Implement the \N'number' (numbered character) roff escape sequence.

Don't use it in new manuals, it is inherently non-portable, but we
need it for backward-compatibility with existing manuals, for example
in Xenocara driver pages.
ok kristaps@ jmc@ and tested by Matthieu Herrb (matthieu at openbsd dot org)

7 files changed, 117 insertions, 3 deletions

diff --git a/chars.c b/chars.c
index b9f4b4fd..ae478800 100644
--- a/chars.c
+++ b/chars.c
@@ -1,6 +1,7 @@
 /*	$Id$ */
 /*
  * Copyright (c) 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
+ * Copyright (c) 2011 Ingo Schwarze <schwarze@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -152,6 +153,27 @@ chars_res2cp(void *arg, const char *p, size_t sz)
 }
 
 
+/*
+ * Numbered character to literal character,
+ * represented as a null-terminated string for additional safety.
+ */
+const char *
+chars_num2char(const char *p, size_t sz)
+{
+	int		  i;
+	static char	  c[2];
+
+	if (sz > 3)
+		return(NULL);
+	i = atoi(p);
+	if (i < 0 || i > 255)
+		return(NULL);
+	c[0] = (char)i;
+	c[1] = '\0';
+	return(c);
+}
+
+
 /* 
  * Special character to string array.
  */
diff --git a/chars.h b/chars.h
index 52271f24..70abd3b2 100644
--- a/chars.h
+++ b/chars.h
@@ -1,6 +1,7 @@
 /*	$Id$ */
 /*
  * Copyright (c) 2008, 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
+ * Copyright (c) 2011 Ingo Schwarze <schwarze@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -25,6 +26,7 @@ enum	chars {
 };
 
 void		 *chars_init(enum chars);
+const char	 *chars_num2char(const char *, size_t);
 const char	 *chars_spec2str(void *, const char *, size_t, size_t *);
 int		  chars_spec2cp(void *, const char *, size_t);
 const char	 *chars_res2str(void *, const char *, size_t, size_t *);
diff --git a/html.c b/html.c
index 846d98ef..af9fdb1a 100644
--- a/html.c
+++ b/html.c
@@ -1,6 +1,7 @@
 /*	$Id$ */
 /*
- * Copyright (c) 2008, 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
+ * Copyright (c) 2008, 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
+ * Copyright (c) 2011 Ingo Schwarze <schwarze@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -93,6 +94,7 @@ static	const char	*const htmlattrs[ATTR_MAX] = {
 	"colspan", /* ATTR_COLSPAN */
 };
 
+static	void		  print_num(struct html *, const char *, size_t);
 static	void		  print_spec(struct html *, enum roffdeco,
 				const char *, size_t);
 static	void		  print_res(struct html *, const char *, size_t);
@@ -214,6 +216,17 @@ print_gen_head(struct html *h)
 
 
 static void
+print_num(struct html *h, const char *p, size_t len)
+{
+	const char	*rhs;
+
+	rhs = chars_num2char(p, len);
+	if (rhs)
+		putchar((int)*rhs);
+}
+
+
+static void
 print_spec(struct html *h, enum roffdeco d, const char *p, size_t len)
 {
 	int		 cp;
@@ -333,6 +346,9 @@ print_encode(struct html *h, const char *p, int norecurse)
 		len = a2roffdeco(&deco, &seq, &sz);
 
 		switch (deco) {
+		case (DECO_NUMBERED):
+			print_num(h, seq, sz);
+			break;
 		case (DECO_RESERVED):
 			print_res(h, seq, sz);
 			break;
diff --git a/mandoc_char.7 b/mandoc_char.7
index a2fc091a..b7372d26 100644
--- a/mandoc_char.7
+++ b/mandoc_char.7
@@ -513,6 +513,21 @@ implementations:
 .It \e*(aa   Ta \*(aa       Ta acute
 .It \e*(ga   Ta \*(ga       Ta grave
 .El
+.Sh NUMBERED CHARACTERS
+For backward compatibility with existing manuals,
+.Xr mandoc 1
+also supports the
+.Pp
+.Dl \eN\(aq Ns Ar number Ns \(aq
+.Pp
+escape sequence, inserting the character
+.Ar number
+from the current character set into the output.
+Of course, this is inherently non-portable and is already marked
+as deprecated in the Heirloom roff manual.
+For example, do not use \eN'34', use \e(dq, or even the plain
+.Sq \(dq
+character where possible.
 .Sh COMPATIBILITY
 This section documents compatibility of
 .Nm
diff --git a/out.c b/out.c
index d76a9702..be54abcd 100644
--- a/out.c
+++ b/out.c
@@ -1,6 +1,7 @@
 /*	$Id$ */
 /*
  * Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
+ * Copyright (c) 2011 Ingo Schwarze <schwarze@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -251,6 +252,49 @@ a2roffdeco(enum roffdeco *d, const char **word, size_t *sz)
 			break;
 		}
 		break;
+
+	case ('N'):
+
+		/*
+		 * Sequence of characters:  backslash,  'N' (i = 0),
+		 * starting delimiter (i = 1), character number (i = 2).
+		 */
+
+		*word = wp + 2;
+		*sz = 0;
+
+		/*
+		 * Cannot use a digit as a starting delimiter;
+		 * but skip the digit anyway.
+		 */
+
+		if (isdigit((int)wp[1]))
+			return(2);
+
+		/*
+		 * Any non-digit terminates the character number.
+		 * That is, the terminating delimiter need not
+		 * match the starting delimiter.
+		 */
+
+		for (i = 2; isdigit((int)wp[i]); i++)
+			(*sz)++;
+
+		/*
+		 * This is only a numbered character
+		 * if the character number has at least one digit.
+		 */
+
+		if (*sz)
+			*d = DECO_NUMBERED;
+
+		/*
+		 * Skip the terminating delimiter, even if it does not
+		 * match, and even if there is no character number.
+		 */
+
+		return(++i);
+
 	case ('h'):
 		/* FALLTHROUGH */
 	case ('v'):
diff --git a/out.h b/out.h
index 9802389f..f18e42e7 100644
--- a/out.h
+++ b/out.h
@@ -1,6 +1,6 @@
 /*	$Id$ */
 /*
- * Copyright (c) 2009 Kristaps Dzonsons <kristaps@bsd.lv>
+ * Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -52,6 +52,7 @@ enum	roffscale {
 
 enum	roffdeco {
 	DECO_NONE,
+	DECO_NUMBERED, /* numbered character */
 	DECO_SPECIAL, /* special character */
 	DECO_SSPECIAL, /* single-char special */
 	DECO_RESERVED, /* reserved word */
diff --git a/term.c b/term.c
index 5d18a69d..0ffdedd7 100644
--- a/term.c
+++ b/term.c
@@ -1,7 +1,7 @@
 /*	$Id$ */
 /*
  * Copyright (c) 2008, 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
- * Copyright (c) 2010 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2010, 2011 Ingo Schwarze <schwarze@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -353,6 +353,17 @@ term_vspace(struct termp *p)
 
 
 static void
+numbered(struct termp *p, const char *word, size_t len)
+{
+	const char	*rhs;
+
+	rhs = chars_num2char(word, len);
+	if (rhs) 
+		encode(p, rhs, 1);
+}
+
+
+static void
 spec(struct termp *p, enum roffdeco d, const char *word, size_t len)
 {
 	const char	*rhs;
@@ -511,6 +522,9 @@ term_word(struct termp *p, const char *word)
 		word += a2roffdeco(&deco, &seq, &ssz);
 
 		switch (deco) {
+		case (DECO_NUMBERED):
+			numbered(p, seq, ssz);
+			break;
 		case (DECO_RESERVED):
 			res(p, seq, ssz);
 			break;