#!/usr/bin/env python # Copyright (C) 2010 Google Inc. All rights reserved. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions are # met: # # * Redistributions of source code must retain the above copyright # notice, this list of conditions and the following disclaimer. # * Redistributions in binary form must reproduce the above # copyright notice, this list of conditions and the following disclaimer # in the documentation and/or other materials provided with the # distribution. # * Neither the name of Google Inc. nor the names of its # contributors may be used to endorse or promote products derived from # this software without specific prior written permission. # # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. """ Package that implements a stream wrapper that has 'meters' as well as regular output. A 'meter' is a single line of text that can be erased and rewritten repeatedly, without producing multiple lines of output. It can be used to produce effects like progress bars. """ import logging _log = logging.getLogger("webkitpy.layout_tests.metered_stream") class MeteredStream: """This class is a wrapper around a stream that allows you to implement meters. It can be used like a stream, but calling update() will print the string followed by only a carriage return (instead of a carriage return and a line feed). This can be used to implement progress bars and other sorts of meters. Note that anything written by update() will be erased by a subsequent update(), write(), or flush().""" def __init__(self, verbose, stream): """ Args: verbose: whether update is a no-op stream: output stream to write to """ self._dirty = False self._verbose = verbose self._stream = stream self._last_update = "" def write(self, txt): """Write to the stream, overwriting and resetting the meter.""" if self._dirty: self.update("") self._dirty = False self._stream.write(txt) def flush(self): """Flush any buffered output.""" self._stream.flush() def progress(self, str): """ Write a message to the stream that will get overwritten. This is used for progress updates that don't need to be preserved in the log. If the MeteredStream was initialized with verbose==True, then this output is discarded. We have this in case we are logging lots of output and the update()s will get lost or won't work properly (typically because verbose streams are redirected to files). """ if self._verbose: return self._write(str) def update(self, str): """ Write a message that is also included when logging verbosely. This routine preserves the same console logging behavior as progress(), but will also log the message if verbose() was true. """ # Note this is a separate routine that calls either into the logger # or the metering stream. We have to be careful to avoid a layering # inversion (stream calling back into the logger). if self._verbose: _log.info(str) else: self._write(str) def _write(self, str): """Actually write the message to the stream.""" # FIXME: Figure out if there is a way to detect if we're writing # to a stream that handles CRs correctly (e.g., terminals). That might # be a cleaner way of handling this. # Print the necessary number of backspaces to erase the previous # message. self._stream.write("\b" * len(self._last_update)) self._stream.write(str) num_remaining = len(self._last_update) - len(str) if num_remaining > 0: self._stream.write(" " * num_remaining + "\b" * num_remaining) self._last_update = str self._dirty = True