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# Copyright (C) 2009, 2010 Roman Zimbelmann <romanz@lavabit.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
class HistoryEmptyException(Exception):
pass
class History(object):
def __init__(self, maxlen = None):
from collections import deque
self.history = deque(maxlen = maxlen)
self.history_forward = deque(maxlen = maxlen)
def add(self, item):
if len(self.history) == 0 or self.history[-1] != item:
self.history.append(item)
self.history_forward.clear()
def modify(self, item):
try:
self.history[-1] = item
except IndexError:
raise HistoryEmptyException
def __len__(self):
return len(self.history)
def current(self):
try:
return self.history[-1]
except IndexError:
raise HistoryEmptyException()
def top(self):
try:
return self.history_forward[-1]
except IndexError:
try:
return self.history[-1]
except IndexError:
raise HistoryEmptyException()
def bottom(self):
try:
return self.history[0]
except IndexError:
raise HistoryEmptyException()
def back(self):
if len(self.history) > 1:
self.history_forward.appendleft( self.history.pop() )
return self.current()
def move(self, n):
if n > 0:
return self.forward()
if n < 0:
return self.back()
def __iter__(self):
return self.history.__iter__()
def next(self):
return self.history.next()
def forward(self):
if len(self.history_forward) > 0:
self.history.append( self.history_forward.popleft() )
return self.current()
def fast_forward(self):
if self.history_forward:
self.history.extend(self.history_forward)
self.history_forward.clear()
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