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60 lines
1.7 KiB
Python
60 lines
1.7 KiB
Python
3 years ago
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import struct
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import binascii
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def get_bin(value, padn=0, sep=None):
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"""Prints a binary textual representation of a value in """
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return format(value, 'b').zfill(padn)
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# Packing a data structure
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values = (1, b'ab', 2.7)
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s = struct.Struct('I 2s f')
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packed_data = s.pack(*values)
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print("\n##### Struct Packing Example #####\n\n")
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print('Original values :', values)
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print('Packed Type :', type(packed_data))
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# This is most likely going to contain non ascii characters when printed.
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# So it's not suitable to copy it over the printed string and then try to
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# hexlify
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print('Packed print :', packed_data)
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print('Format string :', s.format)
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print('Uses :', s.size, 'bytes')
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print('Packed Value (hex) :', binascii.hexlify(packed_data))
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# binascii.hexlify(data[, sep[, bytes_per_sep=1]]) can also make more
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# human readable values
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print('Spaced Value (hex) :', binascii.hexlify(packed_data, b"_", 4))
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# Unpacking a data structure
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packed_data = binascii.unhexlify('0100000061620000cdcc2c40')
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unpacked_data = s.unpack(packed_data)
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print("\n##### Struct Unpacking Example #####\n\n")
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print('Unpacked Values:', unpacked_data)
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# Endianness in binary data
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print("\n##### Endianness Demonstration #####\n\n")
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print('Original values:', values)
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endianness = [
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('@', 'native, native'),
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('=', 'native, standard'),
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('<', 'little-endian'),
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('>', 'big-endian'),
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('!', 'network'),
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]
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for code, name in endianness:
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s = struct.Struct(code + ' I 2s f')
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packed_data = s.pack(*values)
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print('Format string :', s.format, 'for', name)
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print('Uses :', s.size, 'bytes')
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print('Packed Value :', binascii.hexlify(packed_data))
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print('Unpacked Value :', s.unpack(packed_data), "\n")
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