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amazing-qr/ecc.py
2016-08-29 23:02:17 +08:00

60 lines
1.3 KiB
Python

# -*- coding: utf-8 -*-
from mylibs.constant import *
#ecc: Error Correction Codewords
def encode(ver, ecl, data_codewords):
en = ecc_num_per_block[ver-1][lindex[ecl]]
ecc = []
for dc in data_codewords:
ecc.append(get_ecc(dc, en))
return ecc
def get_ecc(dc, ecc_num):
gp = GP_list[ecc_num]
remainder = dc
for i in range(len(dc)):
remainder = divide(remainder, *gp)
return remainder
def divide(MP, *GP):
po2 = get_power_of_2_list()
log = get_log_list(po2)
GP = list(GP)
for i in range(len(GP)):
GP[i] += log[MP[0]]
if GP[i] > 255:
GP[i] %= 255
GP[i] = po2[GP[i]]
return XOR(GP, *MP)
def XOR(GP, *MP):
MP = list(MP)
a = len(MP) - len(GP)
if a < 0:
MP += [0] * (-a)
elif a > 0:
GP += [0] * a
remainder = []
for i in range(len(MP)):
remainder.append(MP[i]^GP[i])
remainder = [i for i in remainder if i]
return remainder
def get_power_of_2_list():
po2 = [1]
for i in range(255):
a = po2[i] * 2
if a > 255:
a ^= 285
po2.append(a)
return po2
def get_log_list(po2):
log = [None]*256
for i in range(255):
log[po2[i]] = i
return log