#!/usr/bin/python

#encoding: UTF-8

#################################################################

# script: encode.py

# description: 实现对文件相关加密解密

# version: 0.1 实现对普通文件的加密解密

# usage: python  encode.py [encode | decode] filename [key]

#################################################################

import sys, os, struct

# 加密字符串

def encodeString(str):

key_index = 0

# 定义加密字符串

str_encode = ''

# 字符串转换成字节数组

bytes = bytearray(str)

# 按字节加密

for b in bytes:

b_encode = (b + key_bytes[key_index]) % 256

str_encode += struct.pack('B', b_encode)

key_index = (key_index + 1) % len(key_bytes)

# 返回加密字符串

return str_encode

# 解密字符串

def decodeString(str):

key_index = 0

# 定义解密字符串

str_decode = ''

# 字符串转换成字节数组

bytes = bytearray(str)

for b in bytes:

b_decode = (b + 256 - key_bytes[key_index]) % 256

str_decode += struct.pack('B', b_decode)

key_index = (key_index + 1) % len(key_bytes)

# 返回解密字符串

return str_decode

# 检查命令行参数

if len(sys.argv) < 3 or len(sys.argv) > 4:

print 'Usage: python', sys.argv[0], '[encode | decode] filename [key]'

exit(1)

if sys.argv[1] not in ('encode', 'decode'):

print 'Usage: python', sys.argv[0], '[encode | decode] filename [key]'

exit(1)

# 文件名

filename = sys.argv[2]

if not os.path.isfile(filename):

print 'File "' + filename + '" is not exsisted'

print 'Usage: python', sys.argv[0], '[encode | decode] filename [key]'

exit(1)

# 定义密钥。加密方式：字符串每个字节与密钥对应字节相加后求余

key = 'TESTKEY'

if len(sys.argv) == 4:

key = sys.argv[3]

key_bytes = bytearray(key)

# 加密或解密

mode = sys.argv[1]

# 加密或解密文件

file_mode_name = filename + '.' + mode

# 执行加密或解密

if mode == 'encode':

file = open(filename, 'r')

file_encode = open(file_mode_name, 'w')

str = file.read()

str_encode = encodeString(str)

file_encode.write(str_encode)

file.close()

file_encode.close()

else:

file = open(filename, 'r')

file_decode = open(file_mode_name, 'w')

str = file.read()

str_decode = decodeString(str)

file_decode.write(str_decode)

file.close()

file_decode.close()

print 'Succeed to', mode, 'file "' + filename + '", result file is "' + file_mode_name + '"'