contrib/less/brac.c

   1 /*
   2  * Copyright (C) 1984-2008  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 to perform bracket matching functions.
  14  */
  15
  16 #include "less.h"
  17 #include "position.h"
  18
  19 /*
  20  * Try to match the n-th open bracket
  21  *  which appears in the top displayed line (forwdir),
  22  * or the n-th close bracket
  23  *  which appears in the bottom displayed line (!forwdir).
  24  * The characters which serve as "open bracket" and
  25  * "close bracket" are given.
  26  */
  27         public void
  28 match_brac(obrac, cbrac, forwdir, n)
  29         register int obrac;
  30         register int cbrac;
  31         int forwdir;
  32         int n;
  33 {
  34         register int c;
  35         register int nest;
  36         POSITION pos;
  37         int (*chget)();
  38
  39         extern int ch_forw_get(), ch_back_get();
  40
  41         /*
  42          * Seek to the line containing the open bracket.
  43          * This is either the top or bottom line on the screen,
  44          * depending on the type of bracket.
  45          */
  46         pos = position((forwdir) ? TOP : BOTTOM);
  47         if (pos == NULL_POSITION || ch_seek(pos))
  48         {
  49                 if (forwdir)
  50                         error("Nothing in top line", NULL_PARG);
  51                 else
  52                         error("Nothing in bottom line", NULL_PARG);
  53                 return;
  54         }
  55
  56         /*
  57          * Look thru the line to find the open bracket to match.
  58          */
  59         do
  60         {
  61                 if ((c = ch_forw_get()) == '\n' || c == EOI)
  62                 {
  63                         if (forwdir)
  64                                 error("No bracket in top line", NULL_PARG);
  65                         else
  66                                 error("No bracket in bottom line", NULL_PARG);
  67                         return;
  68                 }
  69         } while (c != obrac || --n > 0);
  70
  71         /*
  72          * Position the file just "after" the open bracket
  73          * (in the direction in which we will be searching).
  74          * If searching forward, we are already after the bracket.
  75          * If searching backward, skip back over the open bracket.
  76          */
  77         if (!forwdir)
  78                 (void) ch_back_get();
  79
  80         /*
  81          * Search the file for the matching bracket.
  82          */
  83         chget = (forwdir) ? ch_forw_get : ch_back_get;
  84         nest = 0;
  85         while ((c = (*chget)()) != EOI)
  86         {
  87                 if (c == obrac)
  88                         nest++;
  89                 else if (c == cbrac && --nest < 0)
  90                 {
  91                         /*
  92                          * Found the matching bracket.
  93                          * If searching backward, put it on the top line.
  94                          * If searching forward, put it on the bottom line.
  95                          */
  96                         jump_line_loc(ch_tell(), forwdir ? -1 : 1);
  97                         return;
  98                 }
  99         }
 100         error("No matching bracket", NULL_PARG);
 101 }