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