Tolerate cut-off UTF-8 messages

I've had this happen to me on Russian channels and it's highly
annoying because you lose the entire message.  On the contrary,
this at worst screws up the last few characters of it.

Closes #2

1 files changed, 22 insertions, 1 deletions

diff --git a/degesch.c b/degesch.c
index 76721e5..10f96af 100644
--- a/degesch.c
+++ b/degesch.c
@@ -3022,7 +3022,7 @@ irc_skip_statusmsg (struct server *s, const char *target)
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
-// As of 2015, everything should be in UTF-8.  And if it's not, we'll decode it
+// As of 2020, everything should be in UTF-8.  And if it's not, we'll decode it
 // as ISO Latin 1.  This function should not be called on the whole message.
 static char *
 irc_to_utf8 (const char *text)
@@ -7812,8 +7812,29 @@ irc_process_numeric (struct server *s,
 }
 
 static void
+irc_fix_cut_off_utf8 (char **line)
+{
+	// A variation on utf8_validate(), we need to detect the -2 return
+	const char *p = *line, *end = strchr (p, 0);
+	int32_t codepoint;
+	while ((codepoint = utf8_decode (&p, end - p)) >= 0
+		&& codepoint <= 0x10FFFF /* TODO: move this check into a function */)
+		;
+	if (codepoint != -2)
+		return;
+
+	struct str fixed_up = str_make ();
+	str_append_data (&fixed_up, *line, p - *line);
+	str_append (&fixed_up, "\xEF\xBF\xBD" /* U+FFFD */);
+	cstr_set (line, str_steal (&fixed_up));
+}
+
+static void
 irc_process_message (const struct irc_message *msg, struct server *s)
 {
+	if (msg->params.len)
+		irc_fix_cut_off_utf8 (&msg->params.vector[msg->params.len - 1]);
+
 	// TODO: make use of IRCv3.2 server-time (with fallback to unixtime_msec())
 	//   -> change all calls to log_{server,nick,outcoming,ctcp}*() to take
 	//   an extra argument specifying time