source: mainline/tools/xstruct.py@ 67435b1

#
# 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