71 lines
1.9 KiB
Python
71 lines
1.9 KiB
Python
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# Copyright 2011 Florent Le Coz <louiz@louiz.org>
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#
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# This file is part of Poezio.
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#
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# Poezio is free software: you can redistribute it and/or modify
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# it under the terms of the zlib license. See the COPYING file.
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"""
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Defines the Fifo class
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"""
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import logging
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log = logging.getLogger(__name__)
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import os
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import threading
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class OpenTrick(threading.Thread):
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"""
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A threaded trick to make the open for writing succeed.
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A fifo cannot be opened for writing if it has not been
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yet opened by the other hand for reading.
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So, we just open the fifo for reading and close it
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immediately afterwards.
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Once that is done, we can freely keep the fifo open for
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writing and write things in it. The writing can fail if
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there’s still nothing reading that fifo, but we just yell
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an error in that case.
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"""
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def __init__(self, path):
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threading.Thread.__init__(self)
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self.path = path
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def run(self):
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open(self.path, 'r').close()
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class Fifo(object):
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"""
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Just a simple file handler, writing and reading in a fifo.
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Mode is either 'r' or 'w', just like the mode for the open()
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function.
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"""
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def __init__(self, path, mode):
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self.trick = None
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if not os.path.exists(path):
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os.mkfifo(path)
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if mode == 'w':
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self.trick = OpenTrick(path)
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# that thread will wait until we open it for writing
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self.trick.start()
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self.fd = open(path, mode)
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def write(self, data):
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"""
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Try to write on the fifo. If that fails, this means
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that nothing has that fifo opened, so the writing is useless,
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so we just return (and display an error telling that, somewhere).
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"""
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self.fd.write(data)
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self.fd.flush()
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def readline(self):
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return self.fd.readline()
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def __del__(self):
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try:
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self.fd.close()
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except:
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pass
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