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1 | /* |
2 | * Copyright (c) 1988 Mark Nudleman | |
3 | * Copyright (c) 1988 Regents of the University of California. | |
4 | * All rights reserved. | |
5 | * | |
6 | * Redistribution and use in source and binary forms, with or without | |
7 | * modification, are permitted provided that the following conditions | |
8 | * are met: | |
9 | * 1. Redistributions of source code must retain the above copyright | |
10 | * notice, this list of conditions and the following disclaimer. | |
11 | * 2. Redistributions in binary form must reproduce the above copyright | |
12 | * notice, this list of conditions and the following disclaimer in the | |
13 | * documentation and/or other materials provided with the distribution. | |
14 | * 3. All advertising materials mentioning features or use of this software | |
15 | * must display the following acknowledgement: | |
16 | * This product includes software developed by the University of | |
17 | * California, Berkeley and its contributors. | |
18 | * 4. Neither the name of the University nor the names of its contributors | |
19 | * may be used to endorse or promote products derived from this software | |
20 | * without specific prior written permission. | |
21 | * | |
22 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
23 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
24 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
25 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
26 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
27 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
28 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
29 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
30 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
31 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
32 | * SUCH DAMAGE. | |
33 | */ | |
34 | ||
35 | #ifndef lint | |
36 | static char sccsid[] = "@(#)position.c 5.7 (Berkeley) 6/1/90"; | |
37 | #endif /* not lint */ | |
38 | ||
39 | /* | |
40 | * Routines dealing with the "position" table. | |
41 | * This is a table which tells the position (in the input file) of the | |
42 | * first char on each currently displayed line. | |
43 | * | |
44 | * {{ The position table is scrolled by moving all the entries. | |
45 | * Would be better to have a circular table | |
46 | * and just change a couple of pointers. }} | |
47 | */ | |
48 | ||
49 | #include <sys/types.h> | |
50 | #include <less.h> | |
51 | ||
52 | static off_t *table; /* The position table */ | |
53 | static int tablesize; | |
54 | ||
55 | extern int sc_height; | |
56 | ||
57 | /* | |
58 | * Return the starting file position of a line displayed on the screen. | |
59 | * The line may be specified as a line number relative to the top | |
60 | * of the screen, but is usually one of these special cases: | |
61 | * the top (first) line on the screen | |
62 | * the second line on the screen | |
63 | * the bottom line on the screen | |
64 | * the line after the bottom line on the screen | |
65 | */ | |
66 | off_t | |
67 | position(where) | |
68 | int where; | |
69 | { | |
70 | switch (where) | |
71 | { | |
72 | case BOTTOM: | |
73 | where = sc_height - 2; | |
74 | break; | |
75 | case BOTTOM_PLUS_ONE: | |
76 | where = sc_height - 1; | |
77 | break; | |
78 | case MIDDLE: | |
79 | where = sc_height / 2; | |
80 | } | |
81 | return (table[where]); | |
82 | } | |
83 | ||
84 | /* | |
85 | * Add a new file position to the bottom of the position table. | |
86 | */ | |
87 | add_forw_pos(pos) | |
88 | off_t pos; | |
89 | { | |
90 | register int i; | |
91 | ||
92 | /* | |
93 | * Scroll the position table up. | |
94 | */ | |
95 | for (i = 1; i < sc_height; i++) | |
96 | table[i-1] = table[i]; | |
97 | table[sc_height - 1] = pos; | |
98 | } | |
99 | ||
100 | /* | |
101 | * Add a new file position to the top of the position table. | |
102 | */ | |
103 | add_back_pos(pos) | |
104 | off_t pos; | |
105 | { | |
106 | register int i; | |
107 | ||
108 | /* | |
109 | * Scroll the position table down. | |
110 | */ | |
111 | for (i = sc_height - 1; i > 0; i--) | |
112 | table[i] = table[i-1]; | |
113 | table[0] = pos; | |
114 | } | |
115 | ||
116 | copytable() | |
117 | { | |
118 | register int a, b; | |
119 | ||
120 | for (a = 0; a < sc_height && table[a] == NULL_POSITION; a++); | |
121 | for (b = 0; a < sc_height; a++, b++) { | |
122 | table[b] = table[a]; | |
123 | table[a] = NULL_POSITION; | |
124 | } | |
125 | } | |
126 | ||
127 | /* | |
128 | * Initialize the position table, done whenever we clear the screen. | |
129 | */ | |
130 | pos_clear() | |
131 | { | |
132 | register int i; | |
133 | extern char *malloc(), *realloc(); | |
134 | ||
135 | if (table == 0) { | |
136 | tablesize = sc_height > 25 ? sc_height : 25; | |
137 | table = (off_t *)malloc(tablesize * sizeof *table); | |
138 | } else if (sc_height >= tablesize) { | |
139 | tablesize = sc_height; | |
140 | table = (off_t *)realloc(table, tablesize * sizeof *table); | |
141 | } | |
142 | ||
143 | for (i = 0; i < sc_height; i++) | |
144 | table[i] = NULL_POSITION; | |
145 | } | |
146 | ||
147 | /* | |
148 | * See if the byte at a specified position is currently on the screen. | |
149 | * Check the position table to see if the position falls within its range. | |
150 | * Return the position table entry if found, -1 if not. | |
151 | */ | |
152 | onscreen(pos) | |
153 | off_t pos; | |
154 | { | |
155 | register int i; | |
156 | ||
157 | if (pos < table[0]) | |
158 | return (-1); | |
159 | for (i = 1; i < sc_height; i++) | |
160 | if (pos < table[i]) | |
161 | return (i-1); | |
162 | return (-1); | |
163 | } |