[unix-history] / usr / othersrc / public / less-177 / linenum.c

/*
 * Code to handle displaying line numbers.
 *
 * Finding the line number of a given file position is rather tricky.
 * We don't want to just start at the beginning of the file and
 * count newlines, because that is slow for large files (and also
 * wouldn't work if we couldn't get to the start of the file; e.g.
 * if input is a long pipe).
 *
 * So we use the function add_lnum to cache line numbers.
 * We try to be very clever and keep only the more interesting
 * line numbers when we run out of space in our table.  A line
 * number is more interesting than another when it is far from
 * other line numbers.   For example, we'd rather keep lines
 * 100,200,300 than 100,101,300.  200 is more interesting than
 * 101 because 101 can be derived very cheaply from 100, while
 * 200 is more expensive to derive from 100.
 *
 * The function currline() returns the line number of a given
 * position in the file.  As a side effect, it calls add_lnum
 * to cache the line number.  Therefore currline is occasionally
 * called to make sure we cache line numbers often enough.
 */

#include "less.h"
#include "position.h"

/*
 * Structure to keep track of a line number and the associated file position.
 * A doubly-linked circular list of line numbers is kept ordered by line number.
 */
struct linenum
{
	struct linenum *next;		/* Link to next in the list */
	struct linenum *prev;		/* Line to previous in the list */
	POSITION pos;			/* File position */
	POSITION gap;			/* Gap between prev and next */
	int line;			/* Line number */
};
/*
 * "gap" needs some explanation: the gap of any particular line number
 * is the distance between the previous one and the next one in the list.
 * ("Distance" means difference in file position.)  In other words, the
 * gap of a line number is the gap which would be introduced if this
 * line number were deleted.  It is used to decide which one to replace
 * when we have a new one to insert and the table is full.
 */

#define	NPOOL	50			/* Size of line number pool */

#define	LONGTIME	(2)		/* In seconds */

public int lnloop = 0;			/* Are we in the line num loop? */

static struct linenum anchor;		/* Anchor of the list */
static struct linenum *freelist;	/* Anchor of the unused entries */
static struct linenum pool[NPOOL];	/* The pool itself */
static struct linenum *spare;		/* We always keep one spare entry */

extern int linenums;
extern int sigs;
extern int sc_height;

/*
 * Initialize the line number structures.
 */
	public void
clr_linenum()
{
	register struct linenum *p;

	/*
	 * Put all the entries on the free list.
	 * Leave one for the "spare".
	 */
	for (p = pool;  p < &pool[NPOOL-2];  p++)
		p->next = p+1;
	pool[NPOOL-2].next = NULL;
	freelist = pool;

	spare = &pool[NPOOL-1];

	/*
	 * Initialize the anchor.
	 */
	anchor.next = anchor.prev = &anchor;
	anchor.gap = 0;
	anchor.pos = (POSITION)0;
	anchor.line = 1;
}

/*
 * Calculate the gap for an entry.
 */
	static void
calcgap(p)
	register struct linenum *p;
{
	/*
	 * Don't bother to compute a gap for the anchor.
	 * Also don't compute a gap for the last one in the list.
	 * The gap for that last one should be considered infinite,
	 * but we never look at it anyway.
	 */
	if (p == &anchor || p->next == &anchor)
		return;
	p->gap = p->next->pos - p->prev->pos;
}

/*
 * Add a new line number to the cache.
 * The specified position (pos) should be the file position of the
 * FIRST character in the specified line.
 */
	public void
add_lnum(lno, pos)
	int lno;
	POSITION pos;
{
	register struct linenum *p;
	register struct linenum *new;
	register struct linenum *nextp;
	register struct linenum *prevp;
	register POSITION mingap;

	/*
	 * Find the proper place in the list for the new one.
	 * The entries are sorted by position.
	 */
	for (p = anchor.next;  p != &anchor && p->pos < pos;  p = p->next)
		if (p->line == lno)
			/* We already have this one. */
			return;
	nextp = p;
	prevp = p->prev;

	if (freelist != NULL)
	{
		/*
		 * We still have free (unused) entries.
		 * Use one of them.
		 */
		new = freelist;
		freelist = freelist->next;
	} else
	{
		/*
		 * No free entries.
		 * Use the "spare" entry.
		 */
		new = spare;
		spare = NULL;
	}

	/*
	 * Fill in the fields of the new entry,
	 * and insert it into the proper place in the list.
	 */
	new->next = nextp;
	new->prev = prevp;
	new->pos = pos;
	new->line = lno;

	nextp->prev = new;
	prevp->next = new;

	/*
	 * Recalculate gaps for the new entry and the neighboring entries.
	 */
	calcgap(new);
	calcgap(nextp);
	calcgap(prevp);

	if (spare == NULL)
	{
		/*
		 * We have used the spare entry.
		 * Scan the list to find the one with the smallest
		 * gap, take it out and make it the spare.
		 * We should never remove the last one, so stop when
		 * we get to p->next == &anchor.  This also avoids
		 * looking at the gap of the last one, which is
		 * not computed by calcgap.
		 */
		mingap = anchor.next->gap;
		for (p = anchor.next;  p->next != &anchor;  p = p->next)
		{
			if (p->gap <= mingap)
			{
				spare = p;
				mingap = p->gap;
			}
		}
		spare->next->prev = spare->prev;
		spare->prev->next = spare->next;
	}
}

/*
 * If we get stuck in a long loop trying to figure out the
 * line number, print a message to tell the user what we're doing.
 */
	static void
longloopmessage()
{
	ierror("Calculating line numbers", NULL_PARG);
	/*
	 * Set the lnloop flag here, so if the user interrupts while
	 * we are calculating line numbers, the signal handler will 
	 * turn off line numbers (linenums=0).
	 */
	lnloop = 1;
}

static int loopcount;
#if GET_TIME
static long startime;
#endif

	static void
longish()
{
#if GET_TIME
	if (loopcount >= 0 && ++loopcount > 100)
	{
		loopcount = 0;
		if (get_time() >= startime + LONGTIME)
		{
			longloopmessage();
			loopcount = -1;
		}
	}
#else
	if (loopcount >= 0 && ++loopcount > LONGLOOP)
	{
		longloopmessage();
		loopcount = -1;
	}
#endif
}

/*
 * Find the line number associated with a given position.
 * Return 0 if we can't figure it out.
 */
	public int
find_linenum(pos)
	POSITION pos;
{
	register struct linenum *p;
	register int lno;
	POSITION cpos;

	if (!linenums)
		/*
		 * We're not using line numbers.
		 */
		return (0);
	if (pos == NULL_POSITION)
		/*
		 * Caller doesn't know what he's talking about.
		 */
		return (0);
	if (pos <= ch_zero())
		/*
		 * Beginning of file is always line number 1.
		 */
		return (1);

	/*
	 * Find the entry nearest to the position we want.
	 */
	for (p = anchor.next;  p != &anchor && p->pos < pos;  p = p->next)
		continue;
	if (p->pos == pos)
		/* Found it exactly. */
		return (p->line);

	/*
	 * This is the (possibly) time-consuming part.
	 * We start at the line we just found and start
	 * reading the file forward or backward till we
	 * get to the place we want.
	 *
	 * First decide whether we should go forward from the 
	 * previous one or backwards from the next one.
	 * The decision is based on which way involves 
	 * traversing fewer bytes in the file.
	 */
	flush();
#if GET_TIME
	startime = get_time();
#endif
	if (p == &anchor || pos - p->prev->pos < p->pos - pos)
	{
		/*
		 * Go forward.
		 */
		p = p->prev;
		if (ch_seek(p->pos))
			return (0);
		loopcount = 0;
		for (lno = p->line, cpos = p->pos;  cpos < pos;  lno++)
		{
			/*
			 * Allow a signal to abort this loop.
			 */
			cpos = forw_raw_line(cpos, (char **)NULL);
			if (sigs || cpos == NULL_POSITION)
				return (0);
			longish();
		}
		lnloop = 0;
		/*
		 * We might as well cache it.
		 */
		add_lnum(lno, cpos);
		/*
		 * If the given position is not at the start of a line,
		 * make sure we return the correct line number.
		 */
		if (cpos > pos)
			lno--;
	} else
	{
		/*
		 * Go backward.
		 */
		if (ch_seek(p->pos))
			return (0);
		loopcount = 0;
		for (lno = p->line, cpos = p->pos;  cpos > pos;  lno--)
		{
			/*
			 * Allow a signal to abort this loop.
			 */
			cpos = back_raw_line(cpos, (char **)NULL);
			if (sigs || cpos == NULL_POSITION)
				return (0);
			longish();
		}
		lnloop = 0;
		/*
		 * We might as well cache it.
		 */
		add_lnum(lno, cpos);
	}

	return (lno);
}

/*
 * Find the position of a given line number.
 * Return NULL_POSITION if we can't figure it out.
 */
	public POSITION
find_pos(lno)
	int lno;
{
	register struct linenum *p;
	POSITION cpos;
	int clno;

	if (lno <= 1)
		/*
		 * Line number 1 is beginning of file.
		 */
		return (ch_zero());

	/*
	 * Find the entry nearest to the line number we want.
	 */
	for (p = anchor.next;  p != &anchor && p->line < lno;  p = p->next)
		continue;
	if (p->line == lno)
		/* Found it exactly. */
		return (p->pos);

	flush();
	if (p == &anchor || lno - p->prev->line < p->line - lno)
	{
		/*
		 * Go forward.
		 */
		p = p->prev;
		if (ch_seek(p->pos))
			return (NULL_POSITION);
		for (clno = p->line, cpos = p->pos;  clno < lno;  clno++)
		{
			/*
			 * Allow a signal to abort this loop.
			 */
			cpos = forw_raw_line(cpos, (char **)NULL);
			if (sigs || cpos == NULL_POSITION)
				return (NULL_POSITION);
		}
	} else
	{
		/*
		 * Go backward.
		 */
		if (ch_seek(p->pos))
			return (NULL_POSITION);
		for (clno = p->line, cpos = p->pos;  clno > lno;  clno--)
		{
			/*
			 * Allow a signal to abort this loop.
			 */
			cpos = back_raw_line(cpos, (char **)NULL);
			if (sigs || cpos == NULL_POSITION)
				return (NULL_POSITION);
		}
	}
	/*
	 * We might as well cache it.
	 */
	add_lnum(clno, cpos);
	return (cpos);
}

/*
 * Return the line number of the "current" line.
 * The argument "where" tells which line is to be considered
 * the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc).
 */
	public int
currline(where)
	int where;
{
	POSITION pos;
	POSITION len;
	int lnum;

	pos = position(where);
	len = ch_length();
	while (pos == NULL_POSITION && where >= 0 && where < sc_height)
		pos = position(++where);
	if (pos == NULL_POSITION)
		pos = len;
	lnum = find_linenum(pos);
	if (pos == len)
		lnum--;
	return (lnum);
}
Commit	Line	Data
77e25d77 WJ	1	/*
	2	* Code to handle displaying line numbers.
	3	*
	4	* Finding the line number of a given file position is rather tricky.
	5	* We don't want to just start at the beginning of the file and
	6	* count newlines, because that is slow for large files (and also
	7	* wouldn't work if we couldn't get to the start of the file; e.g.
	8	* if input is a long pipe).
	9	*
	10	* So we use the function add_lnum to cache line numbers.
	11	* We try to be very clever and keep only the more interesting
	12	* line numbers when we run out of space in our table. A line
	13	* number is more interesting than another when it is far from
	14	* other line numbers. For example, we'd rather keep lines
	15	* 100,200,300 than 100,101,300. 200 is more interesting than
	16	* 101 because 101 can be derived very cheaply from 100, while
	17	* 200 is more expensive to derive from 100.
	18	*
	19	* The function currline() returns the line number of a given
	20	* position in the file. As a side effect, it calls add_lnum
	21	* to cache the line number. Therefore currline is occasionally
	22	* called to make sure we cache line numbers often enough.
	23	*/
	24
	25	#include "less.h"
	26	#include "position.h"
	27
	28	/*
	29	* Structure to keep track of a line number and the associated file position.
	30	* A doubly-linked circular list of line numbers is kept ordered by line number.
	31	*/
	32	struct linenum
	33	{
	34	struct linenum next; / Link to next in the list */
	35	struct linenum prev; / Line to previous in the list */
	36	POSITION pos; /* File position */
	37	POSITION gap; /* Gap between prev and next */
	38	int line; /* Line number */
	39	};
	40	/*
	41	* "gap" needs some explanation: the gap of any particular line number
	42	* is the distance between the previous one and the next one in the list.
	43	* ("Distance" means difference in file position.) In other words, the
	44	* gap of a line number is the gap which would be introduced if this
	45	* line number were deleted. It is used to decide which one to replace
	46	* when we have a new one to insert and the table is full.
	47	*/
	48
	49	#define NPOOL 50 /* Size of line number pool */
	50
	51	#define LONGTIME (2) /* In seconds */
	52
	53	public int lnloop = 0; /* Are we in the line num loop? */
	54
	55	static struct linenum anchor; /* Anchor of the list */
	56	static struct linenum freelist; / Anchor of the unused entries */
	57	static struct linenum pool[NPOOL]; /* The pool itself */
	58	static struct linenum spare; / We always keep one spare entry */
	59
	60	extern int linenums;
	61	extern int sigs;
	62	extern int sc_height;
	63
	64	/*
65	* Initialize the line number structures.
66	*/
67	public void
68	clr_linenum()
69	{
70	register struct linenum *p;
71
72	/*
73	* Put all the entries on the free list.
74	* Leave one for the "spare".
75	*/
76	for (p = pool; p < &pool[NPOOL-2]; p++)
77	p->next = p+1;
78	pool[NPOOL-2].next = NULL;
79	freelist = pool;
80
81	spare = &pool[NPOOL-1];
82
83	/*
84	* Initialize the anchor.
85	*/
86	anchor.next = anchor.prev = &anchor;
87	anchor.gap = 0;
88	anchor.pos = (POSITION)0;
89	anchor.line = 1;
90	}
91
92	/*
93	* Calculate the gap for an entry.
94	*/
95	static void
96	calcgap(p)
97	register struct linenum *p;
98	{
99	/*
100	* Don't bother to compute a gap for the anchor.
101	* Also don't compute a gap for the last one in the list.
102	* The gap for that last one should be considered infinite,
103	* but we never look at it anyway.
104	*/
105	if (p == &anchor \|\| p->next == &anchor)
106	return;
107	p->gap = p->next->pos - p->prev->pos;
108	}
109
110	/*
111	* Add a new line number to the cache.
112	* The specified position (pos) should be the file position of the
113	* FIRST character in the specified line.
114	*/
115	public void
116	add_lnum(lno, pos)
117	int lno;
118	POSITION pos;
119	{
120	register struct linenum *p;
121	register struct linenum *new;
122	register struct linenum *nextp;
123	register struct linenum *prevp;
124	register POSITION mingap;
125
126	/*
127	* Find the proper place in the list for the new one.
128	* The entries are sorted by position.
129	*/
130	for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
131	if (p->line == lno)
132	/* We already have this one. */
133	return;
134	nextp = p;
135	prevp = p->prev;
136
137	if (freelist != NULL)
138	{
139	/*
140	* We still have free (unused) entries.
141	* Use one of them.
142	*/
143	new = freelist;
144	freelist = freelist->next;
145	} else
146	{
147	/*
148	* No free entries.
149	* Use the "spare" entry.
150	*/
151	new = spare;
152	spare = NULL;
153	}
154
155	/*
156	* Fill in the fields of the new entry,
157	* and insert it into the proper place in the list.
158	*/
159	new->next = nextp;
160	new->prev = prevp;
161	new->pos = pos;
162	new->line = lno;
163
164	nextp->prev = new;
165	prevp->next = new;
166
167	/*
168	* Recalculate gaps for the new entry and the neighboring entries.
169	*/
170	calcgap(new);
171	calcgap(nextp);
172	calcgap(prevp);
173
174	if (spare == NULL)
175	{
176	/*
177	* We have used the spare entry.
178	* Scan the list to find the one with the smallest
179	* gap, take it out and make it the spare.
180	* We should never remove the last one, so stop when
181	* we get to p->next == &anchor. This also avoids
182	* looking at the gap of the last one, which is
183	* not computed by calcgap.
184	*/
185	mingap = anchor.next->gap;
186	for (p = anchor.next; p->next != &anchor; p = p->next)
187	{
188	if (p->gap <= mingap)
189	{
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	/*
200	* If we get stuck in a long loop trying to figure out the
201	* line number, print a message to tell the user what we're doing.
202	*/
203	static void
204	longloopmessage()
205	{
206	ierror("Calculating line numbers", NULL_PARG);
207	/*
208	* Set the lnloop flag here, so if the user interrupts while
209	* we are calculating line numbers, the signal handler will
210	* turn off line numbers (linenums=0).
211	*/
212	lnloop = 1;
213	}
214
215	static int loopcount;
216	#if GET_TIME
217	static long startime;
218	#endif
219
220	static void
221	longish()
222	{
223	#if GET_TIME
224	if (loopcount >= 0 && ++loopcount > 100)
225	{
226	loopcount = 0;
227	if (get_time() >= startime + LONGTIME)
228	{
229	longloopmessage();
230	loopcount = -1;
231	}
232	}
233	#else
234	if (loopcount >= 0 && ++loopcount > LONGLOOP)
235	{
236	longloopmessage();
237	loopcount = -1;
238	}
239	#endif
240	}
241
242	/*
243	* Find the line number associated with a given position.
244	* Return 0 if we can't figure it out.
245	*/
246	public int
247	find_linenum(pos)
248	POSITION pos;
249	{
250	register struct linenum *p;
251	register int lno;
252	POSITION cpos;
253
254	if (!linenums)
255	/*
256	* We're not using line numbers.
257	*/
258	return (0);
259	if (pos == NULL_POSITION)
260	/*
261	* Caller doesn't know what he's talking about.
262	*/
263	return (0);
264	if (pos <= ch_zero())
265	/*
266	* Beginning of file is always line number 1.
267	*/
268	return (1);
269
270	/*
271	* Find the entry nearest to the position we want.
272	*/
273	for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
274	continue;
275	if (p->pos == pos)
276	/* Found it exactly. */
277	return (p->line);
278
279	/*
280	* This is the (possibly) time-consuming part.
281	* We start at the line we just found and start
282	* reading the file forward or backward till we
283	* get to the place we want.
284	*
285	* First decide whether we should go forward from the
286	* previous one or backwards from the next one.
287	* The decision is based on which way involves
288	* traversing fewer bytes in the file.
289	*/
290	flush();
291	#if GET_TIME
292	startime = get_time();
293	#endif
294	if (p == &anchor \|\| pos - p->prev->pos < p->pos - pos)
295	{
296	/*
297	* Go forward.
298	*/
299	p = p->prev;
300	if (ch_seek(p->pos))
301	return (0);
302	loopcount = 0;
303	for (lno = p->line, cpos = p->pos; cpos < pos; lno++)
304	{
305	/*
306	* Allow a signal to abort this loop.
307	*/
308	cpos = forw_raw_line(cpos, (char **)NULL);
309	if (sigs \|\| cpos == NULL_POSITION)
310	return (0);
311	longish();
312	}
313	lnloop = 0;
314	/*
315	* We might as well cache it.
316	*/
317	add_lnum(lno, cpos);
318	/*
319	* If the given position is not at the start of a line,
320	* make sure we return the correct line number.
321	*/
322	if (cpos > pos)
323	lno--;
324	} else
325	{
326	/*
327	* Go backward.
328	*/
329	if (ch_seek(p->pos))
330	return (0);
331	loopcount = 0;
332	for (lno = p->line, cpos = p->pos; cpos > pos; lno--)
333	{
334	/*
335	* Allow a signal to abort this loop.
336	*/
337	cpos = back_raw_line(cpos, (char **)NULL);
338	if (sigs \|\| cpos == NULL_POSITION)
339	return (0);
340	longish();
341	}
342	lnloop = 0;
343	/*
344	* We might as well cache it.
345	*/
346	add_lnum(lno, cpos);
347	}
348
349	return (lno);
350	}
351
352	/*
353	* Find the position of a given line number.
354	* Return NULL_POSITION if we can't figure it out.
355	*/
356	public POSITION
357	find_pos(lno)
358	int lno;
359	{
360	register struct linenum *p;
361	POSITION cpos;
362	int clno;
363
364	if (lno <= 1)
365	/*
366	* Line number 1 is beginning of file.
367	*/
368	return (ch_zero());
369
370	/*
371	* Find the entry nearest to the line number we want.
372	*/
373	for (p = anchor.next; p != &anchor && p->line < lno; p = p->next)
374	continue;
375	if (p->line == lno)
376	/* Found it exactly. */
377	return (p->pos);
378
379	flush();
380	if (p == &anchor \|\| lno - p->prev->line < p->line - lno)
381	{
382	/*
383	* Go forward.
384	*/
385	p = p->prev;
386	if (ch_seek(p->pos))
387	return (NULL_POSITION);
388	for (clno = p->line, cpos = p->pos; clno < lno; clno++)
389	{
390	/*
391	* Allow a signal to abort this loop.
392	*/
393	cpos = forw_raw_line(cpos, (char **)NULL);
394	if (sigs \|\| cpos == NULL_POSITION)
395	return (NULL_POSITION);
396	}
397	} else
398	{
399	/*
400	* Go backward.
401	*/
402	if (ch_seek(p->pos))
403	return (NULL_POSITION);
404	for (clno = p->line, cpos = p->pos; clno > lno; clno--)
405	{
406	/*
407	* Allow a signal to abort this loop.
408	*/
409	cpos = back_raw_line(cpos, (char **)NULL);
410	if (sigs \|\| cpos == NULL_POSITION)
411	return (NULL_POSITION);
412	}
413	}
414	/*
415	* We might as well cache it.
416	*/
417	add_lnum(clno, cpos);
418	return (cpos);
419	}
420
421	/*
422	* Return the line number of the "current" line.
423	* The argument "where" tells which line is to be considered
424	* the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc).
425	*/
426	public int
427	currline(where)
428	int where;
429	{
430	POSITION pos;
431	POSITION len;
432	int lnum;
433
434	pos = position(where);
435	len = ch_length();
436	while (pos == NULL_POSITION && where >= 0 && where < sc_height)
437	pos = position(++where);
438	if (pos == NULL_POSITION)
439	pos = len;
440	lnum = find_linenum(pos);
441	if (pos == len)
442	lnum--;
443	return (lnum);
444	}