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New used block structure for the heap

git-svn-id: svn://svn.cc65.org/cc65/trunk@3347 b7a2c559-68d2-44c3-8de9-860c34a00d81
This commit is contained in:
cuz 2005-01-05 21:05:11 +00:00
parent 802f259b37
commit 842ff39d4c

View File

@ -6,7 +6,7 @@
; Return the size of an allocated block.
;
.importzp ptr1
.importzp ptr1, ptr2
.export __heapblocksize
.include "_heap.inc"
@ -19,33 +19,57 @@
__heapblocksize:
; Decrement the block pointer so it points to the admin data
; Below the user data is a pointer that points to the start of the real
; (raw) memory block. The first word of this block is the size. To access
; the raw block pointer, we will decrement the high byte of the pointer,
; the pointer is then at offset 254/255.
sub #HEAP_ADMIN_SPACE ; Assume it's less than 256
bcs L1
sta ptr1
dex
L1: sta ptr1
stx ptr1+1
; Load the size from the given block
ldy #1
ldy #$FE
lda (ptr1),y
sta ptr2 ; Place the raw block pointer into ptr2
iny
lda (ptr1),y
sta ptr2+2
; Load the size from the raw block
ldy #usedblock::size+1
lda (ptr2),y
tax
.if (.cpu .bitand CPU_ISET_65SC02)
lda (ptr1)
lda (ptr2)
.else
dey
lda (ptr1),y
lda (ptr2),y
.endif
; Adjust it to the user visible size
; Correct the raw block size so that is shows the user visible portion. To
; do that, we must decrease the size by the amount of unused memory, which is
; the difference between the user space pointer and the raw memory block
; pointer. Since we have decremented the user space pointer by 256, we will
; have to correct the result.
;
; return size - (ptr1 + 256 - ptr2)
; return size - ptr1 - 256 + ptr2
sub #HEAP_ADMIN_SPACE
bcs L9
dex
dex ; - 256
add ptr2
pha
txa
adc ptr2+1
tax
pla
sub ptr1
pha
txa
sbc ptr1+1
tax
pla
; Done
L9: rts
rts