# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc. All rights reserved.
# https://developers.google.com/protocol-buffers/
#
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"""Encoding related utilities."""
import re
import six
# Lookup table for utf8
_cescape_utf8_to_str = [chr(i) for i in range(0, 256)]
_cescape_utf8_to_str[9] = r'\t' # optional escape
_cescape_utf8_to_str[10] = r'\n' # optional escape
_cescape_utf8_to_str[13] = r'\r' # optional escape
_cescape_utf8_to_str[39] = r"\'" # optional escape
_cescape_utf8_to_str[34] = r'\"' # necessary escape
_cescape_utf8_to_str[92] = r'\\' # necessary escape
# 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)])
_cescape_byte_to_str[9] = r'\t' # optional escape
_cescape_byte_to_str[10] = r'\n' # optional escape
_cescape_byte_to_str[13] = r'\r' # optional escape
_cescape_byte_to_str[39] = r"\'" # optional escape
_cescape_byte_to_str[34] = r'\"' # necessary escape
_cescape_byte_to_str[92] = r'\\' # necessary escape
def CEscape(text, as_utf8):
"""Escape a bytes string for use in an ascii protocol buffer.
text.encode('string_escape') does not seem to satisfy our needs as it
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.
Args:
text: A byte string to be escaped
as_utf8: Specifies if result should be returned in UTF-8 encoding
Returns:
Escaped string
"""
# PY3 hack: make Ord work for str and bytes:
# //platforms/networking/data uses unicode here, hence basestring.
Ord = ord if isinstance(text, six.string_types) else lambda x: x
if as_utf8:
return ''.join(_cescape_utf8_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])')
_cescape_highbit_to_str = ([chr(i) for i in range(0, 127)] +
[r'\%03o' % i for i in range(127, 256)])
def CUnescape(text):
"""Unescape a text string with C-style escape sequences to UTF-8 bytes."""
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)
if str is bytes: # PY2
return result.decode('string_escape')
result = ''.join(_cescape_highbit_to_str[ord(c)] for c in result)
return (result.encode('ascii') # Make it bytes to allow decode.
.decode('unicode_escape')
# Make it bytes again to return the proper type.
.encode('raw_unicode_escape'))
