;;;;;;;;;;;;;;;;;;; HEADER   ;;;;;;;;;;;;;;;;;;;
read "\SrcCPC\winape_macros.asm"
read "\SrcCPC\MemoryMap.asm"
read "\SrcALL\winapeBuildCompat.asm"
;;;;;;;;;;;;;;;;;;; PROGRAM  ;;;;;;;;;;;;;;;;;;;

org &8000
ld de,27
call doHailstone	
;returns length of sequence, and writes each entry in the sequence
;	to RAM

;print the sequence length (in hex)
ld a,h
call ShowHex	
ld a,l
ld (memdump_smc),a
;just to prove I didn't need to know the sequence length at
;	compile time, I'll store the calculated length as the operand
;	of "doMemDump" which normally takes a constant embedded after
;	it as the number of bytes to display.

;      If that doesn't make sense, don't worry.
;      This has nothing to do with calculating the hailstone sequence, just showing the results.
call ShowHex

call NewLine		;prints CRLF
call NewLine

call doMemDump
memdump_smc:
byte 0			;operand of "doMemDump" (gets overwritten with the sequence length)
word HailstoneBuffer	;operand of "doMemDump"


ret

;;;;;;;;;;;;;;;;;;; LIBRARY  ;;;;;;;;;;;;;;;;;;;
read "\SrcCPC\winape_stringop.asm"
read "\SrcCPC\winape_showhex.asm"


doHailstone:
;you need the proper input for the function "hailstone"
;returns addr. of last element in IX.
call hailstone
ld de,HailstoneBuffer
or a	;clear carry
push ix
pop hl		;returns element count in HL.
sbc hl,de	;subtract the two to get the length of the array.

SRL H
RR L		;divide array size by 2, since each entry is 2 bytes.
INC L
ret nz		;if no carry, don't increment H.
INC H
ret


hailstone:
;input - de = n
ld ix,HailstoneBuffer
ld a,d
or e
ret z	;zero is not allowed.
loop_hailstone:
ld (IX+0),e
ld (IX+1),d
ld a,e
cp 1
jr nz,continue_hailstone
ld a,d
or a
ret z	;if de = 1, stop.
continue_hailstone:
bit 0,e
jr z,DE_IS_EVEN
;de is odd
push de
pop hl		;ld hl,de

SLA E
RL D
add hl,de	;hl = de*3

ld de,1
add hl,de

push hl	
pop de		;ld de,hl

inc ix
inc ix
jr loop_hailstone

DE_IS_EVEN:
SRL D		;A/2
RR E
inc ix
inc ix
jr loop_hailstone


doMemDump:
;show the hailstone sequence to the screen. This is just needed to display the data, if you don't care about that
;you can stop reading here.
pop hl		;get PC
ld b,(hl)	;get byte count
inc hl
ld e,(hl)	;get low byte of start addr.
inc hl
ld d,(hl)	;get high byte of start addr.
inc hl
push hl		;now when we return we'll skip the data block.
ex de,hl


call NewLine

;we'll dump 8 words per line.

ld c,8
loop_doMemDump:
inc hl
ld a,(hl)
call ShowHex
dec hl
ld a,(hl)
call ShowHex
ld a,' '
call PrintChar
inc hl
inc hl
dec c
ld a,c
and %00001111
jr nz,continueMemdump
ld c,8
continueMemdump:
djnz loop_doMemDump
ret



HailstoneBuffer:
ds 512,0