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-rw-r--r--usr.bin/more/linenum.c383
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diff --git a/usr.bin/more/linenum.c b/usr.bin/more/linenum.c
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-/*
- * Copyright (c) 1988 Mark Nudleman
- * Copyright (c) 1988, 1993
- * The Regents of the University of California. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- * must display the following acknowledgement:
- * This product includes software developed by the University of
- * California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#ifndef lint
-static char sccsid[] = "@(#)linenum.c 8.1 (Berkeley) 6/6/93";
-#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));
-}
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