brac.c revision 191930 
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
28match_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}
102