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surrogateescape.py
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""" This is Victor Stinner's pure-Python implementation of PEP 383: the "surrogateescape" error handler of Python 3. Source: misc/python/surrogateescape.py in https://bitbucket.org/haypo/misc """ # This code is released under the Python license and the BSD 2-clause license import codecs import sys from future import utils FS_ERRORS = 'surrogateescape' # # -- Python 2/3 compatibility ------------------------------------- # FS_ERRORS = 'my_surrogateescape' def u(text): if utils.PY3: return text else: return text.decode('unicode_escape') def b(data): if utils.PY3: return data.encode('latin1') else: return data if utils.PY3: _unichr = chr bytes_chr = lambda code: bytes((code,)) else: _unichr = unichr bytes_chr = chr def surrogateescape_handler(exc): """ Pure Python implementation of the PEP 383: the "surrogateescape" error handler of Python 3. Undecodable bytes will be replaced by a Unicode character U+DCxx on decoding, and these are translated into the original bytes on encoding. """ mystring = exc.object[exc.start:exc.end] try: if isinstance(exc, UnicodeDecodeError): # mystring is a byte-string in this case decoded = replace_surrogate_decode(mystring) elif isinstance(exc, UnicodeEncodeError): # In the case of u'\udcc3'.encode('ascii', # 'this_surrogateescape_handler'), both Python 2.x and 3.x raise an # exception anyway after this function is called, even though I think # it's doing what it should. It seems that the strict encoder is called # to encode the unicode string that this function returns ... decoded = replace_surrogate_encode(mystring) else: raise exc except NotASurrogateError: raise exc return (decoded, exc.end) class NotASurrogateError(Exception): pass def replace_surrogate_encode(mystring): """ Returns a (unicode) string, not the more logical bytes, because the codecs register_error functionality expects this. """ decoded = [] for ch in mystring: # if utils.PY3: # code = ch # else: code = ord(ch) # The following magic comes from Py3.3's Python/codecs.c file: if not 0xD800 <= code <= 0xDCFF: # Not a surrogate. Fail with the original exception. raise NotASurrogateError # mybytes = [0xe0 | (code >> 12), # 0x80 | ((code >> 6) & 0x3f), # 0x80 | (code & 0x3f)] # Is this a good idea? if 0xDC00 <= code <= 0xDC7F: decoded.append(_unichr(code - 0xDC00)) elif code <= 0xDCFF: decoded.append(_unichr(code - 0xDC00)) else: raise NotASurrogateError return str().join(decoded) def replace_surrogate_decode(mybytes): """ Returns a (unicode) string """ decoded = [] for ch in mybytes: # We may be parsing newbytes (in which case ch is an int) or a native # str on Py2 if isinstance(ch, int): code = ch else: code = ord(ch) if 0x80 <= code <= 0xFF: decoded.append(_unichr(0xDC00 + code)) elif code <= 0x7F: decoded.append(_unichr(code)) else: # # It may be a bad byte # # Try swallowing it. # continue # print("RAISE!") raise NotASurrogateError return str().join(decoded) def encodefilename(fn): if FS_ENCODING == 'ascii': # ASCII encoder of Python 2 expects that the error handler returns a # Unicode string encodable to ASCII, whereas our surrogateescape error # handler has to return bytes in 0x80-0xFF range. encoded = [] for index, ch in enumerate(fn): code = ord(ch) if code < 128: ch = bytes_chr(code) elif 0xDC80 <= code <= 0xDCFF: ch = bytes_chr(code - 0xDC00) else: raise UnicodeEncodeError(FS_ENCODING, fn, index, index+1, 'ordinal not in range(128)') encoded.append(ch) return bytes().join(encoded) elif FS_ENCODING == 'utf-8': # UTF-8 encoder of Python 2 encodes surrogates, so U+DC80-U+DCFF # doesn't go through our error handler encoded = [] for index, ch in enumerate(fn): code = ord(ch) if 0xD800 <= code <= 0xDFFF: if 0xDC80 <= code <= 0xDCFF: ch = bytes_chr(code - 0xDC00) encoded.append(ch) else: raise UnicodeEncodeError( FS_ENCODING, fn, index, index+1, 'surrogates not allowed') else: ch_utf8 = ch.encode('utf-8') encoded.append(ch_utf8) return bytes().join(encoded) else: return fn.encode(FS_ENCODING, FS_ERRORS) def decodefilename(fn): return fn.decode(FS_ENCODING, FS_ERRORS) FS_ENCODING = 'ascii'; fn = b('[abc\xff]'); encoded = u('[abc\udcff]') # FS_ENCODING = 'cp932'; fn = b('[abc\x81\x00]'); encoded = u('[abc\udc81\x00]') # FS_ENCODING = 'UTF-8'; fn = b('[abc\xff]'); encoded = u('[abc\udcff]') # normalize the filesystem encoding name. # For example, we expect "utf-8", not "UTF8". FS_ENCODING = codecs.lookup(FS_ENCODING).name def register_surrogateescape(): """ Registers the surrogateescape error handler on Python 2 (only) """ if utils.PY3: return try: codecs.lookup_error(FS_ERRORS) except LookupError: codecs.register_error(FS_ERRORS, surrogateescape_handler) if __name__ == '__main__': pass # # Tests: # register_surrogateescape() # b = decodefilename(fn) # assert b == encoded, "%r != %r" % (b, encoded) # c = encodefilename(b) # assert c == fn, '%r != %r' % (c, fn) # # print("ok")