1/*	$NetBSD: position.c,v 1.4 2003/08/07 09:28:01 agc Exp $	*/
2
3/*
4 * Copyright (c) 1988 Mark Nudelman
5 * Copyright (c) 1988, 1993
6 *	The Regents of the University of California.  All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#include <sys/cdefs.h>
34#ifndef lint
35#if 0
36static char sccsid[] = "@(#)position.c	8.1 (Berkeley) 6/6/93";
37#else
38__RCSID("$NetBSD: position.c,v 1.4 2003/08/07 09:28:01 agc Exp $");
39#endif
40#endif /* not lint */
41
42/*
43 * Routines dealing with the "position" table.
44 * This is a table which tells the position (in the input file) of the
45 * first char on each currently displayed line.
46 *
47 * {{ The position table is scrolled by moving all the entries.
48 *    Would be better to have a circular table
49 *    and just change a couple of pointers. }}
50 */
51
52#include <sys/types.h>
53#include <stdlib.h>
54
55#include "less.h"
56#include "extern.h"
57
58static off_t *table;		/* The position table */
59static int tablesize;
60
61/*
62 * Return the starting file position of a line displayed on the screen.
63 * The line may be specified as a line number relative to the top
64 * of the screen, but is usually one of these special cases:
65 *	the top (first) line on the screen
66 *	the second line on the screen
67 *	the bottom line on the screen
68 *	the line after the bottom line on the screen
69 */
70off_t
71position(where)
72	int where;
73{
74	switch (where)
75	{
76	case BOTTOM:
77		where = sc_height - 2;
78		break;
79	case BOTTOM_PLUS_ONE:
80		where = sc_height - 1;
81		break;
82	case MIDDLE:
83		where = sc_height / 2;
84	}
85	return (table[where]);
86}
87
88/*
89 * Add a new file position to the bottom of the position table.
90 */
91void
92add_forw_pos(pos)
93	off_t pos;
94{
95	int i;
96
97	/*
98	 * Scroll the position table up.
99	 */
100	for (i = 1;  i < sc_height;  i++)
101		table[i-1] = table[i];
102	table[sc_height - 1] = pos;
103}
104
105/*
106 * Add a new file position to the top of the position table.
107 */
108void
109add_back_pos(pos)
110	off_t pos;
111{
112	int i;
113
114	/*
115	 * Scroll the position table down.
116	 */
117	for (i = sc_height - 1;  i > 0;  i--)
118		table[i] = table[i-1];
119	table[0] = pos;
120}
121
122void
123copytable()
124{
125	int a, b;
126
127	for (a = 0; a < sc_height && table[a] == NULL_POSITION; a++);
128	for (b = 0; a < sc_height; a++, b++) {
129		table[b] = table[a];
130		table[a] = NULL_POSITION;
131	}
132}
133
134/*
135 * Initialize the position table, done whenever we clear the screen.
136 */
137void
138pos_clear()
139{
140	int i;
141
142	if (table == 0) {
143		tablesize = sc_height > 25 ? sc_height : 25;
144		table = (off_t *)malloc(tablesize * sizeof *table);
145	} else if (sc_height >= tablesize) {
146		tablesize = sc_height;
147		table = (off_t *)realloc(table, tablesize * sizeof *table);
148	}
149
150	for (i = 0;  i < sc_height;  i++)
151		table[i] = NULL_POSITION;
152}
153
154/*
155 * See if the byte at a specified position is currently on the screen.
156 * Check the position table to see if the position falls within its range.
157 * Return the position table entry if found, -1 if not.
158 */
159int
160onscreen(pos)
161	off_t pos;
162{
163	int i;
164
165	if (pos < table[0])
166		return (-1);
167	for (i = 1;  i < sc_height;  i++)
168		if (pos < table[i])
169			return (i-1);
170	return (-1);
171}
172