Adding data to existing segment may fail depending on how segment was previously created #53

Hello,

depending on how data was added to a bincopy.BinFile(), the stored data may be mutable or immutable, causing modifying data operations to fail.

Example:

binaryFileElf = bincopy.BinFile()
binaryFileElf.add_elf_file(pathElf)
binaryFileElf.add_binary(data, address=0, overwrite=True)

In this case the data provided by .elf file pathElf and the data inserted afterwards overlaps, therefore overwrite=True was used.

Observed:

  File "/usr/lib/python3/dist-packages/bincopy.py", line 1107, in add_binary
    self._segments.add(Segment(address,
  File "/usr/lib/python3/dist-packages/bincopy.py", line 605, in add
    s.add_data(segment.minimum_address,
  File "/usr/lib/python3/dist-packages/bincopy.py", line 444, in add_data
    self.data[self_data_offset:self_data_offset + len(data)] = data
    ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'bytes' object does not support item assignment

Expectation:
Data was successfully replaced/overwritten/modified.

Analysis:
Specifically, in the following line during reading the elf file, a new segment is created while using a bytes type instead of a bytearray. Therefore causing segment to take over the type and making the data immutable: https://github.com/eerimoq/bincopy/blob/d7a55099a54dee3f3b6781c488b0a1000969b0ce/bincopy.py#L1145C21-L1145C45

add_binary for initial data creation is not affected as it creates a segment based on a bytearray:

binaryFile = bincopy.BinFile()
binaryFile.add_binary(binaryFileElf.as_binary())
binaryFile.add_binary(data, address=0, overwrite=True) # This works as add_binary uses a bytearray

Suggestion: potentially specifying self.data of class Segment to always be a mutable bytearray could be an option if there is no need for immutable segments.