contrib/less/input.c

   1 /*
   2  * Copyright (C) 1984-2009  Mark Nudelman
   3  *
   4  * You may distribute under the terms of either the GNU General Public
   5  * License or the Less License, as specified in the README file.
   6  *
   7  * For more information about less, or for information on how to
   8  * contact the author, see the README file.
   9  */
  10
  11
  12 /*
  13  * High level routines dealing with getting lines of input
  14  * from the file being viewed.
  15  *
  16  * When we speak of "lines" here, we mean PRINTABLE lines;
  17  * lines processed with respect to the screen width.
  18  * We use the term "raw line" to refer to lines simply
  19  * delimited by newlines; not processed with respect to screen width.
  20  */
  21
  22 #include "less.h"
  23
  24 extern int squeeze;
  25 extern int chopline;
  26 extern int hshift;
  27 extern int quit_if_one_screen;
  28 extern int sigs;
  29 extern int ignore_eoi;
  30 extern int status_col;
  31 extern POSITION start_attnpos;
  32 extern POSITION end_attnpos;
  33 #if HILITE_SEARCH
  34 extern int hilite_search;
  35 extern int size_linebuf;
  36 #endif
  37
  38 /*
  39  * Get the next line.
  40  * A "current" position is passed and a "new" position is returned.
  41  * The current position is the position of the first character of
  42  * a line.  The new position is the position of the first character
  43  * of the NEXT line.  The line obtained is the line starting at curr_pos.
  44  */
  45         public POSITION
  46 forw_line(curr_pos)
  47         POSITION curr_pos;
  48 {
  49         POSITION base_pos;
  50         POSITION new_pos;
  51         register int c;
  52         int blankline;
  53         int endline;
  54         int backchars;
  55
  56 get_forw_line:
  57         if (curr_pos == NULL_POSITION)
  58         {
  59                 null_line();
  60                 return (NULL_POSITION);
  61         }
  62 #if HILITE_SEARCH
  63         if (hilite_search == OPT_ONPLUS || is_filtering() || status_col)
  64                 /*
  65                  * If we are ignoring EOI (command F), only prepare
  66                  * one line ahead, to avoid getting stuck waiting for
  67                  * slow data without displaying the data we already have.
  68                  * If we're not ignoring EOI, we *could* do the same, but
  69                  * for efficiency we prepare several lines ahead at once.
  70                  */
  71                 prep_hilite(curr_pos, curr_pos + 3*size_linebuf,
  72                                 ignore_eoi ? 1 : -1);
  73 #endif
  74         if (ch_seek(curr_pos))
  75         {
  76                 null_line();
  77                 return (NULL_POSITION);
  78         }
  79
  80         /*
  81          * Step back to the beginning of the line.
  82          */
  83         base_pos = curr_pos;
  84         for (;;)
  85         {
  86                 if (ABORT_SIGS())
  87                 {
  88                         null_line();
  89                         return (NULL_POSITION);
  90                 }
  91                 c = ch_back_get();
  92                 if (c == EOI)
  93                         break;
  94                 if (c == '\n')
  95                 {
  96                         (void) ch_forw_get();
  97                         break;
  98                 }
  99                 --base_pos;
 100         }
 101
 102         /*
 103          * Read forward again to the position we should start at.
 104          */
 105         prewind();
 106         plinenum(base_pos);
 107         (void) ch_seek(base_pos);
 108         new_pos = base_pos;
 109         while (new_pos < curr_pos)
 110         {
 111                 if (ABORT_SIGS())
 112                 {
 113                         null_line();
 114                         return (NULL_POSITION);
 115                 }
 116                 c = ch_forw_get();
 117                 backchars = pappend(c, new_pos);
 118                 new_pos++;
 119                 if (backchars > 0)
 120                 {
 121                         pshift_all();
 122                         new_pos -= backchars;
 123                         while (--backchars >= 0)
 124                                 (void) ch_back_get();
 125                 }
 126         }
 127         (void) pflushmbc();
 128         pshift_all();
 129
 130         /*
 131          * Read the first character to display.
 132          */
 133         c = ch_forw_get();
 134         if (c == EOI)
 135         {
 136                 null_line();
 137                 return (NULL_POSITION);
 138         }
 139         blankline = (c == '\n' || c == '\r');
 140
 141         /*
 142          * Read each character in the line and append to the line buffer.
 143          */
 144         for (;;)
 145         {
 146                 if (ABORT_SIGS())
 147                 {
 148                         null_line();
 149                         return (NULL_POSITION);
 150                 }
 151                 if (c == '\n' || c == EOI)
 152                 {
 153                         /*
 154                          * End of the line.
 155                          */
 156                         backchars = pflushmbc();
 157                         new_pos = ch_tell();
 158                         if (backchars > 0 && !chopline && hshift == 0)
 159                         {
 160                                 new_pos -= backchars + 1;
 161                                 endline = FALSE;
 162                         } else
 163                                 endline = TRUE;
 164                         break;
 165                 }
 166                 if (c != '\r')
 167                         blankline = 0;
 168
 169                 /*
 170                  * Append the char to the line and get the next char.
 171                  */
 172                 backchars = pappend(c, ch_tell()-1);
 173                 if (backchars > 0)
 174                 {
 175                         /*
 176                          * The char won't fit in the line; the line
 177                          * is too long to print in the screen width.
 178                          * End the line here.
 179                          */
 180                         if (chopline || hshift > 0)
 181                         {
 182                                 do
 183                                 {
 184                                         c = ch_forw_get();
 185                                 } while (c != '\n' && c != EOI);
 186                                 new_pos = ch_tell();
 187                                 endline = TRUE;
 188                                 quit_if_one_screen = FALSE;
 189                         } else
 190                         {
 191                                 new_pos = ch_tell() - backchars;
 192                                 endline = FALSE;
 193                         }
 194                         break;
 195                 }
 196                 c = ch_forw_get();
 197         }
 198
 199         pdone(endline, 1);
 200
 201 #if HILITE_SEARCH
 202         if (is_filtered(base_pos))
 203         {
 204                 /*
 205                  * We don't want to display this line.
 206                  * Get the next line.
 207                  */
 208                 curr_pos = new_pos;
 209                 goto get_forw_line;
 210         }
 211
 212         if (status_col && is_hilited(base_pos, ch_tell()-1, 1, NULL))
 213                 set_status_col('*');
 214 #endif
 215
 216         if (squeeze && blankline)
 217         {
 218                 /*
 219                  * This line is blank.
 220                  * Skip down to the last contiguous blank line
 221                  * and pretend it is the one which we are returning.
 222                  */
 223                 while ((c = ch_forw_get()) == '\n' || c == '\r')
 224                         if (ABORT_SIGS())
 225                         {
 226                                 null_line();
 227                                 return (NULL_POSITION);
 228                         }
 229                 if (c != EOI)
 230                         (void) ch_back_get();
 231                 new_pos = ch_tell();
 232         }
 233
 234         return (new_pos);
 235 }
 236
 237 /*
 238  * Get the previous line.
 239  * A "current" position is passed and a "new" position is returned.
 240  * The current position is the position of the first character of
 241  * a line.  The new position is the position of the first character
 242  * of the PREVIOUS line.  The line obtained is the one starting at new_pos.
 243  */
 244         public POSITION
 245 back_line(curr_pos)
 246         POSITION curr_pos;
 247 {
 248         POSITION new_pos, begin_new_pos, base_pos;
 249         int c;
 250         int endline;
 251         int backchars;
 252
 253 get_back_line:
 254         if (curr_pos == NULL_POSITION || curr_pos <= ch_zero())
 255         {
 256                 null_line();
 257                 return (NULL_POSITION);
 258         }
 259 #if HILITE_SEARCH
 260         if (hilite_search == OPT_ONPLUS || is_filtering() || status_col)
 261                 prep_hilite((curr_pos < 3*size_linebuf) ?
 262                                 0 : curr_pos - 3*size_linebuf, curr_pos, -1);
 263 #endif
 264         if (ch_seek(curr_pos-1))
 265         {
 266                 null_line();
 267                 return (NULL_POSITION);
 268         }
 269
 270         if (squeeze)
 271         {
 272                 /*
 273                  * Find out if the "current" line was blank.
 274                  */
 275                 (void) ch_forw_get();    /* Skip the newline */
 276                 c = ch_forw_get();       /* First char of "current" line */
 277                 (void) ch_back_get();    /* Restore our position */
 278                 (void) ch_back_get();
 279
 280                 if (c == '\n' || c == '\r')
 281                 {
 282                         /*
 283                          * The "current" line was blank.
 284                          * Skip over any preceding blank lines,
 285                          * since we skipped them in forw_line().
 286                          */
 287                         while ((c = ch_back_get()) == '\n' || c == '\r')
 288                                 if (ABORT_SIGS())
 289                                 {
 290                                         null_line();
 291                                         return (NULL_POSITION);
 292                                 }
 293                         if (c == EOI)
 294                         {
 295                                 null_line();
 296                                 return (NULL_POSITION);
 297                         }
 298                         (void) ch_forw_get();
 299                 }
 300         }
 301
 302         /*
 303          * Scan backwards until we hit the beginning of the line.
 304          */
 305         for (;;)
 306         {
 307                 if (ABORT_SIGS())
 308                 {
 309                         null_line();
 310                         return (NULL_POSITION);
 311                 }
 312                 c = ch_back_get();
 313                 if (c == '\n')
 314                 {
 315                         /*
 316                          * This is the newline ending the previous line.
 317                          * We have hit the beginning of the line.
 318                          */
 319                         base_pos = ch_tell() + 1;
 320                         break;
 321                 }
 322                 if (c == EOI)
 323                 {
 324                         /*
 325                          * We have hit the beginning of the file.
 326                          * This must be the first line in the file.
 327                          * This must, of course, be the beginning of the line.
 328                          */
 329                         base_pos = ch_tell();
 330                         break;
 331                 }
 332         }
 333
 334         /*
 335          * Now scan forwards from the beginning of this line.
 336          * We keep discarding "printable lines" (based on screen width)
 337          * until we reach the curr_pos.
 338          *
 339          * {{ This algorithm is pretty inefficient if the lines
 340          *    are much longer than the screen width,
 341          *    but I don't know of any better way. }}
 342          */
 343         new_pos = base_pos;
 344         if (ch_seek(new_pos))
 345         {
 346                 null_line();
 347                 return (NULL_POSITION);
 348         }
 349         endline = FALSE;
 350         prewind();
 351         plinenum(new_pos);
 352     loop:
 353         begin_new_pos = new_pos;
 354         (void) ch_seek(new_pos);
 355
 356         do
 357         {
 358                 c = ch_forw_get();
 359                 if (c == EOI || ABORT_SIGS())
 360                 {
 361                         null_line();
 362                         return (NULL_POSITION);
 363                 }
 364                 new_pos++;
 365                 if (c == '\n')
 366                 {
 367                         backchars = pflushmbc();
 368                         if (backchars > 0 && !chopline && hshift == 0)
 369                         {
 370                                 backchars++;
 371                                 goto shift;
 372                         }
 373                         endline = TRUE;
 374                         break;
 375                 }
 376                 backchars = pappend(c, ch_tell()-1);
 377                 if (backchars > 0)
 378                 {
 379                         /*
 380                          * Got a full printable line, but we haven't
 381                          * reached our curr_pos yet.  Discard the line
 382                          * and start a new one.
 383                          */
 384                         if (chopline || hshift > 0)
 385                         {
 386                                 endline = TRUE;
 387                                 quit_if_one_screen = FALSE;
 388                                 break;
 389                         }
 390                 shift:
 391                         pshift_all();
 392                         while (backchars-- > 0)
 393                         {
 394                                 (void) ch_back_get();
 395                                 new_pos--;
 396                         }
 397                         goto loop;
 398                 }
 399         } while (new_pos < curr_pos);
 400
 401         pdone(endline, 0);
 402
 403 #if HILITE_SEARCH
 404         if (is_filtered(base_pos))
 405         {
 406                 /*
 407                  * We don't want to display this line.
 408                  * Get the previous line.
 409                  */
 410                 curr_pos = begin_new_pos;
 411                 goto get_back_line;
 412         }
 413
 414         if (status_col && is_hilited(base_pos, ch_tell()-1, 1, NULL))
 415                 set_status_col('*');
 416 #endif
 417
 418         return (begin_new_pos);
 419 }
 420
 421 /*
 422  * Set attnpos.
 423  */
 424         public void
 425 set_attnpos(pos)
 426         POSITION pos;
 427 {
 428         int c;
 429
 430         if (pos != NULL_POSITION)
 431         {
 432                 if (ch_seek(pos))
 433                         return;
 434                 for (;;)
 435                 {
 436                         c = ch_forw_get();
 437                         if (c == EOI)
 438                                 return;
 439                         if (c != '\n' && c != '\r')
 440                                 break;
 441                         pos++;
 442                 }
 443         }
 444         start_attnpos = pos;
 445         for (;;)
 446         {
 447                 c = ch_forw_get();
 448                 pos++;
 449                 if (c == EOI || c == '\n' || c == '\r')
 450                         break;
 451         }
 452         end_attnpos = pos;
 453 }