1 #!/usr/bin/env python 2 3 """ 4 State management classes for iterators. 5 6 Copyright (C) 2011 Paul Boddie <paul@boddie.org.uk> 7 8 This program is free software; you can redistribute it and/or modify it under 9 the terms of the GNU General Public License as published by the Free Software 10 Foundation; either version 3 of the License, or (at your option) any later 11 version. 12 13 This program is distributed in the hope that it will be useful, but WITHOUT ANY 14 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A 15 PARTICULAR PURPOSE. See the GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License along 18 with this program. If not, see <http://www.gnu.org/licenses/>. 19 """ 20 21 from os.path import commonprefix 22 23 class CommonPrefixState: 24 25 "A class whose instances maintain common prefix state." 26 27 def __init__(self, initial=""): 28 self.initial = initial 29 self.reset() 30 31 def reset(self): 32 self.value = self.initial 33 34 class CommonPrefixDecoder(CommonPrefixState): 35 36 "A class whose instances decode common prefix information." 37 38 def update(self, common_plus_suffix): 39 common, suffix = common_plus_suffix 40 self.value = self.value[:common] + suffix 41 return self.value 42 43 class CommonPrefixEncoder(CommonPrefixState): 44 45 "A class whose instances encode common prefix information." 46 47 def update(self, value): 48 common = len(commonprefix((self.value, value))) 49 suffix = value[common:] 50 self.value = value 51 return common, suffix 52 53 # vim: tabstop=4 expandtab shiftwidth=4