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77e25d77 WJ |
1 | /* |
2 | * High level routines dealing with getting lines of input | |
3 | * from the file being viewed. | |
4 | * | |
5 | * When we speak of "lines" here, we mean PRINTABLE lines; | |
6 | * lines processed with respect to the screen width. | |
7 | * We use the term "raw line" to refer to lines simply | |
8 | * delimited by newlines; not processed with respect to screen width. | |
9 | */ | |
10 | ||
11 | #include "less.h" | |
12 | ||
13 | extern int squeeze; | |
14 | extern int chopline; | |
15 | extern int sigs; | |
16 | ||
17 | /* | |
18 | * Get the next line. | |
19 | * A "current" position is passed and a "new" position is returned. | |
20 | * The current position is the position of the first character of | |
21 | * a line. The new position is the position of the first character | |
22 | * of the NEXT line. The line obtained is the line starting at curr_pos. | |
23 | */ | |
24 | public POSITION | |
25 | forw_line(curr_pos) | |
26 | POSITION curr_pos; | |
27 | { | |
28 | POSITION new_pos; | |
29 | register int c; | |
30 | int blankline; | |
31 | int endline; | |
32 | ||
33 | if (curr_pos == NULL_POSITION || ch_seek(curr_pos)) | |
34 | { | |
35 | null_line(); | |
36 | return (NULL_POSITION); | |
37 | } | |
38 | ||
39 | prewind(); | |
40 | plinenum(curr_pos); | |
41 | (void) ch_seek(curr_pos); | |
42 | ||
43 | c = ch_forw_get(); | |
44 | if (c == EOI) | |
45 | { | |
46 | null_line(); | |
47 | return (NULL_POSITION); | |
48 | } | |
49 | blankline = (c == '\n' || c == '\r'); | |
50 | ||
51 | for (;;) | |
52 | { | |
53 | if (sigs) | |
54 | { | |
55 | null_line(); | |
56 | return (NULL_POSITION); | |
57 | } | |
58 | if (c == '\n' || c == EOI) | |
59 | { | |
60 | /* | |
61 | * End of the line. | |
62 | */ | |
63 | new_pos = ch_tell(); | |
64 | endline = 1; | |
65 | break; | |
66 | } | |
67 | ||
68 | /* | |
69 | * Append the char to the line and get the next char. | |
70 | */ | |
71 | if (pappend(c)) | |
72 | { | |
73 | /* | |
74 | * The char won't fit in the line; the line | |
75 | * is too long to print in the screen width. | |
76 | * End the line here. | |
77 | */ | |
78 | if (chopline) | |
79 | { | |
80 | do | |
81 | { | |
82 | c = ch_forw_get(); | |
83 | } while (c != '\n' && c != EOI); | |
84 | new_pos = ch_tell(); | |
85 | endline = 1; | |
86 | } else | |
87 | { | |
88 | new_pos = ch_tell() - 1; | |
89 | endline = 0; | |
90 | } | |
91 | break; | |
92 | } | |
93 | c = ch_forw_get(); | |
94 | } | |
95 | pdone(endline); | |
96 | ||
97 | if (squeeze && blankline) | |
98 | { | |
99 | /* | |
100 | * This line is blank. | |
101 | * Skip down to the last contiguous blank line | |
102 | * and pretend it is the one which we are returning. | |
103 | */ | |
104 | while ((c = ch_forw_get()) == '\n' || c == '\r') | |
105 | if (sigs) | |
106 | { | |
107 | null_line(); | |
108 | return (NULL_POSITION); | |
109 | } | |
110 | if (c != EOI) | |
111 | (void) ch_back_get(); | |
112 | new_pos = ch_tell(); | |
113 | } | |
114 | ||
115 | return (new_pos); | |
116 | } | |
117 | ||
118 | /* | |
119 | * Get the previous line. | |
120 | * A "current" position is passed and a "new" position is returned. | |
121 | * The current position is the position of the first character of | |
122 | * a line. The new position is the position of the first character | |
123 | * of the PREVIOUS line. The line obtained is the one starting at new_pos. | |
124 | */ | |
125 | public POSITION | |
126 | back_line(curr_pos) | |
127 | POSITION curr_pos; | |
128 | { | |
129 | POSITION new_pos, begin_new_pos; | |
130 | int c; | |
131 | int endline; | |
132 | ||
133 | if (curr_pos == NULL_POSITION || curr_pos <= ch_zero() || | |
134 | ch_seek(curr_pos-1)) | |
135 | { | |
136 | null_line(); | |
137 | return (NULL_POSITION); | |
138 | } | |
139 | ||
140 | if (squeeze) | |
141 | { | |
142 | /* | |
143 | * Find out if the "current" line was blank. | |
144 | */ | |
145 | (void) ch_forw_get(); /* Skip the newline */ | |
146 | c = ch_forw_get(); /* First char of "current" line */ | |
147 | (void) ch_back_get(); /* Restore our position */ | |
148 | (void) ch_back_get(); | |
149 | ||
150 | if (c == '\n') | |
151 | { | |
152 | /* | |
153 | * The "current" line was blank. | |
154 | * Skip over any preceding blank lines, | |
155 | * since we skipped them in forw_line(). | |
156 | */ | |
157 | while ((c = ch_back_get()) == '\n' || c == '\r') | |
158 | if (sigs) | |
159 | { | |
160 | null_line(); | |
161 | return (NULL_POSITION); | |
162 | } | |
163 | if (c == EOI) | |
164 | { | |
165 | null_line(); | |
166 | return (NULL_POSITION); | |
167 | } | |
168 | (void) ch_forw_get(); | |
169 | } | |
170 | } | |
171 | ||
172 | /* | |
173 | * Scan backwards until we hit the beginning of the line. | |
174 | */ | |
175 | for (;;) | |
176 | { | |
177 | if (sigs) | |
178 | { | |
179 | null_line(); | |
180 | return (NULL_POSITION); | |
181 | } | |
182 | c = ch_back_get(); | |
183 | if (c == '\n') | |
184 | { | |
185 | /* | |
186 | * This is the newline ending the previous line. | |
187 | * We have hit the beginning of the line. | |
188 | */ | |
189 | new_pos = ch_tell() + 1; | |
190 | break; | |
191 | } | |
192 | if (c == EOI) | |
193 | { | |
194 | /* | |
195 | * We have hit the beginning of the file. | |
196 | * This must be the first line in the file. | |
197 | * This must, of course, be the beginning of the line. | |
198 | */ | |
199 | new_pos = ch_tell(); | |
200 | break; | |
201 | } | |
202 | } | |
203 | ||
204 | /* | |
205 | * Now scan forwards from the beginning of this line. | |
206 | * We keep discarding "printable lines" (based on screen width) | |
207 | * until we reach the curr_pos. | |
208 | * | |
209 | * {{ This algorithm is pretty inefficient if the lines | |
210 | * are much longer than the screen width, | |
211 | * but I don't know of any better way. }} | |
212 | */ | |
213 | if (ch_seek(new_pos)) | |
214 | { | |
215 | null_line(); | |
216 | return (NULL_POSITION); | |
217 | } | |
218 | endline = 0; | |
219 | loop: | |
220 | begin_new_pos = new_pos; | |
221 | prewind(); | |
222 | plinenum(new_pos); | |
223 | (void) ch_seek(new_pos); | |
224 | ||
225 | do | |
226 | { | |
227 | c = ch_forw_get(); | |
228 | if (c == EOI || sigs) | |
229 | { | |
230 | null_line(); | |
231 | return (NULL_POSITION); | |
232 | } | |
233 | new_pos++; | |
234 | if (c == '\n') | |
235 | { | |
236 | endline = 1; | |
237 | break; | |
238 | } | |
239 | if (pappend(c)) | |
240 | { | |
241 | /* | |
242 | * Got a full printable line, but we haven't | |
243 | * reached our curr_pos yet. Discard the line | |
244 | * and start a new one. | |
245 | */ | |
246 | if (chopline) | |
247 | { | |
248 | endline = 1; | |
249 | break; | |
250 | } | |
251 | pdone(0); | |
252 | (void) ch_back_get(); | |
253 | new_pos--; | |
254 | goto loop; | |
255 | } | |
256 | } while (new_pos < curr_pos); | |
257 | ||
258 | pdone(endline); | |
259 | ||
260 | return (begin_new_pos); | |
261 | } |