contrib/less/jump.c

   1 /*
   2  * Copyright (C) 1984-2015  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, see the README file.
   8  */
   9
  10
  11 /*
  12  * Routines which jump to a new location in the file.
  13  */
  14
  15 #include "less.h"
  16 #include "position.h"
  17
  18 extern int jump_sline;
  19 extern int squished;
  20 extern int screen_trashed;
  21 extern int sc_width, sc_height;
  22 extern int show_attn;
  23 extern int top_scroll;
  24
  25 /*
  26  * Jump to the end of the file.
  27  */
  28         public void
  29 jump_forw()
  30 {
  31         POSITION pos;
  32         POSITION end_pos;
  33
  34         if (ch_end_seek())
  35         {
  36                 error("Cannot seek to end of file", NULL_PARG);
  37                 return;
  38         }
  39         /*
  40          * Note; lastmark will be called later by jump_loc, but it fails
  41          * because the position table has been cleared by pos_clear below.
  42          * So call it here before calling pos_clear.
  43          */
  44         lastmark();
  45         /*
  46          * Position the last line in the file at the last screen line.
  47          * Go back one line from the end of the file
  48          * to get to the beginning of the last line.
  49          */
  50         pos_clear();
  51         end_pos = ch_tell();
  52         pos = back_line(end_pos);
  53         if (pos == NULL_POSITION)
  54                 jump_loc((POSITION)0, sc_height-1);
  55         else
  56         {
  57                 jump_loc(pos, sc_height-1);
  58                 if (position(sc_height-1) != end_pos)
  59                         repaint();
  60         }
  61 }
  62
  63 /*
  64  * Jump to the last buffered line in the file.
  65  */
  66         public void
  67 jump_forw_buffered()
  68 {
  69         POSITION end;
  70
  71         if (ch_end_buffer_seek())
  72         {
  73                 error("Cannot seek to end of buffers", NULL_PARG);
  74                 return;
  75         }
  76         end = ch_tell();
  77         if (end != NULL_POSITION && end > 0)
  78                 jump_line_loc(end-1, sc_height-1);
  79 }
  80
  81 /*
  82  * Jump to line n in the file.
  83  */
  84         public void
  85 jump_back(linenum)
  86         LINENUM linenum;
  87 {
  88         POSITION pos;
  89         PARG parg;
  90
  91         /*
  92          * Find the position of the specified line.
  93          * If we can seek there, just jump to it.
  94          * If we can't seek, but we're trying to go to line number 1,
  95          * use ch_beg_seek() to get as close as we can.
  96          */
  97         pos = find_pos(linenum);
  98         if (pos != NULL_POSITION && ch_seek(pos) == 0)
  99         {
 100                 if (show_attn)
 101                         set_attnpos(pos);
 102                 jump_loc(pos, jump_sline);
 103         } else if (linenum <= 1 && ch_beg_seek() == 0)
 104         {
 105                 jump_loc(ch_tell(), jump_sline);
 106                 error("Cannot seek to beginning of file", NULL_PARG);
 107         } else
 108         {
 109                 parg.p_linenum = linenum;
 110                 error("Cannot seek to line number %n", &parg);
 111         }
 112 }
 113
 114 /*
 115  * Repaint the screen.
 116  */
 117         public void
 118 repaint()
 119 {
 120         struct scrpos scrpos;
 121         /*
 122          * Start at the line currently at the top of the screen
 123          * and redisplay the screen.
 124          */
 125         get_scrpos(&scrpos);
 126         pos_clear();
 127         jump_loc(scrpos.pos, scrpos.ln);
 128 }
 129
 130 /*
 131  * Jump to a specified percentage into the file.
 132  */
 133         public void
 134 jump_percent(percent, fraction)
 135         int percent;
 136         long fraction;
 137 {
 138         POSITION pos, len;
 139
 140         /*
 141          * Determine the position in the file
 142          * (the specified percentage of the file's length).
 143          */
 144         if ((len = ch_length()) == NULL_POSITION)
 145         {
 146                 ierror("Determining length of file", NULL_PARG);
 147                 ch_end_seek();
 148         }
 149         if ((len = ch_length()) == NULL_POSITION)
 150         {
 151                 error("Don't know length of file", NULL_PARG);
 152                 return;
 153         }
 154         pos = percent_pos(len, percent, fraction);
 155         if (pos >= len)
 156                 pos = len-1;
 157
 158         jump_line_loc(pos, jump_sline);
 159 }
 160
 161 /*
 162  * Jump to a specified position in the file.
 163  * Like jump_loc, but the position need not be
 164  * the first character in a line.
 165  */
 166         public void
 167 jump_line_loc(pos, sline)
 168         POSITION pos;
 169         int sline;
 170 {
 171         int c;
 172
 173         if (ch_seek(pos) == 0)
 174         {
 175                 /*
 176                  * Back up to the beginning of the line.
 177                  */
 178                 while ((c = ch_back_get()) != '\n' && c != EOI)
 179                         ;
 180                 if (c == '\n')
 181                         (void) ch_forw_get();
 182                 pos = ch_tell();
 183         }
 184         if (show_attn)
 185                 set_attnpos(pos);
 186         jump_loc(pos, sline);
 187 }
 188
 189 /*
 190  * Jump to a specified position in the file.
 191  * The position must be the first character in a line.
 192  * Place the target line on a specified line on the screen.
 193  */
 194         public void
 195 jump_loc(pos, sline)
 196         POSITION pos;
 197         int sline;
 198 {
 199         register int nline;
 200         POSITION tpos;
 201         POSITION bpos;
 202
 203         /*
 204          * Normalize sline.
 205          */
 206         sline = adjsline(sline);
 207
 208         if ((nline = onscreen(pos)) >= 0)
 209         {
 210                 /*
 211                  * The line is currently displayed.
 212                  * Just scroll there.
 213                  */
 214                 nline -= sline;
 215                 if (nline > 0)
 216                         forw(nline, position(BOTTOM_PLUS_ONE), 1, 0, 0);
 217                 else
 218                         back(-nline, position(TOP), 1, 0);
 219 #if HILITE_SEARCH
 220                 if (show_attn)
 221                         repaint_hilite(1);
 222 #endif
 223                 return;
 224         }
 225
 226         /*
 227          * Line is not on screen.
 228          * Seek to the desired location.
 229          */
 230         if (ch_seek(pos))
 231         {
 232                 error("Cannot seek to that file position", NULL_PARG);
 233                 return;
 234         }
 235
 236         /*
 237          * See if the desired line is before or after
 238          * the currently displayed screen.
 239          */
 240         tpos = position(TOP);
 241         bpos = position(BOTTOM_PLUS_ONE);
 242         if (tpos == NULL_POSITION || pos >= tpos)
 243         {
 244                 /*
 245                  * The desired line is after the current screen.
 246                  * Move back in the file far enough so that we can
 247                  * call forw() and put the desired line at the
 248                  * sline-th line on the screen.
 249                  */
 250                 for (nline = 0;  nline < sline;  nline++)
 251                 {
 252                         if (bpos != NULL_POSITION && pos <= bpos)
 253                         {
 254                                 /*
 255                                  * Surprise!  The desired line is
 256                                  * close enough to the current screen
 257                                  * that we can just scroll there after all.
 258                                  */
 259                                 forw(sc_height-sline+nline-1, bpos, 1, 0, 0);
 260 #if HILITE_SEARCH
 261                                 if (show_attn)
 262                                         repaint_hilite(1);
 263 #endif
 264                                 return;
 265                         }
 266                         pos = back_line(pos);
 267                         if (pos == NULL_POSITION)
 268                         {
 269                                 /*
 270                                  * Oops.  Ran into the beginning of the file.
 271                                  * Exit the loop here and rely on forw()
 272                                  * below to draw the required number of
 273                                  * blank lines at the top of the screen.
 274                                  */
 275                                 break;
 276                         }
 277                 }
 278                 lastmark();
 279                 squished = 0;
 280                 screen_trashed = 0;
 281                 forw(sc_height-1, pos, 1, 0, sline-nline);
 282         } else
 283         {
 284                 /*
 285                  * The desired line is before the current screen.
 286                  * Move forward in the file far enough so that we
 287                  * can call back() and put the desired line at the
 288                  * sline-th line on the screen.
 289                  */
 290                 for (nline = sline;  nline < sc_height - 1;  nline++)
 291                 {
 292                         pos = forw_line(pos);
 293                         if (pos == NULL_POSITION)
 294                         {
 295                                 /*
 296                                  * Ran into end of file.
 297                                  * This shouldn't normally happen,
 298                                  * but may if there is some kind of read error.
 299                                  */
 300                                 break;
 301                         }
 302 #if HILITE_SEARCH
 303                         pos = next_unfiltered(pos);
 304 #endif
 305                         if (pos >= tpos)
 306                         {
 307                                 /*
 308                                  * Surprise!  The desired line is
 309                                  * close enough to the current screen
 310                                  * that we can just scroll there after all.
 311                                  */
 312                                 back(nline+1, tpos, 1, 0);
 313 #if HILITE_SEARCH
 314                                 if (show_attn)
 315                                         repaint_hilite(1);
 316 #endif
 317                                 return;
 318                         }
 319                 }
 320                 lastmark();
 321                 if (!top_scroll)
 322                         clear();
 323                 else
 324                         home();
 325                 screen_trashed = 0;
 326                 add_back_pos(pos);
 327                 back(sc_height-1, pos, 1, 0);
 328         }
 329 }