.importzp ptr1, ptr2, ptr3
- .import __hptr, __hfirst, __hlast, __hend
.export _malloc
- .macpack generic
-
-; Offsets into struct freeblock and other constant stuff
-
-size = 0
-next = 2
-prev = 4
-admin_space = 2
-min_size = 6
+ .include "_heap.inc"
+ .macpack generic
+;-----------------------------------------------------------------------------
; Code
_malloc:
- sta ptr1 ; Store size in ptr1
+ sta ptr1 ; Store size in ptr1
stx ptr1+1
; Check for a size of zero, if so, return NULL
ora ptr1+1
- beq Done ; a/x already contains zero
+ beq Done ; a/x already contains zero
; Add the administration space and round up the size if needed
lda ptr1
- add #admin_space
+ add #HEAP_ADMIN_SPACE
sta ptr1
bcc @L1
inc ptr1+1
@L1: ldx ptr1+1
bne @L2
- cmp #min_size+1
+ cmp #HEAP_MIN_BLOCKSIZE+1
bcs @L2
- lda #min_size
- sta ptr1 ; High byte is already zero
+ lda #HEAP_MIN_BLOCKSIZE
+ sta ptr1 ; High byte is already zero
; Load a pointer to the freelist into ptr2
-@L2: lda __hfirst
+@L2: lda __heapfirst
sta ptr2
- lda __hfirst+1
+ lda __heapfirst+1
sta ptr2+1
; Search the freelist for a block that is big enough. We will calculate
jmp @L4
-@L3: ldy #size
+@L3: ldy #freeblock::size
lda (ptr2),y
sub ptr1
- tax ; Remember low byte for later
- iny ; Y points to size+1
+ tax ; Remember low byte for later
+ iny ; Y points to freeblock::size+1
lda (ptr2),y
sbc ptr1+1
- bcs BlockFound ; Beware: Contents of a/x/y are known!
+ bcs BlockFound ; Beware: Contents of a/x/y are known!
; Next block in list
- iny ; Points to next
+ iny ; Points to freeblock::next
lda (ptr2),y
tax
- iny ; Points to next+1
+ iny ; Points to freeblock::next+1
lda (ptr2),y
stx ptr2
sta ptr2+1
; We did not find a block big enough. Try to use new space from the heap top.
- lda __hptr
- add ptr1 ; _hptr + size
+ lda __heapptr
+ add ptr1 ; _heapptr + size
tay
- lda __hptr+1
+ lda __heapptr+1
adc ptr1+1
- bcs OutOfHeapSpace ; On overflow, we're surely out of space
+ bcs OutOfHeapSpace ; On overflow, we're surely out of space
- cmp __hend+1
+ cmp __heapend+1
bne @L5
- cpy __hend
+ cpy __heapend
@L5: bcc TakeFromTop
beq TakeFromTop
lda #0
tax
Done: rts
-
+
; There is enough space left, take it from the heap top
TakeFromTop:
- ldx __hptr ; p = hptr;
+ ldx __heapptr ; p = _heapptr;
stx ptr2
- ldx __hptr+1
+ ldx __heapptr+1
stx ptr2+1
- sty __hptr ; hptr += size;
- sta __hptr+1
- jmp FillSizeAndRet ; Done
+ sty __heapptr ; _heapptr += size;
+ sta __heapptr+1
+ jmp FillSizeAndRet ; Done
; We found a block big enough. If the block can hold just the
; requested size, use the block in full. Beware: When slicing blocks,
; flag is set if the high byte of this remaining size is zero.
BlockFound:
- bne SliceBlock ; Block is large enough to slice
- cpx #min_size+1 ; Check low byte
- bcs SliceBlock ; Jump if block is large enough to slice
+ bne SliceBlock ; Block is large enough to slice
+ cpx #HEAP_MIN_BLOCKSIZE ; Check low byte
+ bcs SliceBlock ; Jump if block is large enough to slice
; The block is too small to slice it. Use the block in full. The block
; does already contain the correct size word, all we have to do is to
; remove it from the free list.
- ldy #prev+1 ; Load f->prev
+ ldy #freeblock::prev+1 ; Load f->prev
lda (ptr2),y
sta ptr3+1
dey
lda (ptr2),y
sta ptr3
- dey ; Points to next+1
+ dey ; Points to freeblock::next+1
ora ptr3+1
- beq @L1 ; Jump if f->prev zero
+ beq @L1 ; Jump if f->prev zero
; We have a previous block, ptr3 contains its address.
; Do f->prev->next = f->next
- lda (ptr2),y ; Load high byte of f->next
- sta (ptr3),y ; Store high byte of f->prev->next
- dey ; Points to next
- lda (ptr2),y ; Load low byte of f->next
- sta (ptr3),y ; Store low byte of f->prev->next
+ lda (ptr2),y ; Load high byte of f->next
+ sta (ptr3),y ; Store high byte of f->prev->next
+ dey ; Points to next
+ lda (ptr2),y ; Load low byte of f->next
+ sta (ptr3),y ; Store low byte of f->prev->next
jmp @L2
; This is the first block, correct the freelist pointer
; Do _hfirst = f->next
-@L1: lda (ptr2),y ; Load high byte of f->next
- sta __hfirst+1
- dey ; Points to next
- lda (ptr2),y ; Load low byte of f->next
- sta __hfirst
+@L1: lda (ptr2),y ; Load high byte of f->next
+ sta __heapfirst+1
+ dey ; Points to next
+ lda (ptr2),y ; Load low byte of f->next
+ sta __heapfirst
; Check f->next. Y points always to next if we come here
-@L2: lda (ptr2),y ; Load low byte of f->next
+@L2: lda (ptr2),y ; Load low byte of f->next
sta ptr3
- iny ; Points to next+1
- lda (ptr2),y ; Load high byte of f->next
+ iny ; Points to next+1
+ lda (ptr2),y ; Load high byte of f->next
sta ptr3+1
- iny ; Points to prev
+ iny ; Points to prev
ora ptr3
- beq @L3 ; Jump if f->next zero
+ beq @L3 ; Jump if f->next zero
; We have a next block, ptr3 contains its address.
; Do f->next->prev = f->prev
- lda (ptr2),y ; Load low byte of f->prev
- sta (ptr3),y ; Store low byte of f->next->prev
- iny ; Points to prev+1
- lda (ptr2),y ; Load high byte of f->prev
- sta (ptr3),y ; Store high byte of f->prev->next
- jmp RetUserPtr ; Done
+ lda (ptr2),y ; Load low byte of f->prev
+ sta (ptr3),y ; Store low byte of f->next->prev
+ iny ; Points to prev+1
+ lda (ptr2),y ; Load high byte of f->prev
+ sta (ptr3),y ; Store high byte of f->prev->next
+ jmp RetUserPtr ; Done
; This is the last block, correct the freelist pointer.
; Do _hlast = f->prev
-@L3: lda (ptr2),y ; Load low byte of f->prev
- sta __hlast
- iny ; Points to prev+1
- lda (ptr2),y ; Load high byte of f->prev
- sta __hlast+1
- jmp RetUserPtr ; Done
+@L3: lda (ptr2),y ; Load low byte of f->prev
+ sta __heaplast
+ iny ; Points to prev+1
+ lda (ptr2),y ; Load high byte of f->prev
+ sta __heaplast+1
+ jmp RetUserPtr ; Done
; We must slice the block found. Cut off space from the upper end, so we
; can leave the actual free block chain intact.
; Decrement the size of the block. Y points to size+1.
- dey ; Points to size
- lda (ptr2),y ; Low byte of f->size
+ dey ; Points to size
+ lda (ptr2),y ; Low byte of f->size
sub ptr1
sta (ptr2),y
- tax ; Save low byte of f->size in X
- iny ; Points to size+1
- lda (ptr2),y ; High byte of f->size
+ tax ; Save low byte of f->size in X
+ iny ; Points to size+1
+ lda (ptr2),y ; High byte of f->size
sbc ptr1+1
sta (ptr2),y
; Set f to the space above the current block, which is the new block returned
; to the caller.
- txa ; Get low byte of f->size
+ txa ; Get low byte of f->size
add ptr2
tax
- lda (ptr2),y ; Get high byte of f->size
+ lda (ptr2),y ; Get high byte of f->size
adc ptr2+1
stx ptr2
sta ptr2+1
-; Fill the size into the admin space of the block and return the user pointer
+; Fill the size and start address into the admin space of the block
+; (struct usedblock) and return the user pointer
FillSizeAndRet:
- ldy #size ; *p = size;
- lda ptr1 ; Low byte of block size
+ ldy #usedblock::size ; p->size = size;
+ lda ptr1 ; Low byte of block size
sta (ptr2),y
- iny ; Points to size+1
+ iny ; Points to freeblock::size+1
lda ptr1+1
sta (ptr2),y
RetUserPtr:
- lda ptr2 ; return ++p;
+ ldy #usedblock::start ; p->start = p
+ lda ptr2
+ sta (ptr2),y
+ iny
+ lda ptr2+1
+ sta (ptr2),y
+
+; Return the user pointer, which points behind the struct usedblock
+
+ lda ptr2 ; return ++p;
ldx ptr2+1
- add #admin_space
+ add #HEAP_ADMIN_SPACE
bcc @L9
inx
@L9: rts
projects / cc65 / blobdiff