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ben
227
ZipFileTransformer/zip.py
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227
ZipFileTransformer/zip.py
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# -*- coding: utf-8 -*-
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import logging
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import re
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class Zip:
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def __init__(self, filename):
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self.filename = filename
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self.buffer = bytearray()
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self.size = 0
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self.end_central_dir = 0
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self.first_local_file_header = 0
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self.offset_local_file = []
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self.offset_central_directory = []
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self.end_of_data = 0
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self.end_of_first_local_file_header = 0
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self.read()
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self.check_header()
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self.call_all_parsers()
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self.check_central_directory()
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self.parse_central_directories()
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self.parse_local_file_headers()
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def call_all_parsers(self):
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self.parse_offset_end_central_dir()
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self.parse_nb_of_disk()
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self.parse_start_disk()
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self.parse_nb_of_central_dir()
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self.parse_nb_total_of_central_dir()
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self.parse_size_central_dir()
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self.parse_central_dir_file_header()
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self.parse_comment_length()
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def read(self):
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with open(self.filename, 'rb') as fd:
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self.buffer = bytearray(fd.read())
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self.size = len(self.buffer)
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logging.info("read " + str(self.size) + " bytes from Zip file")
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def check_header(self):
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if self.buffer[0:4] != b"PK\x03\x04":
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raise Exception("Zip header not found")
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def parse_offset_end_central_dir(self):
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r = re.compile(b'\x06\x05KP')
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s = r.search(self.buffer[::-1])
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if s is None:
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raise Exception("Unable to find end of central directory")
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self.end_central_dir = self.size - s.end()
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logging.info("Offset end of central directory: " +
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hex(self.end_central_dir))
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def parse_nb_of_disk(self):
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self.nb_of_disk = int.from_bytes(
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self.buffer[self.end_central_dir + 4:self.end_central_dir + 6],
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"little")
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logging.debug("Nb of disk: " + str(self.nb_of_disk))
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def parse_start_disk(self):
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self.start_disk = int.from_bytes(
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self.buffer[self.end_central_dir + 6:self.end_central_dir + 8],
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"little")
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logging.debug("Start disk: " + str(self.start_disk))
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def parse_nb_of_central_dir(self):
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self.nb_of_central_dir = int.from_bytes(
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self.buffer[self.end_central_dir + 8:self.end_central_dir + 10],
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"little")
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logging.info("Nb of central directory record: " +
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str(self.nb_of_central_dir))
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def parse_nb_total_of_central_dir(self):
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self.nb_total_of_central_dir = int.from_bytes(
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self.buffer[self.end_central_dir + 10:self.end_central_dir + 12],
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"little")
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logging.info("Nb of total central directory record: " +
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str(self.nb_total_of_central_dir))
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def parse_size_central_dir(self):
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self.size_central_dir = int.from_bytes(
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self.buffer[self.end_central_dir + 12:self.end_central_dir + 14],
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"little")
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logging.info("Size of central directory: " +
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str(self.size_central_dir))
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def parse_central_dir_file_header(self):
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self.central_dir_file_header = int.from_bytes(
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self.buffer[self.end_central_dir + 16:self.end_central_dir + 20],
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"little")
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logging.info("Central directory file header: " +
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hex(self.central_dir_file_header))
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def parse_comment_length(self):
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self.comment_length = int.from_bytes(
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self.buffer[self.end_central_dir + 20:self.end_central_dir + 22],
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"little")
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logging.info("Comment length: " +
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str(self.comment_length))
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def check_central_directory(self):
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offset = self.central_dir_file_header
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if (self.buffer[offset:offset + 4] !=
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b'PK\x01\x02'):
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raise Exception("Unable to find central directory")
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logging.info("Found central directory")
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def parse_central_directories(self):
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if (self.buffer[self.central_dir_file_header:
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self.central_dir_file_header + 4] !=
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b'PK\x01\x02'):
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raise Exception("Unable to find first central directory")
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logging.info("Found first central directory")
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i = 0
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size = 0
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offset = self.central_dir_file_header
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while (self.buffer[size + offset:
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size + offset + 4] ==
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b'PK\x01\x02'):
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logging.info("Parse central directory n°" + str(i))
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logging.info("Offset: " + hex(offset + size))
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self.offset_central_directory.append(offset + size)
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filename_length = int.from_bytes(
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self.buffer[size + offset + 28:size + offset + 30],
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"little")
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logging.info("filename length:" + str(filename_length))
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extra_field_length = int.from_bytes(
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self.buffer[size + offset + 30:size + offset + 32],
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"little")
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logging.info("extra field length:" + str(extra_field_length))
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comment_length = int.from_bytes(
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self.buffer[size + offset + 32:size + offset + 34],
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"little")
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logging.info("comment length:" + str(comment_length))
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local_file_header = int.from_bytes(
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self.buffer[size + offset + 42:size + offset + 46],
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"little")
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if i == 0:
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self.first_local_file_header = local_file_header
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logging.info("local file header:" + hex(local_file_header))
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i = i + 1
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size = (size + filename_length +
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extra_field_length + comment_length + 46)
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logging.debug("parse header at:" + hex(offset + size))
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def parse_local_file_headers(self):
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size = 0
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offset = self.first_local_file_header
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for i in range(self.nb_of_central_dir):
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logging.info("Parse local file n°" + str(i))
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compressed_data_lenght = int.from_bytes(
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self.buffer[size + offset + 18:size + offset + 22],
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"little")
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logging.info("compressed data length:" +
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str(compressed_data_lenght))
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filename_length = int.from_bytes(
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self.buffer[size + offset + 26:size + offset + 28],
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"little")
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logging.info("filename length:" + str(filename_length))
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extra_field_length = int.from_bytes(
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self.buffer[size + offset + 28:size + offset + 30],
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"little")
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logging.info("extra field length:" + str(extra_field_length))
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local_file_size = (compressed_data_lenght +
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filename_length + extra_field_length + 30)
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logging.info("local file length:" + hex(local_file_size))
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size = size + local_file_size
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logging.debug("parse header at:" + hex(offset + size))
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self.offset_local_file.append(offset + size)
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self.end_of_data = offset + size
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if i == 0:
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self.end_of_first_local_file_header = self.end_of_data
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def add_data_to_file(self, data_before_local, data_after_local,
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write_buffer=False):
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logging.info("Add data before local lenght:" +
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str(len(data_before_local)))
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new_buffer = self.buffer
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for i in self.offset_central_directory:
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logging.info("parse central directory at: " + hex(i))
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local_file_header = int.from_bytes(
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self.buffer[i + 42:i + 46],
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"little")
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logging.info("old local file header: " + hex(local_file_header))
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local_file_header = local_file_header + len(data_before_local)
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logging.info("new local file header: " + hex(local_file_header))
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bytes_local_file_header = local_file_header.to_bytes(4, "little")
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logging.info("change value at:" + hex(i + 42))
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new_buffer[i + 42:i + 46] = bytes_local_file_header
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logging.info("old central directory header: " +
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hex(self.central_dir_file_header))
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new_central_dir_file_header = (self.central_dir_file_header +
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len(data_after_local) +
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len(data_before_local))
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logging.info("new central directory header: " +
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hex(new_central_dir_file_header))
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bytes_offset = new_central_dir_file_header.to_bytes(4, "little")
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new_buffer[self.end_central_dir + 16:
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self.end_central_dir + 20] = bytes_offset
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self.buffer = new_buffer
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if write_buffer:
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new_buffer = (data_before_local +
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new_buffer[:self.end_of_data] +
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data_after_local +
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new_buffer[self.central_dir_file_header:])
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self.buffer = new_buffer
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def get_local_file_data(self):
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return self.buffer[:self.end_of_data]
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def get_data_after_central_directory(self):
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return self.buffer[self.central_dir_file_header:]
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def get_first_part_length(self):
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return len(self.get_local_file_data())
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def get_second_part_length(self):
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return len(self.get_data_after_central_directory())
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