def decode(rlp, sedes=None, strict=True, recursive_cache=False, **kwargs):
"""Decode an RLP encoded object.
If the deserialized result `obj` has an attribute :attr:`_cached_rlp` (e.g. if `sedes` is a
subclass of :class:`rlp.Serializable`) it will be set to `rlp`, which will improve performance
on subsequent :func:`rlp.encode` calls. Bear in mind however that `obj` needs to make sure that
this value is updated whenever one of its fields changes or prevent such changes entirely
(:class:`rlp.sedes.Serializable` does the latter).
:param sedes: an object implementing a function ``deserialize(code)`` which will be applied
after decoding, or ``None`` if no deserialization should be performed
:param \*\*kwargs: additional keyword arguments that will be passed to the deserializer
:param strict: if false inputs that are longer than necessary don't cause an exception
:returns: the decoded and maybe deserialized Python object
:raises: :exc:`rlp.DecodingError` if the input string does not end after the root item and
`strict` is true
:raises: :exc:`rlp.DeserializationError` if the deserialization fails
"""
if not is_bytes(rlp):
raise DecodingError('Can only decode RLP bytes, got type %s' % type(rlp).__name__, rlp)
try:
item, per_item_rlp, end = consume_item(rlp, 0)
except IndexError:
raise DecodingError('RLP string too short', rlp)
if end != len(rlp) and strict:
msg = 'RLP string ends with {} superfluous bytes'.format(len(rlp) - end)
raise DecodingError(msg, rlp)
if sedes:
obj = sedes.deserialize(item, **kwargs)
if is_sequence(obj) or hasattr(obj, '_cached_rlp'):
_apply_rlp_cache(obj, per_item_rlp, recursive_cache)
return obj
else:
return item
def consume_length_prefix(rlp, start):
"""Read a length prefix from an RLP string.
:param rlp: the rlp byte string to read from
:param start: the position at which to start reading
:returns: a tuple ``(type, length, end)``, where ``type`` is either ``str``
or ``list`` depending on the type of the following payload,
``length`` is the length of the payload in bytes, and ``end`` is
the position of the first payload byte in the rlp string
"""
b0 = rlp[start]
if b0 < 128: # single byte
return (bytes, 1, start)
elif b0 < SHORT_STRING: # short string
if b0 - 128 == 1 and rlp[start + 1] < 128:
raise DecodingError('Encoded as short string although single byte was possible', rlp)
return (bytes, b0 - 128, start + 1)
elif b0 < 192: # long string
ll = b0 - 183 # - (128 + 56 - 1)
if rlp[start + 1:start + 2] == b'\x00':
raise DecodingError('Length starts with zero bytes', rlp)
l = big_endian_to_int(rlp[start + 1:start + 1 + ll])
if l < 56:
raise DecodingError('Long string prefix used for short string', rlp)
return (bytes, l, start + 1 + ll)
elif b0 < 192 + 56: # short list
return (list, b0 - 192, start + 1)
else: # long list
ll = b0 - 192 - 56 + 1
if rlp[start + 1:start + 2] == b'\x00':
raise DecodingError('Length starts with zero bytes', rlp)
l = big_endian_to_int(rlp[start + 1:start + 1 + ll])
if l < 56:
raise DecodingError('Long list prefix used for short list', rlp)
return (list, l, start + 1 + ll)
def decode_raw(item, strict, _):
try:
result, per_item_rlp, end = consume_item(item, 0)
except IndexError:
raise DecodingError('RLP string too short', item)
if end != len(item) and strict:
msg = 'RLP string ends with {} superfluous bytes'.format(
len(item) - end)
raise DecodingError(msg, item)
return result, per_item_rlp
def consume_payload(rlp, start, type_, length):
"""Read the payload of an item from an RLP string.
:param rlp: the rlp string to read from
:param type_: the type of the payload (``bytes`` or ``list``)
:param start: the position at which to start reading
:param length: the length of the payload in bytes
:returns: a tuple ``(item, end)``, where ``item`` is the read item and
``end`` is the position of the first unprocessed byte
"""
if type_ is bytes:
return (rlp[start:start + length], start + length)
elif type_ is list:
items = []
next_item_start = start
end = next_item_start + length
while next_item_start < end:
# item, next_item_start = consume_item(rlp, next_item_start)
t, l, s = consume_length_prefix(rlp, next_item_start)
item, next_item_start = consume_payload(rlp, s, t, l)
items.append(item)
if next_item_start > end:
raise DecodingError('List length prefix announced a too small '
'length', rlp)
return (items, next_item_start)
else:
raise TypeError('Type must be either list or bytes')
def consume_payload(rlp, prefix, start, type_, length):
"""Read the payload of an item from an RLP string.
:param rlp: the rlp string to read from
:param type_: the type of the payload (``bytes`` or ``list``)
:param start: the position at which to start reading
:param length: the length of the payload in bytes
:returns: a tuple ``(item, per_item_rlp, end)``, where ``item`` is
the read item, per_item_rlp is a list containing the RLP
encoding of each item and ``end`` is the position of the
first unprocessed byte
"""
if type_ is bytes:
item = rlp[start:start + length]
return (item, [prefix + item], start + length)
elif type_ is list:
items = []
per_item_rlp = []
list_rlp = prefix
next_item_start = start
end = next_item_start + length
while next_item_start < end:
p, t, l, s = consume_length_prefix(rlp, next_item_start)
item, item_rlp, next_item_start = consume_payload(rlp, p, s, t, l)
per_item_rlp.append(item_rlp)
# When the item returned above is a single element, item_rlp will also contain a
# single element, but when it's a list, the first element will be the RLP of the
# whole List, which is what we want here.
list_rlp += item_rlp[0]
items.append(item)
per_item_rlp.insert(0, list_rlp)
if next_item_start > end:
raise DecodingError(
'List length prefix announced a too small '
'length', rlp)
return (items, per_item_rlp, next_item_start)
else:
raise TypeError('Type must be either list or bytes')
def decode_raw(item, strict, preserve_per_item_rlp):
try:
return rusty_rlp.decode_raw(item, strict, preserve_per_item_rlp)
except (TypeError, rusty_rlp.DecodingError) as e:
raise DecodingError(e, item)