mirror of
https://github.com/rembo10/headphones.git
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Initial python3 changes
Mostly just updating libraries, removing string encoding/decoding, fixing some edge cases. No new functionality was added in this commit.
This commit is contained in:
rembo10
270
lib/bencode/bencode.py
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270
lib/bencode/bencode.py
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"""Code, which deals with bencoded data."""
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from dataclasses import dataclass
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from typing import Union
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COLON = ord(":")
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END_MARKER = ord("e")
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START_DICT = ord("d")
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START_INTEGER = ord("i")
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START_LIST = ord("l")
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@dataclass
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class BencodedString:
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"""An internal container for bencoded strings"""
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def __init__(self, data):
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"""Called when the object is created, sets its attributes"""
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self.bytes = bytearray(data)
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def del_prefix(self, index):
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"""Delete the prefix of specified length"""
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del self.bytes[:index]
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def get_prefix(self, index):
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"""Get the prefix of specified length (as bytes)"""
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return bytes(self.bytes[:index])
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def _decode(data: BencodedString) -> Union[bytes, dict, int, list]:
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"""Convert the given bencoded string to a Python object.
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Args:
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Some BencodedString
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Raises:
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ValueError:
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If the argument is empty
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If the first byte doesn't match a supported by bencode data type
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Returns:
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A Python object
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"""
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if not data.bytes:
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raise ValueError("Cannot decode an empty bencoded string.")
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if data.bytes[0] == START_DICT:
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return _decode_dict(data)
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if data.bytes[0] == START_LIST:
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return _decode_list(data)
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if data.bytes[0] == START_INTEGER:
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return _decode_int(data)
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if chr(data.bytes[0]).isdigit():
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return _decode_bytes(data)
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raise ValueError(
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"Cannot decode data, expected the first byte to be one of "
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f"'d', 'i', 'l' or a digit, got {chr(data.bytes[0])!r} instead."
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)
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def _decode_bytes(data: BencodedString) -> bytes:
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"""Extract the first byte string from the given bencoded string
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Args:
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Some BencodedString, which starts with a byte string
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Raises:
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ValueError:
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If the byte string doesn't contain a delimiter
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If the real string length is shorter, than the prefix length
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Returns:
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An extracted byte string
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"""
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# Get byte string length
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delimiter_index = data.bytes.find(COLON)
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if delimiter_index > 0:
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length_prefix = data.get_prefix(delimiter_index)
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string_length = int(length_prefix.decode("ascii"))
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data.del_prefix(delimiter_index + 1)
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else:
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raise ValueError(
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"Cannot decode a byte string, it doesn't contain a delimiter. "
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"Most likely the bencoded string is incomplete or incorrect."
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)
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# Get byte string data
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if len(data.bytes) >= string_length:
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result_bytes = data.get_prefix(string_length)
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data.del_prefix(string_length)
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else:
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raise ValueError(
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f"Cannot decode a byte string (prefix length "
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f"- {string_length}, real_length - {len(data.bytes)}. "
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"Most likely the bencoded string is incomplete or incorrect."
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)
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return result_bytes
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def _decode_dict(data: BencodedString) -> dict:
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"""Extract the first dict from the given bencoded string
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Args:
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Some BencodedString, which starts with a dictionary
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Raises:
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ValueError: If bencoded string ended before the end marker was found
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Returns:
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An extracted dictionary
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"""
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result_dict = {}
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data.del_prefix(1)
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while True:
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if data.bytes:
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if data.bytes[0] != END_MARKER:
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key = _decode(data)
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value = _decode(data)
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result_dict[key] = value
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else:
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data.del_prefix(1)
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break
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else:
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raise ValueError(
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"Cannot decode a dictionary, reached end of the bencoded "
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"string before the end marker was found. Most likely the "
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"bencoded string is incomplete or incorrect."
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)
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return result_dict
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def _decode_int(data: BencodedString) -> int:
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"""Extract the first integer from the given bencoded string
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Args:
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Some BencodedString, which starts with an integer
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Raises:
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ValueError: If bencoded string ended before the end marker was found
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Returns:
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An extracted integer
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"""
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data.del_prefix(1)
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end_marker_index = data.bytes.find(END_MARKER)
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if end_marker_index > 0:
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result_bytes = data.get_prefix(end_marker_index)
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data.del_prefix(end_marker_index + 1)
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else:
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raise ValueError(
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"Cannot decode an integer, reached the end of the bencoded "
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"string before the end marker was found. Most likely the "
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"bencoded string is incomplete or incorrect."
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)
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return int(result_bytes.decode("ascii"))
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def _decode_list(data: BencodedString) -> list:
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"""Extract the first list from the given bencoded string
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Args:
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Some BencodedString, which starts with a list
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Raises:
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ValueError: If bencoded string ended before the end marker was found
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Returns:
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An extracted list
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"""
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result_list = []
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data.del_prefix(1)
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while True:
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if data.bytes:
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if data.bytes[0] != END_MARKER:
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result_list.append(_decode(data))
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else:
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data.del_prefix(1)
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break
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else:
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raise ValueError(
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"Cannot decode a list, reached end of the bencoded string "
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"before the end marker was found. Most likely the bencoded "
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"string is incomplete or incorrect."
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)
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return result_list
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def _encode_bytes(source: bytes) -> bytes:
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"""Encode provided bytes as a bencoded string"""
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return str(len(source)).encode("ascii") + b":" + source
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def _encode_dict(source: dict) -> bytes:
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"""Encode provided dictionary as a bencoded string"""
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result_data = b"d"
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for key, value in source.items():
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result_data += encode(key) + encode(value)
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return result_data + b"e"
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def _encode_int(source: int) -> bytes:
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"""Encode provided integer as a bencoded string"""
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return b"i" + str(source).encode("ascii") + b"e"
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def _encode_list(source: list) -> bytes:
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"""Encode provided list as a bencoded string"""
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result_data = b"l"
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for item in source:
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result_data += encode(item)
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return result_data + b"e"
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def decode(data: bytes) -> Union[bytes, dict, int, list]:
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"""Convert the given bencoded string to a Python object.
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Raises:
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ValueError:
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If the argument is not of type bytes or is empty
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If the first byte doesn't match a supported by bencode data type
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Returns:
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A Python object
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"""
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if not isinstance(data, bytes):
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raise ValueError(
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f"Cannot decode data, expected bytes, got {type(data)} instead."
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)
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return _decode(BencodedString(data))
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def encode(data: Union[bytes, dict, int, list]) -> bytes:
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"""Convert the given Python object to a bencoded string.
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Raises:
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ValueError: If the provided object type is not supported
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Returns:
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A bencoded string
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"""
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if isinstance(data, bytes):
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return _encode_bytes(data)
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if isinstance(data, dict):
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return _encode_dict(data)
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if isinstance(data, int):
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return _encode_int(data)
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if isinstance(data, list):
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return _encode_list(data)
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raise ValueError(
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f"Cannot encode data: objects of type {type(data)} are not supported."
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)
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