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# -*- coding: utf-8 -*-
#
# AWL simulator - Word packer
#
# Copyright 2013-2014 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.common.exceptions import *
import struct
class _WordPacker:
"""Pack/unpack bytes/words/dwords into/from a byte stream."""
_wordStruct = struct.Struct(str(">H"))
_dwordStruct = struct.Struct(str(">I"))
def __fromBytes_1(self, buf, byteOffset):
return buf[byteOffset] & 0x01
def __fromBytes_8(self, buf, byteOffset):
return buf[byteOffset]
def __fromBytes_16(self, buf, byteOffset):
return _WordPacker._wordStruct.unpack_from(
buf, byteOffset
)[0]
def __fromBytes_32(self, buf, byteOffset):
return _WordPacker._dwordStruct.unpack_from(
buf, byteOffset
)[0]
__fromBytesHandlers = {
1 : __fromBytes_1,
8 : __fromBytes_8,
16 : __fromBytes_16,
32 : __fromBytes_32,
}
def __toBytes_1(self, buf, byteOffset, value):
buf[byteOffset] = value & 0x01
def __toBytes_8(self, buf, byteOffset, value):
buf[byteOffset] = value & 0xFF
def __toBytes_16(self, buf, byteOffset, value):
if byteOffset + 2 > len(buf):
raise IndexError
buf[byteOffset : byteOffset + 2] =\
_WordPacker._wordStruct.pack(value & 0xFFFF)
def __toBytes_32(self, buf, byteOffset, value):
if byteOffset + 4 > len(buf):
raise IndexError
buf[byteOffset : byteOffset + 4] =\
_WordPacker._dwordStruct.pack(value & 0xFFFFFFFF)
__toBytesHandlers = {
1 : __toBytes_1,
8 : __toBytes_8,
16 : __toBytes_16,
32 : __toBytes_32,
}
def fromBytes(self, byteBuffer, bitWidth, byteOffset=0):
# byteBuffer should not be 'bytes' for Py2 compoatibility reasons.
# 'bytes' indexing returns different results on Py3 (int vs. str).
assert(not isinstance(byteBuffer, bytes))
if bitWidth > 32:
return byteBuffer
try:
handler = self.__fromBytesHandlers[bitWidth]
return handler(self, byteBuffer, byteOffset)
except (IndexError, KeyError, struct.error) as e:
raise AwlSimError("Failed to unpack %d bits from buffer" % bitWidth)
def toBytes(self, byteBuffer, bitWidth, byteOffset=0, value=0):
if bitWidth > 32:
return value
try:
handler = self.__toBytesHandlers[bitWidth]
handler(self, byteBuffer, byteOffset, value)
except (IndexError, KeyError, struct.error) as e:
raise AwlSimError("Failed to pack %d bits into buffer" % bitWidth)
return byteBuffer
WordPacker = _WordPacker()
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