; Internal library routines - always included by the compiler ; Generic machine independent 6502 code. orig_stackpointer .byte 0 ; stores the Stack pointer register at program start read_byte_from_address_in_AY_into_A .proc sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 ldy #0 lda (P8ZP_SCRATCH_W2),y rts .pend write_byte_X_to_address_in_AY .proc sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 ldy #0 txa sta (P8ZP_SCRATCH_W2),y rts .pend reg_less_uw .proc ; AY < P8ZP_SCRATCH_W2? cpy P8ZP_SCRATCH_W2+1 bcc _true bne _false cmp P8ZP_SCRATCH_W2 bcc _true _false lda #0 rts _true lda #1 rts .pend reg_less_w .proc ; -- AY < P8ZP_SCRATCH_W2? cmp P8ZP_SCRATCH_W2 tya sbc P8ZP_SCRATCH_W2+1 bvc + eor #$80 + bmi _true lda #0 rts _true lda #1 rts .pend reg_lesseq_uw .proc ; AY <= P8ZP_SCRATCH_W2? cpy P8ZP_SCRATCH_W2+1 beq + bcc _true lda #0 rts + cmp P8ZP_SCRATCH_W2 bcc _true beq _true lda #0 rts _true lda #1 rts .pend reg_lesseq_w .proc ; -- P8ZP_SCRATCH_W2 <= AY ? (note: order different from other routines) cmp P8ZP_SCRATCH_W2 tya sbc P8ZP_SCRATCH_W2+1 bvc + eor #$80 + bpl + lda #0 rts + lda #1 rts .pend memcopy16_up .proc ; -- copy memory UP from (P8ZP_SCRATCH_W1) to (P8ZP_SCRATCH_W2) of length X/Y (16-bit, X=lo, Y=hi) ; clobbers register A,X,Y source = P8ZP_SCRATCH_W1 dest = P8ZP_SCRATCH_W2 length = P8ZP_SCRATCH_B1 ; (and SCRATCH_ZPREG) stx length sty length+1 ldx length ; move low byte of length into X bne + ; jump to start if X > 0 dec length ; subtract 1 from length + ldy #0 ; set Y to 0 - lda (source),y ; set A to whatever (source) points to offset by Y sta (dest),y ; move A to location pointed to by (dest) offset by Y iny ; increment Y bne + ; if Y<>0 then (rolled over) then still moving bytes inc source+1 ; increment hi byte of source inc dest+1 ; increment hi byte of dest + dex ; decrement X (lo byte counter) bne - ; if X<>0 then move another byte dec length ; we've moved 255 bytes, dec length bpl - ; if length is still positive go back and move more rts ; done .pend memset .proc ; -- fill memory from (P8ZP_SCRATCH_W1), length XY, with value in A. ; clobbers X, Y stx P8ZP_SCRATCH_B1 sty _save_reg ldy #0 ldx _save_reg beq _lastpage _fullpage sta (P8ZP_SCRATCH_W1),y iny bne _fullpage inc P8ZP_SCRATCH_W1+1 ; next page dex bne _fullpage _lastpage ldy P8ZP_SCRATCH_B1 beq + - dey sta (P8ZP_SCRATCH_W1),y bne - + rts _save_reg .byte 0 .pend memsetw .proc ; -- fill memory from (P8ZP_SCRATCH_W1) number of words in P8ZP_SCRATCH_W2, with word value in AY. ; clobbers A, X, Y sta _mod1+1 ; self-modify sty _mod1b+1 ; self-modify sta _mod2+1 ; self-modify sty _mod2b+1 ; self-modify ldx P8ZP_SCRATCH_W1 stx P8ZP_SCRATCH_B1 ldx P8ZP_SCRATCH_W1+1 inx stx P8ZP_SCRATCH_REG ; second page ldy #0 ldx P8ZP_SCRATCH_W2+1 beq _lastpage _fullpage _mod1 lda #0 ; self-modified sta (P8ZP_SCRATCH_W1),y ; first page sta (P8ZP_SCRATCH_B1),y ; second page iny _mod1b lda #0 ; self-modified sta (P8ZP_SCRATCH_W1),y ; first page sta (P8ZP_SCRATCH_B1),y ; second page iny bne _fullpage inc P8ZP_SCRATCH_W1+1 ; next page pair inc P8ZP_SCRATCH_W1+1 ; next page pair inc P8ZP_SCRATCH_B1+1 ; next page pair inc P8ZP_SCRATCH_B1+1 ; next page pair dex bne _fullpage _lastpage ldx P8ZP_SCRATCH_W2 beq _done ldy #0 - _mod2 lda #0 ; self-modified sta (P8ZP_SCRATCH_W1), y inc P8ZP_SCRATCH_W1 bne _mod2b inc P8ZP_SCRATCH_W1+1 _mod2b lda #0 ; self-modified sta (P8ZP_SCRATCH_W1), y inc P8ZP_SCRATCH_W1 bne + inc P8ZP_SCRATCH_W1+1 + dex bne - _done rts .pend ror2_mem_ub .proc ; -- in-place 8-bit ror of byte at memory location in AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 ldy #0 lda (P8ZP_SCRATCH_W1),y lsr a bcc + ora #$80 + sta (P8ZP_SCRATCH_W1),y rts .pend rol2_mem_ub .proc ; -- in-place 8-bit rol of byte at memory location in AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 ldy #0 lda (P8ZP_SCRATCH_W1),y cmp #$80 rol a sta (P8ZP_SCRATCH_W1),y rts .pend strcpy .proc ; copy a string (must be 0-terminated) from A/Y to (P8ZP_SCRATCH_W1) ; it is assumed the target string is large enough. ; returns the length of the string that was copied in Y. sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 ldy #$ff - iny lda (P8ZP_SCRATCH_W2),y sta (P8ZP_SCRATCH_W1),y bne - rts .pend strcmp_expression .proc ; -- compare strings, result in A lda _arg_s2 ldy _arg_s2+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 lda _arg_s1 ldy _arg_s1+1 jmp strcmp_mem _arg_s1 .word 0 _arg_s2 .word 0 .pend strcmp_mem .proc ; -- compares strings in s1 (AY) and s2 (P8ZP_SCRATCH_W2). ; Returns -1,0,1 in A, depending on the ordering. Clobbers Y. sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 ldy #0 _loop lda (P8ZP_SCRATCH_W1),y beq _c1_zero cmp (P8ZP_SCRATCH_W2),y beq _equal bmi _less lda #1 rts _less lda #-1 rts _equal iny bne _loop _c1_zero lda (P8ZP_SCRATCH_W2),y beq + lda #-1 + rts .pend strlen .proc ; -- returns the number of bytes in the string in AY, in Y. Clobbers A. sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 ldy #0 - lda (P8ZP_SCRATCH_W1),y beq + iny bne - + rts .pend containment_bytearray .proc ; -- check if a value exists in a byte array. ; parameters: P8ZP_SCRATCH_W1: address of the byte array, A = byte to check, Y = length of array (>=1). ; returns boolean 0/1 in A. dey - cmp (P8ZP_SCRATCH_W1),y beq + dey cpy #255 bne - lda #0 rts + lda #1 rts .pend containment_wordarray .proc ; -- check if a value exists in a word array. ; parameters: P8ZP_SCRATCH_W1: value to check, P8ZP_SCRATCH_W2: address of the word array, Y = length of array (>=1). ; returns boolean 0/1 in A. dey tya asl a tay - lda P8ZP_SCRATCH_W1 cmp (P8ZP_SCRATCH_W2),y bne + lda P8ZP_SCRATCH_W1+1 iny cmp (P8ZP_SCRATCH_W2),y beq _found dey + dey dey cpy #254 bne - lda #0 rts _found lda #1 rts .pend arraycopy_split_to_normal_words .proc ; P8ZP_SCRATCH_W1 = start of lsb array ; P8ZP_SCRATCH_W2 = start of msb array ; AY = start of normal word target array ; X = number of elements to copy sta _modlsb+1 sty _modlsb+2 clc adc #1 bne + iny + sta _modmsb+1 sty _modmsb+2 ldy #0 - lda (P8ZP_SCRATCH_W1),y _modlsb sta $ffff ; modified lsb store lda _modlsb+1 clc adc #2 sta _modlsb+1 bcc + inc _modlsb+2 + lda (P8ZP_SCRATCH_W2),y _modmsb sta $ffff ; modified msb store lda _modmsb+1 clc adc #2 sta _modmsb+1 bcc + inc _modmsb+2 + iny dex bne - rts .pend arraycopy_normal_to_split_words .proc ; P8ZP_SCRATCH_W1 = start of target lsb array ; P8ZP_SCRATCH_W2 = start of target msb array ; AY = start of normal word source array ; X = number of elements to copy sta _modsrclsb+1 sty _modsrclsb+2 clc adc #1 bne + iny + sta _modsrcmsb+1 sty _modsrcmsb+2 ldy #0 _modsrclsb lda $ffff ; modified lsb read sta (P8ZP_SCRATCH_W1),y lda _modsrclsb+1 clc adc #2 sta _modsrclsb+1 bcc + inc _modsrclsb+2 + _modsrcmsb lda $ffff ; modnfied msb read sta (P8ZP_SCRATCH_W2),y lda _modsrcmsb+1 clc adc #2 sta _modsrcmsb+1 bcc + inc _modsrcmsb+2 + iny dex bne _modsrclsb rts .pend memcopy_small .proc ; copy up to a single page (256 bytes) of memory. ; note: only works for NON-OVERLAPPING memory regions! ; P8ZP_SCRATCH_W1 = from address ; P8ZP_SCRATCH_W2 = destination address ; Y = number of bytes to copy (where 0 means 256) cpy #0 beq _fullpage dey beq _lastbyte _loop lda (P8ZP_SCRATCH_W1),y sta (P8ZP_SCRATCH_W2),y dey bne _loop _lastbyte lda (P8ZP_SCRATCH_W1),y sta (P8ZP_SCRATCH_W2),y rts _fullpage lda (P8ZP_SCRATCH_W1),y sta (P8ZP_SCRATCH_W2),y dey bne _fullpage rts .pend