[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.
 *
 * 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 Mark Nudleman and the University of California, Berkeley.  The
 * name of Mark Nudleman or 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	5.5 (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	*
bfe13c81 KB	6	* Redistribution and use in source and binary forms are permitted
	7	* provided that the above copyright notice and this paragraph are
	8	* duplicated in all such forms and that any documentation,
	9	* advertising materials, and other materials related to such
	10	* distribution and use acknowledge that the software was developed
a942b40b KB	11	* by Mark Nudleman and the University of California, Berkeley. The
a942b40b KB	12	* name of Mark Nudleman or the
bfe13c81 KB	13	* University may not be used to endorse or promote products derived
	14	* from this software without specific prior written permission.
	15	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
	16	* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
	17	* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
	18	*/
	19
	20	#ifndef lint
bc258617	21	static char sccsid[] = "@(#)linenum.c 5.5 (Berkeley) %G%";
bfe13c81 KB	22	#endif /* not lint */
	23
	24	/*
	25	* Code to handle displaying line numbers.
	26	*
	27	* Finding the line number of a given file position is rather tricky.
	28	* We don't want to just start at the beginning of the file and
	29	* count newlines, because that is slow for large files (and also
	30	* wouldn't work if we couldn't get to the start of the file; e.g.
	31	* if input is a long pipe).
	32	*
	33	* So we use the function add_lnum to cache line numbers.
	34	* We try to be very clever and keep only the more interesting
	35	* line numbers when we run out of space in our table. A line
	36	* number is more interesting than another when it is far from
	37	* other line numbers. For example, we'd rather keep lines
	38	* 100,200,300 than 100,101,300. 200 is more interesting than
	39	* 101 because 101 can be derived very cheaply from 100, while
	40	* 200 is more expensive to derive from 100.
	41	*
	42	* The function currline() returns the line number of a given
	43	* position in the file. As a side effect, it calls add_lnum
	44	* to cache the line number. Therefore currline is occasionally
	45	* called to make sure we cache line numbers often enough.
	46	*/
	47
bc258617 KB	48	#include <sys/types.h>
	49	#include <stdio.h>
	50	#include <less.h>
bfe13c81 KB	51
	52	/*
	53	* Structure to keep track of a line number and the associated file position.
	54	* A doubly-linked circular list of line numbers is kept ordered by line number.
	55	*/
	56	struct linenum
	57	{
	58	struct linenum next; / Link to next in the list */
	59	struct linenum prev; / Line to previous in the list */
bc258617 KB	60	off_t pos; /* File position */
bc258617 KB	61	off_t gap; /* Gap between prev and next */
bfe13c81 KB	62	int line; /* Line number */
	63	};
	64	/*
	65	* "gap" needs some explanation: the gap of any particular line number
	66	* is the distance between the previous one and the next one in the list.
	67	* ("Distance" means difference in file position.) In other words, the
	68	* gap of a line number is the gap which would be introduced if this
	69	* line number were deleted. It is used to decide which one to replace
	70	* when we have a new one to insert and the table is full.
	71	*/
	72
	73	#define NPOOL 50 /* Size of line number pool */
	74
	75	#define LONGTIME (2) /* In seconds */
	76
bc258617	77	int lnloop = 0; /* Are we in the line num loop? */
bfe13c81 KB	78
	79	static struct linenum anchor; /* Anchor of the list */
	80	static struct linenum freelist; / Anchor of the unused entries */
	81	static struct linenum pool[NPOOL]; /* The pool itself */
	82	static struct linenum spare; / We always keep one spare entry */
	83
	84	extern int linenums;
	85	extern int sigs;
	86
	87	/*
	88	* Initialize the line number structures.
	89	*/
bfe13c81 KB	90	clr_linenum()
	91	{
	92	register struct linenum *p;
	93
	94	/*
	95	* Put all the entries on the free list.
	96	* Leave one for the "spare".
	97	*/
	98	for (p = pool; p < &pool[NPOOL-2]; p++)
	99	p->next = p+1;
	100	pool[NPOOL-2].next = NULL;
	101	freelist = pool;
	102
	103	spare = &pool[NPOOL-1];
	104
	105	/*
	106	* Initialize the anchor.
	107	*/
	108	anchor.next = anchor.prev = &anchor;
	109	anchor.gap = 0;
bc258617	110	anchor.pos = (off_t)0;
bfe13c81 KB	111	anchor.line = 1;
	112	}
	113
	114	/*
	115	* Calculate the gap for an entry.
	116	*/
bc258617	117	static
bfe13c81 KB	118	calcgap(p)
	119	register struct linenum *p;
	120	{
	121	/*
	122	* Don't bother to compute a gap for the anchor.
	123	* Also don't compute a gap for the last one in the list.
	124	* The gap for that last one should be considered infinite,
	125	* but we never look at it anyway.
	126	*/
	127	if (p == &anchor \|\| p->next == &anchor)
	128	return;
	129	p->gap = p->next->pos - p->prev->pos;
	130	}
	131
	132	/*
	133	* Add a new line number to the cache.
	134	* The specified position (pos) should be the file position of the
	135	* FIRST character in the specified line.
	136	*/
bfe13c81 KB	137	add_lnum(line, pos)
bfe13c81 KB	138	int line;
bc258617	139	off_t pos;
bfe13c81 KB	140	{
	141	register struct linenum *p;
	142	register struct linenum *new;
	143	register struct linenum *nextp;
	144	register struct linenum *prevp;
bc258617	145	register off_t mingap;
bfe13c81 KB	146
	147	/*
	148	* Find the proper place in the list for the new one.
	149	* The entries are sorted by position.
	150	*/
	151	for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
	152	if (p->line == line)
	153	/* We already have this one. */
	154	return;
	155	nextp = p;
	156	prevp = p->prev;
	157
	158	if (freelist != NULL)
	159	{
	160	/*
	161	* We still have free (unused) entries.
	162	* Use one of them.
	163	*/
	164	new = freelist;
	165	freelist = freelist->next;
	166	} else
	167	{
	168	/*
	169	* No free entries.
	170	* Use the "spare" entry.
	171	*/
	172	new = spare;
	173	spare = NULL;
	174	}
	175
	176	/*
	177	* Fill in the fields of the new entry,
	178	* and insert it into the proper place in the list.
	179	*/
	180	new->next = nextp;
	181	new->prev = prevp;
	182	new->pos = pos;
	183	new->line = line;
	184
	185	nextp->prev = new;
	186	prevp->next = new;
	187
	188	/*
	189	* Recalculate gaps for the new entry and the neighboring entries.
	190	*/
	191	calcgap(new);
	192	calcgap(nextp);
	193	calcgap(prevp);
	194
	195	if (spare == NULL)
	196	{
	197	/*
	198	* We have used the spare entry.
	199	* Scan the list to find the one with the smallest
	200	* gap, take it out and make it the spare.
	201	* We should never remove the last one, so stop when
	202	* we get to p->next == &anchor. This also avoids
	203	* looking at the gap of the last one, which is
	204	* not computed by calcgap.
	205	*/
	206	mingap = anchor.next->gap;
	207	for (p = anchor.next; p->next != &anchor; p = p->next)
	208	{
	209	if (p->gap <= mingap)
210	{
211	spare = p;
212	mingap = p->gap;
213	}
214	}
215	spare->next->prev = spare->prev;
216	spare->prev->next = spare->next;
217	}
218	}
219
220	/*
221	* If we get stuck in a long loop trying to figure out the
222	* line number, print a message to tell the user what we're doing.
223	*/
bc258617	224	static
bfe13c81 KB	225	longloopmessage()
	226	{
	227	ierror("Calculating line numbers");
	228	/*
	229	* Set the lnloop flag here, so if the user interrupts while
	230	* we are calculating line numbers, the signal handler will
	231	* turn off line numbers (linenums=0).
	232	*/
	233	lnloop = 1;
	234	}
	235
	236	/*
	237	* Find the line number associated with a given position.
	238	* Return 0 if we can't figure it out.
	239	*/
bfe13c81	240	find_linenum(pos)
bc258617	241	off_t pos;
bfe13c81 KB	242	{
	243	register struct linenum *p;
	244	register int lno;
	245	register int loopcount;
bc258617 KB	246	off_t cpos, back_raw_line(), forw_raw_line();
bc258617 KB	247	time_t startime, time();
bfe13c81 KB	248
	249	if (!linenums)
	250	/*
	251	* We're not using line numbers.
	252	*/
	253	return (0);
	254	if (pos == NULL_POSITION)
	255	/*
	256	* Caller doesn't know what he's talking about.
	257	*/
	258	return (0);
bc258617	259	if (pos == (off_t)0)
bfe13c81 KB	260	/*
	261	* Beginning of file is always line number 1.
	262	*/
	263	return (1);
	264
	265	/*
	266	* Find the entry nearest to the position we want.
	267	*/
	268	for (p = anchor.next; p != &anchor && p->pos < pos; p = p->next)
	269	continue;
	270	if (p->pos == pos)
	271	/* Found it exactly. */
	272	return (p->line);
	273
	274	/*
	275	* This is the (possibly) time-consuming part.
	276	* We start at the line we just found and start
	277	* reading the file forward or backward till we
	278	* get to the place we want.
	279	*
	280	* First decide whether we should go forward from the
	281	* previous one or backwards from the next one.
	282	* The decision is based on which way involves
	283	* traversing fewer bytes in the file.
	284	*/
	285	flush();
bc258617	286	(void)time(&startime);
bfe13c81 KB	287	if (p == &anchor \|\| pos - p->prev->pos < p->pos - pos)
	288	{
	289	/*
	290	* Go forward.
	291	*/
	292	p = p->prev;
	293	if (ch_seek(p->pos))
	294	return (0);
	295	loopcount = 0;
	296	for (lno = p->line, cpos = p->pos; cpos < pos; lno++)
	297	{
	298	/*
	299	* Allow a signal to abort this loop.
	300	*/
	301	cpos = forw_raw_line(cpos);
	302	if (sigs \|\| cpos == NULL_POSITION)
	303	return (0);
bc258617	304	if (loopcount >= 0 && ++loopcount > 100) {
bfe13c81	305	loopcount = 0;
bc258617 KB	306	if (time((time_t *)NULL)
bc258617 KB	307	>= startime + LONGTIME) {
bfe13c81 KB	308	longloopmessage();
	309	loopcount = -1;
	310	}
	311	}
bfe13c81 KB	312	}
	313	lnloop = 0;
	314	/*
	315	* If the given position is not at the start of a line,
	316	* make sure we return the correct line number.
	317	*/
	318	if (cpos > pos)
	319	lno--;
	320	} else
	321	{
	322	/*
	323	* Go backward.
	324	*/
	325	if (ch_seek(p->pos))
	326	return (0);
	327	loopcount = 0;
	328	for (lno = p->line, cpos = p->pos; cpos > pos; lno--)
	329	{
	330	/*
	331	* Allow a signal to abort this loop.
	332	*/
	333	cpos = back_raw_line(cpos);
	334	if (sigs \|\| cpos == NULL_POSITION)
	335	return (0);
bc258617	336	if (loopcount >= 0 && ++loopcount > 100) {
bfe13c81	337	loopcount = 0;
bc258617 KB	338	if (time((time_t *)NULL)
bc258617 KB	339	>= startime + LONGTIME) {
bfe13c81 KB	340	longloopmessage();
	341	loopcount = -1;
	342	}
	343	}
bfe13c81 KB	344	}
	345	lnloop = 0;
	346	}
	347
	348	/*
	349	* We might as well cache it.
	350	*/
	351	add_lnum(lno, cpos);
	352	return (lno);
	353	}
	354
	355	/*
	356	* Return the line number of the "current" line.
	357	* The argument "where" tells which line is to be considered
	358	* the "current" line (e.g. TOP, BOTTOM, MIDDLE, etc).
	359	*/
bfe13c81 KB	360	currline(where)
	361	int where;
	362	{
bc258617	363	off_t pos, ch_length(), position();
bfe13c81	364
bc258617	365	if ((pos = position(where)) == NULL_POSITION)
bfe13c81	366	pos = ch_length();
bc258617	367	return(find_linenum(pos));
bfe13c81	368	}