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