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# -*- coding: utf-8 -*-
#
# AWL simulator - L-stack handling
#
# Copyright 2014 Michael Buesch <m@bues.ch>
#
# 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 2 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, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
from __future__ import division, absolute_import, print_function, unicode_literals
from awlsim.common.compat import *
from awlsim.core.util import *
from awlsim.core.datatypes import *
class LStackAllocator(object):
"Memory allocator for the L-stack"
def __init__(self, maxSize):
# maxSize -> max size of the L-stack, in bytes.
self.localdata = ByteArray(maxSize)
self.reset(maxSize)
# Reset all allocations on the L-stack.
# Sets the maximum possible allocation to maxAllocBytes.
# maxAllocBytes must be smaller or equal to self.localdata size.
def reset(self, maxAllocBytes, curAllocBytes=0):
self.__maxAllocBytes = maxAllocBytes
self.__curAllocBytes = curAllocBytes
self.__curAllocBits = 0
# Allocate a number of bits on the L-stack.
# Returns an AwlOffset as the offset the bits are allocated on.
def alloc(self, nrBits):
curAllocBytes, curAllocBits =\
self.__curAllocBytes, self.__curAllocBits
if nrBits == 1:
# Bit-aligned allocation
offset = AwlOffset(curAllocBytes,
curAllocBits)
curAllocBits += 1
if curAllocBits >= 8:
curAllocBytes += 1
curAllocBits = 0
else:
# Byte-aligned allocation
if curAllocBits > 0:
curAllocBytes += 1
curAllocBits = 0
nrBytes = intDivRoundUp(nrBits, 8)
offset = AwlOffset(curAllocBytes, 0)
curAllocBytes += nrBytes
if curAllocBytes >= self.__maxAllocBytes:
raise AwlSimError(
"Cannot allocate another %d bits on L-stack. "
"The L-stack is exhausted." %\
nrBits)
self.__curAllocBytes, self.__curAllocBits =\
curAllocBytes, curAllocBits
return offset
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