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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 | * | |
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6 | * Redistribution and use in source and binary forms are permitted |
7 | * provided that the above copyright notice and this paragraph are | |
8 | * duplicated in all such forms and that any documentation, | |
9 | * advertising materials, and other materials related to such | |
10 | * distribution and use acknowledge that the software was developed | |
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11 | * by Mark Nudleman and the University of California, Berkeley. The |
12 | * name of Mark Nudleman or the | |
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13 | * University may not be used to endorse or promote products derived |
14 | * from this software without specific prior written permission. | |
15 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
16 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
17 | * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
18 | */ | |
19 | ||
20 | #ifndef lint | |
4a7551ea | 21 | static char sccsid[] = "@(#)position.c 5.4 (Berkeley) %G%"; |
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22 | #endif /* not lint */ |
23 | ||
24 | /* | |
25 | * Routines dealing with the "position" table. | |
26 | * This is a table which tells the position (in the input file) of the | |
27 | * first char on each currently displayed line. | |
28 | * | |
29 | * {{ The position table is scrolled by moving all the entries. | |
30 | * Would be better to have a circular table | |
31 | * and just change a couple of pointers. }} | |
32 | */ | |
33 | ||
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34 | #include <sys/types.h> |
35 | #include <less.h> | |
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36 | |
37 | #define NPOS 100 /* {{ sc_height must be less than NPOS }} */ | |
966c6ec0 | 38 | static off_t table[NPOS]; /* The position table */ |
bfe13c81 | 39 | |
966c6ec0 | 40 | extern int sc_height; |
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41 | |
42 | /* | |
43 | * Return the starting file position of a line displayed on the screen. | |
44 | * The line may be specified as a line number relative to the top | |
45 | * of the screen, but is usually one of these special cases: | |
46 | * the top (first) line on the screen | |
47 | * the second line on the screen | |
48 | * the bottom line on the screen | |
49 | * the line after the bottom line on the screen | |
50 | */ | |
966c6ec0 | 51 | off_t |
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52 | position(where) |
53 | int where; | |
54 | { | |
55 | switch (where) | |
56 | { | |
57 | case BOTTOM: | |
58 | where = sc_height - 2; | |
59 | break; | |
60 | case BOTTOM_PLUS_ONE: | |
61 | where = sc_height - 1; | |
62 | break; | |
63 | case MIDDLE: | |
64 | where = sc_height / 2; | |
65 | } | |
66 | return (table[where]); | |
67 | } | |
68 | ||
69 | /* | |
70 | * Add a new file position to the bottom of the position table. | |
71 | */ | |
bfe13c81 | 72 | add_forw_pos(pos) |
966c6ec0 | 73 | off_t pos; |
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74 | { |
75 | register int i; | |
76 | ||
77 | /* | |
78 | * Scroll the position table up. | |
79 | */ | |
80 | for (i = 1; i < sc_height; i++) | |
81 | table[i-1] = table[i]; | |
82 | table[sc_height - 1] = pos; | |
83 | } | |
84 | ||
85 | /* | |
86 | * Add a new file position to the top of the position table. | |
87 | */ | |
bfe13c81 | 88 | add_back_pos(pos) |
966c6ec0 | 89 | off_t pos; |
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90 | { |
91 | register int i; | |
92 | ||
93 | /* | |
94 | * Scroll the position table down. | |
95 | */ | |
96 | for (i = sc_height - 1; i > 0; i--) | |
97 | table[i] = table[i-1]; | |
98 | table[0] = pos; | |
99 | } | |
100 | ||
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101 | copytable() |
102 | { | |
103 | register int a, b; | |
104 | ||
105 | for (a = 0; a < sc_height && table[a] == NULL_POSITION; a++); | |
106 | for (b = 0; a < sc_height; a++, b++) { | |
107 | table[b] = table[a]; | |
108 | table[a] = NULL_POSITION; | |
109 | } | |
110 | } | |
111 | ||
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112 | /* |
113 | * Initialize the position table, done whenever we clear the screen. | |
114 | */ | |
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115 | pos_clear() |
116 | { | |
117 | register int i; | |
118 | ||
119 | for (i = 0; i < sc_height; i++) | |
120 | table[i] = NULL_POSITION; | |
121 | } | |
122 | ||
123 | /* | |
124 | * See if the byte at a specified position is currently on the screen. | |
125 | * Check the position table to see if the position falls within its range. | |
126 | * Return the position table entry if found, -1 if not. | |
127 | */ | |
bfe13c81 | 128 | onscreen(pos) |
966c6ec0 | 129 | off_t pos; |
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130 | { |
131 | register int i; | |
132 | ||
133 | if (pos < table[0]) | |
134 | return (-1); | |
135 | for (i = 1; i < sc_height; i++) | |
136 | if (pos < table[i]) | |
137 | return (i-1); | |
138 | return (-1); | |
139 | } |