1 /* $NetBSD: position.c,v 1.4 2013/09/04 19:44:21 tron Exp $ */
2
3 /*
4 * Copyright (C) 1984-2012 Mark Nudelman
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 /*
14 * Routines dealing with the "position" table.
15 * This is a table which tells the position (in the input file) of the
16 * first char on each currently displayed line.
17 *
18 * {{ The position table is scrolled by moving all the entries.
19 * Would be better to have a circular table
20 * and just change a couple of pointers. }}
21 */
22
23 #include "less.h"
24 #include "position.h"
25
26 static POSITION *table = NULL; /* The position table */
27 static int table_size;
28
29 extern int sc_width, sc_height;
30
31 /*
32 * Return the starting file position of a line displayed on the screen.
33 * The line may be specified as a line number relative to the top
34 * of the screen, but is usually one of these special cases:
35 * the top (first) line on the screen
36 * the second line on the screen
37 * the bottom line on the screen
38 * the line after the bottom line on the screen
39 */
40 public POSITION
position(where)41 position(where)
42 int where;
43 {
44 switch (where)
45 {
46 case BOTTOM:
47 where = sc_height - 2;
48 break;
49 case BOTTOM_PLUS_ONE:
50 where = sc_height - 1;
51 break;
52 case MIDDLE:
53 where = (sc_height - 1) / 2;
54 }
55 return (table[where]);
56 }
57
58 /*
59 * Add a new file position to the bottom of the position table.
60 */
61 public void
add_forw_pos(pos)62 add_forw_pos(pos)
63 POSITION pos;
64 {
65 register int i;
66
67 /*
68 * Scroll the position table up.
69 */
70 for (i = 1; i < sc_height; i++)
71 table[i-1] = table[i];
72 table[sc_height - 1] = pos;
73 }
74
75 /*
76 * Add a new file position to the top of the position table.
77 */
78 public void
add_back_pos(pos)79 add_back_pos(pos)
80 POSITION pos;
81 {
82 register int i;
83
84 /*
85 * Scroll the position table down.
86 */
87 for (i = sc_height - 1; i > 0; i--)
88 table[i] = table[i-1];
89 table[0] = pos;
90 }
91
92 /*
93 * Initialize the position table, done whenever we clear the screen.
94 */
95 public void
pos_clear()96 pos_clear()
97 {
98 register int i;
99
100 for (i = 0; i < sc_height; i++)
101 table[i] = NULL_POSITION;
102 }
103
104 /*
105 * Allocate or reallocate the position table.
106 */
107 public void
pos_init()108 pos_init()
109 {
110 struct scrpos scrpos;
111 scrpos.pos = scrpos.ln = 0; /* XXX: GCC */
112
113 if (sc_height <= table_size)
114 return;
115 /*
116 * If we already have a table, remember the first line in it
117 * before we free it, so we can copy that line to the new table.
118 */
119 if (table != NULL)
120 {
121 get_scrpos(&scrpos);
122 free((char*)table);
123 } else
124 scrpos.pos = NULL_POSITION;
125 table = (POSITION *) ecalloc(sc_height, sizeof(POSITION));
126 table_size = sc_height;
127 pos_clear();
128 if (scrpos.pos != NULL_POSITION)
129 table[scrpos.ln-1] = scrpos.pos;
130 }
131
132 /*
133 * See if the byte at a specified position is currently on the screen.
134 * Check the position table to see if the position falls within its range.
135 * Return the position table entry if found, -1 if not.
136 */
137 public int
onscreen(pos)138 onscreen(pos)
139 POSITION pos;
140 {
141 register int i;
142
143 if (pos < table[0])
144 return (-1);
145 for (i = 1; i < sc_height; i++)
146 if (pos < table[i])
147 return (i-1);
148 return (-1);
149 }
150
151 /*
152 * See if the entire screen is empty.
153 */
154 public int
empty_screen()155 empty_screen()
156 {
157 return (empty_lines(0, sc_height-1));
158 }
159
160 public int
empty_lines(s,e)161 empty_lines(s, e)
162 int s;
163 int e;
164 {
165 register int i;
166
167 for (i = s; i <= e; i++)
168 if (table[i] != NULL_POSITION && table[i] != 0)
169 return (0);
170 return (1);
171 }
172
173 /*
174 * Get the current screen position.
175 * The screen position consists of both a file position and
176 * a screen line number where the file position is placed on the screen.
177 * Normally the screen line number is 0, but if we are positioned
178 * such that the top few lines are empty, we may have to set
179 * the screen line to a number > 0.
180 */
181 public void
get_scrpos(scrpos)182 get_scrpos(scrpos)
183 struct scrpos *scrpos;
184 {
185 register int i;
186
187 /*
188 * Find the first line on the screen which has something on it,
189 * and return the screen line number and the file position.
190 */
191 for (i = 0; i < sc_height; i++)
192 if (table[i] != NULL_POSITION)
193 {
194 scrpos->ln = i+1;
195 scrpos->pos = table[i];
196 return;
197 }
198 /*
199 * The screen is empty.
200 */
201 scrpos->pos = NULL_POSITION;
202 }
203
204 /*
205 * Adjust a screen line number to be a simple positive integer
206 * in the range { 0 .. sc_height-2 }.
207 * (The bottom line, sc_height-1, is reserved for prompts, etc.)
208 * The given "sline" may be in the range { 1 .. sc_height-1 }
209 * to refer to lines relative to the top of the screen (starting from 1),
210 * or it may be in { -1 .. -(sc_height-1) } to refer to lines
211 * relative to the bottom of the screen.
212 */
213 public int
adjsline(sline)214 adjsline(sline)
215 int sline;
216 {
217 /*
218 * Negative screen line number means
219 * relative to the bottom of the screen.
220 */
221 if (sline < 0)
222 sline += sc_height;
223 /*
224 * Can't be less than 1 or greater than sc_height-1.
225 */
226 if (sline <= 0)
227 sline = 1;
228 if (sline >= sc_height)
229 sline = sc_height - 1;
230 /*
231 * Return zero-based line number, not one-based.
232 */
233 return (sline-1);
234 }
235