def decompress_data()

in nightMARE/src/nightmare/analysis/compression/lznt1.py [0:0]

• 40 lines of code
• 9 McCabe index (conditional complexity)

def decompress_data(cdata: bytes) -> bytes:
    """Decompresses the data."""

    in_fd = BytesIO(cdata)
    output_fd = BytesIO()
    block_end = 0

    while in_fd.tell() < len(cdata):
        block_offset = in_fd.tell()
        uncompressed_chunk_offset = output_fd.tell()

        block_header = struct.unpack("<H", in_fd.read(2))[0]

        if block_header & SIGNATURE_MASK != SIGNATURE_MASK:
            break

        size = block_header & SIZE_MASK

        block_end = block_offset + size + 3

        if block_header & COMPRESSED_MASK:
            while in_fd.tell() < block_end:
                header = ord(in_fd.read(1))

                for mask in TAG_MASKS:
                    if in_fd.tell() >= block_end:
                        break

                    if header & mask:
                        pointer = struct.unpack("<H", in_fd.read(2))[0]
                        displacement = DISPLACEMENT_TABLE[
                            output_fd.tell() - uncompressed_chunk_offset - 1
                        ]

                        symbol_offset = (pointer >> (12 - displacement)) + 1
                        symbol_length = (pointer & (0xFFF >> displacement)) + 3

                        output_fd.seek(-symbol_offset, 2)
                        data = output_fd.read(symbol_length)

                        # Pad the data to make it fit.
                        if 0 < len(data) < symbol_length:
                            data = data * (symbol_length // len(data) + 1)
                            data = data[:symbol_length]

                        output_fd.seek(0, 2)

                        output_fd.write(data)

                    else:
                        data = in_fd.read(1)

                        output_fd.write(data)

        else:
            # Block is not compressed
            data = in_fd.read(size + 1)
            output_fd.write(data)

    result = output_fd.getvalue()

    return result