1 /* 2 * Copyright (C) 1984-2012 Mark Nudelman 3 * Modified for use with illumos by Garrett D'Amore. 4 * Copyright 2014 Garrett D'Amore <garrett@damore.org> 5 * 6 * You may distribute under the terms of either the GNU General Public 7 * License or the Less License, as specified in the README file. 8 * 9 * For more information, see the README file. 10 */ 11 12 /* 13 * Code to handle displaying line numbers. 14 * 15 * Finding the line number of a given file position is rather tricky. 16 * We don't want to just start at the beginning of the file and 17 * count newlines, because that is slow for large files (and also 18 * wouldn't work if we couldn't get to the start of the file; e.g. 19 * if input is a long pipe). 20 * 21 * So we use the function add_lnum to cache line numbers. 22 * We try to be very clever and keep only the more interesting 23 * line numbers when we run out of space in our table. A line 24 * number is more interesting than another when it is far from 25 * other line numbers. For example, we'd rather keep lines 26 * 100,200,300 than 100,101,300. 200 is more interesting than 27 * 101 because 101 can be derived very cheaply from 100, while 28 * 200 is more expensive to derive from 100. 29 * 30 * The function currline() returns the line number of a given 31 * position in the file. As a side effect, it calls add_lnum 32 * to cache the line number. Therefore currline is occasionally 33 * called to make sure we cache line numbers often enough. 34 */ 35 36 #include "less.h" 37 38 /* 39 * Structure to keep track of a line number and the associated file position. 40 * A doubly-linked circular list of line numbers is kept ordered by line number. 41 */ 42 struct linenum_info { 43 struct linenum_info *next; /* Link to next in the list */ 44 struct linenum_info *prev; /* Line to previous in the list */ 45 off_t pos; /* File position */ 46 off_t gap; /* Gap between prev and next */ 47 off_t line; /* Line number */ 48 }; 49 /* 50 * "gap" needs some explanation: the gap of any particular line number 51 * is the distance between the previous one and the next one in the list. 52 * ("Distance" means difference in file position.) In other words, the 53 * gap of a line number is the gap which would be introduced if this 54 * line number were deleted. It is used to decide which one to replace 55 * when we have a new one to insert and the table is full. 56 */ 57 58 #define NPOOL 200 /* Size of line number pool */ 59 60 #define LONGTIME (2) /* In seconds */ 61 62 static struct linenum_info anchor; /* Anchor of the list */ 63 static struct linenum_info *freelist; /* Anchor of the unused entries */ 64 static struct linenum_info pool[NPOOL]; /* The pool itself */ 65 static struct linenum_info *spare; /* We always keep one spare entry */ 66 67 extern int linenums; 68 extern volatile sig_atomic_t sigs; 69 extern int sc_height; 70 extern int screen_trashed; 71 72 /* 73 * Initialize the line number structures. 74 */ 75 void 76 clr_linenum(void) 77 { 78 struct linenum_info *p; 79 80 /* 81 * Put all the entries on the free list. 82 * Leave one for the "spare". 83 */ 84 for (p = pool; p < &pool[NPOOL-2]; p++) 85 p->next = p+1; 86 pool[NPOOL-2].next = NULL; 87 freelist = pool; 88 89 spare = &pool[NPOOL-1]; 90 91 /* 92 * Initialize the anchor. 93 */ 94 anchor.next = anchor.prev = &anchor; 95 anchor.gap = 0; 96 anchor.pos = 0; 97 anchor.line = 1; 98 } 99 100 /* 101 * Calculate the gap for an entry. 102 */ 103 static void 104 calcgap(struct linenum_info *p) 105 { 106 /* 107 * Don't bother to compute a gap for the anchor. 108 * Also don't compute a gap for the last one in the list. 109 * The gap for that last one should be considered infinite, 110 * but we never look at it anyway. 111 */ 112 if (p == &anchor || p->next == &anchor) 113 return; 114 p->gap = p->next->pos - p->prev->pos; 115 } 116 117 /* 118 * Add a new line number to the cache. 119 * The specified position (pos) should be the file position of the 120 * FIRST character in the specified line. 121 */ 122 void 123 add_lnum(off_t linenum, off_t pos) 124 { 125 struct linenum_info *p; 126 struct linenum_info *new; 127 struct linenum_info *nextp; 128 struct linenum_info *prevp; 129 off_t mingap; 130 131 /* 132 * Find the proper place in the list for the new one. 133 * The entries are sorted by position. 134 */ 135 for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next) 136 if (p->line == linenum) 137 /* We already have this one. */ 138 return; 139 nextp = p; 140 prevp = p->prev; 141 142 if (freelist != NULL) { 143 /* 144 * We still have free (unused) entries. 145 * Use one of them. 146 */ 147 new = freelist; 148 freelist = freelist->next; 149 } else { 150 /* 151 * No free entries. 152 * Use the "spare" entry. 153 */ 154 new = spare; 155 spare = NULL; 156 } 157 158 /* 159 * Fill in the fields of the new entry, 160 * and insert it into the proper place in the list. 161 */ 162 new->next = nextp; 163 new->prev = prevp; 164 new->pos = pos; 165 new->line = linenum; 166 167 nextp->prev = new; 168 prevp->next = new; 169 170 /* 171 * Recalculate gaps for the new entry and the neighboring entries. 172 */ 173 calcgap(new); 174 calcgap(nextp); 175 calcgap(prevp); 176 177 if (spare == NULL) { 178 /* 179 * We have used the spare entry. 180 * Scan the list to find the one with the smallest 181 * gap, take it out and make it the spare. 182 * We should never remove the last one, so stop when 183 * we get to p->next == &anchor. This also avoids 184 * looking at the gap of the last one, which is 185 * not computed by calcgap. 186 */ 187 mingap = anchor.next->gap; 188 for (p = anchor.next; p->next != &anchor; p = p->next) { 189 if (p->gap <= mingap) { 190 spare = p; 191 mingap = p->gap; 192 } 193 } 194 spare->next->prev = spare->prev; 195 spare->prev->next = spare->next; 196 } 197 } 198 199 static int loopcount; 200 static time_t startime; 201 202 static void 203 longish(void) 204 { 205 if (++loopcount > 100) { 206 loopcount = 0; 207 if (time(NULL) >= startime + LONGTIME) { 208 ierror("Calculating line numbers", NULL); 209 loopcount = -1; 210 } 211 } 212 } 213 214 /* 215 * Turn off line numbers because the user has interrupted 216 * a lengthy line number calculation. 217 */ 218 static void 219 abort_long(void) 220 { 221 if (linenums == OPT_ONPLUS) 222 /* 223 * We were displaying line numbers, so need to repaint. 224 */ 225 screen_trashed = 1; 226 linenums = 0; 227 error("Line numbers turned off", NULL); 228 } 229 230 /* 231 * Find the line number associated with a given position. 232 * Return 0 if we can't figure it out. 233 */ 234 off_t 235 find_linenum(off_t pos) 236 { 237 struct linenum_info *p; 238 off_t linenum; 239 off_t cpos; 240 241 if (!linenums) 242 /* 243 * We're not using line numbers. 244 */ 245 return (0); 246 if (pos == -1) 247 /* 248 * Caller doesn't know what he's talking about. 249 */ 250 return (0); 251 if (pos <= ch_zero()) 252 /* 253 * Beginning of file is always line number 1. 254 */ 255 return (1); 256 257 /* 258 * Find the entry nearest to the position we want. 259 */ 260 for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next) 261 continue; 262 if (p->pos == pos) 263 /* Found it exactly. */ 264 return (p->line); 265 266 /* 267 * This is the (possibly) time-consuming part. 268 * We start at the line we just found and start 269 * reading the file forward or backward till we 270 * get to the place we want. 271 * 272 * First decide whether we should go forward from the 273 * previous one or backwards from the next one. 274 * The decision is based on which way involves 275 * traversing fewer bytes in the file. 276 */ 277 startime = time(NULL); 278 if (p == &anchor || pos - p->prev->pos < p->pos - pos) { 279 /* 280 * Go forward. 281 */ 282 p = p->prev; 283 if (ch_seek(p->pos)) 284 return (0); 285 loopcount = 0; 286 for (linenum = p->line, cpos = p->pos; cpos < pos; linenum++) { 287 /* 288 * Allow a signal to abort this loop. 289 */ 290 cpos = forw_raw_line(cpos, NULL, NULL); 291 if (ABORT_SIGS()) { 292 abort_long(); 293 return (0); 294 } 295 if (cpos == -1) 296 return (0); 297 longish(); 298 } 299 /* 300 * We might as well cache it. 301 */ 302 add_lnum(linenum, cpos); 303 /* 304 * If the given position is not at the start of a line, 305 * make sure we return the correct line number. 306 */ 307 if (cpos > pos) 308 linenum--; 309 } else { 310 /* 311 * Go backward. 312 */ 313 if (ch_seek(p->pos)) 314 return (0); 315 loopcount = 0; 316 for (linenum = p->line, cpos = p->pos; cpos > pos; linenum--) { 317 /* 318 * Allow a signal to abort this loop. 319 */ 320 cpos = back_raw_line(cpos, NULL, NULL); 321 if (ABORT_SIGS()) { 322 abort_long(); 323 return (0); 324 } 325 if (cpos == -1) 326 return (0); 327 longish(); 328 } 329 /* 330 * We might as well cache it. 331 */ 332 add_lnum(linenum, cpos); 333 } 334 335 return (linenum); 336 } 337 338 /* 339 * Find the position of a given line number. 340 * Return -1 if we can't figure it out. 341 */ 342 off_t 343 find_pos(off_t linenum) 344 { 345 struct linenum_info *p; 346 off_t cpos; 347 off_t clinenum; 348 349 if (linenum <= 1) 350 /* 351 * Line number 1 is beginning of file. 352 */ 353 return (ch_zero()); 354 355 /* 356 * Find the entry nearest to the line number we want. 357 */ 358 for (p = anchor.next; p != &anchor && p->line < linenum; p = p->next) 359 continue; 360 if (p->line == linenum) 361 /* Found it exactly. */ 362 return (p->pos); 363 364 if (p == &anchor || linenum - p->prev->line < p->line - linenum) { 365 /* 366 * Go forward. 367 */ 368 p = p->prev; 369 if (ch_seek(p->pos)) 370 return (-1); 371 for (clinenum = p->line, cpos = p->pos; 372 clinenum < linenum; 373 clinenum++) { 374 /* 375 * Allow a signal to abort this loop. 376 */ 377 cpos = forw_raw_line(cpos, NULL, NULL); 378 if (ABORT_SIGS()) 379 return (-1); 380 if (cpos == -1) 381 return (-1); 382 } 383 } else { 384 /* 385 * Go backward. 386 */ 387 if (ch_seek(p->pos)) 388 return (-1); 389 for (clinenum = p->line, cpos = p->pos; 390 clinenum > linenum; 391 clinenum--) { 392 /* 393 * Allow a signal to abort this loop. 394 */ 395 cpos = back_raw_line(cpos, (char **)NULL, (int *)NULL); 396 if (ABORT_SIGS()) 397 return (-1); 398 if (cpos == -1) 399 return (-1); 400 } 401 } 402 /* 403 * We might as well cache it. 404 */ 405 add_lnum(clinenum, cpos); 406 return (cpos); 407 } 408 409 /* 410 * Return the line number of the "current" line. 411 * The argument "where" tells which line is to be considered 412 * the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc). 413 */ 414 off_t 415 currline(int where) 416 { 417 off_t pos; 418 off_t len; 419 off_t linenum; 420 421 pos = position(where); 422 len = ch_length(); 423 while (pos == -1 && where >= 0 && where < sc_height) 424 pos = position(++where); 425 if (pos == -1) 426 pos = len; 427 linenum = find_linenum(pos); 428 if (pos == len) 429 linenum--; 430 return (linenum); 431 } 432