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Rewrite elf serialization from xor to BytesIO #20

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Rewrite elf serialization from xor to BytesIO #20

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26 changes: 22 additions & 4 deletions makeelf/elfstruct.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
from makeelf.type.uint16 import uint16
from makeelf.type.uint32 import uint32
import makeelf.utils
from io import BytesIO

## \class ELFCLASS
# \brief File class
Expand Down Expand Up @@ -884,8 +885,17 @@ def __bytes__(self):
end_of_file = sorted(headers.keys())[-1]
end_of_file += len(headers[end_of_file])

b = BytesIO(bytes(end_of_file))

regions = list()

# check if two half segments [x1, x2) and [y1; y2) intersect
def segments_intersect(x, y):
x1, x2 = x
y1, y2 = y
return x2 > y1 and y2 > x1

# create and populate buffer
b = bytes(end_of_file)
for off in headers:
# TODO: there's something wrong, when hdr is not bytes, but only
# simulates it
Expand All @@ -899,12 +909,20 @@ def __bytes__(self):
hdr = bytes(hdr)
size = len(hdr)

region = (off, off + size)
if any(segments_intersect(x, region) for x in regions):
raise Exception('Attempt to write at intersecting parts of a file')
regions.append(region)

b.seek(off)
b.write(hdr)

# expand to file size
aligned = align(bytes(off) + hdr, end_of_file)
#aligned = align(bytes(off) + hdr, end_of_file)

# xor into b
b = makeelf.utils.bytes_xor(b, aligned)
return b
#b = makeelf.utils.bytes_xor(b, aligned)
return b.getvalue()

##
# \brief Deserialization of object
Expand Down