Convert CP437 message subject to UTF-8 when posting a UTF-8 encoded message

This is a solution for issue #842, but only for messages posted/sent from the
terminal server using built-in functions and not via JS or other means. A more
universal/generic solution would be nice (beyond just always storing message
headers and bodies in UTF-8), but nothing has come to mind.

src/sbbs3/email.cpp

@@ -280,6 +280,8 @@ bool sbbs_t::email(int usernumber, const char *top, const char *subj, int mode,
 	msg_client_hfields(&msg,&client);
 	smb_hfield_str(&msg,SENDERSERVER,server_host_name());
 
+	normalize_msg_hfield_encoding(charset, title, sizeof title);
+
 	smb_hfield_str(&msg,SUBJECT,title);
 
 	add_msg_ids(&cfg, &smb, &msg, remsg);

src/sbbs3/netmail.cpp

@@ -309,6 +309,8 @@ bool sbbs_t::netmail(const char *into, const char *title, int mode, smb_t* resmb
 	smb_hfield(&msg,RECIPIENTNETTYPE, sizeof(nettype), &nettype); 
 	smb_hfield(&msg,RECIPIENTNETADDR, sizeof(dest_addr), &dest_addr);
 
+	normalize_msg_hfield_encoding(charset, subj, sizeof subj);
+
 	smb_hfield_str(&msg,SUBJECT, subj);
 
 	editor_info_to_msg(&msg, editor, charset);
@@ -1138,6 +1140,8 @@ bool sbbs_t::inetmail(const char *into, const char *subj, int mode, smb_t* resmb
 	msg_client_hfields(&msg,&client);
 	smb_hfield_str(&msg,SENDERSERVER, server_host_name());
 
+	normalize_msg_hfield_encoding(charset, title, sizeof title);
+
 	smb_hfield_str(&msg,SUBJECT,title);
 
 	editor_info_to_msg(&msg, editor, charset);
@@ -1422,6 +1426,8 @@ bool sbbs_t::qnetmail(const char *into, const char *subj, int mode, smb_t* resmb
 	msg_client_hfields(&msg,&client);
 	smb_hfield_str(&msg,SENDERSERVER, server_host_name());
 
+	normalize_msg_hfield_encoding(charset, title, sizeof title);
+
 	smb_hfield_str(&msg,SUBJECT,title);
 
 	add_msg_ids(&cfg, &smb, &msg, /* remsg: */NULL);

src/sbbs3/postmsg.cpp

@@ -304,6 +304,7 @@ bool sbbs_t::postmsg(int subnum, int wm_mode, smb_t* resmb, smbmsg_t* remsg)
 
 	if(remsg != NULL && remsg->subj != NULL && strcmp(title, org_title) == 0)
 		SAFECOPY(title, remsg->subj); // If msg subject not changed by user, use original (possibly UTF-8 encoded) subject
+	normalize_msg_hfield_encoding(charset, title, sizeof title);
 	smb_hfield_str(&msg,SUBJECT,title);
 
 	add_msg_ids(&cfg, &smb, &msg, remsg);
@@ -369,6 +370,18 @@ bool sbbs_t::postmsg(int subnum, int wm_mode, smb_t* resmb, smbmsg_t* remsg)
 	return(true);
 }
 
+// When message body is UTF-8 encoded, insure header files are UTF-8 (not CP437) encoded too
+extern "C" void normalize_msg_hfield_encoding(const char* charset, char* str, size_t size)
+{
+	char utf8_str[128];
+
+	if(charset != NULL && strcmp(charset, FIDO_CHARSET_UTF8) == 0) {
+		if(!str_is_ascii(str) && !utf8_str_is_valid(str))
+			if(cp437_to_utf8_str(str, utf8_str, sizeof utf8_str, '\x80') > 1)
+				strlcpy(str, utf8_str, size);
+	}
+}
+
 extern "C" void signal_sub_sem(scfg_t* cfg, int subnum)
 {
 	char str[MAX_PATH+1];

src/sbbs3/sbbs.h

@@ -1401,6 +1401,7 @@ extern "C" {
 	DLLEXPORT void		signal_sub_sem(scfg_t*, int subnum);
 	DLLEXPORT int		msg_client_hfields(smbmsg_t*, client_t*);
 	DLLEXPORT int		notify(scfg_t*, uint usernumber, const char* subject, const char* msg);
+	DLLEXPORT void		normalize_msg_hfield_encoding(const char* charset, char* str, size_t size);
 
 	/* logfile.cpp */
 	DLLEXPORT int		errorlog(scfg_t* cfg, struct mqtt*, int level, const char* host, const char* text);