[unix-history] / usr / src / usr.bin / more / linenum.c

/*
 * Copyright (c) 1988 Mark Nudleman
 * Copyright (c) 1988 Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Mark Nudleman.
 * 
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char sccsid[] = "@(#)linenum.c	5.2 (Berkeley) %G%";
#endif /* not lint */

/*
 * 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;

/*
 * 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(line, pos)
	int line;
	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 == line)
			/* 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 = line;

	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");
	/*
	 * 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;
}

/*
 * 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;
	register int loopcount;
	POSITION cpos;
	long startime;

	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 == (POSITION)0)
		/*
		 * 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();
	startime = get_time();
	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);
			if (sigs || cpos == NULL_POSITION)
				return (0);
			if (loopcount >= 0 && ++loopcount > 100)
			{
				loopcount = 0;
				if (get_time() >= startime + LONGTIME)
				{
					longloopmessage();
					loopcount = -1;
				}
			}
		}
		lnloop = 0;
		/*
		 * 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);
			if (sigs || cpos == NULL_POSITION)
				return (0);
			if (loopcount >= 0 && ++loopcount > 100)
			{
				loopcount = 0;
				if (get_time() >= startime + LONGTIME)
				{
					longloopmessage();
					loopcount = -1;
				}
			}
		}
		lnloop = 0;
	}

	/*
	 * We might as well cache it.
	 */
	add_lnum(lno, cpos);
	return (lno);
}

/*
 * 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;

	pos = position(where);
	if (pos == NULL_POSITION)
		pos = ch_length();
	return (find_linenum(pos));
}

#if DEBUG_STUFF
debug()
{
	register struct linenum *p;
	char buf[20];

	lower_left();
	clear_eol();
	for (p = anchor.next;  p != &anchor;  p = p->next)
	{
		sprintf(buf, "%d-%d ", p->line, p->pos);
		putstr(buf);
	}
	putstr("\n");
	error("DEBUG");
}
#endif /*DEBUG_STUFF*/
Commit	Line	Data
bfe13c81 KB	1	/*
	2	* Copyright (c) 1988 Mark Nudleman
	3	* Copyright (c) 1988 Regents of the University of California.
	4	* All rights reserved.
	5	*
	6	* This code is derived from software contributed to Berkeley by
	7	* Mark Nudleman.
	8	*
	9	* Redistribution and use in source and binary forms are permitted
	10	* provided that the above copyright notice and this paragraph are
	11	* duplicated in all such forms and that any documentation,
	12	* advertising materials, and other materials related to such
	13	* distribution and use acknowledge that the software was developed
	14	* by the University of California, Berkeley. The name of the
	15	* University may not be used to endorse or promote products derived
	16	* from this software without specific prior written permission.
	17	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
	18	* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
	19	* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
	20	*/
	21
	22	#ifndef lint
54795006	23	static char sccsid[] = "@(#)linenum.c 5.2 (Berkeley) %G%";
bfe13c81 KB	24	#endif /* not lint */
	25
	26	/*
	27	* Code to handle displaying line numbers.
	28	*
	29	* Finding the line number of a given file position is rather tricky.
	30	* We don't want to just start at the beginning of the file and
	31	* count newlines, because that is slow for large files (and also
	32	* wouldn't work if we couldn't get to the start of the file; e.g.
	33	* if input is a long pipe).
	34	*
	35	* So we use the function add_lnum to cache line numbers.
	36	* We try to be very clever and keep only the more interesting
	37	* line numbers when we run out of space in our table. A line
	38	* number is more interesting than another when it is far from
	39	* other line numbers. For example, we'd rather keep lines
	40	* 100,200,300 than 100,101,300. 200 is more interesting than
	41	* 101 because 101 can be derived very cheaply from 100, while
	42	* 200 is more expensive to derive from 100.
	43	*
	44	* The function currline() returns the line number of a given
	45	* position in the file. As a side effect, it calls add_lnum
	46	* to cache the line number. Therefore currline is occasionally
	47	* called to make sure we cache line numbers often enough.
	48	*/
	49
	50	#include "less.h"
	51	#include "position.h"
	52
	53	/*
	54	* Structure to keep track of a line number and the associated file position.
	55	* A doubly-linked circular list of line numbers is kept ordered by line number.
	56	*/
	57	struct linenum
	58	{
	59	struct linenum next; / Link to next in the list */
	60	struct linenum prev; / Line to previous in the list */
	61	POSITION pos; /* File position */
	62	POSITION gap; /* Gap between prev and next */
	63	int line; /* Line number */
	64	};
	65	/*
	66	* "gap" needs some explanation: the gap of any particular line number
	67	* is the distance between the previous one and the next one in the list.
	68	* ("Distance" means difference in file position.) In other words, the
	69	* gap of a line number is the gap which would be introduced if this
	70	* line number were deleted. It is used to decide which one to replace
	71	* when we have a new one to insert and the table is full.
	72	*/
	73
	74	#define NPOOL 50 /* Size of line number pool */
	75
	76	#define LONGTIME (2) /* In seconds */
	77
	78	public int lnloop = 0; /* Are we in the line num loop? */
	79
	80	static struct linenum anchor; /* Anchor of the list */
	81	static struct linenum freelist; / Anchor of the unused entries */
	82	static struct linenum pool[NPOOL]; /* The pool itself */
	83	static struct linenum spare; / We always keep one spare entry */
	84
	85	extern int linenums;
	86	extern int sigs;
	87
88	/*
89	* Initialize the line number structures.
90	*/
91	public void
92	clr_linenum()
93	{
94	register struct linenum *p;
95
96	/*
97	* Put all the entries on the free list.
98	* Leave one for the "spare".
99	*/
100	for (p = pool; p < &pool[NPOOL-2]; p++)
101	p->next = p+1;
102	pool[NPOOL-2].next = NULL;
103	freelist = pool;
104
105	spare = &pool[NPOOL-1];
106
107	/*
108	* Initialize the anchor.
109	*/
110	anchor.next = anchor.prev = &anchor;
111	anchor.gap = 0;
112	anchor.pos = (POSITION)0;
113	anchor.line = 1;
114	}
115
116	/*
117	* Calculate the gap for an entry.
118	*/
119	static void
120	calcgap(p)
121	register struct linenum *p;
122	{
123	/*
124	* Don't bother to compute a gap for the anchor.
125	* Also don't compute a gap for the last one in the list.
126	* The gap for that last one should be considered infinite,
127	* but we never look at it anyway.
128	*/
129	if (p == &anchor \|\| p->next == &anchor)
130	return;
131	p->gap = p->next->pos - p->prev->pos;
132	}
133
134	/*
135	* Add a new line number to the cache.
136	* The specified position (pos) should be the file position of the
137	* FIRST character in the specified line.
138	*/
139	public void
140	add_lnum(line, pos)
141	int line;
142	POSITION pos;
143	{
144	register struct linenum *p;
145	register struct linenum *new;
146	register struct linenum *nextp;
147	register struct linenum *prevp;
148	register POSITION mingap;
149
150	/*
151	* Find the proper place in the list for the new one.
152	* The entries are sorted by position.
153	*/
154	for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
155	if (p->line == line)
156	/* We already have this one. */
157	return;
158	nextp = p;
159	prevp = p->prev;
160
161	if (freelist != NULL)
162	{
163	/*
164	* We still have free (unused) entries.
165	* Use one of them.
166	*/
167	new = freelist;
168	freelist = freelist->next;
169	} else
170	{
171	/*
172	* No free entries.
173	* Use the "spare" entry.
174	*/
175	new = spare;
176	spare = NULL;
177	}
178
179	/*
180	* Fill in the fields of the new entry,
181	* and insert it into the proper place in the list.
182	*/
183	new->next = nextp;
184	new->prev = prevp;
185	new->pos = pos;
186	new->line = line;
187
188	nextp->prev = new;
189	prevp->next = new;
190
191	/*
192	* Recalculate gaps for the new entry and the neighboring entries.
193	*/
194	calcgap(new);
195	calcgap(nextp);
196	calcgap(prevp);
197
198	if (spare == NULL)
199	{
200	/*
201	* We have used the spare entry.
202	* Scan the list to find the one with the smallest
203	* gap, take it out and make it the spare.
204	* We should never remove the last one, so stop when
205	* we get to p->next == &anchor. This also avoids
206	* looking at the gap of the last one, which is
207	* not computed by calcgap.
208	*/
209	mingap = anchor.next->gap;
210	for (p = anchor.next; p->next != &anchor; p = p->next)
211	{
212	if (p->gap <= mingap)
213	{
214	spare = p;
215	mingap = p->gap;
216	}
217	}
218	spare->next->prev = spare->prev;
219	spare->prev->next = spare->next;
220	}
221	}
222
223	/*
224	* If we get stuck in a long loop trying to figure out the
225	* line number, print a message to tell the user what we're doing.
226	*/
227	static void
228	longloopmessage()
229	{
230	ierror("Calculating line numbers");
231	/*
232	* Set the lnloop flag here, so if the user interrupts while
233	* we are calculating line numbers, the signal handler will
234	* turn off line numbers (linenums=0).
235	*/
236	lnloop = 1;
237	}
238
239	/*
240	* Find the line number associated with a given position.
241	* Return 0 if we can't figure it out.
242	*/
243	public int
244	find_linenum(pos)
245	POSITION pos;
246	{
247	register struct linenum *p;
248	register int lno;
249	register int loopcount;
250	POSITION cpos;
bfe13c81	251	long startime;
bfe13c81 KB	252
	253	if (!linenums)
	254	/*
	255	* We're not using line numbers.
	256	*/
	257	return (0);
	258	if (pos == NULL_POSITION)
	259	/*
	260	* Caller doesn't know what he's talking about.
	261	*/
	262	return (0);
	263	if (pos == (POSITION)0)
	264	/*
	265	* Beginning of file is always line number 1.
	266	*/
	267	return (1);
	268
	269	/*
	270	* Find the entry nearest to the position we want.
	271	*/
	272	for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
	273	continue;
	274	if (p->pos == pos)
	275	/* Found it exactly. */
	276	return (p->line);
	277
	278	/*
	279	* This is the (possibly) time-consuming part.
	280	* We start at the line we just found and start
	281	* reading the file forward or backward till we
	282	* get to the place we want.
	283	*
	284	* First decide whether we should go forward from the
	285	* previous one or backwards from the next one.
	286	* The decision is based on which way involves
	287	* traversing fewer bytes in the file.
	288	*/
	289	flush();
bfe13c81	290	startime = get_time();
bfe13c81 KB	291	if (p == &anchor \|\| pos - p->prev->pos < p->pos - pos)
	292	{
	293	/*
	294	* Go forward.
	295	*/
	296	p = p->prev;
	297	if (ch_seek(p->pos))
	298	return (0);
	299	loopcount = 0;
	300	for (lno = p->line, cpos = p->pos; cpos < pos; lno++)
	301	{
	302	/*
	303	* Allow a signal to abort this loop.
	304	*/
	305	cpos = forw_raw_line(cpos);
	306	if (sigs \|\| cpos == NULL_POSITION)
	307	return (0);
bfe13c81 KB	308	if (loopcount >= 0 && ++loopcount > 100)
	309	{
	310	loopcount = 0;
	311	if (get_time() >= startime + LONGTIME)
	312	{
	313	longloopmessage();
	314	loopcount = -1;
	315	}
	316	}
bfe13c81 KB	317	}
	318	lnloop = 0;
	319	/*
	320	* If the given position is not at the start of a line,
	321	* make sure we return the correct line number.
	322	*/
	323	if (cpos > pos)
	324	lno--;
	325	} else
	326	{
	327	/*
	328	* Go backward.
	329	*/
	330	if (ch_seek(p->pos))
	331	return (0);
	332	loopcount = 0;
	333	for (lno = p->line, cpos = p->pos; cpos > pos; lno--)
	334	{
	335	/*
	336	* Allow a signal to abort this loop.
	337	*/
	338	cpos = back_raw_line(cpos);
	339	if (sigs \|\| cpos == NULL_POSITION)
	340	return (0);
bfe13c81 KB	341	if (loopcount >= 0 && ++loopcount > 100)
	342	{
	343	loopcount = 0;
	344	if (get_time() >= startime + LONGTIME)
	345	{
	346	longloopmessage();
	347	loopcount = -1;
	348	}
	349	}
bfe13c81 KB	350	}
	351	lnloop = 0;
	352	}
	353
	354	/*
	355	* We might as well cache it.
	356	*/
	357	add_lnum(lno, cpos);
	358	return (lno);
	359	}
	360
	361	/*
	362	* Return the line number of the "current" line.
	363	* The argument "where" tells which line is to be considered
	364	* the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc).
	365	*/
	366	public int
	367	currline(where)
	368	int where;
	369	{
	370	POSITION pos;
	371
	372	pos = position(where);
	373	if (pos == NULL_POSITION)
	374	pos = ch_length();
	375	return (find_linenum(pos));
	376	}
	377
	378	#if DEBUG_STUFF
	379	debug()
	380	{
	381	register struct linenum *p;
	382	char buf[20];
	383
	384	lower_left();
	385	clear_eol();
	386	for (p = anchor.next; p != &anchor; p = p->next)
	387	{
	388	sprintf(buf, "%d-%d ", p->line, p->pos);
	389	putstr(buf);
	390	}
	391	putstr("\n");
	392	error("DEBUG");
	393	}
	394	#endif /DEBUG_STUFF/