1/*
2 * Copyright (C) 1984-2012  Mark Nudelman
3 * Modified for use with illumos by Garrett D'Amore.
4 * Copyright 2014 Garrett D'Amore <garrett@damore.org>
5 *
6 * You may distribute under the terms of either the GNU General Public
7 * License or the Less License, as specified in the README file.
8 *
9 * For more information, see the README file.
10 */
11
12/*
13 * Routines dealing with the "position" table.
14 * This is a table which tells the position (in the input file) of the
15 * first char on each currently displayed line.
16 *
17 * {{ The position table is scrolled by moving all the entries.
18 * Would be better to have a circular table
19 * and just change a couple of pointers. }}
20 */
21
22#include "less.h"
23#include "position.h"
24
25static off_t *table = NULL;	/* The position table */
26static int table_size;
27
28extern int sc_width, sc_height;
29
30/*
31 * Return the starting file position of a line displayed on the screen.
32 * The line may be specified as a line number relative to the top
33 * of the screen, but is usually one of these special cases:
34 *	the top (first) line on the screen
35 *	the second line on the screen
36 *	the bottom line on the screen
37 *	the line after the bottom line on the screen
38 */
39off_t
40position(int where)
41{
42	switch (where) {
43	case BOTTOM:
44		where = sc_height - 2;
45		break;
46	case BOTTOM_PLUS_ONE:
47		where = sc_height - 1;
48		break;
49	case MIDDLE:
50		where = (sc_height - 1) / 2;
51	}
52	return (table[where]);
53}
54
55/*
56 * Add a new file position to the bottom of the position table.
57 */
58void
59add_forw_pos(off_t pos)
60{
61	int i;
62
63	/*
64	 * Scroll the position table up.
65	 */
66	for (i = 1; i < sc_height; i++)
67		table[i-1] = table[i];
68	table[sc_height - 1] = pos;
69}
70
71/*
72 * Add a new file position to the top of the position table.
73 */
74void
75add_back_pos(off_t pos)
76{
77	int i;
78
79	/*
80	 * Scroll the position table down.
81	 */
82	for (i = sc_height - 1; i > 0; i--)
83		table[i] = table[i-1];
84	table[0] = pos;
85}
86
87/*
88 * Initialize the position table, done whenever we clear the screen.
89 */
90void
91pos_clear(void)
92{
93	int i;
94
95	for (i = 0; i < sc_height; i++)
96		table[i] = -1;
97}
98
99/*
100 * Allocate or reallocate the position table.
101 */
102void
103pos_init(void)
104{
105	struct scrpos scrpos;
106
107	if (sc_height <= table_size)
108		return;
109	/*
110	 * If we already have a table, remember the first line in it
111	 * before we free it, so we can copy that line to the new table.
112	 */
113	if (table != NULL) {
114		get_scrpos(&scrpos);
115		free(table);
116	} else {
117		scrpos.pos = -1;
118	}
119	table = ecalloc(sc_height, sizeof (off_t));
120	table_size = sc_height;
121	pos_clear();
122	if (scrpos.pos != -1)
123		table[scrpos.ln-1] = scrpos.pos;
124}
125
126/*
127 * See if the byte at a specified position is currently on the screen.
128 * Check the position table to see if the position falls within its range.
129 * Return the position table entry if found, -1 if not.
130 */
131int
132onscreen(off_t pos)
133{
134	int i;
135
136	if (pos < table[0])
137		return (-1);
138	for (i = 1; i < sc_height; i++)
139		if (pos < table[i])
140			return (i-1);
141	return (-1);
142}
143
144/*
145 * See if the entire screen is empty.
146 */
147int
148empty_screen(void)
149{
150	return (empty_lines(0, sc_height-1));
151}
152
153int
154empty_lines(int s, int e)
155{
156	int i;
157
158	for (i = s; i <= e; i++)
159		if (table[i] != -1 && table[i] != 0)
160			return (0);
161	return (1);
162}
163
164/*
165 * Get the current screen position.
166 * The screen position consists of both a file position and
167 * a screen line number where the file position is placed on the screen.
168 * Normally the screen line number is 0, but if we are positioned
169 * such that the top few lines are empty, we may have to set
170 * the screen line to a number > 0.
171 */
172void
173get_scrpos(struct scrpos *scrpos)
174{
175	int i;
176
177	/*
178	 * Find the first line on the screen which has something on it,
179	 * and return the screen line number and the file position.
180	 */
181	for (i = 0; i < sc_height; i++)
182		if (table[i] != -1) {
183			scrpos->ln = i+1;
184			scrpos->pos = table[i];
185			return;
186		}
187	/*
188	 * The screen is empty.
189	 */
190	scrpos->pos = -1;
191}
192
193/*
194 * Adjust a screen line number to be a simple positive integer
195 * in the range { 0 .. sc_height-2 }.
196 * (The bottom line, sc_height-1, is reserved for prompts, etc.)
197 * The given "sline" may be in the range { 1 .. sc_height-1 }
198 * to refer to lines relative to the top of the screen (starting from 1),
199 * or it may be in { -1 .. -(sc_height-1) } to refer to lines
200 * relative to the bottom of the screen.
201 */
202int
203adjsline(int sline)
204{
205	/*
206	 * Negative screen line number means
207	 * relative to the bottom of the screen.
208	 */
209	if (sline < 0)
210		sline += sc_height;
211	/*
212	 * Can't be less than 1 or greater than sc_height-1.
213	 */
214	if (sline <= 0)
215		sline = 1;
216	if (sline >= sc_height)
217		sline = sc_height - 1;
218	/*
219	 * Return zero-based line number, not one-based.
220	 */
221	return (sline-1);
222}
223