Source Code for Module google.protobuf.text_encoding

  1  # Protocol Buffers - Google's data interchange format 
  2  # Copyright 2008 Google Inc.  All rights reserved. 
  3  # https://developers.google.com/protocol-buffers/ 
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 30   
 31  """Encoding related utilities.""" 
 32  import re 
 33   
 34  import six 
 35   
 36  _cescape_chr_to_symbol_map = {} 
 37  _cescape_chr_to_symbol_map[9] = r'\t'  # optional escape 
 38  _cescape_chr_to_symbol_map[10] = r'\n'  # optional escape 
 39  _cescape_chr_to_symbol_map[13] = r'\r'  # optional escape 
 40  _cescape_chr_to_symbol_map[34] = r'\"'  # necessary escape 
 41  _cescape_chr_to_symbol_map[39] = r"\'"  # optional escape 
 42  _cescape_chr_to_symbol_map[92] = r'\\'  # necessary escape 
 43   
 44  # Lookup table for unicode 
 45  _cescape_unicode_to_str = [chr(i) for i in range(0, 256)] 
 46  for byte, string in _cescape_chr_to_symbol_map.items(): 
 47    _cescape_unicode_to_str[byte] = string 
 48   
 49  # Lookup table for non-utf8, with necessary escapes at (o >= 127 or o < 32) 
 50  _cescape_byte_to_str = ([r'\%03o' % i for i in range(0, 32)] + 
 51                          [chr(i) for i in range(32, 127)] + 
 52                          [r'\%03o' % i for i in range(127, 256)]) 
 53  for byte, string in _cescape_chr_to_symbol_map.items(): 
 54    _cescape_byte_to_str[byte] = string 
 55  del byte, string 
 56   
 57   
 58 -def CEscape(text, as_utf8): 
 59    # type: (...) -> str 
 60    """Escape a bytes string for use in an text protocol buffer. 
 61   
 62    Args: 
 63      text: A byte string to be escaped. 
 64      as_utf8: Specifies if result may contain non-ASCII characters. 
 65          In Python 3 this allows unescaped non-ASCII Unicode characters. 
 66          In Python 2 the return value will be valid UTF-8 rather than only ASCII. 
 67    Returns: 
 68      Escaped string (str). 
 69    """ 
 70    # Python's text.encode() 'string_escape' or 'unicode_escape' codecs do not 
 71    # satisfy our needs; they encodes unprintable characters using two-digit hex 
 72    # escapes whereas our C++ unescaping function allows hex escapes to be any 
 73    # length.  So, "\0011".encode('string_escape') ends up being "\\x011", which 
 74    # will be decoded in C++ as a single-character string with char code 0x11. 
 75    if six.PY3: 
 76      text_is_unicode = isinstance(text, str) 
 77      if as_utf8 and text_is_unicode: 
 78        # We're already unicode, no processing beyond control char escapes. 
 79        return text.translate(_cescape_chr_to_symbol_map) 
 80      ord_ = ord if text_is_unicode else lambda x: x  # bytes iterate as ints. 
 81    else: 
 82      ord_ = ord  # PY2 
 83    if as_utf8: 
 84      return ''.join(_cescape_unicode_to_str[ord_(c)] for c in text) 
 85    return ''.join(_cescape_byte_to_str[ord_(c)] for c in text) 
 86   
 87   
 88  _CUNESCAPE_HEX = re.compile(r'(\\+)x([0-9a-fA-F])(?![0-9a-fA-F])') 
 89   
 90   
 91 -def CUnescape(text): 
 92    # type: (str) -> bytes 
 93    """Unescape a text string with C-style escape sequences to UTF-8 bytes. 
 94   
 95    Args: 
 96      text: The data to parse in a str. 
 97    Returns: 
 98      A byte string. 
 99    """ 
100   
101    def ReplaceHex(m): 
102      # Only replace the match if the number of leading back slashes is odd. i.e. 
103      # the slash itself is not escaped. 
104      if len(m.group(1)) & 1: 
105        return m.group(1) + 'x0' + m.group(2) 
106      return m.group(0) 
107   
108    # This is required because the 'string_escape' encoding doesn't 
109    # allow single-digit hex escapes (like '\xf'). 
110    result = _CUNESCAPE_HEX.sub(ReplaceHex, text) 
111   
112    if six.PY2: 
113      return result.decode('string_escape') 
114    return (result.encode('utf-8')  # PY3: Make it bytes to allow decode. 
115            .decode('unicode_escape') 
116            # Make it bytes again to return the proper type. 
117            .encode('raw_unicode_escape')) 
118