##### Filtered/traced streams

class FilterStream(WrapStream):

    '''Wraps a stream, filtering each string read or written'''

    def __init__(self, filter_, stream):

        self.filter = filter_

    def readline(self): return self.filter(self.stream.readline())

    def write(self, str_): return self.stream.write(self.filter(str_))

class TracedStream(FilterStream):

    '''Wraps a stream, running a trace function on each string read or written

    '''

    def __init__(self, trace, stream):

        def filter_(str_):

            trace(str_)

            return str_

        FilterStream.__init__(self, filter_, stream)