fxg1a: always add a sensible internal name

The internal name is required to exist and have a certain format for the
add-in to appear in the main menu; this should be enforced at the lowest
possible level to avoid unpleasant surprises.

This change defaults the internal name to essentially @INTERNAL, where
the letters of INTERNAL are the upper-case variables of every letter
found in the standard name (up to 7).

fxg1a/fxg1a.h

@@ -75,6 +75,14 @@ uint16_t checksum(struct g1a const *g1a, size_t size);
    @output  Output file name */
 void default_output(const char *name, const char *suffix, char *output);
 
+/* default_internal(): Calculate default internal name
+   This function determines a default internal name, which is '@' followed by
+   at most 7 uppercase letters taken from the application name.
+
+   @name    Application name
+   @output  Internal name string (9 bytes) */
+void default_internal(const char *name, char *output);
+
 
 /*
 **  File manipulation (file.c)

fxg1a/main.c

@@ -174,6 +174,12 @@ int main(int argc, char **argv)
 		strftime(date, 15, "%Y.%m%d.%H%M", now);
 		edit_date(g1a, date);
 
+		/* Start with an uppercase name as internal name */
+		char internal[9];
+		default_internal(fields.name ? fields.name : g1a->header.name,
+			internal);
+		edit_internal(g1a, internal);
+
 		/* Edit the fields with user-customized values */
 		fields_edit(g1a, &fields);
 

fxg1a/util.c

@@ -1,4 +1,5 @@
 #include <string.h>
+#include <ctype.h>
 #include <endianness.h>
 #include <fxg1a.h>
 
@@ -46,3 +47,17 @@ void default_output(const char *name, const char *suffix, char *output)
 		strcpy(output + end, suffix);
 	}
 }
+
+/* default_internal(): Calculate default internal name */
+void default_internal(const char *name, char *output)
+{
+	output[0] = '@';
+	int i=1;
+
+	for(int j=0; name[j] && i < 8; j++)
+	{
+		if(isalpha(name[j])) output[i++] = toupper(name[j]);
+	}
+
+	output[i] = 0;
+}