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280 lines
8.4 KiB
280 lines
8.4 KiB
"""
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Minimalistic CBOR implementation, supports only what we need in cardano.
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"""
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import ustruct as struct
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from micropython import const
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from trezor import log, utils
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from . import readers, writers
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if False:
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from typing import Any, Union, Iterator, Tuple
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Value = Any
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CborSequence = Union[list[Value], Tuple[Value, ...]]
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_CBOR_TYPE_MASK = const(0xE0)
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_CBOR_INFO_BITS = const(0x1F)
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_CBOR_UNSIGNED_INT = const(0b000 << 5)
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_CBOR_NEGATIVE_INT = const(0b001 << 5)
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_CBOR_BYTE_STRING = const(0b010 << 5)
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_CBOR_TEXT_STRING = const(0b011 << 5)
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_CBOR_ARRAY = const(0b100 << 5)
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_CBOR_MAP = const(0b101 << 5)
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_CBOR_TAG = const(0b110 << 5)
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_CBOR_PRIMITIVE = const(0b111 << 5)
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_CBOR_UINT8_FOLLOWS = const(0x18)
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_CBOR_UINT16_FOLLOWS = const(0x19)
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_CBOR_UINT32_FOLLOWS = const(0x1A)
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_CBOR_UINT64_FOLLOWS = const(0x1B)
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_CBOR_VAR_FOLLOWS = const(0x1F)
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_CBOR_FALSE = const(0x14)
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_CBOR_TRUE = const(0x15)
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_CBOR_NULL = const(0x16)
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_CBOR_BREAK = const(0x1F)
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_CBOR_RAW_TAG = const(0x18)
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def _header(typ: int, l: int) -> bytes:
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if l < 24:
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return struct.pack(">B", typ + l)
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elif l < 2 ** 8:
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return struct.pack(">BB", typ + 24, l)
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elif l < 2 ** 16:
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return struct.pack(">BH", typ + 25, l)
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elif l < 2 ** 32:
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return struct.pack(">BI", typ + 26, l)
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elif l < 2 ** 64:
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return struct.pack(">BQ", typ + 27, l)
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else:
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raise NotImplementedError("Length %d not suppported" % l)
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def _cbor_encode(value: Value) -> Iterator[bytes]:
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if isinstance(value, int):
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if value >= 0:
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yield _header(_CBOR_UNSIGNED_INT, value)
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else:
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yield _header(_CBOR_NEGATIVE_INT, -1 - value)
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elif isinstance(value, bytes):
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yield _header(_CBOR_BYTE_STRING, len(value))
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yield value
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elif isinstance(value, bytearray):
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yield _header(_CBOR_BYTE_STRING, len(value))
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yield bytes(value)
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elif isinstance(value, str):
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encoded_value = value.encode()
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yield _header(_CBOR_TEXT_STRING, len(encoded_value))
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yield encoded_value
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elif isinstance(value, list) or isinstance(value, tuple):
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# definite-length valued list
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yield _header(_CBOR_ARRAY, len(value))
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for x in value:
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yield from _cbor_encode(x)
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elif isinstance(value, dict):
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yield _header(_CBOR_MAP, len(value))
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sorted_map = sorted((encode(k), v) for k, v in value.items())
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for k, v in sorted_map:
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yield k
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yield from _cbor_encode(v)
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elif isinstance(value, Tagged):
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yield _header(_CBOR_TAG, value.tag)
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yield from _cbor_encode(value.value)
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elif isinstance(value, IndefiniteLengthArray):
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yield bytes([_CBOR_ARRAY + 31])
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for x in value.array:
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yield from _cbor_encode(x)
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yield bytes([_CBOR_PRIMITIVE + 31])
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elif isinstance(value, bool):
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if value:
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yield bytes([_CBOR_PRIMITIVE + _CBOR_TRUE])
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else:
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yield bytes([_CBOR_PRIMITIVE + _CBOR_FALSE])
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elif isinstance(value, Raw):
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yield value.value
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elif value is None:
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yield bytes([_CBOR_PRIMITIVE + _CBOR_NULL])
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else:
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if __debug__:
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log.debug(__name__, "not implemented (encode): %s", type(value))
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raise NotImplementedError
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def _read_length(r: utils.BufferReader, aux: int) -> int:
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if aux < _CBOR_UINT8_FOLLOWS:
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return aux
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elif aux == _CBOR_UINT8_FOLLOWS:
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return r.get()
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elif aux == _CBOR_UINT16_FOLLOWS:
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return readers.read_uint16_be(r)
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elif aux == _CBOR_UINT32_FOLLOWS:
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return readers.read_uint32_be(r)
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elif aux == _CBOR_UINT64_FOLLOWS:
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return readers.read_uint64_be(r)
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else:
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raise NotImplementedError("Length %d not suppported" % aux)
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def _cbor_decode(r: utils.BufferReader) -> Value:
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fb = r.get()
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fb_type = fb & _CBOR_TYPE_MASK
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fb_aux = fb & _CBOR_INFO_BITS
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if fb_type == _CBOR_UNSIGNED_INT:
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return _read_length(r, fb_aux)
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elif fb_type == _CBOR_NEGATIVE_INT:
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val = _read_length(r, fb_aux)
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return -1 - val
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elif fb_type == _CBOR_BYTE_STRING:
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ln = _read_length(r, fb_aux)
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return r.read(ln)
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elif fb_type == _CBOR_TEXT_STRING:
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ln = _read_length(r, fb_aux)
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return r.read(ln).decode()
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elif fb_type == _CBOR_ARRAY:
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if fb_aux == _CBOR_VAR_FOLLOWS:
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res: Value = []
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while True:
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item = _cbor_decode(r)
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if item == _CBOR_PRIMITIVE + _CBOR_BREAK:
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break
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res.append(item)
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return res
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else:
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ln = _read_length(r, fb_aux)
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res = []
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for _ in range(ln):
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item = _cbor_decode(r)
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res.append(item)
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return res
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elif fb_type == _CBOR_MAP:
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res = {}
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if fb_aux == _CBOR_VAR_FOLLOWS:
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while True:
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key = _cbor_decode(r)
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if key in res:
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raise ValueError
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if key == _CBOR_PRIMITIVE + _CBOR_BREAK:
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break
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value = _cbor_decode(r)
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res[key] = value
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else:
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ln = _read_length(r, fb_aux)
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for _ in range(ln):
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key = _cbor_decode(r)
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if key in res:
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raise ValueError
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value = _cbor_decode(r)
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res[key] = value
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return res
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elif fb_type == _CBOR_TAG:
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val = _read_length(r, fb_aux)
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item = _cbor_decode(r)
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if val == _CBOR_RAW_TAG: # only tag 24 (0x18) is supported
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return item
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else:
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return Tagged(val, item)
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elif fb_type == _CBOR_PRIMITIVE:
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if fb_aux == _CBOR_FALSE:
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return False
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elif fb_aux == _CBOR_TRUE:
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return True
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elif fb_aux == _CBOR_NULL:
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return None
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elif fb_aux == _CBOR_BREAK:
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return fb
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else:
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raise NotImplementedError
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else:
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if __debug__:
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log.debug(__name__, "not implemented (decode): %s", fb)
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raise NotImplementedError
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class Tagged:
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def __init__(self, tag: int, value: Value) -> None:
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self.tag = tag
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self.value = value
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def __eq__(self, other: object) -> bool:
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return (
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isinstance(other, Tagged)
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and self.tag == other.tag
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and self.value == other.value
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)
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class Raw:
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def __init__(self, value: Value):
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self.value = value
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class IndefiniteLengthArray:
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def __init__(self, array: list[Value]) -> None:
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self.array = array
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def __eq__(self, other: object) -> bool:
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if isinstance(other, IndefiniteLengthArray):
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return self.array == other.array
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elif isinstance(other, list):
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return self.array == other
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else:
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return False
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def encode(value: Value) -> bytes:
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return b"".join(_cbor_encode(value))
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def encode_streamed(value: Value) -> Iterator[bytes]:
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"""
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Returns the encoded value as an iterable of the individual
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CBOR "chunks", removing the need to reserve a continuous
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chunk of memory for the full serialized representation of the value
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"""
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return _cbor_encode(value)
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def encode_chunked(value: Value, max_chunk_size: int) -> Iterator[bytes]:
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"""
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Returns the encoded value as an iterable of chunks of a given size,
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removing the need to reserve a continuous chunk of memory for the
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full serialized representation of the value.
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"""
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if max_chunk_size <= 0:
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raise ValueError
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chunks = encode_streamed(value)
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chunk_buffer = writers.empty_bytearray(max_chunk_size)
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try:
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current_chunk_view = utils.BufferReader(next(chunks))
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while True:
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num_bytes_to_write = min(
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current_chunk_view.remaining_count(),
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max_chunk_size - len(chunk_buffer),
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)
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chunk_buffer.extend(current_chunk_view.read(num_bytes_to_write))
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if len(chunk_buffer) >= max_chunk_size:
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yield chunk_buffer
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chunk_buffer[:] = bytes()
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if current_chunk_view.remaining_count() == 0:
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current_chunk_view = utils.BufferReader(next(chunks))
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except StopIteration:
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if len(chunk_buffer) > 0:
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yield chunk_buffer
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def decode(cbor: bytes) -> Value:
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r = utils.BufferReader(cbor)
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res = _cbor_decode(r)
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if r.remaining_count():
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raise ValueError
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return res
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