def parse(cls, buf):
(hdr, ) = struct.unpack_from(cls._hdr_fmt_str, buf, 0)
rest = buf[struct.calcsize(cls._hdr_fmt_str):]
if hdr == 0:
return None, rest # all-0 header is no-op for padding
src_type = (hdr >> 13) & 0x1
dst_type = (hdr >> 11) & 0x3
n_bits = hdr & 0x3ff
subcls = cls._subclasses[dst_type]
if src_type == 0: # subfield
src = cls._parse_subfield(rest)
rest = rest[6:]
elif src_type == 1: # immediate
src_len = (n_bits + 15) // 16 * 2
src_bin = rest[:src_len]
src = type_desc.IntDescr(size=src_len).to_user(src_bin)
rest = rest[src_len:]
if dst_type == 0: # match
dst = cls._parse_subfield(rest)
rest = rest[6:]
elif dst_type == 1: # load
dst = cls._parse_subfield(rest)
rest = rest[6:]
elif dst_type == 2: # output
dst = '' # empty
return subcls(src=src, dst=dst, n_bits=n_bits), rest
def serialize(self):
buf = bytearray()
if isinstance(self.src, tuple):
src_type = 0 # subfield
else:
src_type = 1 # immediate
# header
val = (src_type << 13) | (self._dst_type << 11) | self.n_bits
msg_pack_into(self._hdr_fmt_str, buf, 0, val)
# src
if src_type == 0: # subfield
buf += self._serialize_subfield(self.src)
elif src_type == 1: # immediate
src_len = (self.n_bits + 15) // 16 * 2
buf += type_desc.IntDescr(size=src_len).from_user(self.src)
# dst
if self._dst_type == 0: # match
buf += self._serialize_subfield(self.dst)
elif self._dst_type == 1: # load
buf += self._serialize_subfield(self.dst)
elif self._dst_type == 2: # output
pass # empty
return buf