contrib/less/jump.c

   1 /*
   2  * Copyright (C) 1984-2007  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  * Routines which jump to a new location in the file.
  14  */
  15
  16 #include "less.h"
  17 #include "position.h"
  18
  19 extern int hit_eof;
  20 extern int jump_sline;
  21 extern int squished;
  22 extern int screen_trashed;
  23 extern int sc_width, sc_height;
  24 extern int show_attn;
  25 extern int top_scroll;
  26
  27 /*
  28  * Jump to the end of the file.
  29  */
  30         public void
  31 jump_forw()
  32 {
  33         POSITION pos;
  34         POSITION end_pos;
  35
  36         if (ch_end_seek())
  37         {
  38                 error("Cannot seek to end of file", NULL_PARG);
  39                 return;
  40         }
  41         /*
  42          * Position the last line in the file at the last screen line.
  43          * Go back one line from the end of the file
  44          * to get to the beginning of the last line.
  45          */
  46         pos_clear();
  47         end_pos = ch_tell();
  48         pos = back_line(end_pos);
  49         if (pos == NULL_POSITION)
  50                 jump_loc((POSITION)0, sc_height-1);
  51         else
  52         {
  53                 jump_loc(pos, sc_height-1);
  54                 if (position(sc_height-1) != end_pos)
  55                         repaint();
  56         }
  57 }
  58
  59 /*
  60  * Jump to line n in the file.
  61  */
  62         public void
  63 jump_back(linenum)
  64         LINENUM linenum;
  65 {
  66         POSITION pos;
  67         PARG parg;
  68
  69         /*
  70          * Find the position of the specified line.
  71          * If we can seek there, just jump to it.
  72          * If we can't seek, but we're trying to go to line number 1,
  73          * use ch_beg_seek() to get as close as we can.
  74          */
  75         pos = find_pos(linenum);
  76         if (pos != NULL_POSITION && ch_seek(pos) == 0)
  77         {
  78                 if (show_attn)
  79                         set_attnpos(pos);
  80                 jump_loc(pos, jump_sline);
  81         } else if (linenum <= 1 && ch_beg_seek() == 0)
  82         {
  83                 jump_loc(ch_tell(), jump_sline);
  84                 error("Cannot seek to beginning of file", NULL_PARG);
  85         } else
  86         {
  87                 parg.p_linenum = linenum;
  88                 error("Cannot seek to line number %n", &parg);
  89         }
  90 }
  91
  92 /*
  93  * Repaint the screen.
  94  */
  95         public void
  96 repaint()
  97 {
  98         struct scrpos scrpos;
  99         /*
 100          * Start at the line currently at the top of the screen
 101          * and redisplay the screen.
 102          */
 103         get_scrpos(&scrpos);
 104         pos_clear();
 105         jump_loc(scrpos.pos, scrpos.ln);
 106 }
 107
 108 /*
 109  * Jump to a specified percentage into the file.
 110  */
 111         public void
 112 jump_percent(percent, fraction)
 113         int percent;
 114         long fraction;
 115 {
 116         POSITION pos, len;
 117
 118         /*
 119          * Determine the position in the file
 120          * (the specified percentage of the file's length).
 121          */
 122         if ((len = ch_length()) == NULL_POSITION)
 123         {
 124                 ierror("Determining length of file", NULL_PARG);
 125                 ch_end_seek();
 126         }
 127         if ((len = ch_length()) == NULL_POSITION)
 128         {
 129                 error("Don't know length of file", NULL_PARG);
 130                 return;
 131         }
 132         pos = percent_pos(len, percent, fraction);
 133         if (pos >= len)
 134                 pos = len-1;
 135
 136         jump_line_loc(pos, jump_sline);
 137 }
 138
 139 /*
 140  * Jump to a specified position in the file.
 141  * Like jump_loc, but the position need not be
 142  * the first character in a line.
 143  */
 144         public void
 145 jump_line_loc(pos, sline)
 146         POSITION pos;
 147         int sline;
 148 {
 149         int c;
 150
 151         if (ch_seek(pos) == 0)
 152         {
 153                 /*
 154                  * Back up to the beginning of the line.
 155                  */
 156                 while ((c = ch_back_get()) != '\n' && c != EOI)
 157                         ;
 158                 if (c == '\n')
 159                         (void) ch_forw_get();
 160                 pos = ch_tell();
 161         }
 162         if (show_attn)
 163                 set_attnpos(pos);
 164         jump_loc(pos, sline);
 165 }
 166
 167 /*
 168  * Jump to a specified position in the file.
 169  * The position must be the first character in a line.
 170  * Place the target line on a specified line on the screen.
 171  */
 172         public void
 173 jump_loc(pos, sline)
 174         POSITION pos;
 175         int sline;
 176 {
 177         register int nline;
 178         POSITION tpos;
 179         POSITION bpos;
 180
 181         /*
 182          * Normalize sline.
 183          */
 184         sline = adjsline(sline);
 185
 186         if ((nline = onscreen(pos)) >= 0)
 187         {
 188                 /*
 189                  * The line is currently displayed.
 190                  * Just scroll there.
 191                  */
 192                 nline -= sline;
 193                 if (nline > 0)
 194                         forw(nline, position(BOTTOM_PLUS_ONE), 1, 0, 0);
 195                 else
 196                         back(-nline, position(TOP), 1, 0);
 197                 if (show_attn)
 198                         repaint_hilite(1);
 199                 return;
 200         }
 201
 202         /*
 203          * Line is not on screen.
 204          * Seek to the desired location.
 205          */
 206         if (ch_seek(pos))
 207         {
 208                 error("Cannot seek to that file position", NULL_PARG);
 209                 return;
 210         }
 211
 212         /*
 213          * See if the desired line is before or after
 214          * the currently displayed screen.
 215          */
 216         tpos = position(TOP);
 217         bpos = position(BOTTOM_PLUS_ONE);
 218         if (tpos == NULL_POSITION || pos >= tpos)
 219         {
 220                 /*
 221                  * The desired line is after the current screen.
 222                  * Move back in the file far enough so that we can
 223                  * call forw() and put the desired line at the
 224                  * sline-th line on the screen.
 225                  */
 226                 for (nline = 0;  nline < sline;  nline++)
 227                 {
 228                         if (bpos != NULL_POSITION && pos <= bpos)
 229                         {
 230                                 /*
 231                                  * Surprise!  The desired line is
 232                                  * close enough to the current screen
 233                                  * that we can just scroll there after all.
 234                                  */
 235                                 forw(sc_height-sline+nline-1, bpos, 1, 0, 0);
 236                                 if (show_attn)
 237                                         repaint_hilite(1);
 238                                 return;
 239                         }
 240                         pos = back_line(pos);
 241                         if (pos == NULL_POSITION)
 242                         {
 243                                 /*
 244                                  * Oops.  Ran into the beginning of the file.
 245                                  * Exit the loop here and rely on forw()
 246                                  * below to draw the required number of
 247                                  * blank lines at the top of the screen.
 248                                  */
 249                                 break;
 250                         }
 251                 }
 252                 lastmark();
 253                 hit_eof = 0;
 254                 squished = 0;
 255                 screen_trashed = 0;
 256                 forw(sc_height-1, pos, 1, 0, sline-nline);
 257         } else
 258         {
 259                 /*
 260                  * The desired line is before the current screen.
 261                  * Move forward in the file far enough so that we
 262                  * can call back() and put the desired line at the
 263                  * sline-th line on the screen.
 264                  */
 265                 for (nline = sline;  nline < sc_height - 1;  nline++)
 266                 {
 267                         pos = forw_line(pos);
 268                         if (pos == NULL_POSITION)
 269                         {
 270                                 /*
 271                                  * Ran into end of file.
 272                                  * This shouldn't normally happen,
 273                                  * but may if there is some kind of read error.
 274                                  */
 275                                 break;
 276                         }
 277                         if (pos >= tpos)
 278                         {
 279                                 /*
 280                                  * Surprise!  The desired line is
 281                                  * close enough to the current screen
 282                                  * that we can just scroll there after all.
 283                                  */
 284                                 back(nline+1, tpos, 1, 0);
 285                                 if (show_attn)
 286                                         repaint_hilite(1);
 287                                 return;
 288                         }
 289                 }
 290                 lastmark();
 291                 if (!top_scroll)
 292                         clear();
 293                 else
 294                         home();
 295                 screen_trashed = 0;
 296                 add_back_pos(pos);
 297                 back(sc_height-1, pos, 1, 0);
 298         }
 299 }