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# Copyright 2011 Lars Wirzenius
#
# 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/>.
import os
class NameGenerator(object):
'''Generate names for new output files.
If the target directory is empty, the sequence of output files is
always the same for the same parameters.
A directory structure is also generated. The shape of the tree is
defined by two parameters: 'max' and 'depth'. 'depth' is the number
of levels of subdirectories to create, and 'max' is the maximum
number of files/dirs to allow per output directory. Thus, if max is
3 and depth is 2, the output files are: 0/0/0, 0/0/1, 0/0/2,
0/1/0, 0/1/1, etc.
If depth is zero, all output files go directly to the target
directory, and max is ignored.
'''
def __init__(self, dirname, depth, max):
self.dirname = dirname
self.depth = depth
self.max = max
self.counter = 0
def _path_tuple(self, n):
'''Return tuple for dir/file numbers for nth output file.
The last item in the tuple gives the file number, the precding
items the directory numbers. Thus, a tuple (1, 2, 3) would
mean path '1/2/3', but it is given as a tuple for easier
manipulation.
'''
if self.depth == 0:
return (n,)
else:
items = []
for i in range(self.depth):
items.append(n % self.max)
n /= self.max
items.append(n)
items.reverse()
return tuple(items)
def _next_candidate_name(self):
items = self._path_tuple(self.counter)
self.counter += 1
return os.path.join(self.dirname, *[str(i) for i in items])
def new(self):
while True:
name = self._next_candidate_name()
if not os.path.exists(name):
return name
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