用于将纯文本（ASCII）转换为GSM 7位字符集的Python库？

Question

有没有一个Python库可以把ASCII数据编码成7位的GSM字符集（用于发送短信）？

Answer 1

以上所有的解决方案都不正确。GSM 03.38 编码只使用 7 位来表示一个字符，而上述所有方案都使用了字节对齐的输出，这在大多数情况下与 ASCII 的结果是一样的。这里有一个正确的解决方案，使用了位字符串。

我在使用 Python 的一个额外模块：

pip3 install gsm0338

gsmencode.py：

import sys

import gsm0338


def __create_septets__(octets: bytes) -> (bytes, int):
    num_bits = 0
    data = 0
    septets = bytearray()
    for i in range(len(octets)):
        gsm_char = octets[i]
        data |= (gsm_char << num_bits)
        num_bits += 7
        while num_bits >= 8:
            septets.append(data & 0xff)
            data >>= 8
            num_bits -= 8
    if num_bits > 0:
        septets.append(data & 0xff)
    return bytes(septets), len(octets) % 8


if __name__ == '__main__':
    octets = sys.argv[1].encode('gsm03.38')
    septets, sparse = __create_septets__(octets)
    print("sparse bits: %d" % sparse)
    print("encoded (hex): %s" % septets.hex())

python3 gsmencode.py Sample

输出：

sparse bits: 6
encoded (hex): d3701bce2e03

Answer 2

我从gnibbler的回答中得到了些建议。这里有一个我自己想出来的脚本，灵感来自一个在线转换器：http://smstools3.kekekasvi.com/topic.php?id=288，这个脚本对我来说运行得很好，既可以编码也可以解码。

#!/usr/bin/env python
# -*- coding: utf-8 -*-

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

def get_encode(currentByte, index, bitRightCount, position, nextPosition, leftShiftCount, bytesLength, bytes):
    if index < 8:
        byte = currentByte >> bitRightCount
        if nextPosition < bytesLength:
            idx2 = bytes[nextPosition]
            byte = byte | ((idx2) << leftShiftCount)
            byte = byte & 0x000000FF
        else:
            byte = byte & 0x000000FF
        return chr(byte).encode('hex').upper()
    return ''

def getBytes(plaintext):
    if type(plaintext) != str:
         plaintext = str(plaintext)
    bytes = []
    for c in plaintext.decode('utf-8'):
        idx = gsm.find(c)
        if idx != -1:
            bytes.append(idx)
        else:
            idx = ext.find(c)
            if idx != -1:
                bytes.append(27)
                bytes.append(idx)
    return bytes

def gsm_encode(plaintext):
    res = ""
    f = -1
    t = 0
    bytes = getBytes(plaintext)
    bytesLength = len(bytes)
    for b in bytes:
        f = f+1
        t = (f%8)+1
        res += get_encode(b, t, t-1, f, f+1, 8-t, bytesLength, bytes)

    return res


def chunks(l, n):
    if n < 1:
        n = 1
    return [l[i:i + n] for i in range(0, len(l), n)]

def gsm_decode(codedtext):
    hexparts = chunks(codedtext, 2)
    number   = 0
    bitcount = 0
    output   = ''
    found_external = False
    for byte in hexparts:
    byte = int(byte, 16);
        # add data on to the end
        number = number + (byte << bitcount)
        # increase the counter
        bitcount = bitcount + 1
        # output the first 7 bits
        if number % 128 == 27:
             '''skip'''
             found_external = True
        else:
            if found_external == True:                
                 character = ext[number % 128]
                 found_external = False
            else:
                 character = gsm[number % 128]
            output = output + character

        # then throw them away
        number = number >> 7
        # every 7th letter you have an extra one in the buffer
        if bitcount == 7:
            if number % 128 == 27:
                '''skip'''
                found_external = True
            else:
                if found_external == True:                
                    character = ext[number % 128]
                    found_external = False
                else:
                    character = gsm[number % 128]
                output = output + character

            bitcount = 0
            number = 0
    return output

Answer 3

现在有了 :)

感谢 Chad 指出这个说法不太准确

Python2 版本

# -*- coding: utf8 -*- 
gsm = (u"@£$¥èéùìòÇ\nØø\rÅåΔ_ΦΓΛΩΠΨΣΘΞ\x1bÆæßÉ !\"#¤%&'()*+,-./0123456789:;<=>"
       u"?¡ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÑܧ¿abcdefghijklmnopqrstuvwxyzäöñüà")
ext = (u"````````````````````^```````````````````{}`````\\````````````[~]`"
       u"|````````````````````````````````````€``````````````````````````")

def gsm_encode(plaintext):
    res = ""
    for c in plaintext:
        idx = gsm.find(c)
        if idx != -1:
            res += chr(idx)
            continue
        idx = ext.find(c)
        if idx != -1:
            res += chr(27) + chr(idx)
    return res.encode('hex')

print gsm_encode(u"Hello World")

输出是十六进制的。如果你想要二进制流，可以直接跳过这个。

Python3 版本

# -*- coding: utf8 -*- 
import binascii
gsm = ("@£$¥èéùìòÇ\nØø\rÅåΔ_ΦΓΛΩΠΨΣΘΞ\x1bÆæßÉ !\"#¤%&'()*+,-./0123456789:;<=>?"
       "¡ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÑܧ¿abcdefghijklmnopqrstuvwxyzäöñüà")
ext = ("````````````````````^```````````````````{}`````\\````````````[~]`"
       "|````````````````````````````````````€``````````````````````````")

def gsm_encode(plaintext):
    res = ""
    for c in plaintext:
        idx = gsm.find(c);
        if idx != -1:
            res += chr(idx)
            continue
        idx = ext.find(c)
        if idx != -1:
            res += chr(27) + chr(idx)
    return binascii.b2a_hex(res.encode('utf-8'))

print(gsm_encode("Hello World"))