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# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc. All rights reserved.
#
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file or at
# https://developers.google.com/open-source/licenses/bsd
"""Encoding related utilities."""
import re
_cescape_chr_to_symbol_map = {}
_cescape_chr_to_symbol_map[9] = r'\t' # optional escape
_cescape_chr_to_symbol_map[10] = r'\n' # optional escape
_cescape_chr_to_symbol_map[13] = r'\r' # optional escape
_cescape_chr_to_symbol_map[34] = r'\"' # necessary escape
_cescape_chr_to_symbol_map[39] = r"\'" # optional escape
_cescape_chr_to_symbol_map[92] = r'\\' # necessary escape
# Lookup table for unicode
_cescape_unicode_to_str = [chr(i) for i in range(0, 256)]
for byte, string in _cescape_chr_to_symbol_map.items():
_cescape_unicode_to_str[byte] = string
# Lookup table for non-utf8, with necessary escapes at (o >= 127 or o < 32)
_cescape_byte_to_str = ([r'\%03o' % i for i in range(0, 32)] +
[chr(i) for i in range(32, 127)] +
[r'\%03o' % i for i in range(127, 256)])
for byte, string in _cescape_chr_to_symbol_map.items():
_cescape_byte_to_str[byte] = string
del byte, string
def CEscape(text, as_utf8) -> str:
"""Escape a bytes string for use in an text protocol buffer.
Args:
text: A byte string to be escaped.
as_utf8: Specifies if result may contain non-ASCII characters.
In Python 3 this allows unescaped non-ASCII Unicode characters.
In Python 2 the return value will be valid UTF-8 rather than only ASCII.
Returns:
Escaped string (str).
"""
# Python's text.encode() 'string_escape' or 'unicode_escape' codecs do not
# satisfy our needs; they encodes unprintable characters using two-digit hex
# escapes whereas our C++ unescaping function allows hex escapes to be any
# length. So, "\0011".encode('string_escape') ends up being "\\x011", which
# will be decoded in C++ as a single-character string with char code 0x11.
text_is_unicode = isinstance(text, str)
if as_utf8 and text_is_unicode:
# We're already unicode, no processing beyond control char escapes.
return text.translate(_cescape_chr_to_symbol_map)
ord_ = ord if text_is_unicode else lambda x: x # bytes iterate as ints.
if as_utf8:
return ''.join(_cescape_unicode_to_str[ord_(c)] for c in text)
return ''.join(_cescape_byte_to_str[ord_(c)] for c in text)
_CUNESCAPE_HEX = re.compile(r'(\\+)x([0-9a-fA-F])(?![0-9a-fA-F])')
def CUnescape(text: str) -> bytes:
"""Unescape a text string with C-style escape sequences to UTF-8 bytes.
Args:
text: The data to parse in a str.
Returns:
A byte string.
"""
def ReplaceHex(m):
# Only replace the match if the number of leading back slashes is odd. i.e.
# the slash itself is not escaped.
if len(m.group(1)) & 1:
return m.group(1) + 'x0' + m.group(2)
return m.group(0)
# This is required because the 'string_escape' encoding doesn't
# allow single-digit hex escapes (like '\xf').
result = _CUNESCAPE_HEX.sub(ReplaceHex, text)
return (result.encode('utf-8') # Make it bytes to allow decode.
.decode('unicode_escape')
# Make it bytes again to return the proper type.
.encode('raw_unicode_escape'))
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