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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 | |
a942b40b | 21 | static char sccsid[] = "@(#)input.c 5.2 (Berkeley) %G%"; |
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22 | #endif /* not lint */ |
23 | ||
24 | /* | |
25 | * High level routines dealing with getting lines of input | |
26 | * from the file being viewed. | |
27 | * | |
28 | * When we speak of "lines" here, we mean PRINTABLE lines; | |
29 | * lines processed with respect to the screen width. | |
30 | * We use the term "raw line" to refer to lines simply | |
31 | * delimited by newlines; not processed with respect to screen width. | |
32 | */ | |
33 | ||
34 | #include "less.h" | |
35 | ||
36 | extern int squeeze; | |
37 | extern int sigs; | |
38 | extern char *line; | |
39 | ||
40 | /* | |
41 | * Get the next line. | |
42 | * A "current" position is passed and a "new" position is returned. | |
43 | * The current position is the position of the first character of | |
44 | * a line. The new position is the position of the first character | |
45 | * of the NEXT line. The line obtained is the line starting at curr_pos. | |
46 | */ | |
47 | public POSITION | |
48 | forw_line(curr_pos) | |
49 | POSITION curr_pos; | |
50 | { | |
51 | POSITION new_pos; | |
52 | register int c; | |
53 | ||
54 | if (curr_pos == NULL_POSITION || ch_seek(curr_pos)) | |
55 | return (NULL_POSITION); | |
56 | ||
57 | c = ch_forw_get(); | |
58 | if (c == EOI) | |
59 | return (NULL_POSITION); | |
60 | ||
61 | prewind(); | |
62 | for (;;) | |
63 | { | |
64 | if (sigs) | |
65 | return (NULL_POSITION); | |
66 | if (c == '\n' || c == EOI) | |
67 | { | |
68 | /* | |
69 | * End of the line. | |
70 | */ | |
71 | new_pos = ch_tell(); | |
72 | break; | |
73 | } | |
74 | ||
75 | /* | |
76 | * Append the char to the line and get the next char. | |
77 | */ | |
78 | if (pappend(c)) | |
79 | { | |
80 | /* | |
81 | * The char won't fit in the line; the line | |
82 | * is too long to print in the screen width. | |
83 | * End the line here. | |
84 | */ | |
85 | new_pos = ch_tell() - 1; | |
86 | break; | |
87 | } | |
88 | c = ch_forw_get(); | |
89 | } | |
90 | (void) pappend('\0'); | |
91 | ||
92 | if (squeeze && *line == '\0') | |
93 | { | |
94 | /* | |
95 | * This line is blank. | |
96 | * Skip down to the last contiguous blank line | |
97 | * and pretend it is the one which we are returning. | |
98 | */ | |
99 | while ((c = ch_forw_get()) == '\n') | |
100 | if (sigs) | |
101 | return (NULL_POSITION); | |
102 | if (c != EOI) | |
103 | (void) ch_back_get(); | |
104 | new_pos = ch_tell(); | |
105 | } | |
106 | ||
107 | return (new_pos); | |
108 | } | |
109 | ||
110 | /* | |
111 | * Get the previous line. | |
112 | * A "current" position is passed and a "new" position is returned. | |
113 | * The current position is the position of the first character of | |
114 | * a line. The new position is the position of the first character | |
115 | * of the PREVIOUS line. The line obtained is the one starting at new_pos. | |
116 | */ | |
117 | public POSITION | |
118 | back_line(curr_pos) | |
119 | POSITION curr_pos; | |
120 | { | |
121 | POSITION new_pos, begin_new_pos; | |
122 | int c; | |
123 | ||
124 | if (curr_pos == NULL_POSITION || curr_pos <= (POSITION)0 || | |
125 | ch_seek(curr_pos-1)) | |
126 | return (NULL_POSITION); | |
127 | ||
128 | if (squeeze) | |
129 | { | |
130 | /* | |
131 | * Find out if the "current" line was blank. | |
132 | */ | |
133 | (void) ch_forw_get(); /* Skip the newline */ | |
134 | c = ch_forw_get(); /* First char of "current" line */ | |
135 | (void) ch_back_get(); /* Restore our position */ | |
136 | (void) ch_back_get(); | |
137 | ||
138 | if (c == '\n') | |
139 | { | |
140 | /* | |
141 | * The "current" line was blank. | |
142 | * Skip over any preceeding blank lines, | |
143 | * since we skipped them in forw_line(). | |
144 | */ | |
145 | while ((c = ch_back_get()) == '\n') | |
146 | if (sigs) | |
147 | return (NULL_POSITION); | |
148 | if (c == EOI) | |
149 | return (NULL_POSITION); | |
150 | (void) ch_forw_get(); | |
151 | } | |
152 | } | |
153 | ||
154 | /* | |
155 | * Scan backwards until we hit the beginning of the line. | |
156 | */ | |
157 | for (;;) | |
158 | { | |
159 | if (sigs) | |
160 | return (NULL_POSITION); | |
161 | c = ch_back_get(); | |
162 | if (c == '\n') | |
163 | { | |
164 | /* | |
165 | * This is the newline ending the previous line. | |
166 | * We have hit the beginning of the line. | |
167 | */ | |
168 | new_pos = ch_tell() + 1; | |
169 | break; | |
170 | } | |
171 | if (c == EOI) | |
172 | { | |
173 | /* | |
174 | * We have hit the beginning of the file. | |
175 | * This must be the first line in the file. | |
176 | * This must, of course, be the beginning of the line. | |
177 | */ | |
178 | new_pos = ch_tell(); | |
179 | break; | |
180 | } | |
181 | } | |
182 | ||
183 | /* | |
184 | * Now scan forwards from the beginning of this line. | |
185 | * We keep discarding "printable lines" (based on screen width) | |
186 | * until we reach the curr_pos. | |
187 | * | |
188 | * {{ This algorithm is pretty inefficient if the lines | |
189 | * are much longer than the screen width, | |
190 | * but I don't know of any better way. }} | |
191 | */ | |
192 | if (ch_seek(new_pos)) | |
193 | return (NULL_POSITION); | |
194 | loop: | |
195 | begin_new_pos = new_pos; | |
196 | prewind(); | |
197 | ||
198 | do | |
199 | { | |
200 | c = ch_forw_get(); | |
201 | if (c == EOI || sigs) | |
202 | return (NULL_POSITION); | |
203 | new_pos++; | |
204 | if (c == '\n') | |
205 | break; | |
206 | if (pappend(c)) | |
207 | { | |
208 | /* | |
209 | * Got a full printable line, but we haven't | |
210 | * reached our curr_pos yet. Discard the line | |
211 | * and start a new one. | |
212 | */ | |
213 | (void) pappend('\0'); | |
214 | (void) ch_back_get(); | |
215 | new_pos--; | |
216 | goto loop; | |
217 | } | |
218 | } while (new_pos < curr_pos); | |
219 | ||
220 | (void) pappend('\0'); | |
221 | ||
222 | return (begin_new_pos); | |
223 | } |