[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.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)linenum.c	5.6 (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 <sys/types.h>
#include <stdio.h>
#include <less.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 */
	off_t pos;			/* File position */
	off_t 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 */

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.
 */
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 = (off_t)0;
	anchor.line = 1;
}

/*
 * Calculate the gap for an entry.
 */
static
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.
 */
add_lnum(line, pos)
	int line;
	off_t pos;
{
	register struct linenum *p;
	register struct linenum *new;
	register struct linenum *nextp;
	register struct linenum *prevp;
	register off_t 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
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.
 */
find_linenum(pos)
	off_t pos;
{
	register struct linenum *p;
	register int lno;
	register int loopcount;
	off_t cpos, back_raw_line(), forw_raw_line();
	time_t startime, time();

	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 == (off_t)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();
	(void)time(&startime);
	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 (time((time_t *)NULL)
				    >= 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 (time((time_t *)NULL)
				    >= 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).
 */
currline(where)
	int where;
{
	off_t pos, ch_length(), position();

	if ((pos = position(where)) == NULL_POSITION)
		pos = ch_length();
	return(find_linenum(pos));
}
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	*
f15db449	6	* %sccs.include.redist.c%
bfe13c81 KB	7	*/
	8
	9	#ifndef lint
f15db449	10	static char sccsid[] = "@(#)linenum.c 5.6 (Berkeley) %G%";
bfe13c81 KB	11	#endif /* not lint */
	12
	13	/*
	14	* Code to handle displaying line numbers.
	15	*
	16	* Finding the line number of a given file position is rather tricky.
	17	* We don't want to just start at the beginning of the file and
	18	* count newlines, because that is slow for large files (and also
	19	* wouldn't work if we couldn't get to the start of the file; e.g.
	20	* if input is a long pipe).
	21	*
	22	* So we use the function add_lnum to cache line numbers.
	23	* We try to be very clever and keep only the more interesting
	24	* line numbers when we run out of space in our table. A line
	25	* number is more interesting than another when it is far from
	26	* other line numbers. For example, we'd rather keep lines
	27	* 100,200,300 than 100,101,300. 200 is more interesting than
	28	* 101 because 101 can be derived very cheaply from 100, while
	29	* 200 is more expensive to derive from 100.
	30	*
	31	* The function currline() returns the line number of a given
	32	* position in the file. As a side effect, it calls add_lnum
	33	* to cache the line number. Therefore currline is occasionally
	34	* called to make sure we cache line numbers often enough.
	35	*/
	36
bc258617 KB	37	#include <sys/types.h>
	38	#include <stdio.h>
	39	#include <less.h>
bfe13c81 KB	40
	41	/*
	42	* Structure to keep track of a line number and the associated file position.
	43	* A doubly-linked circular list of line numbers is kept ordered by line number.
	44	*/
	45	struct linenum
	46	{
	47	struct linenum next; / Link to next in the list */
	48	struct linenum prev; / Line to previous in the list */
bc258617 KB	49	off_t pos; /* File position */
bc258617 KB	50	off_t gap; /* Gap between prev and next */
bfe13c81 KB	51	int line; /* Line number */
	52	};
	53	/*
	54	* "gap" needs some explanation: the gap of any particular line number
	55	* is the distance between the previous one and the next one in the list.
	56	* ("Distance" means difference in file position.) In other words, the
	57	* gap of a line number is the gap which would be introduced if this
	58	* line number were deleted. It is used to decide which one to replace
	59	* when we have a new one to insert and the table is full.
	60	*/
	61
	62	#define NPOOL 50 /* Size of line number pool */
	63
	64	#define LONGTIME (2) /* In seconds */
	65
bc258617	66	int lnloop = 0; /* Are we in the line num loop? */
bfe13c81 KB	67
	68	static struct linenum anchor; /* Anchor of the list */
	69	static struct linenum freelist; / Anchor of the unused entries */
	70	static struct linenum pool[NPOOL]; /* The pool itself */
	71	static struct linenum spare; / We always keep one spare entry */
	72
	73	extern int linenums;
	74	extern int sigs;
	75
	76	/*
	77	* Initialize the line number structures.
	78	*/
bfe13c81 KB	79	clr_linenum()
	80	{
	81	register struct linenum *p;
	82
	83	/*
	84	* Put all the entries on the free list.
	85	* Leave one for the "spare".
	86	*/
	87	for (p = pool; p < &pool[NPOOL-2]; p++)
	88	p->next = p+1;
	89	pool[NPOOL-2].next = NULL;
	90	freelist = pool;
	91
	92	spare = &pool[NPOOL-1];
	93
	94	/*
	95	* Initialize the anchor.
	96	*/
	97	anchor.next = anchor.prev = &anchor;
	98	anchor.gap = 0;
bc258617	99	anchor.pos = (off_t)0;
bfe13c81 KB	100	anchor.line = 1;
	101	}
	102
	103	/*
	104	* Calculate the gap for an entry.
	105	*/
bc258617	106	static
bfe13c81 KB	107	calcgap(p)
	108	register struct linenum *p;
	109	{
	110	/*
	111	* Don't bother to compute a gap for the anchor.
	112	* Also don't compute a gap for the last one in the list.
	113	* The gap for that last one should be considered infinite,
	114	* but we never look at it anyway.
	115	*/
	116	if (p == &anchor \|\| p->next == &anchor)
	117	return;
	118	p->gap = p->next->pos - p->prev->pos;
	119	}
	120
	121	/*
	122	* Add a new line number to the cache.
	123	* The specified position (pos) should be the file position of the
	124	* FIRST character in the specified line.
	125	*/
bfe13c81 KB	126	add_lnum(line, pos)
bfe13c81 KB	127	int line;
bc258617	128	off_t pos;
bfe13c81 KB	129	{
	130	register struct linenum *p;
	131	register struct linenum *new;
	132	register struct linenum *nextp;
	133	register struct linenum *prevp;
bc258617	134	register off_t mingap;
bfe13c81 KB	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 == line)
	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 = line;
	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	*/
bc258617	213	static
bfe13c81 KB	214	longloopmessage()
	215	{
	216	ierror("Calculating line numbers");
	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
	225	/*
	226	* Find the line number associated with a given position.
	227	* Return 0 if we can't figure it out.
	228	*/
bfe13c81	229	find_linenum(pos)
bc258617	230	off_t pos;
bfe13c81 KB	231	{
	232	register struct linenum *p;
	233	register int lno;
	234	register int loopcount;
bc258617 KB	235	off_t cpos, back_raw_line(), forw_raw_line();
bc258617 KB	236	time_t startime, time();
bfe13c81 KB	237
	238	if (!linenums)
	239	/*
	240	* We're not using line numbers.
	241	*/
	242	return (0);
	243	if (pos == NULL_POSITION)
	244	/*
	245	* Caller doesn't know what he's talking about.
	246	*/
	247	return (0);
bc258617	248	if (pos == (off_t)0)
bfe13c81 KB	249	/*
	250	* Beginning of file is always line number 1.
	251	*/
	252	return (1);
	253
	254	/*
	255	* Find the entry nearest to the position we want.
	256	*/
	257	for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
	258	continue;
	259	if (p->pos == pos)
	260	/* Found it exactly. */
	261	return (p->line);
	262
	263	/*
	264	* This is the (possibly) time-consuming part.
	265	* We start at the line we just found and start
	266	* reading the file forward or backward till we
	267	* get to the place we want.
	268	*
	269	* First decide whether we should go forward from the
	270	* previous one or backwards from the next one.
	271	* The decision is based on which way involves
	272	* traversing fewer bytes in the file.
	273	*/
	274	flush();
bc258617	275	(void)time(&startime);
bfe13c81 KB	276	if (p == &anchor \|\| pos - p->prev->pos < p->pos - pos)
	277	{
	278	/*
	279	* Go forward.
	280	*/
	281	p = p->prev;
	282	if (ch_seek(p->pos))
	283	return (0);
	284	loopcount = 0;
	285	for (lno = p->line, cpos = p->pos; cpos < pos; lno++)
	286	{
	287	/*
	288	* Allow a signal to abort this loop.
	289	*/
	290	cpos = forw_raw_line(cpos);
	291	if (sigs \|\| cpos == NULL_POSITION)
	292	return (0);
bc258617	293	if (loopcount >= 0 && ++loopcount > 100) {
bfe13c81	294	loopcount = 0;
bc258617 KB	295	if (time((time_t *)NULL)
bc258617 KB	296	>= startime + LONGTIME) {
bfe13c81 KB	297	longloopmessage();
	298	loopcount = -1;
	299	}
	300	}
bfe13c81 KB	301	}
	302	lnloop = 0;
	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	lno--;
	309	} else
	310	{
	311	/*
	312	* Go backward.
	313	*/
	314	if (ch_seek(p->pos))
	315	return (0);
	316	loopcount = 0;
	317	for (lno = p->line, cpos = p->pos; cpos > pos; lno--)
	318	{
	319	/*
	320	* Allow a signal to abort this loop.
	321	*/
	322	cpos = back_raw_line(cpos);
	323	if (sigs \|\| cpos == NULL_POSITION)
	324	return (0);
bc258617	325	if (loopcount >= 0 && ++loopcount > 100) {
bfe13c81	326	loopcount = 0;
bc258617 KB	327	if (time((time_t *)NULL)
bc258617 KB	328	>= startime + LONGTIME) {
bfe13c81 KB	329	longloopmessage();
	330	loopcount = -1;
	331	}
	332	}
bfe13c81 KB	333	}
	334	lnloop = 0;
	335	}
	336
	337	/*
	338	* We might as well cache it.
	339	*/
	340	add_lnum(lno, cpos);
	341	return (lno);
	342	}
	343
	344	/*
	345	* Return the line number of the "current" line.
	346	* The argument "where" tells which line is to be considered
	347	* the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc).
	348	*/
bfe13c81 KB	349	currline(where)
	350	int where;
	351	{
bc258617	352	off_t pos, ch_length(), position();
bfe13c81	353
bc258617	354	if ((pos = position(where)) == NULL_POSITION)
bfe13c81	355	pos = ch_length();
bc258617	356	return(find_linenum(pos));
bfe13c81	357	}