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# Source code for mopidy.mpd.tokenize

    from __future__ import absolute_import, unicode_literals

    import re

    from mopidy.mpd import exceptions

    WORD_RE = re.compile(r"""
        ^
        (\s*)             # Leading whitespace not allowed, capture it to report.
        ([a-z][a-z0-9_]*) # A command name
        (?:\s+|$)         # trailing whitespace or EOS
        (.*)              # Possibly a remainder to be parsed
        """, re.VERBOSE)

    # Quotes matching is an unrolled version of "(?:[^"\\]|\\.)*"
    PARAM_RE = re.compile(r"""
        ^                               # Leading whitespace is not allowed
        (?:
            ([^%(unprintable)s"']+)     # ord(char) < 0x20, not ", not '
            |                           # or
            "([^"\\]*(?:\\.[^"\\]*)*)"  # anything surrounded by quotes
        )
        (?:\s+|$)                       # trailing whitespace or EOS
        (.*)                            # Possibly a remainder to be parsed
        """ % {'unprintable': ''.join(map(chr, range(0x21)))}, re.VERBOSE)

    BAD_QUOTED_PARAM_RE = re.compile(r"""
        ^
        "[^"\\]*(?:\\.[^"\\]*)*  # start of a quoted value
        (?:                      # followed by:
            ("[^\s])             # non-escaped quote, followed by non-whitespace
            |                    # or
            ([^"])               # anything that is not a quote
        )
        """, re.VERBOSE)

    UNESCAPE_RE = re.compile(r'\\(.)')  # Backslash escapes any following char.

    def split(line):
        """Splits a line into tokens using same rules as MPD.

        - Lines may not start with whitespace
        - Tokens are split by arbitrary amount of spaces or tabs
        - First token must match `[a-z][a-z0-9_]*`
        - Remaining tokens can be unquoted or quoted tokens.
        - Unquoted tokens consist of all printable characters except double quotes,
          single quotes, spaces and tabs.
        - Quoted tokens are surrounded by a matching pair of double quotes.
        - The closing quote must be followed by space, tab or end of line.
        - Any value is allowed inside a quoted token. Including double quotes,
          assuming it is correctly escaped.
        - Backslash inside a quoted token is used to escape the following
          character.

        For examples see the tests for this function.
        """
        if not line.strip():
            raise exceptions.MpdNoCommand('No command given')
        match = WORD_RE.match(line)
        if not match:
            raise exceptions.MpdUnknownError('Invalid word character')
        whitespace, command, remainder = match.groups()
        if whitespace:
            raise exceptions.MpdUnknownError('Letter expected')

        result = [command]
        while remainder:
            match = PARAM_RE.match(remainder)
            if not match:
                msg = _determine_error_message(remainder)
                raise exceptions.MpdArgError(msg, command=command)
            unquoted, quoted, remainder = match.groups()
            result.append(unquoted or UNESCAPE_RE.sub(r'\g<1>', quoted))
        return result

    def _determine_error_message(remainder):
        """Helper to emulate MPD errors."""
        # Following checks are simply to match MPD error messages:
        match = BAD_QUOTED_PARAM_RE.match(remainder)
        if match:
            if match.group(1):
                return 'Space expected after closing \'"\''
            else:
                return 'Missing closing \'"\''
        return 'Invalid unquoted character'

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