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linenum.c (60786) linenum.c (89019)
1/*
2 * Copyright (C) 1984-2000 Mark Nudelman
3 *
4 * You may distribute under the terms of either the GNU General Public
5 * License or the Less License, as specified in the README file.
6 *
7 * For more information about less, or for information on how to
8 * contact the author, see the README file.
9 */
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 */
42struct linenum
43{
44 struct linenum *next; /* Link to next in the list */
45 struct linenum *prev; /* Line to previous in the list */
46 POSITION pos; /* File position */
47 POSITION gap; /* Gap between prev and next */
48 int line; /* Line number */
49};
50/*
51 * "gap" needs some explanation: the gap of any particular line number
52 * is the distance between the previous one and the next one in the list.
53 * ("Distance" means difference in file position.) In other words, the
54 * gap of a line number is the gap which would be introduced if this
55 * line number were deleted. It is used to decide which one to replace
56 * when we have a new one to insert and the table is full.
57 */
58
59#define NPOOL 50 /* Size of line number pool */
60
61#define LONGTIME (2) /* In seconds */
62
63public int lnloop = 0; /* Are we in the line num loop? */
64
65static struct linenum anchor; /* Anchor of the list */
66static struct linenum *freelist; /* Anchor of the unused entries */
67static struct linenum pool[NPOOL]; /* The pool itself */
68static struct linenum *spare; /* We always keep one spare entry */
69
70extern int linenums;
71extern int sigs;
72extern int sc_height;
73
74/*
75 * Initialize the line number structures.
76 */
77 public void
78clr_linenum()
79{
80 register struct linenum *p;
81
82 /*
83 * Put all the entries on the free list.
84 * Leave one for the "spare".
85 */
86 for (p = pool; p < &pool[NPOOL-2]; p++)
87 p->next = p+1;
88 pool[NPOOL-2].next = NULL;
89 freelist = pool;
90
91 spare = &pool[NPOOL-1];
92
93 /*
94 * Initialize the anchor.
95 */
96 anchor.next = anchor.prev = &anchor;
97 anchor.gap = 0;
98 anchor.pos = (POSITION)0;
99 anchor.line = 1;
100}
101
102/*
103 * Calculate the gap for an entry.
104 */
105 static void
106calcgap(p)
107 register struct linenum *p;
108{
109 /*
110 * Don't bother to compute a gap for the anchor.
111 * Also don't compute a gap for the last one in the list.
112 * The gap for that last one should be considered infinite,
113 * but we never look at it anyway.
114 */
115 if (p == &anchor || p->next == &anchor)
116 return;
117 p->gap = p->next->pos - p->prev->pos;
118}
119
120/*
121 * Add a new line number to the cache.
122 * The specified position (pos) should be the file position of the
123 * FIRST character in the specified line.
124 */
125 public void
126add_lnum(lno, pos)
127 int lno;
128 POSITION pos;
129{
130 register struct linenum *p;
131 register struct linenum *new;
132 register struct linenum *nextp;
133 register struct linenum *prevp;
134 register POSITION mingap;
135
136 /*
137 * Find the proper place in the list for the new one.
138 * The entries are sorted by position.
139 */
140 for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
141 if (p->line == lno)
142 /* We already have this one. */
143 return;
144 nextp = p;
145 prevp = p->prev;
146
147 if (freelist != NULL)
148 {
149 /*
150 * We still have free (unused) entries.
151 * Use one of them.
152 */
153 new = freelist;
154 freelist = freelist->next;
155 } else
156 {
157 /*
158 * No free entries.
159 * Use the "spare" entry.
160 */
161 new = spare;
162 spare = NULL;
163 }
164
165 /*
166 * Fill in the fields of the new entry,
167 * and insert it into the proper place in the list.
168 */
169 new->next = nextp;
170 new->prev = prevp;
171 new->pos = pos;
172 new->line = lno;
173
174 nextp->prev = new;
175 prevp->next = new;
176
177 /*
178 * Recalculate gaps for the new entry and the neighboring entries.
179 */
180 calcgap(new);
181 calcgap(nextp);
182 calcgap(prevp);
183
184 if (spare == NULL)
185 {
186 /*
187 * We have used the spare entry.
188 * Scan the list to find the one with the smallest
189 * gap, take it out and make it the spare.
190 * We should never remove the last one, so stop when
191 * we get to p->next == &anchor. This also avoids
192 * looking at the gap of the last one, which is
193 * 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 int
257find_linenum(pos)
258 POSITION pos;
259{
260 register struct linenum *p;
261 register int lno;
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 */
1/*
2 * Copyright (C) 1984-2000 Mark Nudelman
3 *
4 * You may distribute under the terms of either the GNU General Public
5 * License or the Less License, as specified in the README file.
6 *
7 * For more information about less, or for information on how to
8 * contact the author, see the README file.
9 */
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 */
42struct linenum
43{
44 struct linenum *next; /* Link to next in the list */
45 struct linenum *prev; /* Line to previous in the list */
46 POSITION pos; /* File position */
47 POSITION gap; /* Gap between prev and next */
48 int line; /* Line number */
49};
50/*
51 * "gap" needs some explanation: the gap of any particular line number
52 * is the distance between the previous one and the next one in the list.
53 * ("Distance" means difference in file position.) In other words, the
54 * gap of a line number is the gap which would be introduced if this
55 * line number were deleted. It is used to decide which one to replace
56 * when we have a new one to insert and the table is full.
57 */
58
59#define NPOOL 50 /* Size of line number pool */
60
61#define LONGTIME (2) /* In seconds */
62
63public int lnloop = 0; /* Are we in the line num loop? */
64
65static struct linenum anchor; /* Anchor of the list */
66static struct linenum *freelist; /* Anchor of the unused entries */
67static struct linenum pool[NPOOL]; /* The pool itself */
68static struct linenum *spare; /* We always keep one spare entry */
69
70extern int linenums;
71extern int sigs;
72extern int sc_height;
73
74/*
75 * Initialize the line number structures.
76 */
77 public void
78clr_linenum()
79{
80 register struct linenum *p;
81
82 /*
83 * Put all the entries on the free list.
84 * Leave one for the "spare".
85 */
86 for (p = pool; p < &pool[NPOOL-2]; p++)
87 p->next = p+1;
88 pool[NPOOL-2].next = NULL;
89 freelist = pool;
90
91 spare = &pool[NPOOL-1];
92
93 /*
94 * Initialize the anchor.
95 */
96 anchor.next = anchor.prev = &anchor;
97 anchor.gap = 0;
98 anchor.pos = (POSITION)0;
99 anchor.line = 1;
100}
101
102/*
103 * Calculate the gap for an entry.
104 */
105 static void
106calcgap(p)
107 register struct linenum *p;
108{
109 /*
110 * Don't bother to compute a gap for the anchor.
111 * Also don't compute a gap for the last one in the list.
112 * The gap for that last one should be considered infinite,
113 * but we never look at it anyway.
114 */
115 if (p == &anchor || p->next == &anchor)
116 return;
117 p->gap = p->next->pos - p->prev->pos;
118}
119
120/*
121 * Add a new line number to the cache.
122 * The specified position (pos) should be the file position of the
123 * FIRST character in the specified line.
124 */
125 public void
126add_lnum(lno, pos)
127 int lno;
128 POSITION pos;
129{
130 register struct linenum *p;
131 register struct linenum *new;
132 register struct linenum *nextp;
133 register struct linenum *prevp;
134 register POSITION mingap;
135
136 /*
137 * Find the proper place in the list for the new one.
138 * The entries are sorted by position.
139 */
140 for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
141 if (p->line == lno)
142 /* We already have this one. */
143 return;
144 nextp = p;
145 prevp = p->prev;
146
147 if (freelist != NULL)
148 {
149 /*
150 * We still have free (unused) entries.
151 * Use one of them.
152 */
153 new = freelist;
154 freelist = freelist->next;
155 } else
156 {
157 /*
158 * No free entries.
159 * Use the "spare" entry.
160 */
161 new = spare;
162 spare = NULL;
163 }
164
165 /*
166 * Fill in the fields of the new entry,
167 * and insert it into the proper place in the list.
168 */
169 new->next = nextp;
170 new->prev = prevp;
171 new->pos = pos;
172 new->line = lno;
173
174 nextp->prev = new;
175 prevp->next = new;
176
177 /*
178 * Recalculate gaps for the new entry and the neighboring entries.
179 */
180 calcgap(new);
181 calcgap(nextp);
182 calcgap(prevp);
183
184 if (spare == NULL)
185 {
186 /*
187 * We have used the spare entry.
188 * Scan the list to find the one with the smallest
189 * gap, take it out and make it the spare.
190 * We should never remove the last one, so stop when
191 * we get to p->next == &anchor. This also avoids
192 * looking at the gap of the last one, which is
193 * 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 int
257find_linenum(pos)
258 POSITION pos;
259{
260 register struct linenum *p;
261 register int lno;
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 flush();
301#if HAVE_TIME
302 startime = get_time();
303#endif
304 if (p == &anchor || pos - p->prev->pos < p->pos - pos)
305 {
306 /*
307 * Go forward.
308 */
309 p = p->prev;
310 if (ch_seek(p->pos))
311 return (0);
312 loopcount = 0;
313 for (lno = p->line, cpos = p->pos; cpos < pos; lno++)
314 {
315 /*
316 * Allow a signal to abort this loop.
317 */
318 cpos = forw_raw_line(cpos, (char **)NULL);
319 if (ABORT_SIGS() || cpos == NULL_POSITION)
320 return (0);
321 longish();
322 }
323 lnloop = 0;
324 /*
325 * We might as well cache it.
326 */
327 add_lnum(lno, cpos);
328 /*
329 * If the given position is not at the start of a line,
330 * make sure we return the correct line number.
331 */
332 if (cpos > pos)
333 lno--;
334 } else
335 {
336 /*
337 * Go backward.
338 */
339 if (ch_seek(p->pos))
340 return (0);
341 loopcount = 0;
342 for (lno = p->line, cpos = p->pos; cpos > pos; lno--)
343 {
344 /*
345 * Allow a signal to abort this loop.
346 */
347 cpos = back_raw_line(cpos, (char **)NULL);
348 if (ABORT_SIGS() || cpos == NULL_POSITION)
349 return (0);
350 longish();
351 }
352 lnloop = 0;
353 /*
354 * We might as well cache it.
355 */
356 add_lnum(lno, cpos);
357 }
358
359 return (lno);
360}
361
362/*
363 * Find the position of a given line number.
364 * Return NULL_POSITION if we can't figure it out.
365 */
366 public POSITION
367find_pos(lno)
368 int lno;
369{
370 register struct linenum *p;
371 POSITION cpos;
372 int clno;
373
374 if (lno <= 1)
375 /*
376 * Line number 1 is beginning of file.
377 */
378 return (ch_zero());
379
380 /*
381 * Find the entry nearest to the line number we want.
382 */
383 for (p = anchor.next; p != &anchor && p->line < lno; p = p->next)
384 continue;
385 if (p->line == lno)
386 /* Found it exactly. */
387 return (p->pos);
388
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 (lno = p->line, cpos = p->pos; cpos < pos; lno++)
313 {
314 /*
315 * Allow a signal to abort this loop.
316 */
317 cpos = forw_raw_line(cpos, (char **)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(lno, 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 lno--;
333 } else
334 {
335 /*
336 * Go backward.
337 */
338 if (ch_seek(p->pos))
339 return (0);
340 loopcount = 0;
341 for (lno = p->line, cpos = p->pos; cpos > pos; lno--)
342 {
343 /*
344 * Allow a signal to abort this loop.
345 */
346 cpos = back_raw_line(cpos, (char **)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(lno, cpos);
356 }
357
358 return (lno);
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(lno)
367 int lno;
368{
369 register struct linenum *p;
370 POSITION cpos;
371 int clno;
372
373 if (lno <= 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 < lno; p = p->next)
383 continue;
384 if (p->line == lno)
385 /* Found it exactly. */
386 return (p->pos);
387
389 flush();
390 if (p == &anchor || lno - p->prev->line < p->line - lno)
391 {
392 /*
393 * Go forward.
394 */
395 p = p->prev;
396 if (ch_seek(p->pos))
397 return (NULL_POSITION);
398 for (clno = p->line, cpos = p->pos; clno < lno; clno++)
399 {
400 /*
401 * Allow a signal to abort this loop.
402 */
403 cpos = forw_raw_line(cpos, (char **)NULL);
404 if (ABORT_SIGS() || cpos == NULL_POSITION)
405 return (NULL_POSITION);
406 }
407 } else
408 {
409 /*
410 * Go backward.
411 */
412 if (ch_seek(p->pos))
413 return (NULL_POSITION);
414 for (clno = p->line, cpos = p->pos; clno > lno; clno--)
415 {
416 /*
417 * Allow a signal to abort this loop.
418 */
419 cpos = back_raw_line(cpos, (char **)NULL);
420 if (ABORT_SIGS() || cpos == NULL_POSITION)
421 return (NULL_POSITION);
422 }
423 }
424 /*
425 * We might as well cache it.
426 */
427 add_lnum(clno, cpos);
428 return (cpos);
429}
430
431/*
432 * Return the line number of the "current" line.
433 * The argument "where" tells which line is to be considered
434 * the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc).
435 */
436 public int
437currline(where)
438 int where;
439{
440 POSITION pos;
441 POSITION len;
442 int lnum;
443
444 pos = position(where);
445 len = ch_length();
446 while (pos == NULL_POSITION && where >= 0 && where < sc_height)
447 pos = position(++where);
448 if (pos == NULL_POSITION)
449 pos = len;
450 lnum = find_linenum(pos);
451 if (pos == len)
452 lnum--;
453 return (lnum);
454}
388 if (p == &anchor || lno - p->prev->line < p->line - lno)
389 {
390 /*
391 * Go forward.
392 */
393 p = p->prev;
394 if (ch_seek(p->pos))
395 return (NULL_POSITION);
396 for (clno = p->line, cpos = p->pos; clno < lno; clno++)
397 {
398 /*
399 * Allow a signal to abort this loop.
400 */
401 cpos = forw_raw_line(cpos, (char **)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 (clno = p->line, cpos = p->pos; clno > lno; clno--)
413 {
414 /*
415 * Allow a signal to abort this loop.
416 */
417 cpos = back_raw_line(cpos, (char **)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(clno, 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 int
435currline(where)
436 int where;
437{
438 POSITION pos;
439 POSITION len;
440 int lnum;
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 lnum = find_linenum(pos);
449 if (pos == len)
450 lnum--;
451 return (lnum);
452}