解码7位GSM

Question

我发现这个post关于如何将ascii数据编码为7位GSM字符集，如何再次解码7位GSM字符(将其反转回ascii)？

Answer 1

对于Python2：

import binascii
gsm = ("@£$¥èéùìòÇ\nØø\rÅåΔ_ΦΓΛΩΠΨΣΘΞ\x1bÆæßÉ !\"#¤%&'()*+,-./0123456789:;<=>?"
       "¡ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÑÜ`¿abcdefghijklmnopqrstuvwxyzäöñüà")
ext = ("````````````````````^```````````````````{}`````\\````````````[~]`"
       "|````````````````````````````````````€``````````````````````````")

def gsm_encode(plaintext):
    result = []
    for c in plaintext:
        idx = gsm.find(c)
        if idx != -1:
            result.append(chr(idx))
            continue
        idx = ext.find(c)
        if idx != -1:
            result.append(chr(27) + chr(idx))
    return ''.join(result).encode('hex')

def gsm_decode(hexstr):
    res = hexstr.decode('hex')
    res = iter(res)
    result = []
    for c in res:
        if c == chr(27):
            c = next(res)
            result.append(ext[ord(c)])
        else:
            result.append(gsm[ord(c)])
    return ''.join(result)

code = gsm_encode("Hello World {}")
print(code)
# 64868d8d903a7390938d853a1b281b29
print(gsm_decode(code))
# Hello World {}

Answer 2

例如：

C7F7FBCC2E03代表“谷歌”

Python 3.4

def gsm7bitdecode(f):
   f = ''.join(["{0:08b}".format(int(f[i:i+2], 16)) for i in range(0, len(f), 2)][::-1])
   return ''.join([chr(int(f[::-1][i:i+7][::-1], 2)) for i in range(0, len(f), 7)])

print(gsm7bitdecode('C7F7FBCC2E03'))

谷歌

Answer 3

有一个非常简单的解决方案：

将十六进制转换为二进制八位数，将每个八位数放入一个数组中，但顺序相反(整个八位数，而不是位)，因为这是发送它们的方式。从右到左以7位为一组读取字符串，数字为GSM 7位表中的字符代码

例如：

C7F7FBCC2E03代表“谷歌”

相反顺序的字符串是

03-2E-CC-FB-F7-C7

六个二进制八位数是

00000011-00101110-11001100-11111011-11110111-11000111

七重奏是

000000-1100101-1101100-1100111-1101111-1101111-1000111

然后从右到左阅读如下：

GSM7位表中的septet decimal valor-Char

1000111-71-G

1101111-111-o

1101111-111-o

1100111-103-g

1101100-108-l

1100101-101-e

丢弃最后0000000个值