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# Version: MPL 1.1/GPL 2.0/LGPL 2.1
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# The contents of this file are subject to the Mozilla Public License Version
# 1.1 (the "License"); you may not use this file except in compliance with
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# The Original Code is the Python Computer Graphics Kit.
#
# The Initial Developer of the Original Code is Matthias Baas.
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## \file idmanager.py
## \brief Contains the IDManager class.
# Exceptions...
class IDNotAllocated(Exception):
"""Exception class."""
pass
# IDManager
class IDManager:
"""This class manages IDs.
This class is used to generate IDs for GUI elements such as menu items.
You can call allocID() to get an unused ID and later on freeID() to
make the ID available again.
"""
def __init__(self, startid=1):
"""Constructor.
\param startid (\c int) The starting value for the IDs (default: 1)
"""
# Each interval is given by its start and its end (=last item+1)
self._intervals = [[startid,None]]
self._startid = startid
def __call__(self):
return self.allocID()
# allocID
def allocID(self):
"""Request an ID.
\return An unused ID (\c int).
"""
id = self._intervals[0][0]
self._intervals[0][0]+=1
# Is the interval eaten up? then remove it
if self._intervals[0][0]==self._intervals[0][1]:
del self._intervals[0]
return id
# freeID
def freeID(self, id):
"""Releases an ID.
\param id (\c int) A previously allocated ID
"""
if id<self._startid:
raise IDNotAllocated, "ID %d hasn't been allocated."%id
idx = 0
for istart,iend in self._intervals:
if id<istart:
break
# Check if id is in the current interval (=attempt to free an ID
# which wasn't allocated)
if iend==None:
iend = id+1
if id>=istart and id<iend:
raise IDNotAllocated, "ID %d hasn't been allocated."%id
idx+=1
# Is the freed id id directly before the interval
if id==self._intervals[idx][0]-1:
self._intervals[idx][0]-=1
# Check if the interval can be merged with the previous interval
if idx!=0 and self._intervals[idx-1][1]==self._intervals[idx][0]:
self._intervals[idx-1][1]=self._intervals[idx][1]
del self._intervals[idx]
# Is the freed id directly behind the previous interval? then enlarge
elif idx!=0 and id==self._intervals[idx-1][1]:
self._intervals[idx-1][1]+=1
# Check if the enlarged interval can be merged with its successor
if self._intervals[idx-1][1]==self._intervals[idx][0]:
self._intervals[idx-1][1]=self._intervals[idx][1]
del self._intervals[idx]
else:
# Create a new interval with one element
self._intervals.insert(idx,[id,id+1])
######################################################################
if __name__=="__main__":
im = IDManager(5)
print im.allocID()
print im.allocID()
print im.allocID()
print im._intervals
im.freeID(4)
im.freeID(5)
im.freeID(6)
print im._intervals
print im.allocID()
print im._intervals
print im.allocID()
print im.allocID()
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