sizeof.py

from construct import * 

def sizeof_struct(subcon, value, parent=None):
    ctx = Container(value)
    ctx._ = parent or Container()
    ctx._params = Container()
    ctx._parsing = False
    ctx._sizing = True
    ctx._building = False

    size = 0
    for sc in subcon.subcons:
        if sc.name:
            size += sizeof(sc.subcon, ctx[sc.name], parent=ctx)
        else:
            size += sc._sizeof(ctx, "(sizeof)")

    return size


def sizeof(subcon, value, parent=None):
    if not parent or not hasattr(parent, "_params"):
        parent = Container(parent) if parent else Container()
        parent._params = Container()
        parent._parsing = False
        parent._sizing = True
        parent._building = False

    try:
        return subcon._sizeof(parent, "(sizeof)")
    except SizeofError:
        pass

    if isinstance(subcon, (Hex, Dec, HexDump, Aligned, StringEncoded, OffsettedEnd)):
        return sizeof(subcon.subcon, value, parent)
    if isinstance(subcon, (GreedyRange, RepeatUntil)):
        subcon = subcon.subcon
        itemsize = subcon.sizeof()
        if itemsize:
            return len(value) * itemsize
        elif value and hasattr(value[name][0], "sizeof"):
            return sum([x.sizeof() for x in value])
        else:
            return sum([sizeof(subcon, x, parent) for x in value])
    if subcon == GreedyBytes:
        return len(value)
    if isinstance(subcon, Prefixed):
        return subcon.lengthfield.sizeof() + len(value)
    if isinstance(subcon, NullTerminated):
        return sizeof(subcon.subcon, value, parent) + 1
    if isinstance(subcon, Struct):
        return sizeof_struct(subcon, value, parent)

    raise Exception(f"Don't know how to calculate size for {subcon}, {value}")