use custom long-to-ascii routine

1 files changed, 79 insertions, 0 deletions

diff --git a/ultostr.s b/ultostr.s
new file mode 100644
index 0000000..29420e4
--- /dev/null
+++ b/ultostr.s
@@ -0,0 +1,79 @@
+;
+; Modified from cc65's libsrc/common/ltoa.s
+; Originally by Ullrich von Bassewitz, 11.06.1998
+
+; modified version by B. Watson
+
+; - rename ultoa => ultostr
+; - got rid of ltoa (don't need it)
+; - hardcode radix to 10
+; - don't need __hextab since we don't do hex (saves 16 bytes)
+; - inline dopop subroutine
+
+; char* ultostr (unsigned long value, char* s);
+
+        .export         _ultostr
+        .import         popax
+        .importzp       sreg, ptr1, ptr2, ptr3
+
+radix = 10
+
+.code
+
+_ultostr:
+        ; pop the arguments
+        sta     ptr1
+        stx     ptr1+1
+        sta     sreg            ; save for return
+        stx     sreg+1
+        jsr     popax           ; get low word of value
+        sta     ptr2
+        stx     ptr2+1
+        jsr     popax           ; get high word of value
+        sta     ptr3
+        stx     ptr3+1
+
+; Convert to string by dividing and push the result onto the stack
+
+ultostr:  lda     #$00
+        pha                     ; sentinel
+
+; Divide val/radix -> val, remainder in a
+
+L5:     ldy     #32             ; 32 bit
+        lda     #0              ; remainder
+L6:     asl     ptr2
+        rol     ptr2+1
+        rol     ptr3
+        rol     ptr3+1
+        rol     a
+        cmp     #radix
+        bcc     L7
+        sbc     #radix
+        inc     ptr2
+L7:     dey
+        bne     L6
+
+        ora #'0'                ; get ascii character
+        pha                     ; save char value on stack
+
+        lda     ptr2
+        ora     ptr2+1
+        ora     ptr3
+        ora     ptr3+1
+        bne     L5
+
+; Get the characters from the stack into the string
+
+        ldy     #0
+L9:     pla
+        sta     (ptr1),y
+        beq     L10             ; jump if sentinel
+        iny
+        bne     L9              ; jump always
+
+; Done! Return the target string
+
+L10:    lda     sreg
+        ldx     sreg+1
+        rts