Shortened names and adjusted style.

libsrc/common/ctypemask.s

@@ -0,0 +1,50 @@
+; ctypemask.s
+;
+; This file is part of
+; cc65 - a freeware C compiler for 6502 based systems
+;
+; https://cc65.github.io
+;
+; See "LICENSE" file for legal information.
+;
+; ctypemask(int c)
+;
+; converts a character to test via the is*-functions to the matching ctype-masks 
+; If c is out of the 8-bit range, the function returns with carry set and accu cleared.
+; Return value is in accu and x has to be always clear when returning
+; (makes calling code shorter)!
+;
+; IMPORTANT: stricmp, strlower, strnicmp, strupper and atoi rely that Y is not changed
+; while calling this function!
+;
+
+        .export         ctypemask
+        .export         ctypemaskdirect
+        .import         __ctype
+        .import         __ctypeidx
+
+ctypemask:
+        cpx     #$00            ; char range ok?
+        bne     SC              ; branch if not
+ctypemaskdirect:
+        lsr     a
+        tax
+        lda     __ctypeidx,x
+        bcc     @lowerNibble
+@upperNibble:
+        lsr     a
+        lsr     a
+        lsr     a
+        lsr     a
+        clc                     ; remove out of bounds flag
+@lowerNibble:
+        and     #%00001111
+        tax
+        lda     __ctype,x
+        ldx     #$00
+        rts
+
+SC:     sec
+        lda     #$00
+        tax
+        rts