def AlignedStruct(*members):
"""
Algorithm taken from http://en.wikipedia.org/wiki/Data_structure_alignment#Computing_padding
Example::
s = AlignedStruct(
"a" / word8, # 0
# padding (1) # 1
"b" / word16, # 2-3
"c" / word16, # 4-5
# padding (2) # 6-7
"d" / word32, # 8-11
"e" / word8, # 12
"f" / BitStruct( # 13
"x" / nibble,
"y" / nibble,
)
# padding (2) # 14-15
# total size = 16
)
"""
members2 = []
offset = 0
largest = 0
# align each member to its native size, e.g., int32 is aligned to 4-bytes
for name, pkr in members:
align = pkr.sizeof()
largest = max(align, largest)
padding = (align - offset % align) % align
offset += align + padding
if padding > 0:
members2.append(Padding(padding))
members2.append((name, pkr))
# the struct must be aligned to its largest member
if offset % largest != 0:
members2.append(Padding(largest - offset % largest))
return Struct(*members2)
def _unpack(self, stream, ctx):
digestor = ctx["__digestor__"] = self.digestor_factory()
obj = Struct._unpack(self, stream, ctx)
del ctx["__digestor__"]
return obj, digestor
def __init__(self, *members, **kwargs):
self.digestor_factory = kwargs.pop("digestor_factory")
Struct.__init__(self, *members, **kwargs)
def BitStruct(*args, **kwargs):
return Bitwise(Struct(*args, **kwargs))
def _generate_unpacker(pkr, streamvar, ctxvar):
return _get_visitor(pkr).generate_unpacker(pkr, streamvar, ctxvar)
def generate(pkr, name):
with PythonModule(name) as mod:
_get_visitor(pkr).setup(pkr)
SEP()
with DEF("%s_unpack" % (name, ), ["stream"]):
ctx = {}
res = _generate_unpacker(pkr, "stream", ctx)
STMT("return {0}", res)
return mod
if __name__ == "__main__":
from construct3.lib import this
from construct3.numbers import byte
from construct3.adapters import LengthPrefixed
#testpkr = Sequence(byte, byte, Sequence(byte, byte, Raw(this[0] + this[1] + this._[0] + this._[1])))
testpkr = Struct("len" / byte, "gth" / byte,
"data" / Raw(this.len + this.gth))
mod = generate(testpkr, "test")
print testpkr
mod.dump("testpacker.py")
import testpacker
from io import BytesIO
data = BytesIO("\x03\x02helloXX")
#data = BytesIO("\x01\x01\x01\x02helloXX")
print testpacker.test_unpack(data)
def _unpack(self, stream, ctx):
digestor = ctx["__digestor__"] = self.digestor_factory()
obj = Struct._unpack(self, stream, ctx)
del ctx["__digestor__"]
return obj, digestor
def __init__(self, *members, **kwargs):
self.digestor_factory = kwargs.pop("digestor_factory")
Struct.__init__(self, *members, **kwargs)
def _unpack(self, stream, ctx, cfg):
digestor = self.digestor_factory()
with cfg.set(digestor = digestor):
obj = Struct._unpack(self, stream, ctx, cfg)
obj["__digest__"] = digestor.digest()
return obj
def _unpack(self, stream, ctx, cfg):
digestor = self.digestor_factory()
with cfg.set(digestor=digestor):
obj = Struct._unpack(self, stream, ctx, cfg)
obj["__digest__"] = digestor.digest()
return obj
