1 files changed, 63 insertions, 0 deletions
diff --git a/src/a2uint.s b/src/a2uint.s
new file mode 100644
index 0000000..c296181
--- /dev/null
+++ b/src/a2uint.s
@@ -0,0 +1,63 @@
+
+ ; replacement for atoi() that doesn't use cc65's bloated ctype.
+ ; also, doesn't handle signed results (not needed).
+
+ .export _a2uint
+ .import _isnum
+ .importzp ptr1, sreg
+
+ result = sreg
+ temp16 = sreg+2
+
+_a2uint:
+ sta ptr1
+ stx ptr1+1
+
+ lda #0
+ sta result
+ sta result+1
+ tay
+
+@chrloop:
+ lda (ptr1),y ; get next character
+ jsr _isnum   ; is is a digit?
+ beq @done    ; Z set = non-digit
+
+ ; multiply result by 10
+ lda result
+ asl
+ sta temp16
+ lda result+1
+ rol
+ sta temp16+1 ; temp16 now result * 2
+
+ ldx #3
+@x8loop:
+ asl result
+ rol result+1
+ dex
+ bne @x8loop
+
+ ; result now result * 8
+ clc
+ lda result
+ adc temp16
+ sta result
+ lda result+1
+ adc temp16+1
+ sta result+1 ; result now original result * 10
+
+ lda (ptr1),y ; get character again
+ iny          ; point to next char
+ and #$0f     ; de-ASCIIfy
+ clc
+ adc result
+ sta result
+ bcc @chrloop
+ inc result+1
+ bne @chrloop
+
+@done:
+ lda result
+ ldx result+1
+ rts