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mrkn/gist:8692143

Created Jan 29, 2014
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GC_DEBUG = false
CHAR_BIT = 8
BITS_SIZE = 8
BITS_BITLENGTH = BITS_SIZE * CHAR_BIT
SIZEOF_RVALUE = GC_DEBUG ? 56 : 40
SIZEOF_SIZE_T = 8
SIZEOF_STRUCT_HEAP_PAGE_HEADER = 8
def ceildiv(i, mod)
((i + mod - 1) / mod).to_i
end
HEAP_ALIGN_LOG = 14
HEAP_ALIGN = 1 << HEAP_ALIGN_LOG
HEAP_ALIGN_MASK = ~(~0 << HEAP_ALIGN_LOG)
REQUIRED_SIZE_BY_MALLOC = SIZEOF_SIZE_T * 5
HEAP_SIZE = HEAP_ALIGN - REQUIRED_SIZE_BY_MALLOC
HEAP_OBJ_LIMIT = ((HEAP_SIZE - SIZEOF_STRUCT_HEAP_PAGE_HEADER)/SIZEOF_RVALUE).to_i
HEAP_BITMAP_LIMIT = ceildiv(ceildiv(HEAP_SIZE, SIZEOF_RVALUE), BITS_BITLENGTH)
HEAP_BITMAP_SIZE = (BITS_SIZE * HEAP_BITMAP_LIMIT)
HEAP_BITMAP_PLANES = 3
def num_in_page(p)
((p & HEAP_ALIGN_MASK) / SIZEOF_RVALUE).to_i
end
def bitmap_index(p)
num_in_page(p) / BITS_BITLENGTH
end
def page_start_limit(page_body)
start = page_body + SIZEOF_STRUCT_HEAP_PAGE_HEADER
limit = HEAP_OBJ_LIMIT
if start % SIZEOF_RVALUE != 0
delta = SIZEOF_RVALUE - (start % SIZEOF_RVALUE)
start = start + delta
limit = ((HEAP_SIZE - (start - page_body))/SIZEOF_RVALUE).to_i
end
[ start, limit ]
end
0.step(HEAP_ALIGN, SIZEOF_SIZE_T) do |addr|
start, limit = page_start_limit(addr)
nip = num_in_page(start)
offset = start - nip
bi = bitmap_index(start)
sub = start - addr
p body: addr, start: start, limit: limit, offset: offset if sub == nip
end
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