mandoc: Mostly complete implementation of the 'c' (character available)

mandoc: Mostly complete implementation of the 'c' (character available)

[schwarze]

Log Message:
-----------
Mostly complete implementation of the 'c' (character available)
roff conditional, except that the .char request still isn't supported 
and that behaviour differs from groff in many edge cases.
But at least valid character names and numbers are now distinguished
from invalid ones.
This also fixes the bug that parsing of the 'c' conditional was
incomplete, which resulted in leaking the tested character to the
input parser at the beginning of the body when the condition was
inverted.

Modified Files:
--------------
    mandoc:
        TODO
        roff.7
        roff.c

Revision Data
-------------
Index: roff.7
===================================================================
RCS file: /home/cvs/mandoc/mandoc/roff.7,v
retrieving revision 1.100
retrieving revision 1.101
diff -Lroff.7 -Lroff.7 -u -p -r1.100 -r1.101
--- roff.7
+++ roff.7
@@ -1005,13 +1005,13 @@ is
 or
 .Sq o
 .Pq odd page ,
-it evaluates to true.
+it evaluates to true, and the
+.Ar body
+starts with the next character.
 .It
 If the first character of
 .Ar condition
 is
-.Sq c
-.Pq character available ,
 .Sq e
 .Pq even page ,
 .Sq t
@@ -1019,7 +1019,20 @@ is
 or
 .Sq v
 .Pq vroff mode ,
-it evaluates to false.
+it evaluates to false, and the
+.Ar body
+starts with the next character.
+.It
+If the first character of
+.Ar condition
+is
+.Sq c
+.Pq character available ,
+it evaluates to true if the following character is an ASCII character
+or a valid character escape sequence, or to false otherwise.
+The
+.Ar body
+starts with the character following that next character.
 .It
 If the first character of
 .Ar condition
Index: TODO
===================================================================
RCS file: /home/cvs/mandoc/mandoc/TODO,v
retrieving revision 1.266
retrieving revision 1.267
diff -LTODO -LTODO -u -p -r1.266 -r1.267
--- TODO
+++ TODO
@@ -181,9 +181,6 @@ are mere guesses, and some may be wrong.
   pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
   loc *  exist ***  algo ***  size **  imp *
 
-- support .ds requests inside tbl(7) code,
-  see tbl(1) for an example
-
 - support mdoc(7) and man(7) macros inside tbl(7) code;
   probably requires the parser reorg and letting tbl(7)
   use roff_node such that macro sets can mix;
@@ -319,9 +316,6 @@ are mere guesses, and some may be wrong.
 ************************************************************************
 * formatting issues: ugly output
 ************************************************************************
-
-- .UR can nest inside .TP,
-  see roff(7) for examples
 
 - revisit empty in-line macros
   look at the difference between "Em x Em ." and "Sq x Em ."
Index: roff.c
===================================================================
RCS file: /home/cvs/mandoc/mandoc/roff.c,v
retrieving revision 1.335
retrieving revision 1.336
diff -Lroff.c -Lroff.c -u -p -r1.335 -r1.336
--- roff.c
+++ roff.c
@@ -2168,9 +2168,10 @@ out:
 static int
 roff_evalcond(struct roff *r, int ln, char *v, int *pos)
 {
-	char	*cp, *name;
-	size_t	 sz;
-	int	 deftype, number, savepos, istrue, wanttrue;
+	const char	*start, *end;
+	char		*cp, *name;
+	size_t		 sz;
+	int		 deftype, len, number, savepos, istrue, wanttrue;
 
 	if ('!' == v[*pos]) {
 		wanttrue = 0;
@@ -2185,12 +2186,50 @@ roff_evalcond(struct roff *r, int ln, ch
 	case 'o':
 		(*pos)++;
 		return wanttrue;
-	case 'c':
 	case 'e':
 	case 't':
 	case 'v':
 		(*pos)++;
 		return !wanttrue;
+	case 'c':
+		do {
+			(*pos)++;
+		} while (v[*pos] == ' ');
+
+		/*
+		 * Quirk for groff compatibility:
+		 * The horizontal tab is neither available nor unavailable.
+		 */
+
+		if (v[*pos] == '\t') {
+			(*pos)++;
+			return 0;
+		}
+
+		/* Printable ASCII characters are available. */
+
+		if (v[*pos] != '\\') {
+			(*pos)++;
+			return wanttrue;
+		}
+
+		end = v + ++*pos;
+		switch (mandoc_escape(&end, &start, &len)) {
+		case ESCAPE_SPECIAL:
+			istrue = mchars_spec2cp(start, len) != -1;
+			break;
+		case ESCAPE_UNICODE:
+			istrue = 1;
+			break;
+		case ESCAPE_NUMBERED:
+			istrue = mchars_num2char(start, len) != -1;
+			break;
+		default:
+			istrue = !wanttrue;
+			break;
+		}
+		*pos = end - v;
+		return istrue == wanttrue;
 	case 'd':
 	case 'r':
 		cp = v + *pos + 1;
--
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