contrib/less/brac.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 to perform bracket matching functions.
  13  */
  14
  15 #include "less.h"
  16 #include "position.h"
  17
  18 /*
  19  * Try to match the n-th open bracket
  20  *  which appears in the top displayed line (forwdir),
  21  * or the n-th close bracket
  22  *  which appears in the bottom displayed line (!forwdir).
  23  * The characters which serve as "open bracket" and
  24  * "close bracket" are given.
  25  */
  26         public void
  27 match_brac(obrac, cbrac, forwdir, n)
  28         register int obrac;
  29         register int cbrac;
  30         int forwdir;
  31         int n;
  32 {
  33         register int c;
  34         register int nest;
  35         POSITION pos;
  36         int (*chget)();
  37
  38         extern int ch_forw_get(), ch_back_get();
  39
  40         /*
  41          * Seek to the line containing the open bracket.
  42          * This is either the top or bottom line on the screen,
  43          * depending on the type of bracket.
  44          */
  45         pos = position((forwdir) ? TOP : BOTTOM);
  46         if (pos == NULL_POSITION || ch_seek(pos))
  47         {
  48                 if (forwdir)
  49                         error("Nothing in top line", NULL_PARG);
  50                 else
  51                         error("Nothing in bottom line", NULL_PARG);
  52                 return;
  53         }
  54
  55         /*
  56          * Look thru the line to find the open bracket to match.
  57          */
  58         do
  59         {
  60                 if ((c = ch_forw_get()) == '\n' || c == EOI)
  61                 {
  62                         if (forwdir)
  63                                 error("No bracket in top line", NULL_PARG);
  64                         else
  65                                 error("No bracket in bottom line", NULL_PARG);
  66                         return;
  67                 }
  68         } while (c != obrac || --n > 0);
  69
  70         /*
  71          * Position the file just "after" the open bracket
  72          * (in the direction in which we will be searching).
  73          * If searching forward, we are already after the bracket.
  74          * If searching backward, skip back over the open bracket.
  75          */
  76         if (!forwdir)
  77                 (void) ch_back_get();
  78
  79         /*
  80          * Search the file for the matching bracket.
  81          */
  82         chget = (forwdir) ? ch_forw_get : ch_back_get;
  83         nest = 0;
  84         while ((c = (*chget)()) != EOI)
  85         {
  86                 if (c == obrac)
  87                         nest++;
  88                 else if (c == cbrac && --nest < 0)
  89                 {
  90                         /*
  91                          * Found the matching bracket.
  92                          * If searching backward, put it on the top line.
  93                          * If searching forward, put it on the bottom line.
  94                          */
  95                         jump_line_loc(ch_tell(), forwdir ? -1 : 1);
  96                         return;
  97                 }
  98         }
  99         error("No matching bracket", NULL_PARG);
 100 }