Allow specifying range end as a size

doc/da65.sgml

@@ -461,7 +461,8 @@ following attributes are recognized:
   <tag><tt>END</tt></tag>
   This gives the end address of the range. The end address is inclusive, that
   means, it is part of the range. Of course, it may not be smaller than the
-  start address.
+  start address. Optionally, the end may be given as a decimal offset instead
+  of an absolute address, "+3", to specify it as a size.
 
   <tag><tt>NAME</tt></tag>
   This is a convenience attribute. It takes a string argument and will cause

src/da65/infofile.c

@@ -592,9 +592,19 @@ static void RangeSection (void)
             case INFOTOK_END:
                 AddAttr ("END", &Attributes, tEnd);
                 InfoNextTok ();
-                InfoAssureInt ();
-                InfoRangeCheck (0x0000, 0xFFFF);
-                End = InfoIVal;
+
+                if (InfoTok == INFOTOK_OFFSET_INTCON) {
+                    InfoRangeCheck (0x0000, 0xFFFF);
+                    if (!(Attributes & tStart))
+                        InfoError ("When using End with an offset, Start must be specified before");
+                    End = Start + InfoIVal - 1;
+                    if (End > 0xFFFF)
+                        InfoError ("Range error");
+                } else {
+                    InfoAssureInt ();
+                    InfoRangeCheck (0x0000, 0xFFFF);
+                    End = InfoIVal;
+                }
                 InfoNextTok ();
                 break;
 

src/da65/scanner.c

@@ -372,6 +372,14 @@ Again:
         return;
     }
 
+    /* Decimal number offset? */
+    if (C == '+') {
+        NextChar ();
+        InfoIVal = GetDecimalToken ();
+        InfoTok = INFOTOK_OFFSET_INTCON;
+        return;
+    }
+
     /* Other characters */
     switch (C) {
 

src/da65/scanner.h

@@ -48,6 +48,7 @@
 typedef enum token_t {
     INFOTOK_NONE,
     INFOTOK_INTCON,
+    INFOTOK_OFFSET_INTCON,
     INFOTOK_STRCON,
     INFOTOK_CHARCON,
     INFOTOK_IDENT,