File: position.c

package info (click to toggle)
jless 382-iso262-2
  • links: PTS
  • area: main
  • in suites: squeeze
  • size: 1,808 kB
  • ctags: 1,332
  • sloc: sh: 18,019; ansic: 15,553; makefile: 81; awk: 7
file content (232 lines) | stat: -rw-r--r-- 4,902 bytes parent folder | download | duplicates (5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
/*
 * Copyright (C) 1984-2002  Mark Nudelman
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information about less, or for information on how to 
 * contact the author, see the README file.
 */


/*
 * Routines dealing with the "position" table.
 * This is a table which tells the position (in the input file) of the
 * first char on each currently displayed line.
 *
 * {{ The position table is scrolled by moving all the entries.
 *    Would be better to have a circular table 
 *    and just change a couple of pointers. }}
 */

#include "less.h"
#include "position.h"

static POSITION *table = NULL;	/* The position table */
static int table_size;

extern int sc_width, sc_height;

/*
 * Return the starting file position of a line displayed on the screen.
 * The line may be specified as a line number relative to the top
 * of the screen, but is usually one of these special cases:
 *	the top (first) line on the screen
 *	the second line on the screen
 *	the bottom line on the screen
 *	the line after the bottom line on the screen
 */
	public POSITION
position(where)
	int where;
{
	switch (where)
	{
	case BOTTOM:
		where = sc_height - 2;
		break;
	case BOTTOM_PLUS_ONE:
		where = sc_height - 1;
		break;
	case MIDDLE:
		where = (sc_height - 1) / 2;
	}
	return (table[where]);
}

/*
 * Add a new file position to the bottom of the position table.
 */
	public void
add_forw_pos(pos)
	POSITION pos;
{
	register int i;

	/*
	 * Scroll the position table up.
	 */
	for (i = 1;  i < sc_height;  i++)
		table[i-1] = table[i];
	table[sc_height - 1] = pos;
}

/*
 * Add a new file position to the top of the position table.
 */
	public void
add_back_pos(pos)
	POSITION pos;
{
	register int i;

	/*
	 * Scroll the position table down.
	 */
	for (i = sc_height - 1;  i > 0;  i--)
		table[i] = table[i-1];
	table[0] = pos;
}

/*
 * Initialize the position table, done whenever we clear the screen.
 */
	public void
pos_clear()
{
	register int i;

	for (i = 0;  i < sc_height;  i++)
		table[i] = NULL_POSITION;
}

/*
 * Allocate or reallocate the position table.
 */
	public void
pos_init()
{
	struct scrpos scrpos;

	if (sc_height <= table_size)
		return;
	/*
	 * If we already have a table, remember the first line in it
	 * before we free it, so we can copy that line to the new table.
	 */
	if (table != NULL)
	{
		get_scrpos(&scrpos);
		free((char*)table);
	} else
		scrpos.pos = NULL_POSITION;
	table = (POSITION *) ecalloc(sc_height, sizeof(POSITION));
	table_size = sc_height;
	pos_clear();
	if (scrpos.pos != NULL_POSITION)
		table[scrpos.ln-1] = scrpos.pos;
}

/*
 * See if the byte at a specified position is currently on the screen.
 * Check the position table to see if the position falls within its range.
 * Return the position table entry if found, -1 if not.
 */
	public int
onscreen(pos)
	POSITION pos;
{
	register int i;

	if (pos < table[0])
		return (-1);
	for (i = 1;  i < sc_height;  i++)
		if (pos < table[i])
			return (i-1);
	return (-1);
}

/*
 * See if the entire screen is empty.
 */
	public int
empty_screen()
{
	return (empty_lines(0, sc_height-1));
}

	public int
empty_lines(s, e)
	int s;
	int e;
{
	register int i;

	for (i = s;  i <= e;  i++)
		if (table[i] != NULL_POSITION)
			return (0);
	return (1);
}

/*
 * Get the current screen position.
 * The screen position consists of both a file position and
 * a screen line number where the file position is placed on the screen.
 * Normally the screen line number is 0, but if we are positioned
 * such that the top few lines are empty, we may have to set
 * the screen line to a number > 0.
 */
	public void
get_scrpos(scrpos)
	struct scrpos *scrpos;
{
	register int i;

	/*
	 * Find the first line on the screen which has something on it,
	 * and return the screen line number and the file position.
	 */
	for (i = 0; i < sc_height;  i++)
		if (table[i] != NULL_POSITION)
		{
			scrpos->ln = i+1;
			scrpos->pos = table[i];
			return;
		}
	/*
	 * The screen is empty.
	 */
	scrpos->pos = NULL_POSITION;
}

/*
 * Adjust a screen line number to be a simple positive integer
 * in the range { 0 .. sc_height-2 }.
 * (The bottom line, sc_height-1, is reserved for prompts, etc.)
 * The given "sline" may be in the range { 1 .. sc_height-1 }
 * to refer to lines relative to the top of the screen (starting from 1),
 * or it may be in { -1 .. -(sc_height-1) } to refer to lines
 * relative to the bottom of the screen.
 */
	public int
adjsline(sline)
	int sline;
{
	/*
	 * Negative screen line number means
	 * relative to the bottom of the screen.
	 */
	if (sline < 0)
		sline += sc_height;
	/*
	 * Can't be less than 1 or greater than sc_height-1.
	 */
	if (sline <= 0)
		sline = 1;
	if (sline >= sc_height)
		sline = sc_height - 1;
	/*
	 * Return zero-based line number, not one-based.
	 */
	return (sline-1);
}