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"""
A serializer that extends cbor2 to specify recommended parameters and adds a
4 byte length prefix to store multiple objects per file.
"""
import cbor2
from struct import Struct
from typing import Any, BinaryIO
# Define the Struct for prefixing serialized objects with their byte length
length_struct = Struct("<L")
def dump(value: Any, fp: BinaryIO, sort_keys: bool = False) -> None:
"""
Serialize value as cbor2 to a byte-mode file object with a length prefix.
Args:
value: The Python object to serialize.
fp: A file-like object supporting binary write operations.
sort_keys: If True, the output of dictionaries will be sorted by key.
Returns:
None
"""
# If sorting is required and the value is a dictionary, sort it by keys
if sort_keys and isinstance(value, dict):
value = {key: value[key] for key in sorted(value)}
packed = cbor2.dumps(value)
length = length_struct.pack(len(packed))
fp.write(length)
fp.write(packed)
def dumps(value: Any, sort_keys: bool = False) -> bytes:
"""
Serialize value as cbor2 to bytes without length prefix.
Args:
value: The Python object to serialize.
sort_keys: If True, the output of dictionaries will be sorted by key.
Returns:
A bytes object containing the serialized representation of the value.
"""
# If sorting is required and the value is a dictionary, sort it by keys
if sort_keys and isinstance(value, dict):
value = {key: value[key] for key in sorted(value)}
return cbor2.dumps(value)
def load(fp: BinaryIO) -> Any:
"""
Deserialize one cbor2 value from a byte-mode file object
using length prefix.
Args:
fp: A file-like object supporting binary read operations.
Returns:
The deserialized Python object.
"""
# Read the 4-byte length prefix and determine the length of the
# serialized object
length = length_struct.unpack(fp.read(4))[0]
# Read the serialized object using the determined length and
# deserialize it
return cbor2.loads(fp.read(length))
def loads(bytes_value: bytes) -> Any:
"""
Deserialize one cbor2 value from bytes.
Args:
bytes_value: The bytes object containing the serialized representation.
Returns:
The deserialized Python object.
"""
return cbor2.loads(bytes_value)
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