1# Protocol Buffers - Google's data interchange format 2# Copyright 2008 Google Inc. All rights reserved. 3# https://developers.google.com/protocol-buffers/ 4# 5# Redistribution and use in source and binary forms, with or without 6# modification, are permitted provided that the following conditions are 7# met: 8# 9# * Redistributions of source code must retain the above copyright 10# notice, this list of conditions and the following disclaimer. 11# * Redistributions in binary form must reproduce the above 12# copyright notice, this list of conditions and the following disclaimer 13# in the documentation and/or other materials provided with the 14# distribution. 15# * Neither the name of Google Inc. nor the names of its 16# contributors may be used to endorse or promote products derived from 17# this software without specific prior written permission. 18# 19# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31"""Encoding related utilities.""" 32import re 33 34_cescape_chr_to_symbol_map = {} 35_cescape_chr_to_symbol_map[9] = r'\t' # optional escape 36_cescape_chr_to_symbol_map[10] = r'\n' # optional escape 37_cescape_chr_to_symbol_map[13] = r'\r' # optional escape 38_cescape_chr_to_symbol_map[34] = r'\"' # necessary escape 39_cescape_chr_to_symbol_map[39] = r"\'" # optional escape 40_cescape_chr_to_symbol_map[92] = r'\\' # necessary escape 41 42# Lookup table for unicode 43_cescape_unicode_to_str = [chr(i) for i in range(0, 256)] 44for byte, string in _cescape_chr_to_symbol_map.items(): 45 _cescape_unicode_to_str[byte] = string 46 47# Lookup table for non-utf8, with necessary escapes at (o >= 127 or o < 32) 48_cescape_byte_to_str = ([r'\%03o' % i for i in range(0, 32)] + 49 [chr(i) for i in range(32, 127)] + 50 [r'\%03o' % i for i in range(127, 256)]) 51for byte, string in _cescape_chr_to_symbol_map.items(): 52 _cescape_byte_to_str[byte] = string 53del byte, string 54 55 56def CEscape(text, as_utf8): 57 # type: (...) -> str 58 """Escape a bytes string for use in an text protocol buffer. 59 60 Args: 61 text: A byte string to be escaped. 62 as_utf8: Specifies if result may contain non-ASCII characters. 63 In Python 3 this allows unescaped non-ASCII Unicode characters. 64 In Python 2 the return value will be valid UTF-8 rather than only ASCII. 65 Returns: 66 Escaped string (str). 67 """ 68 # Python's text.encode() 'string_escape' or 'unicode_escape' codecs do not 69 # satisfy our needs; they encodes unprintable characters using two-digit hex 70 # escapes whereas our C++ unescaping function allows hex escapes to be any 71 # length. So, "\0011".encode('string_escape') ends up being "\\x011", which 72 # will be decoded in C++ as a single-character string with char code 0x11. 73 text_is_unicode = isinstance(text, str) 74 if as_utf8 and text_is_unicode: 75 # We're already unicode, no processing beyond control char escapes. 76 return text.translate(_cescape_chr_to_symbol_map) 77 ord_ = ord if text_is_unicode else lambda x: x # bytes iterate as ints. 78 if as_utf8: 79 return ''.join(_cescape_unicode_to_str[ord_(c)] for c in text) 80 return ''.join(_cescape_byte_to_str[ord_(c)] for c in text) 81 82 83_CUNESCAPE_HEX = re.compile(r'(\\+)x([0-9a-fA-F])(?![0-9a-fA-F])') 84 85 86def CUnescape(text): 87 # type: (str) -> bytes 88 """Unescape a text string with C-style escape sequences to UTF-8 bytes. 89 90 Args: 91 text: The data to parse in a str. 92 Returns: 93 A byte string. 94 """ 95 96 def ReplaceHex(m): 97 # Only replace the match if the number of leading back slashes is odd. i.e. 98 # the slash itself is not escaped. 99 if len(m.group(1)) & 1: 100 return m.group(1) + 'x0' + m.group(2) 101 return m.group(0) 102 103 # This is required because the 'string_escape' encoding doesn't 104 # allow single-digit hex escapes (like '\xf'). 105 result = _CUNESCAPE_HEX.sub(ReplaceHex, text) 106 107 return (result.encode('utf-8') # Make it bytes to allow decode. 108 .decode('unicode_escape') 109 # Make it bytes again to return the proper type. 110 .encode('raw_unicode_escape')) 111