ctype size optimization

libsrc/common/isascii.s

@@ -0,0 +1,27 @@
+; isascii.s
+;
+; This file is part of
+; cc65 - a freeware C compiler for 6502 based systems
+;
+; https://github.com/cc65/cc65
+;
+; See "LICENSE" file for legal information.
+;
+; int isascii (int c);
+;
+
+        .export         _isascii
+
+_isascii:
+        cpx     #$00            ; Char range ok?
+        bne     @L1             ; Jump if no
+
+        tay
+        bmi     @L1
+
+        inx
+        rts
+
+@L1:    lda     #$00            ; Return false
+        tax
+        rts