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# Copyright (C) 2008 Canonical Limited.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as published
# by the Free Software Foundation.
#
# 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, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#
"""Functions for dealing with a persistent equivalency table."""
SENTINEL = -1
class EquivalenceTable(object):
"""This class tracks equivalencies between lists of hashable objects.
:ivar lines: The 'static' lines that will be preserved between runs.
:ival _matching_lines: A dict of {line:[matching offsets]}
"""
def __init__(self, lines):
self.lines = lines
self._right_lines = None
# For each line in 'left' give the offset to the other lines which
# match it.
self._generate_matching_lines()
def _generate_matching_lines(self):
matches = {}
for idx, line in enumerate(self.lines):
matches.setdefault(line, []).append(idx)
self._matching_lines = matches
def _update_matching_lines(self, new_lines, index):
matches = self._matching_lines
start_idx = len(self.lines)
for idx, do_index in enumerate(index):
if not do_index:
continue
matches.setdefault(new_lines[idx], []).append(start_idx + idx)
def get_matches(self, line):
"""Return the lines which match the line in right."""
try:
return self._matching_lines[line]
except KeyError:
return None
def _get_matching_lines(self):
"""Return a dictionary showing matching lines."""
matching = {}
for line in self.lines:
matching[line] = self.get_matches(line)
return matching
def get_idx_matches(self, right_idx):
"""Return the left lines matching the right line at the given offset."""
line = self._right_lines[right_idx]
try:
return self._matching_lines[line]
except KeyError:
return None
def extend_lines(self, lines, index):
"""Add more lines to the left-lines list.
:param lines: A list of lines to add
:param index: A True/False for each node to define if it should be
indexed.
"""
self._update_matching_lines(lines, index)
self.lines.extend(lines)
def set_right_lines(self, lines):
"""Set the lines we will be matching against."""
self._right_lines = lines
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