[英]Python - decode gsm 7 bit with an offset
我正在对gsm 7位进行解码,并从一个名为noiam的用户的网站上找到了这段代码。
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)])
我在解码方面遇到了十字路口,因为它无助于解码带偏移量的消息。
如果有人可以帮助解释这段代码在做什么,以及如何对其进行更改以解码偏移量为1/2/3 / etc(向前和向后)的消息(向前和向后),那么您将对我有很大帮助。
提前致谢!
它是一个非常紧凑/高效的实现中的字符串解析。 以下是展开后的样子:
'''
First Line: parse passed string:
For i initialized to 0, loop while i < length of f; step by 2 and assign i to
the reverse value in the list of values (so if len(f) = 10, i will be
assigned to 8, 6, 4, 2, 0]
'''
f = ''
parsed_values = []
for i in range(0, len(f), 2)[::-1]:
# get substring of f from index i to i+2, [cast to base 16 int][3]
temp = int(f[i:i+2], 16)
# convert the value "{0:08b}" to the value of temp and add it to the list
parsed_values.append("{0:08b}".format(temp))
# finally, [stitch the parsed values together to make a single string][4]
f.join(parsed_values)
'''
Second Line:
Loop through values of parsed string; starting at index 0, step by 7, and
construct a return value out of the desired characters
'''
parsed_values = [] # reset parsed value array
for i in range(0, len(f), 7):
# get the last char, the chunk (of length 7) that starts at i, and
# the last again. Cast to int base 2, convert to char
temp = char(int(f[::-1][i:i+7][::-1], 2))
# add to parsed value list
parsed_values.append(temp)
return ''.join(parsed_values)
范围文档: http : //pythoncentral.io/pythons-range-function-explained/
扩展切片文档: https : //docs.python.org/release/2.3.5/whatsnew/section-slices.html
诠释文档: https : //docs.python.org/2/library/functions.html#int
加入文档: https : //docs.python.org/2/library/stdtypes.html#str.join
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