class ProgressInputStream(TracedStream):

    '''Wraps an input stream, reporting the # lines read every n lines and after

    the last line is read.

    @param log The output stream for progress messages

    '''

    def __init__(self, stream, log, msg='Read %d line(s)', n=100):

        self.eof = False

        def trace(str_):

            msg_ = msg # may be modified, so can't have same name as outer var

            if str_ == None: # closed

                if self.eof: return # not closed prematurely

                str_ = '' # closed prematurely, so signal EOF

                msg_ += ' (not all input read)'

            self.eof = eof = str_ == ''

            if eof: line_ending = '\n'

            else: line_ending = '\r'

            line_ct = self.stream.line_num - 1 # make it 0-based

            if eof or line_ct % n == 0: log.write((msg_ % line_ct)+line_ending)

        self.trace = trace

        TracedStream.__init__(self, trace, LineCountInputStream(stream))

    def close(self):

        self.trace(None) # signal closed

        TracedStream.close(self)