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"""

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    Iterate over lines in file-like objects (without buffering lines!), write (flushing output).

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"""

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import logging; log = logging.getLogger('pvl.syslog.file')

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class File (object) :

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    """

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        Follow a file-like object, reading lines until no more are available. Never raises EOFError.

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        Works with python file objects that buffer readlines() when using e.g. `tail -f ... | python -u ...`.

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        readline() may block once there is no more input available, or may return None for evermore.

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        There is no fileno(), this is not pollable. At all. Don't even iterate on this with a timeout.

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        XXX: should this really return None? Might really be better to raise EOFError.. except that readlines() should return normally at EOF...

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    """

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    @classmethod

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    def open (cls, path, mode='r', **opts) :

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        return cls(open(path, mode), **opts)

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    EOL = '\n'

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    def __init__ (self, file) :

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        log.debug("%s", file)

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        self.file = file

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    def readline (self) :

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        """

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            Reads a line from the file, without trailing \n.

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            Returns None on EOF.

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        """

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        line = self.file.readline()

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        if not line :

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            line = None

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        else : 

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            line = line.rstrip('\r\n')

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        log.debug("%s", line)

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        return line

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    def readlines (self) :

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        """

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            Reads any available lines from the file.

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        """

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        while True :

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            line = self.readline()

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            if line is None :

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                return

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            else :

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                yield line

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    __iter__ = readlines

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    def writeline (self, line, eol=EOL) :

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        """

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        """

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        self.file.write(eol)

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        self.file.flush()

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