kept ordered by line number. 41189251Ssam */ 42189251Ssamstruct linenum_info 43189251Ssam{ 44189251Ssam struct linenum_info *next; /* Link to next in the list */ 45189251Ssam struct linenum_info *prev; /* Line to previous in the list */ 46189251Ssam POSITION pos; /* File position */ 47189251Ssam POSITION gap; /* Gap between prev and next */ 48189251Ssam LINENUM line; /* Line number */ 49189251Ssam}; 50189251Ssam/* 51189251Ssam * "gap" needs some explanation: the gap of any particular line number 52214734Srpaulo * is the distance between the previous one and the next one in the list. 53189251Ssam * ("Distance" means difference in file position.) In other words, the 54189251Ssam * gap of a line number is the gap which would be introduced if this 55189251Ssam * line number were deleted. It is used to decide which one to replace 56189251Ssam * when we have a new one to insert and the table is full. 57189251Ssam */ 58189251Ssam 59189251Ssam#define NPOOL 50 /* Size of line number pool */ 60189251Ssam 61189251Ssam#define LONGTIME (2) /* In seconds */ 62189251Ssam 63189251Ssampublic int lnloop = 0; /* Are we in the line num loop? */ 64189251Ssam 65189251Ssamstatic struct linenum_info anchor; /* Anchor of the list */ 66214734Srpaulostatic struct linenum_info *freelist; /* Anchor of the unused entries */ 67189251Ssamstatic struct linenum_info pool[NPOOL]; /* The pool itself */ 68189251Ssamstatic struct linenum_info *spare; /* We always keep one spare entry */ 69189251Ssam 70252726Srpauloextern int linenums; 71189251Ssamextern int sigs; 72189251Ssamextern int sc_height; 73189251Ssam 74189251Ssam/* 75189251Ssam * Initialize the line number structures. 76189251Ssam */ 77189251Ssam public void 78189251Ssamclr_linenum() 79189251Ssam{ 80214734Srpaulo register struct linenum_info *p; 81189251Ssam 82189251Ssam /* 83189251Ssam * Put all the entries on the free list. 84189251Ssam * Leave one for the "spare". 85189251Ssam */ 86189251Ssam for (p = pool; p < &pool[NPOOL-2]; p++) 87189251Ssam p->next = p+1; 88189251Ssam pool[NPOOL-2].next = NULL; 89189251Ssam freelist = pool; 90189251Ssam 91214734Srpaulo spare = &pool[NPOOL-1]; 92214734Srpaulo 93189251Ssam /* 94189251Ssam * Initialize the anchor. 95252726Srpaulo */ 96214734Srpaulo anchor.next = anchor.prev = &anchor; 97214734Srpaulo anchor.gap = 0; 98214734Srpaulo anchor.pos = (POSITION)0; 99214734Srpaulo anchor.line = 1; 100214734Srpaulo} 101252726Srpaulo 102214734Srpaulo/* 103189251Ssam * Calculate the gap for an entry. 104189251Ssam */ 105189251Ssam static void 106252726Srpaulocalcgap(p) 107252726Srpaulo register struct linenum_info *p; 108252726Srpaulo{ 109252726Srpaulo /* 110252726Srpaulo * Don't bother to compute a gap for the anchor. 111252726Srpaulo * Also don't compute a gap for the last one in the list. 112252726Srpaulo * The gap for that last one should be considered infinite, 113252726Srpaulo * but we never look at it anyway. 114252726Srpaulo */ 115252726Srpaulo if (p == &anchor || p->next == &anchor) 116189251Ssam return; 117252726Srpaulo p->gap = p->next->pos - p->prev->pos; 118252726Srpaulo} 119252726Srpaulo 120252726Srpaulo/* 121189251Ssam * Add a new line number to the cache. 122189251Ssam * The specified position (pos) should be the file position of the 123189251Ssam * FIRST character in the specified line. 124189251Ssam */ 125252726Srpaulo public void 126189251Ssamadd_lnum(linenum, pos) 127189251Ssam LINENUM linenum; 128189251Ssam POSITION pos; 129189251Ssam{ 130189251Ssam register struct linenum_info *p; 131189251Ssam register struct linenum_info *new; 132189251Ssam register struct linenum_info *nextp; 133189251Ssam register struct linenum_info *prevp; 134189251Ssam register POSITION mingap; 135189251Ssam 136189251Ssam /* 137214734Srpaulo * Find the proper place in the list for the new one. 138189251Ssam * The entries are sorted by position. 139214734Srpaulo */ 140189251Ssam for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next) 141214734Srpaulo if (p->line == linenum) 142189251Ssam /* We already have this one. */ 143189251Ssam return; 144189251Ssam nextp = p; 145189251Ssam prevp = p->prev; 146252726Srpaulo 147252726Srpaulo if (freelist != NULL) 148252726Srpaulo { 149189251Ssam /* 150189251Ssam * We still have free (unused) entries. 151189251Ssam * Use one of them. 152189251Ssam */ 153189251Ssam new = freelist; 154209158Srpaulo freelist = freelist->next; 155189251Ssam } else 156189251Ssam { 157189251Ssam /* 158189251Ssam * No free entries. 159189251Ssam * Use the "spare" entry. 160252726Srpaulo */ 161214734Srpaulo new = spare; 162214734Srpaulo spare = NULL; 163189251Ssam } 164189251Ssam 165189251Ssam /* 166189251Ssam * Fill in the fields of the new entry, 167209158Srpaulo * and insert it into the proper place in the list. 168209158Srpaulo */ 169189251Ssam new->next = nextp; 170189251Ssam new->prev = prevp; 171214734Srpaulo new->pos = pos; 172214734Srpaulo new->line = linenum; 173281806Srpaulo 174189251Ssam nextp->prev = new; 175189251Ssam prevp->next = new; 176189251Ssam 177189251Ssam /* 178189251Ssam * Recalculate gaps for the new entry and the neighboring entries. 179189251Ssam */ 180189251Ssam calcgap(new); 181252726Srpaulo calcgap(nextp); 182189251Ssam calcgap(prevp); 183189251Ssam 184189251Ssam if (spare == NULL) 185189251Ssam { 186214734Srpaulo /* 187214734Srpaulo * We have used the spare entry. 188214734Srpaulo * Scan the list to find the one with the smallest 189214734Srpaulo * gap, take it out and make it the spare. 190252726Srpaulo * We should never remove the last one, so stop when 191252726Srpaulo * we get to p->next == &anchor. This also avoids 192214734Srpaulo * looking at the gap of the last one, which is 193189251Ssam * not computed by calcgap. 194 */ 195 mingap = anchor.next->gap; 196 for (p = anchor.next; p->next != &anchor; p = p->next) 197 { 198 if (p->gap <= mingap) 199 { 200 spare = p; 201 mingap = p->gap; 202 } 203 } 204 spare->next->prev = spare->prev; 205 spare->prev->next = spare->next; 206 } 207} 208 209/* 210 * If we get stuck in a long loop trying to figure out the 211 * line number, print a message to tell the user what we're doing. 212 */ 213 static void 214longloopmessage() 215{ 216 ierror("Calculating line numbers", NULL_PARG); 217 /* 218 * Set the lnloop flag here, so if the user interrupts while 219 * we are calculating line numbers, the signal handler will 220 * turn off line numbers (linenums=0). 221 */ 222 lnloop = 1; 223} 224 225static int loopcount; 226#if HAVE_TIME 227static long startime; 228#endif 229 230 static void 231longish() 232{ 233#if HAVE_TIME 234 if (loopcount >= 0 && ++loopcount > 100) 235 { 236 loopcount = 0; 237 if (get_time() >= startime + LONGTIME) 238 { 239 longloopmessage(); 240 loopcount = -1; 241 } 242 } 243#else 244 if (loopcount >= 0 && ++loopcount > LONGLOOP) 245 { 246 longloopmessage(); 247 loopcount = -1; 248 } 249#endif 250} 251 252/* 253 * Find the line number associated with a given position. 254 * Return 0 if we can't figure it out. 255 */ 256 public LINENUM 257find_linenum(pos) 258 POSITION pos; 259{ 260 register struct linenum_info *p; 261 register LINENUM linenum; 262 POSITION cpos; 263 264 if (!linenums) 265 /* 266 * We're not using line numbers. 267 */ 268 return (0); 269 if (pos == NULL_POSITION) 270 /* 271 * Caller doesn't know what he's talking about. 272 */ 273 return (0); 274 if (pos <= ch_zero()) 275 /* 276 * Beginning of file is always line number 1. 277 */ 278 return (1); 279 280 /* 281 * Find the entry nearest to the position we want. 282 */ 283 for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next) 284 continue; 285 if (p->pos == pos) 286 /* Found it exactly. */ 287 return (p->line); 288 289 /* 290 * This is the (possibly) time-consuming part. 291 * We start at the line we just found and start 292 * reading the file forward or backward till we 293 * get to the place we want. 294 * 295 * First decide whether we should go forward from the 296 * previous one or backwards from the next one. 297 * The decision is based on which way involves 298 * traversing fewer bytes in the file. 299 */ 300#if HAVE_TIME 301 startime = get_time(); 302#endif 303 if (p == &anchor || pos - p->prev->pos < p->pos - pos) 304 { 305 /* 306 * Go forward. 307 */ 308 p = p->prev; 309 if (ch_seek(p->pos)) 310 return (0); 311 loopcount = 0; 312 for (linenum = p->line, cpos = p->pos; cpos < pos; linenum++) 313 { 314 /* 315 * Allow a signal to abort this loop. 316 */ 317 cpos = forw_raw_line(cpos, (char **)NULL, (int *)NULL); 318 if (ABORT_SIGS() || cpos == NULL_POSITION) 319 return (0); 320 longish(); 321 } 322 lnloop = 0; 323 /* 324 * We might as well cache it. 325 */ 326 add_lnum(linenum, cpos); 327 /* 328 * If the given position is not at the start of a line, 329 * make sure we return the correct line number. 330 */ 331 if (cpos > pos) 332 linenum--; 333 } else 334 { 335 /* 336 * Go backward. 337 */ 338 if (ch_seek(p->pos)) 339 return (0); 340 loopcount = 0; 341 for (linenum = p->line, cpos = p->pos; cpos > pos; linenum--) 342 { 343 /* 344 * Allow a signal to abort this loop. 345 */ 346 cpos = back_raw_line(cpos, (char **)NULL, (int *)NULL); 347 if (ABORT_SIGS() || cpos == NULL_POSITION) 348 return (0); 349 longish(); 350 } 351 lnloop = 0; 352 /* 353 * We might as well cache it. 354 */ 355 add_lnum(linenum, cpos); 356 } 357 358 return (linenum); 359} 360 361/* 362 * Find the position of a given line number. 363 * Return NULL_POSITION if we can't figure it out. 364 */ 365 public POSITION 366find_pos(linenum) 367 LINENUM linenum; 368{ 369 register struct linenum_info *p; 370 POSITION cpos; 371 LINENUM clinenum; 372 373 if (linenum <= 1) 374 /* 375 * Line number 1 is beginning of file. 376 */ 377 return (ch_zero()); 378 379 /* 380 * Find the entry nearest to the line number we want. 381 */ 382 for (p = anchor.next; p != &anchor && p->line < linenum; p = p->next) 383 continue; 384 if (p->line == linenum) 385 /* Found it exactly. */ 386 return (p->pos); 387 388 if (p == &anchor || linenum - p->prev->line < p->line - linenum) 389 { 390 /* 391 * Go forward. 392 */ 393 p = p->prev; 394 if (ch_seek(p->pos)) 395 return (NULL_POSITION); 396 for (clinenum = p->line, cpos = p->pos; clinenum < linenum; clinenum++) 397 { 398 /* 399 * Allow a signal to abort this loop. 400 */ 401 cpos = forw_raw_line(cpos, (char **)NULL, (int *)NULL); 402 if (ABORT_SIGS() || cpos == NULL_POSITION) 403 return (NULL_POSITION); 404 } 405 } else 406 { 407 /* 408 * Go backward. 409 */ 410 if (ch_seek(p->pos)) 411 return (NULL_POSITION); 412 for (clinenum = p->line, cpos = p->pos; clinenum > linenum; clinenum--) 413 { 414 /* 415 * Allow a signal to abort this loop. 416 */ 417 cpos = back_raw_line(cpos, (char **)NULL, (int *)NULL); 418 if (ABORT_SIGS() || cpos == NULL_POSITION) 419 return (NULL_POSITION); 420 } 421 } 422 /* 423 * We might as well cache it. 424 */ 425 add_lnum(clinenum, cpos); 426 return (cpos); 427} 428 429/* 430 * Return the line number of the "current" line. 431 * The argument "where" tells which line is to be considered 432 * the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc). 433 */ 434 public LINENUM 435currline(where) 436 int where; 437{ 438 POSITION pos; 439 POSITION len; 440 LINENUM linenum; 441 442 pos = position(where); 443 len = ch_length(); 444 while (pos == NULL_POSITION && where >= 0 && where < sc_height) 445 pos = position(++where); 446 if (pos == NULL_POSITION) 447 pos = len; 448 linenum = find_linenum(pos); 449 if (pos == len) 450 linenum--; 451 return (linenum); 452} 453