From 3d012d9bd07efebffadcab368c6695f2e295bb21 Mon Sep 17 00:00:00 2001
From: Jacob Nevins <jacobn@chiark.greenend.org.uk>
Date: Tue, 19 Apr 2005 18:58:29 +0000
Subject: [PATCH] Pull out parsing of ^C style strings from the terminal
 answerback code to its own function, since I'll be wanting it for
 `terminal-modes'.

[originally from svn r5646]
---
 misc.c     | 36 ++++++++++++++++++++++++++++++++++++
 misc.h     |  1 +
 terminal.c | 26 ++++++++++----------------
 3 files changed, 47 insertions(+), 16 deletions(-)

diff --git a/misc.c b/misc.c
index 17d8f39b..1beab5e7 100644
--- a/misc.c
+++ b/misc.c
@@ -43,6 +43,42 @@ unsigned long parse_blocksize(const char *bs)
     return r;
 }
 
+/*
+ * Parse a ^C style character specification.
+ * Returns NULL in `next' if we didn't recognise it as a control character,
+ * in which case `c' should be ignored.
+ * The precise current parsing is an oddity inherited from the terminal
+ * answerback-string parsing code. All sequences are two characters,
+ * starting with '^'. The ones that are worth keeping are probably:
+ *   ^?		    127
+ *   ^@A-Z[\]^_	    0-31
+ *   a-z	    1-26
+ *   ~		    ^ escape
+ */
+char ctrlparse(char *s, char **next)
+{
+    char c = 0;
+    if (*s != '^') {
+	*next = NULL;
+	return c;
+    } else {
+	s++;
+	if (*s == '\0') {
+	    *next = NULL;
+	    return c;
+	} else if (*s >= 'a' && *s <= 'z') {
+	    c = (*s - ('a' - 1));
+	} else if ((*s >= '@' && *s <= '_') || *s == '?' || (*s & 0x80)) {
+	    c = ('@' ^ *s);
+	} else if (*s == '~') {
+	    c = '^';
+	}
+	s++;
+	*next = s;
+	return c;
+    }
+}
+
 /* ----------------------------------------------------------------------
  * String handling routines.
  */
diff --git a/misc.h b/misc.h
index 73467793..f4363e44 100644
--- a/misc.h
+++ b/misc.h
@@ -18,6 +18,7 @@ typedef struct Filename Filename;
 typedef struct FontSpec FontSpec;
 
 unsigned long parse_blocksize(const char *bs);
+char ctrlparse(char *s, char **next);
 
 char *dupstr(const char *s);
 char *dupcat(const char *s1, ...);
diff --git a/terminal.c b/terminal.c
index cd175ba5..dfd9a19e 100644
--- a/terminal.c
+++ b/terminal.c
@@ -2677,22 +2677,16 @@ static void term_out(Terminal *term)
 		 */
 		compatibility(ANSIMIN);
 		if (term->ldisc) {
-		    char abuf[256], *s, *d;
-		    int state = 0;
-		    for (s = term->cfg.answerback, d = abuf; *s; s++) {
-			if (state) {
-			    if (*s >= 'a' && *s <= 'z')
-				*d++ = (*s - ('a' - 1));
-			    else if ((*s >= '@' && *s <= '_') ||
-				     *s == '?' || (*s & 0x80))
-				*d++ = ('@' ^ *s);
-			    else if (*s == '~')
-				*d++ = '^';
-			    state = 0;
-			} else if (*s == '^') {
-			    state = 1;
-			} else
-			    *d++ = *s;
+		    char abuf[lenof(term->cfg.answerback)], *s, *d;
+		    for (s = term->cfg.answerback, d = abuf; *s;) {
+			char *n;
+			char c = ctrlparse(s, &n);
+			if (n) {
+			    *d++ = c;
+			    s = n;
+			} else {
+			    *d++ = *s++;
+			}
 		    }
 		    lpage_send(term->ldisc, DEFAULT_CODEPAGE,
 			       abuf, d - abuf, 0);