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
25 static off_t *table = NULL; /* The position table */
26 static int table_size;
27
28 extern 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 */
39 off_t
position(int where)40 position(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 */
58 void
add_forw_pos(off_t pos)59 add_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 */
74 void
add_back_pos(off_t pos)75 add_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 */
90 void
pos_clear(void)91 pos_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 */
102 void
pos_init(void)103 pos_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 */
131 int
onscreen(off_t pos)132 onscreen(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 */
147 int
empty_screen(void)148 empty_screen(void)
149 {
150 return (empty_lines(0, sc_height-1));
151 }
152
153 int
empty_lines(int s,int e)154 empty_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 */
172 void
get_scrpos(struct scrpos * scrpos)173 get_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 */
202 int
adjsline(int sline)203 adjsline(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