A problem in unpacking strings

If a string to be packed is shorter than its format, it'll be followed by '\x00's when unpacked.

One example, in which every length of the string fits the format:

python 代码

>>> import struct
>>> fmt = 'c4si5s'
>>>
>>> verb = 'have'
>>> p = struct.pack(fmt, 'i', verb, 2, 'books')
>>> unp = struct.unpack(fmt, p)
>>> p
'ihave\x00\x00\x00\x02\x00\x00\x00books'
>>> unp
('i', 'have', 2, 'books')
>>> unp[1] == verb
True

Here comes another one, in which the verb is changed into 'had':

python 代码

>>> import struct
>>> fmt = 'c4si5s'
>>>
>>> verb = 'had'
>>> p = struct.pack(fmt, 'i', verb, 2, 'books')
>>> unp = struct.unpack(fmt, p)
>>> p
'ihad\x00\x00\x00\x00\x02\x00\x00\x00books'
>>> unp
('i', 'had\x00', 2, 'books')
>>> unp[1] == verb
False
>>>
>>> unp[1].rstrip('\x00') == verb
True

 So .rstrip('\x00') in Line14 is needed now.

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• 2007-12-07 11:11
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