;; Note that this is scheme syntax wrapping asm for a stack machine
(variable scan 0)
(variable free 0)
(variable eom 1024)
;; These need to be initialized later
(variable root 0)
(variable the-cars 0) 
(variable the-cdrs 0)
(variable new-cars 0)
(variable new-cdrs 0)


(push main)
(jmp)

alloc
;; Test if free will go beyond eom
(push free)
(@)
(dup) ; ( -- free free)
(push 8)
(+)
(dup) ; ( -- free free+8 free+8)
(push eom)
(@)
(<) ; ( -- free free+8 (free+8 < eom))
(branch alloc-do-gc)
;; write free+8 to free
(push free)
(!)
;; return the old free, it is memory the program can use
(return)
alloc-do-gc
;; Empty the stack
(drop)
(drop)
;; Run garbage collection
(push gc-start)
(call)
;; Tail-call allocation
(push alloc)
(jmp)

gc-start
; Move scan & free back to 0
(push 0)
(push free)
(!)
(push 0)
(push scan)
(!)
; Push the first cons to relocate (root)
(push root)
(@)
; Call the relocation routine
(push gc-loop)
(call)
; Swap new and old cars and cdrs
(push new-cars)
(@)
(push the-cars)
(@)
(push new-cars)
(!)
(push the-cars)
(!)
(push new-cdrs)
(@)
(push the-cdrs)
(@)
(push new-cdrs)
(!)
(push the-cdrs)
(!)
; return to allocation
(return)