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cc65/libsrc/common/_heapblocksize.s

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;
; Ullrich von Bassewitz, 2004-07-17
;
; size_t __fastcall__ _heapblocksize (const void* ptr);
;
; Return the size of an allocated block.
;
.importzp ptr1
.export __heapblocksize
.include "_heap.inc"
;-----------------------------------------------------------------------------
; Code
__heapblocksize:
; Decrement the block pointer so it points to the admin data
sec
sbc #HEAP_ADMIN_SPACE ; Assume it's less than 256
bcs L1
dex
L1: sta ptr1
stx ptr1+1
; Load the size from the given block
ldy #1
lda (ptr1),y
tax
dey
lda (ptr1),y
; Done
rts