| 1 | /* |
| 2 | * Copyright (c) 1988 Mark Nudleman |
| 3 | * Copyright (c) 1988 Regents of the University of California. |
| 4 | * All rights reserved. |
| 5 | * |
| 6 | * %sccs.include.redist.c% |
| 7 | */ |
| 8 | |
| 9 | #ifndef lint |
| 10 | static char sccsid[] = "@(#)input.c 5.4 (Berkeley) %G%"; |
| 11 | #endif /* not lint */ |
| 12 | |
| 13 | /* |
| 14 | * High level routines dealing with getting lines of input |
| 15 | * from the file being viewed. |
| 16 | * |
| 17 | * When we speak of "lines" here, we mean PRINTABLE lines; |
| 18 | * lines processed with respect to the screen width. |
| 19 | * We use the term "raw line" to refer to lines simply |
| 20 | * delimited by newlines; not processed with respect to screen width. |
| 21 | */ |
| 22 | |
| 23 | #include <sys/types.h> |
| 24 | #include <less.h> |
| 25 | |
| 26 | extern int squeeze; |
| 27 | extern int sigs; |
| 28 | extern char *line; |
| 29 | |
| 30 | off_t ch_tell(); |
| 31 | |
| 32 | /* |
| 33 | * Get the next line. |
| 34 | * A "current" position is passed and a "new" position is returned. |
| 35 | * The current position is the position of the first character of |
| 36 | * a line. The new position is the position of the first character |
| 37 | * of the NEXT line. The line obtained is the line starting at curr_pos. |
| 38 | */ |
| 39 | off_t |
| 40 | forw_line(curr_pos) |
| 41 | off_t curr_pos; |
| 42 | { |
| 43 | off_t new_pos; |
| 44 | register int c; |
| 45 | |
| 46 | if (curr_pos == NULL_POSITION || ch_seek(curr_pos)) |
| 47 | return (NULL_POSITION); |
| 48 | |
| 49 | c = ch_forw_get(); |
| 50 | if (c == EOI) |
| 51 | return (NULL_POSITION); |
| 52 | |
| 53 | prewind(); |
| 54 | for (;;) |
| 55 | { |
| 56 | if (sigs) |
| 57 | return (NULL_POSITION); |
| 58 | if (c == '\n' || c == EOI) |
| 59 | { |
| 60 | /* |
| 61 | * End of the line. |
| 62 | */ |
| 63 | new_pos = ch_tell(); |
| 64 | break; |
| 65 | } |
| 66 | |
| 67 | /* |
| 68 | * Append the char to the line and get the next char. |
| 69 | */ |
| 70 | if (pappend(c)) |
| 71 | { |
| 72 | /* |
| 73 | * The char won't fit in the line; the line |
| 74 | * is too long to print in the screen width. |
| 75 | * End the line here. |
| 76 | */ |
| 77 | new_pos = ch_tell() - 1; |
| 78 | break; |
| 79 | } |
| 80 | c = ch_forw_get(); |
| 81 | } |
| 82 | (void) pappend('\0'); |
| 83 | |
| 84 | if (squeeze && *line == '\0') |
| 85 | { |
| 86 | /* |
| 87 | * This line is blank. |
| 88 | * Skip down to the last contiguous blank line |
| 89 | * and pretend it is the one which we are returning. |
| 90 | */ |
| 91 | while ((c = ch_forw_get()) == '\n') |
| 92 | if (sigs) |
| 93 | return (NULL_POSITION); |
| 94 | if (c != EOI) |
| 95 | (void) ch_back_get(); |
| 96 | new_pos = ch_tell(); |
| 97 | } |
| 98 | |
| 99 | return (new_pos); |
| 100 | } |
| 101 | |
| 102 | /* |
| 103 | * Get the previous line. |
| 104 | * A "current" position is passed and a "new" position is returned. |
| 105 | * The current position is the position of the first character of |
| 106 | * a line. The new position is the position of the first character |
| 107 | * of the PREVIOUS line. The line obtained is the one starting at new_pos. |
| 108 | */ |
| 109 | off_t |
| 110 | back_line(curr_pos) |
| 111 | off_t curr_pos; |
| 112 | { |
| 113 | off_t new_pos, begin_new_pos; |
| 114 | int c; |
| 115 | |
| 116 | if (curr_pos == NULL_POSITION || curr_pos <= (off_t)0 || |
| 117 | ch_seek(curr_pos-1)) |
| 118 | return (NULL_POSITION); |
| 119 | |
| 120 | if (squeeze) |
| 121 | { |
| 122 | /* |
| 123 | * Find out if the "current" line was blank. |
| 124 | */ |
| 125 | (void) ch_forw_get(); /* Skip the newline */ |
| 126 | c = ch_forw_get(); /* First char of "current" line */ |
| 127 | (void) ch_back_get(); /* Restore our position */ |
| 128 | (void) ch_back_get(); |
| 129 | |
| 130 | if (c == '\n') |
| 131 | { |
| 132 | /* |
| 133 | * The "current" line was blank. |
| 134 | * Skip over any preceeding blank lines, |
| 135 | * since we skipped them in forw_line(). |
| 136 | */ |
| 137 | while ((c = ch_back_get()) == '\n') |
| 138 | if (sigs) |
| 139 | return (NULL_POSITION); |
| 140 | if (c == EOI) |
| 141 | return (NULL_POSITION); |
| 142 | (void) ch_forw_get(); |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | /* |
| 147 | * Scan backwards until we hit the beginning of the line. |
| 148 | */ |
| 149 | for (;;) |
| 150 | { |
| 151 | if (sigs) |
| 152 | return (NULL_POSITION); |
| 153 | c = ch_back_get(); |
| 154 | if (c == '\n') |
| 155 | { |
| 156 | /* |
| 157 | * This is the newline ending the previous line. |
| 158 | * We have hit the beginning of the line. |
| 159 | */ |
| 160 | new_pos = ch_tell() + 1; |
| 161 | break; |
| 162 | } |
| 163 | if (c == EOI) |
| 164 | { |
| 165 | /* |
| 166 | * We have hit the beginning of the file. |
| 167 | * This must be the first line in the file. |
| 168 | * This must, of course, be the beginning of the line. |
| 169 | */ |
| 170 | new_pos = ch_tell(); |
| 171 | break; |
| 172 | } |
| 173 | } |
| 174 | |
| 175 | /* |
| 176 | * Now scan forwards from the beginning of this line. |
| 177 | * We keep discarding "printable lines" (based on screen width) |
| 178 | * until we reach the curr_pos. |
| 179 | * |
| 180 | * {{ This algorithm is pretty inefficient if the lines |
| 181 | * are much longer than the screen width, |
| 182 | * but I don't know of any better way. }} |
| 183 | */ |
| 184 | if (ch_seek(new_pos)) |
| 185 | return (NULL_POSITION); |
| 186 | loop: |
| 187 | begin_new_pos = new_pos; |
| 188 | prewind(); |
| 189 | |
| 190 | do |
| 191 | { |
| 192 | c = ch_forw_get(); |
| 193 | if (c == EOI || sigs) |
| 194 | return (NULL_POSITION); |
| 195 | new_pos++; |
| 196 | if (c == '\n') |
| 197 | break; |
| 198 | if (pappend(c)) |
| 199 | { |
| 200 | /* |
| 201 | * Got a full printable line, but we haven't |
| 202 | * reached our curr_pos yet. Discard the line |
| 203 | * and start a new one. |
| 204 | */ |
| 205 | (void) pappend('\0'); |
| 206 | (void) ch_back_get(); |
| 207 | new_pos--; |
| 208 | goto loop; |
| 209 | } |
| 210 | } while (new_pos < curr_pos); |
| 211 | |
| 212 | (void) pappend('\0'); |
| 213 | |
| 214 | return (begin_new_pos); |
| 215 | } |