Всех приветствую.
Нужно указать на скрине запуска программы (стрелочками) информационные биты в строке “Закодированные данные”. Код соответственно ниже.
import random
CHUNK_LENGTH = 8
assert not CHUNK_LENGTH % 8
CHECK_BITS = [i for i in range(1, CHUNK_LENGTH + 1) if not i & (i - 1)]
def chars_to_bin(chars):
assert not len(chars) * 8 % CHUNK_LENGTH
return ''.join([bin(ord(c))[2:].zfill(8) for c in chars])
def chunk_iterator(text_bin, chunk_size=CHUNK_LENGTH):
for i in range(len(text_bin)):
if not i % chunk_size:
yield text_bin[i:i + chunk_size]
def get_check_bits_data(value_bin):
check_bits_count_map = {k: 0 for k in CHECK_BITS}
for index, value in enumerate(value_bin, 1):
if int(value):
bin_char_list = list(bin(index)[2:].zfill(8))
bin_char_list.reverse()
for degree in [2 ** int(i) for i, value in enumerate(bin_char_list) if int(value)]:
check_bits_count_map[degree] += 1
check_bits_value_map = {}
for check_bit, count in check_bits_count_map.items():
check_bits_value_map[check_bit] = 0 if not count % 2 else 1
return check_bits_value_map
def set_empty_check_bits(value_bin):
for bit in CHECK_BITS:
value_bin = value_bin[:bit - 1] + '0' + value_bin[bit - 1:]
return value_bin
def set_check_bits(value_bin):
value_bin = set_empty_check_bits(value_bin)
check_bits_data = get_check_bits_data(value_bin)
for check_bit, bit_value in check_bits_data.items():
value_bin = '{0}{1}{2}'.format(
value_bin[:check_bit - 1], bit_value, value_bin[check_bit:])
return value_bin
def get_check_bits(value_bin):
check_bits = {}
for index, value in enumerate(value_bin, 1):
if index in CHECK_BITS:
check_bits[index] = int(value)
return check_bits
def exclude_check_bits(value_bin):
clean_value_bin = ''
for index, char_bin in enumerate(list(value_bin), 1):
if index not in CHECK_BITS:
clean_value_bin += char_bin
return clean_value_bin
def set_errors(encoded):
result = ''
for chunk in chunk_iterator(encoded, CHUNK_LENGTH + len(CHECK_BITS)):
num_bit = random.randint(1, len(chunk))
chunk = '{0}{1}{2}'.format(chunk[:num_bit - 1], int(chunk[num_bit - 1]) ^ 1, chunk[num_bit:])
result += (chunk)
return result
def check_and_fix_error(encoded_chunk):
check_bits_encoded = get_check_bits(encoded_chunk)
check_item = exclude_check_bits(encoded_chunk)
check_item = set_check_bits(check_item)
check_bits = get_check_bits(check_item)
if check_bits_encoded != check_bits:
invalid_bits = []
for check_bit_encoded, value in check_bits_encoded.items():
if check_bits[check_bit_encoded] != value:
invalid_bits.append(check_bit_encoded)
num_bit = sum(invalid_bits)
encoded_chunk = '{0}{1}{2}'.format(
encoded_chunk[:num_bit - 1],
int(encoded_chunk[num_bit - 1]) ^ 1,
encoded_chunk[num_bit:])
return encoded_chunk
def get_diff_index_list(value_bin1, value_bin2):
diff_index_list = []
for index, char_bin_items in enumerate(zip(list(value_bin1), list(value_bin2)), 1):
if char_bin_items[0] != char_bin_items[1]:
diff_index_list.append(index)
return diff_index_list
def encode(source):
text_bin = chars_to_bin(source)
result = ''
for chunk_bin in chunk_iterator(text_bin):
chunk_bin = set_check_bits(chunk_bin)
result += chunk_bin
return result
def decode(encoded, fix_errors=True):
decoded_value = ''
fixed_encoded_list = []
for encoded_chunk in chunk_iterator(encoded, CHUNK_LENGTH + len(CHECK_BITS)):
if fix_errors:
encoded_chunk = check_and_fix_error(encoded_chunk)
fixed_encoded_list.append(encoded_chunk)
clean_chunk_list = []
for encoded_chunk in fixed_encoded_list:
encoded_chunk = exclude_check_bits(encoded_chunk)
clean_chunk_list.append(encoded_chunk)
for clean_chunk in clean_chunk_list:
for clean_char in [clean_chunk[i:i + 8] for i in range(len(clean_chunk)) if not i % 8]:
decoded_value += chr(int(clean_char, 2))
return decoded_value
if __name__ == '__main__':
source = input('Укажите текст для кодирования/декодирования:')
print('Длина блока кодирования: {0}'.format(CHUNK_LENGTH))
print('Контрольные биты: {0}'.format(CHECK_BITS))
encoded = encode(source)
print('Закодированные данные: {0}'.format(encoded))
decoded = decode(encoded)
print('Результат декодирования: {0}'.format(decoded))
encoded_with_error = set_errors(encoded)
print('Допускаем ошибки в закодированных данных: {0}'.format(encoded_with_error))
diff_index_list = get_diff_index_list(encoded, encoded_with_error)
print('Допущены ошибки в битах: {0}'.format(diff_index_list))
decoded = decode(encoded_with_error, fix_errors=False)
decoded = decode(encoded_with_error)