什么编码与ASCII完全相同，但每个字节前都有NULL字节？

Question

我有一个字符串，它的样子和表现如下（提供了Python代码）。这到底是什么编码啊？

s = u'\x00Q\x00u\x00i\x00c\x00k'
>>> print s
Quick
>>>
>>> s == 'Quick'
False
>>>
>>> import re
>>> re.search('Quick', s)
>>>
>>> import chardet
>>> chardet.detect(s)
/usr/lib/pymodules/python2.6/chardet/universaldetector.py:69: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  if aBuf[:3] == '\xEF\xBB\xBF':
/usr/lib/pymodules/python2.6/chardet/universaldetector.py:72: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  elif aBuf[:4] == '\xFF\xFE\x00\x00':
/usr/lib/pymodules/python2.6/chardet/universaldetector.py:75: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  elif aBuf[:4] == '\x00\x00\xFE\xFF':
/usr/lib/pymodules/python2.6/chardet/universaldetector.py:78: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  elif aBuf[:4] == '\xFE\xFF\x00\x00':
/usr/lib/pymodules/python2.6/chardet/universaldetector.py:81: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  elif aBuf[:4] == '\x00\x00\xFF\xFE':
/usr/lib/pymodules/python2.6/chardet/universaldetector.py:84: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  elif aBuf[:2] == '\xFF\xFE':
/usr/lib/pymodules/python2.6/chardet/universaldetector.py:87: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  elif aBuf[:2] == '\xFE\xFF':
{'confidence': 1.0, 'encoding': 'ascii'}
>>>
>>> chardet.detect(s)
{'confidence': 1.0, 'encoding': 'ascii'}
>>> 

Answer 1

你有一种叫UTF-16BE的编码方式，但没有使用BOM（字节顺序标记）。根据文档，chardet这个工具无法识别没有BOM的UTF-nnxE编码。

>>> s = '\x00Q\x00u\x00i\x00c\x00k' #### Note: dropping the spurious `u` prefix
>>> s.decode('utf_16be')
u'Quick'
>>>

而且，chardet也没有那么聪明，如果你给它传入unicode，它不会抛出一个叫“别傻了”的异常来提醒你 :-)

Answer 2

UTF-16 大端字节序