contrib/less-381/jump.c

   1 /*
   2  * Copyright (C) 1984-2002  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
  26 /*
  27  * Jump to the end of the file.
  28  */
  29         public void
  30 jump_forw()
  31 {
  32         POSITION pos;
  33
  34         if (ch_end_seek())
  35         {
  36                 error("Cannot seek to end of file", NULL_PARG);
  37                 return;
  38         }
  39         /*
  40          * Position the last line in the file at the last screen line.
  41          * Go back one line from the end of the file
  42          * to get to the beginning of the last line.
  43          */
  44         pos = back_line(ch_tell());
  45         if (pos == NULL_POSITION)
  46                 jump_loc((POSITION)0, sc_height-1);
  47         else
  48                 jump_loc(pos, sc_height-1);
  49 }
  50
  51 /*
  52  * Jump to line n in the file.
  53  */
  54         public void
  55 jump_back(linenum)
  56         LINENUM linenum;
  57 {
  58         POSITION pos;
  59         PARG parg;
  60
  61         /*
  62          * Find the position of the specified line.
  63          * If we can seek there, just jump to it.
  64          * If we can't seek, but we're trying to go to line number 1,
  65          * use ch_beg_seek() to get as close as we can.
  66          */
  67         pos = find_pos(linenum);
  68         if (pos != NULL_POSITION && ch_seek(pos) == 0)
  69         {
  70                 if (show_attn)
  71                         set_attnpos(pos);
  72                 jump_loc(pos, jump_sline);
  73         } else if (linenum <= 1 && ch_beg_seek() == 0)
  74         {
  75                 jump_loc(ch_tell(), jump_sline);
  76                 error("Cannot seek to beginning of file", NULL_PARG);
  77         } else
  78         {
  79                 parg.p_linenum = linenum;
  80                 error("Cannot seek to line number %n", &parg);
  81         }
  82 }
  83
  84 /*
  85  * Repaint the screen.
  86  */
  87         public void
  88 repaint()
  89 {
  90         struct scrpos scrpos;
  91         /*
  92          * Start at the line currently at the top of the screen
  93          * and redisplay the screen.
  94          */
  95         get_scrpos(&scrpos);
  96         pos_clear();
  97         jump_loc(scrpos.pos, scrpos.ln);
  98 }
  99
 100 /*
 101  * Jump to a specified percentage into the file.
 102  */
 103         public void
 104 jump_percent(percent)
 105         int percent;
 106 {
 107         POSITION pos, len;
 108
 109         /*
 110          * Determine the position in the file
 111          * (the specified percentage of the file's length).
 112          */
 113         if ((len = ch_length()) == NULL_POSITION)
 114         {
 115                 ierror("Determining length of file", NULL_PARG);
 116                 ch_end_seek();
 117         }
 118         if ((len = ch_length()) == NULL_POSITION)
 119         {
 120                 error("Don't know length of file", NULL_PARG);
 121                 return;
 122         }
 123         pos = percent_pos(len, percent);
 124         if (pos >= len)
 125                 pos = len-1;
 126
 127         jump_line_loc(pos, jump_sline);
 128 }
 129
 130 /*
 131  * Jump to a specified position in the file.
 132  * Like jump_loc, but the position need not be
 133  * the first character in a line.
 134  */
 135         public void
 136 jump_line_loc(pos, sline)
 137         POSITION pos;
 138         int sline;
 139 {
 140         int c;
 141
 142         if (ch_seek(pos) == 0)
 143         {
 144                 /*
 145                  * Back up to the beginning of the line.
 146                  */
 147                 while ((c = ch_back_get()) != '\n' && c != EOI)
 148                         ;
 149                 if (c == '\n')
 150                         (void) ch_forw_get();
 151                 pos = ch_tell();
 152         }
 153         if (show_attn)
 154                 set_attnpos(pos);
 155         jump_loc(pos, sline);
 156 }
 157
 158 /*
 159  * Jump to a specified position in the file.
 160  * The position must be the first character in a line.
 161  * Place the target line on a specified line on the screen.
 162  */
 163         public void
 164 jump_loc(pos, sline)
 165         POSITION pos;
 166         int sline;
 167 {
 168         register int nline;
 169         POSITION tpos;
 170         POSITION bpos;
 171
 172         /*
 173          * Normalize sline.
 174          */
 175         sline = adjsline(sline);
 176
 177         if ((nline = onscreen(pos)) >= 0)
 178         {
 179                 /*
 180                  * The line is currently displayed.
 181                  * Just scroll there.
 182                  */
 183                 nline -= sline;
 184                 if (nline > 0)
 185                         forw(nline, position(BOTTOM_PLUS_ONE), 1, 0, 0);
 186                 else
 187                         back(-nline, position(TOP), 1, 0);
 188                 if (show_attn)
 189                         repaint_hilite(1);
 190                 return;
 191         }
 192
 193         /*
 194          * Line is not on screen.
 195          * Seek to the desired location.
 196          */
 197         if (ch_seek(pos))
 198         {
 199                 error("Cannot seek to that file position", NULL_PARG);
 200                 return;
 201         }
 202
 203         /*
 204          * See if the desired line is before or after
 205          * the currently displayed screen.
 206          */
 207         tpos = position(TOP);
 208         bpos = position(BOTTOM_PLUS_ONE);
 209         if (tpos == NULL_POSITION || pos >= tpos)
 210         {
 211                 /*
 212                  * The desired line is after the current screen.
 213                  * Move back in the file far enough so that we can
 214                  * call forw() and put the desired line at the
 215                  * sline-th line on the screen.
 216                  */
 217                 for (nline = 0;  nline < sline;  nline++)
 218                 {
 219                         if (bpos != NULL_POSITION && pos <= bpos)
 220                         {
 221                                 /*
 222                                  * Surprise!  The desired line is
 223                                  * close enough to the current screen
 224                                  * that we can just scroll there after all.
 225                                  */
 226                                 forw(sc_height-sline+nline-1, bpos, 1, 0, 0);
 227                                 if (show_attn)
 228                                         repaint_hilite(1);
 229                                 return;
 230                         }
 231                         pos = back_line(pos);
 232                         if (pos == NULL_POSITION)
 233                         {
 234                                 /*
 235                                  * Oops.  Ran into the beginning of the file.
 236                                  * Exit the loop here and rely on forw()
 237                                  * below to draw the required number of
 238                                  * blank lines at the top of the screen.
 239                                  */
 240                                 break;
 241                         }
 242                 }
 243                 lastmark();
 244                 hit_eof = 0;
 245                 squished = 0;
 246                 screen_trashed = 0;
 247                 forw(sc_height-1, pos, 1, 0, sline-nline);
 248         } else
 249         {
 250                 /*
 251                  * The desired line is before the current screen.
 252                  * Move forward in the file far enough so that we
 253                  * can call back() and put the desired line at the
 254                  * sline-th line on the screen.
 255                  */
 256                 for (nline = sline;  nline < sc_height - 1;  nline++)
 257                 {
 258                         pos = forw_line(pos);
 259                         if (pos == NULL_POSITION)
 260                         {
 261                                 /*
 262                                  * Ran into end of file.
 263                                  * This shouldn't normally happen,
 264                                  * but may if there is some kind of read error.
 265                                  */
 266                                 break;
 267                         }
 268                         if (pos >= tpos)
 269                         {
 270                                 /*
 271                                  * Surprise!  The desired line is
 272                                  * close enough to the current screen
 273                                  * that we can just scroll there after all.
 274                                  */
 275                                 back(nline+1, tpos, 1, 0);
 276                                 if (show_attn)
 277                                         repaint_hilite(1);
 278                                 return;
 279                         }
 280                 }
 281                 lastmark();
 282                 clear();
 283                 screen_trashed = 0;
 284                 add_back_pos(pos);
 285                 back(sc_height-1, pos, 1, 0);
 286         }
 287 }