mirror of
https://github.com/cc65/cc65.git
synced 2024-11-11 01:05:25 +00:00
340 lines
9.1 KiB
ArmAsm
340 lines
9.1 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 17.7.2000
|
|
;
|
|
; Allocate a block from the heap.
|
|
;
|
|
; void* __fastcall__ malloc (size_t size);
|
|
;
|
|
;
|
|
; C implementation was:
|
|
;
|
|
; void* malloc (size_t size)
|
|
; /* Allocate memory from the given heap. The function returns a pointer to the
|
|
; * allocated memory block or a NULL pointer if not enough memory is available.
|
|
; * Allocating a zero size block is not allowed.
|
|
; */
|
|
; {
|
|
; struct freeblock* f;
|
|
; unsigned* p;
|
|
;
|
|
;
|
|
; /* Check for a size of zero, then add the administration space and round
|
|
; * up the size if needed.
|
|
; */
|
|
; if (size == 0) {
|
|
; return 0;
|
|
; }
|
|
; size += HEAP_ADMIN_SPACE;
|
|
; if (size < sizeof (struct freeblock)) {
|
|
; size = sizeof (struct freeblock);
|
|
; }
|
|
;
|
|
; /* Search the freelist for a block that is big enough */
|
|
; f = _hfirst;
|
|
; while (f && f->size < size) {
|
|
; f = f->next;
|
|
; }
|
|
;
|
|
; /* Did we find one? */
|
|
; if (f) {
|
|
;
|
|
; /* We found a block big enough. If the block can hold just the
|
|
; * requested size, use the block in full. Beware: When slicing blocks,
|
|
; * there must be space enough to create a new one! If this is not the
|
|
; * case, then use the complete block.
|
|
; */
|
|
; if (f->size - size < sizeof (struct freeblock)) {
|
|
;
|
|
; /* Use the actual size */
|
|
; size = f->size;
|
|
;
|
|
; /* Remove the block from the free list */
|
|
; if (f->prev) {
|
|
; /* We have a previous block */
|
|
; f->prev->next = f->next;
|
|
; } else {
|
|
; /* This is the first block, correct the freelist pointer */
|
|
; _hfirst = f->next;
|
|
; }
|
|
; if (f->next) {
|
|
; /* We have a next block */
|
|
; f->next->prev = f->prev;
|
|
; } else {
|
|
; /* This is the last block, correct the freelist pointer */
|
|
; _hlast = f->prev;
|
|
; }
|
|
;
|
|
; } else {
|
|
;
|
|
; /* 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 */
|
|
; f->size -= size;
|
|
;
|
|
; /* Set f to the now unused space above the current block */
|
|
; f = (struct freeblock*) (((unsigned) f) + f->size);
|
|
;
|
|
; }
|
|
;
|
|
; /* Setup the pointer for the block */
|
|
; p = (unsigned*) f;
|
|
;
|
|
; } else {
|
|
;
|
|
; /* We did not find a block big enough. Try to use new space from the
|
|
; * heap top.
|
|
; */
|
|
; if (((unsigned) _hend) - ((unsigned) _hptr) < size) {
|
|
; /* Out of heap space */
|
|
; return 0;
|
|
; }
|
|
;
|
|
;
|
|
; /* There is enough space left, take it from the heap top */
|
|
; p = _hptr;
|
|
; _hptr = (unsigned*) (((unsigned) _hptr) + size);
|
|
;
|
|
; }
|
|
;
|
|
; /* New block is now in p. Fill in the size and return the user pointer */
|
|
; *p++ = size;
|
|
; return p;
|
|
; }
|
|
;
|
|
|
|
|
|
.importzp ptr1, ptr2, ptr3
|
|
.export _malloc
|
|
|
|
.include "_heap.inc"
|
|
|
|
.macpack generic
|
|
|
|
;-----------------------------------------------------------------------------
|
|
; Code
|
|
|
|
_malloc:
|
|
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
|
|
|
|
; Add the administration space and round up the size if needed
|
|
|
|
lda ptr1
|
|
add #HEAP_ADMIN_SPACE
|
|
sta ptr1
|
|
bcc @L1
|
|
inc ptr1+1
|
|
@L1: ldx ptr1+1
|
|
bne @L2
|
|
cmp #HEAP_MIN_BLOCKSIZE+1
|
|
bcs @L2
|
|
lda #HEAP_MIN_BLOCKSIZE
|
|
sta ptr1 ; High byte is already zero
|
|
|
|
; Load a pointer to the freelist into ptr2
|
|
|
|
@L2: lda __heapfirst
|
|
sta ptr2
|
|
lda __heapfirst+1
|
|
sta ptr2+1
|
|
|
|
; Search the freelist for a block that is big enough. We will calculate
|
|
; (f->size - size) here and keep it, since we need the value later.
|
|
|
|
jmp @L4
|
|
|
|
@L3: ldy #freeblock::size
|
|
lda (ptr2),y
|
|
sub ptr1
|
|
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!
|
|
|
|
; Next block in list
|
|
|
|
iny ; Points to freeblock::next
|
|
lda (ptr2),y
|
|
tax
|
|
iny ; Points to freeblock::next+1
|
|
lda (ptr2),y
|
|
stx ptr2
|
|
sta ptr2+1
|
|
@L4: ora ptr2
|
|
bne @L3
|
|
|
|
; We did not find a block big enough. Try to use new space from the heap top.
|
|
|
|
lda __heapptr
|
|
add ptr1 ; _heapptr + size
|
|
tay
|
|
lda __heapptr+1
|
|
adc ptr1+1
|
|
bcs OutOfHeapSpace ; On overflow, we're surely out of space
|
|
|
|
cmp __heapend+1
|
|
bne @L5
|
|
cpy __heapend
|
|
@L5: bcc TakeFromTop
|
|
beq TakeFromTop
|
|
|
|
; Out of heap space
|
|
|
|
OutOfHeapSpace:
|
|
lda #0
|
|
tax
|
|
Done: rts
|
|
|
|
; There is enough space left, take it from the heap top
|
|
|
|
TakeFromTop:
|
|
ldx __heapptr ; p = _heapptr;
|
|
stx ptr2
|
|
ldx __heapptr+1
|
|
stx ptr2+1
|
|
|
|
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,
|
|
; there must be space enough to create a new one! If this is not the
|
|
; case, then use the complete block.
|
|
; On input, x/a do contain the remaining size of the block. The zero
|
|
; flag is set if the high byte of this remaining size is zero.
|
|
|
|
BlockFound:
|
|
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 #freeblock::prev+1 ; Load f->prev
|
|
lda (ptr2),y
|
|
sta ptr3+1
|
|
dey
|
|
lda (ptr2),y
|
|
sta ptr3
|
|
dey ; Points to freeblock::next+1
|
|
ora ptr3+1
|
|
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
|
|
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 __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
|
|
sta ptr3
|
|
iny ; Points to next+1
|
|
lda (ptr2),y ; Load high byte of f->next
|
|
sta ptr3+1
|
|
iny ; Points to prev
|
|
ora ptr3
|
|
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
|
|
|
|
; This is the last block, correct the freelist pointer.
|
|
; Do _hlast = f->prev
|
|
|
|
@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.
|
|
|
|
SliceBlock:
|
|
|
|
; Decrement the size of the block. Y points to size+1.
|
|
|
|
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
|
|
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
|
|
add ptr2
|
|
tax
|
|
lda (ptr2),y ; Get high byte of f->size
|
|
adc ptr2+1
|
|
stx ptr2
|
|
sta ptr2+1
|
|
|
|
; Fill the size and start address into the admin space of the block
|
|
; (struct usedblock) and return the user pointer
|
|
|
|
FillSizeAndRet:
|
|
ldy #usedblock::size ; p->size = size;
|
|
lda ptr1 ; Low byte of block size
|
|
sta (ptr2),y
|
|
iny ; Points to freeblock::size+1
|
|
lda ptr1+1
|
|
sta (ptr2),y
|
|
|
|
RetUserPtr:
|
|
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 #HEAP_ADMIN_SPACE
|
|
bcc @L9
|
|
inx
|
|
@L9: rts
|
|
|