Annotation of src/usr.bin/less/linenum.c, Revision 1.1.1.4
1.1 etheisen 1: /*
1.1.1.4 ! shadchin 2: * Copyright (C) 1984-2012 Mark Nudelman
1.1 etheisen 3: *
1.1.1.2 millert 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.
1.1 etheisen 6: *
1.1.1.4 ! shadchin 7: * For more information, see the README file.
1.1 etheisen 8: */
9:
10:
11: /*
12: * Code to handle displaying line numbers.
13: *
14: * Finding the line number of a given file position is rather tricky.
15: * We don't want to just start at the beginning of the file and
16: * count newlines, because that is slow for large files (and also
17: * wouldn't work if we couldn't get to the start of the file; e.g.
18: * if input is a long pipe).
19: *
20: * So we use the function add_lnum to cache line numbers.
21: * We try to be very clever and keep only the more interesting
22: * line numbers when we run out of space in our table. A line
23: * number is more interesting than another when it is far from
24: * other line numbers. For example, we'd rather keep lines
25: * 100,200,300 than 100,101,300. 200 is more interesting than
26: * 101 because 101 can be derived very cheaply from 100, while
27: * 200 is more expensive to derive from 100.
28: *
29: * The function currline() returns the line number of a given
30: * position in the file. As a side effect, it calls add_lnum
31: * to cache the line number. Therefore currline is occasionally
32: * called to make sure we cache line numbers often enough.
33: */
34:
35: #include "less.h"
36:
37: /*
38: * Structure to keep track of a line number and the associated file position.
39: * A doubly-linked circular list of line numbers is kept ordered by line number.
40: */
1.1.1.2 millert 41: struct linenum_info
1.1 etheisen 42: {
1.1.1.2 millert 43: struct linenum_info *next; /* Link to next in the list */
44: struct linenum_info *prev; /* Line to previous in the list */
1.1 etheisen 45: POSITION pos; /* File position */
46: POSITION gap; /* Gap between prev and next */
1.1.1.2 millert 47: LINENUM line; /* Line number */
1.1 etheisen 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:
1.1.1.3 shadchin 58: #define NPOOL 200 /* Size of line number pool */
1.1 etheisen 59:
60: #define LONGTIME (2) /* In seconds */
61:
1.1.1.2 millert 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 */
1.1 etheisen 66:
67: extern int linenums;
1.1.1.4 ! shadchin 68: extern volatile sig_atomic_t sigs;
1.1 etheisen 69: extern int sc_height;
1.1.1.3 shadchin 70: extern int screen_trashed;
1.1 etheisen 71:
72: /*
73: * Initialize the line number structures.
74: */
75: public void
76: clr_linenum()
77: {
1.1.1.2 millert 78: register struct linenum_info *p;
1.1 etheisen 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 = (POSITION)0;
97: anchor.line = 1;
98: }
99:
100: /*
101: * Calculate the gap for an entry.
102: */
103: static void
104: calcgap(p)
1.1.1.2 millert 105: register struct linenum_info *p;
1.1 etheisen 106: {
107: /*
108: * Don't bother to compute a gap for the anchor.
109: * Also don't compute a gap for the last one in the list.
110: * The gap for that last one should be considered infinite,
111: * but we never look at it anyway.
112: */
113: if (p == &anchor || p->next == &anchor)
114: return;
115: p->gap = p->next->pos - p->prev->pos;
116: }
117:
118: /*
119: * Add a new line number to the cache.
120: * The specified position (pos) should be the file position of the
121: * FIRST character in the specified line.
122: */
123: public void
1.1.1.2 millert 124: add_lnum(linenum, pos)
125: LINENUM linenum;
1.1 etheisen 126: POSITION pos;
127: {
1.1.1.2 millert 128: register struct linenum_info *p;
129: register struct linenum_info *new;
130: register struct linenum_info *nextp;
131: register struct linenum_info *prevp;
1.1 etheisen 132: register POSITION mingap;
133:
134: /*
135: * Find the proper place in the list for the new one.
136: * The entries are sorted by position.
137: */
138: for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
1.1.1.2 millert 139: if (p->line == linenum)
1.1 etheisen 140: /* We already have this one. */
141: return;
142: nextp = p;
143: prevp = p->prev;
144:
145: if (freelist != NULL)
146: {
147: /*
148: * We still have free (unused) entries.
149: * Use one of them.
150: */
151: new = freelist;
152: freelist = freelist->next;
153: } else
154: {
155: /*
156: * No free entries.
157: * Use the "spare" entry.
158: */
159: new = spare;
160: spare = NULL;
161: }
162:
163: /*
164: * Fill in the fields of the new entry,
165: * and insert it into the proper place in the list.
166: */
167: new->next = nextp;
168: new->prev = prevp;
169: new->pos = pos;
1.1.1.2 millert 170: new->line = linenum;
1.1 etheisen 171:
172: nextp->prev = new;
173: prevp->next = new;
174:
175: /*
176: * Recalculate gaps for the new entry and the neighboring entries.
177: */
178: calcgap(new);
179: calcgap(nextp);
180: calcgap(prevp);
181:
182: if (spare == NULL)
183: {
184: /*
185: * We have used the spare entry.
186: * Scan the list to find the one with the smallest
187: * gap, take it out and make it the spare.
188: * We should never remove the last one, so stop when
189: * we get to p->next == &anchor. This also avoids
190: * looking at the gap of the last one, which is
191: * not computed by calcgap.
192: */
193: mingap = anchor.next->gap;
194: for (p = anchor.next; p->next != &anchor; p = p->next)
195: {
196: if (p->gap <= mingap)
197: {
198: spare = p;
199: mingap = p->gap;
200: }
201: }
202: spare->next->prev = spare->prev;
203: spare->prev->next = spare->next;
204: }
205: }
206:
207: /*
208: * If we get stuck in a long loop trying to figure out the
209: * line number, print a message to tell the user what we're doing.
210: */
211: static void
212: longloopmessage()
213: {
214: ierror("Calculating line numbers", NULL_PARG);
215: }
216:
217: static int loopcount;
218: #if HAVE_TIME
219: static long startime;
220: #endif
221:
222: static void
223: longish()
224: {
225: #if HAVE_TIME
226: if (loopcount >= 0 && ++loopcount > 100)
227: {
228: loopcount = 0;
229: if (get_time() >= startime + LONGTIME)
230: {
231: longloopmessage();
232: loopcount = -1;
233: }
234: }
235: #else
236: if (loopcount >= 0 && ++loopcount > LONGLOOP)
237: {
238: longloopmessage();
239: loopcount = -1;
240: }
241: #endif
242: }
243:
244: /*
1.1.1.3 shadchin 245: * Turn off line numbers because the user has interrupted
246: * a lengthy line number calculation.
247: */
248: static void
249: abort_long()
250: {
251: if (linenums == OPT_ONPLUS)
252: /*
253: * We were displaying line numbers, so need to repaint.
254: */
255: screen_trashed = 1;
256: linenums = 0;
257: error("Line numbers turned off", NULL_PARG);
258: }
259:
260: /*
1.1 etheisen 261: * Find the line number associated with a given position.
262: * Return 0 if we can't figure it out.
263: */
1.1.1.2 millert 264: public LINENUM
1.1 etheisen 265: find_linenum(pos)
266: POSITION pos;
267: {
1.1.1.2 millert 268: register struct linenum_info *p;
269: register LINENUM linenum;
1.1 etheisen 270: POSITION cpos;
271:
272: if (!linenums)
273: /*
274: * We're not using line numbers.
275: */
276: return (0);
277: if (pos == NULL_POSITION)
278: /*
279: * Caller doesn't know what he's talking about.
280: */
281: return (0);
282: if (pos <= ch_zero())
283: /*
284: * Beginning of file is always line number 1.
285: */
286: return (1);
287:
288: /*
289: * Find the entry nearest to the position we want.
290: */
291: for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
292: continue;
293: if (p->pos == pos)
294: /* Found it exactly. */
295: return (p->line);
296:
297: /*
298: * This is the (possibly) time-consuming part.
299: * We start at the line we just found and start
300: * reading the file forward or backward till we
301: * get to the place we want.
302: *
303: * First decide whether we should go forward from the
304: * previous one or backwards from the next one.
305: * The decision is based on which way involves
306: * traversing fewer bytes in the file.
307: */
308: #if HAVE_TIME
309: startime = get_time();
310: #endif
311: if (p == &anchor || pos - p->prev->pos < p->pos - pos)
312: {
313: /*
314: * Go forward.
315: */
316: p = p->prev;
317: if (ch_seek(p->pos))
318: return (0);
319: loopcount = 0;
1.1.1.2 millert 320: for (linenum = p->line, cpos = p->pos; cpos < pos; linenum++)
1.1 etheisen 321: {
322: /*
323: * Allow a signal to abort this loop.
324: */
1.1.1.3 shadchin 325: cpos = forw_raw_line(cpos, (char **)NULL, (int *)NULL);
326: if (ABORT_SIGS()) {
327: abort_long();
328: return (0);
329: }
330: if (cpos == NULL_POSITION)
1.1 etheisen 331: return (0);
332: longish();
333: }
334: /*
335: * We might as well cache it.
336: */
1.1.1.2 millert 337: add_lnum(linenum, cpos);
1.1 etheisen 338: /*
339: * If the given position is not at the start of a line,
340: * make sure we return the correct line number.
341: */
342: if (cpos > pos)
1.1.1.2 millert 343: linenum--;
1.1 etheisen 344: } else
345: {
346: /*
347: * Go backward.
348: */
349: if (ch_seek(p->pos))
350: return (0);
351: loopcount = 0;
1.1.1.2 millert 352: for (linenum = p->line, cpos = p->pos; cpos > pos; linenum--)
1.1 etheisen 353: {
354: /*
355: * Allow a signal to abort this loop.
356: */
1.1.1.3 shadchin 357: cpos = back_raw_line(cpos, (char **)NULL, (int *)NULL);
358: if (ABORT_SIGS()) {
359: abort_long();
360: return (0);
361: }
362: if (cpos == NULL_POSITION)
1.1 etheisen 363: return (0);
364: longish();
365: }
366: /*
367: * We might as well cache it.
368: */
1.1.1.2 millert 369: add_lnum(linenum, cpos);
1.1 etheisen 370: }
371:
1.1.1.2 millert 372: return (linenum);
1.1 etheisen 373: }
374:
375: /*
376: * Find the position of a given line number.
377: * Return NULL_POSITION if we can't figure it out.
378: */
379: public POSITION
1.1.1.2 millert 380: find_pos(linenum)
381: LINENUM linenum;
1.1 etheisen 382: {
1.1.1.2 millert 383: register struct linenum_info *p;
1.1 etheisen 384: POSITION cpos;
1.1.1.2 millert 385: LINENUM clinenum;
1.1 etheisen 386:
1.1.1.2 millert 387: if (linenum <= 1)
1.1 etheisen 388: /*
389: * Line number 1 is beginning of file.
390: */
391: return (ch_zero());
392:
393: /*
394: * Find the entry nearest to the line number we want.
395: */
1.1.1.2 millert 396: for (p = anchor.next; p != &anchor && p->line < linenum; p = p->next)
1.1 etheisen 397: continue;
1.1.1.2 millert 398: if (p->line == linenum)
1.1 etheisen 399: /* Found it exactly. */
400: return (p->pos);
401:
1.1.1.2 millert 402: if (p == &anchor || linenum - p->prev->line < p->line - linenum)
1.1 etheisen 403: {
404: /*
405: * Go forward.
406: */
407: p = p->prev;
408: if (ch_seek(p->pos))
409: return (NULL_POSITION);
1.1.1.2 millert 410: for (clinenum = p->line, cpos = p->pos; clinenum < linenum; clinenum++)
1.1 etheisen 411: {
412: /*
413: * Allow a signal to abort this loop.
414: */
1.1.1.3 shadchin 415: cpos = forw_raw_line(cpos, (char **)NULL, (int *)NULL);
416: if (ABORT_SIGS())
417: return (NULL_POSITION);
418: if (cpos == NULL_POSITION)
1.1 etheisen 419: return (NULL_POSITION);
420: }
421: } else
422: {
423: /*
424: * Go backward.
425: */
426: if (ch_seek(p->pos))
427: return (NULL_POSITION);
1.1.1.2 millert 428: for (clinenum = p->line, cpos = p->pos; clinenum > linenum; clinenum--)
1.1 etheisen 429: {
430: /*
431: * Allow a signal to abort this loop.
432: */
1.1.1.3 shadchin 433: cpos = back_raw_line(cpos, (char **)NULL, (int *)NULL);
434: if (ABORT_SIGS())
435: return (NULL_POSITION);
436: if (cpos == NULL_POSITION)
1.1 etheisen 437: return (NULL_POSITION);
438: }
439: }
440: /*
441: * We might as well cache it.
442: */
1.1.1.2 millert 443: add_lnum(clinenum, cpos);
1.1 etheisen 444: return (cpos);
445: }
446:
447: /*
448: * Return the line number of the "current" line.
449: * The argument "where" tells which line is to be considered
450: * the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc).
451: */
1.1.1.2 millert 452: public LINENUM
1.1 etheisen 453: currline(where)
454: int where;
455: {
456: POSITION pos;
457: POSITION len;
1.1.1.2 millert 458: LINENUM linenum;
1.1 etheisen 459:
460: pos = position(where);
461: len = ch_length();
462: while (pos == NULL_POSITION && where >= 0 && where < sc_height)
463: pos = position(++where);
464: if (pos == NULL_POSITION)
465: pos = len;
1.1.1.2 millert 466: linenum = find_linenum(pos);
1.1 etheisen 467: if (pos == len)
1.1.1.2 millert 468: linenum--;
469: return (linenum);
1.1 etheisen 470: }
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