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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
def _AsciiIsPrint(i):
return i >= 32 and i < 127
def _MakeStrEscapes():
ret = {}
for i in range(0, 128):
if not _AsciiIsPrint(i):
ret[i] = r'\%03o' % i
ret[ord('\t')] = r'\t' # optional escape
ret[ord('\n')] = r'\n' # optional escape
ret[ord('\r')] = r'\r' # optional escape
ret[ord('"')] = r'\"' # necessary escape
ret[ord('\'')] = r"\'" # optional escape
ret[ord('\\')] = r'\\' # necessary escape
return ret
# Maps int -> char, performing string escapes.
_str_escapes = _MakeStrEscapes()
# Maps int -> char, performing byte escaping and string escapes
_byte_escapes = {i: chr(i) for i in range(0, 256)}
_byte_escapes.update(_str_escapes)
_byte_escapes.update({i: r'\%03o' % i for i in range(128, 256)})
def _DecodeUtf8EscapeErrors(text_bytes):
ret = ''
while text_bytes:
try:
ret += text_bytes.decode('utf-8').translate(_str_escapes)
text_bytes = ''
except UnicodeDecodeError as e:
ret += text_bytes[:e.start].decode('utf-8').translate(_str_escapes)
ret += _byte_escapes[text_bytes[e.start]]
text_bytes = text_bytes[e.start+1:]
return ret
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:
if text_is_unicode:
return text.translate(_str_escapes)
else:
return _DecodeUtf8EscapeErrors(text)
else:
if text_is_unicode:
text = text.encode('utf-8')
return ''.join([_byte_escapes[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)
# Replaces Unicode escape sequences with their character equivalents.
result = result.encode('raw_unicode_escape').decode('raw_unicode_escape')
# Encode Unicode characters as UTF-8, then decode to Latin-1 escaping
# unprintable characters.
result = result.encode('utf-8').decode('unicode_escape')
# Convert Latin-1 text back to a byte string (latin-1 codec also works here).
return result.encode('latin-1')
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