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#
# Copyright (c) 2008 Martin Decky
# Copyright (c) 2011 Martin Sucha
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# - The name of the author may not be used to endorse or promote products
# derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
"""
Convert descriptive structure definitions to structure object
"""
import struct
import sys
import types
# Handle long integer conversions nicely in both Python 2 and Python 3
integer_types = (int, long) if sys.version < '3' else (int,)
# Ensure that 's' format for struct receives correct data type depending
# on Python version (needed due to different way to encode into bytes)
ensure_string = \
(lambda value: value if type(value) is str else bytes(value)) \
if sys.version < '3' else \
(lambda value: bytes(value, 'ascii') if type(value) is str else value)
ranges = {
'B': (integer_types, 0x00, 0xff),
'H': (integer_types, 0x0000, 0xffff),
'L': (integer_types, 0x00000000, 0xffffffff),
'Q': (integer_types, 0x0000000000000000, 0xffffffffffffffff),
'b': (integer_types, -0x80, 0x7f),
'h': (integer_types, -0x8000, 0x7fff),
'l': (integer_types, -0x80000000, 0x7fffffff) ,
'q': (integer_types, -0x8000000000000000, 0x7fffffffffffffff),
}
def check_range(varname, fmt, value):
if value == None:
raise ValueError('Variable "%s" not set' % varname)
if not fmt in ranges:
return
vartype, varmin, varmax = ranges[fmt]
if not isinstance(value, vartype):
raise ValueError('Variable "%s" is %s but should be %s' %
(varname, str(type(value)), str(vartype)))
if value < varmin or value > varmax:
raise ValueError('Variable "%s" value %s out of range %s..%s' %
(varname, repr(value), repr(varmin), repr(varmax)))
class Struct:
def size(self):
return struct.calcsize(self._format_)
def pack(self):
args = []
for variable, fmt, length in self._args_:
value = self.__dict__[variable]
if isinstance(value, list):
if length != None and length != len(value):
raise ValueError('Variable "%s" length %u does not match %u' %
(variable, len(value), length))
for index, item in enumerate(value):
check_range(variable + '[' + repr(index) + ']', fmt, item)
args.append(item)
else:
if (fmt == "s"):
value = ensure_string(value)
check_range(variable, fmt, value)
args.append(value)
return struct.pack(self._format_, *args)
def unpack(self, data):
values = struct.unpack(self._format_, data)
i = 0
for variable, fmt, length in self._args_:
self.__dict__[variable] = values[i]
i += 1
def create(definition):
"Create structure object"
tokens = definition.split(None)
# Initial byte order tag
format = {
"little:": lambda: "<",
"big:": lambda: ">",
"network:": lambda: "!"
}[tokens[0]]()
inst = Struct()
args = []
# Member tags
comment = False
variable = None
for token in tokens[1:]:
if (comment):
if (token == "*/"):
comment = False
continue
if (token == "/*"):
comment = True
continue
if (variable != None):
subtokens = token.split("[")
length = None
if (len(subtokens) > 1):
length = int(subtokens[1].split("]")[0])
format += "%d" % length
format += variable
inst.__dict__[subtokens[0]] = None
args.append((subtokens[0], variable, length))
variable = None
continue
if (token[0:8] == "padding["):
size = token[8:].split("]")[0]
format += "%dx" % int(size)
continue
variable = {
"char": lambda: "s",
"uint8_t": lambda: "B",
"uint16_t": lambda: "H",
"uint32_t": lambda: "L",
"uint64_t": lambda: "Q",
"int8_t": lambda: "b",
"int16_t": lambda: "h",
"int32_t": lambda: "l",
"int64_t": lambda: "q"
}[token]()
inst.__dict__['_format_'] = format
inst.__dict__['_args_'] = args
return inst
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