diplodocus.org Git - nmh/blob - docs/historical/mh-6.8.5/miscellany/less-177/brac.c

   1 /*
   2  * Routines to perform bracket matching functions.
   3  */
   4
   5 #include "less.h"
   6 #include "position.h"
   7
   8 /*
   9  * Try to match the n-th open bracket
  10  *  which appears in the top displayed line (forwdir),
  11  * or the n-th close bracket
  12  *  which appears in the bottom displayed line (!forwdir).
  13  * The characters which serve as "open bracket" and
  14  * "close bracket" are given.
  15  */
  16         public void
  17 match_brac(obrac, cbrac, forwdir, n)
  18         register int obrac;
  19         register int cbrac;
  20         int forwdir;
  21         int n;
  22 {
  23         register int c;
  24         register int nest;
  25         POSITION pos;
  26         int (*chget)();
  27
  28         extern int ch_forw_get(), ch_back_get();
  29
  30         /*
  31          * Seek to the line containing the open bracket.
  32          * This is either the top or bottom line on the screen,
  33          * depending on the type of bracket.
  34          */
  35         pos = position((forwdir) ? TOP : BOTTOM);
  36         if (pos == NULL_POSITION || ch_seek(pos))
  37         {
  38                 if (forwdir)
  39                         error("Nothing in top line", NULL_PARG);
  40                 else
  41                         error("Nothing in bottom line", NULL_PARG);
  42                 return;
  43         }
  44
  45         /*
  46          * Look thru the line to find the open bracket to match.
  47          */
  48         do
  49         {
  50                 if ((c = ch_forw_get()) == '\n' || c == EOI)
  51                 {
  52                         if (forwdir)
  53                                 error("No bracket in top line", NULL_PARG);
  54                         else
  55                                 error("No bracket in bottom line", NULL_PARG);
  56                         return;
  57                 }
  58         } while (c != obrac || --n > 0);
  59
  60         /*
  61          * Position the file just "after" the open bracket
  62          * (in the direction in which we will be searching).
  63          * If searching forward, we are already after the bracket.
  64          * If searching backward, skip back over the open bracket.
  65          */
  66         if (!forwdir)
  67                 (void) ch_back_get();
  68
  69         /*
  70          * Search the file for the matching bracket.
  71          */
  72         chget = (forwdir) ? ch_forw_get : ch_back_get;
  73         nest = 0;
  74         while ((c = (*chget)()) != EOI)
  75         {
  76                 if (c == obrac)
  77                         nest++;
  78                 else if (c == cbrac && --nest < 0)
  79                 {
  80                         /*
  81                          * Found the matching bracket.
  82                          * If searching backward, put it on the top line.
  83                          * If searching forward, put it on the bottom line.
  84                          */
  85                         jump_line_loc(ch_tell(), forwdir ? -1 : 1);
  86                         return;
  87                 }
  88         }
  89         error("No matching bracket", NULL_PARG);
  90 }