85 lines
2.6 KiB
Python
85 lines
2.6 KiB
Python
"""
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``msgio`` is an implementation of `https://github.com/libp2p/go-msgio`.
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from that repo: "a simple package to r/w length-delimited slices."
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NOTE: currently missing the capability to indicate lengths by "varint" method.
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"""
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# TODO unify w/ https://github.com/libp2p/py-libp2p/blob/1aed52856f56a4b791696bbcbac31b5f9c2e88c9/libp2p/utils.py#L85-L99 # noqa: E501
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from typing import Optional, cast
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from libp2p.io.abc import Closer, ReadCloser, Reader, ReadWriteCloser, WriteCloser
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from libp2p.io.utils import read_exactly
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SIZE_LEN_BYTES = 4
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BYTE_ORDER = "big"
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async def read_length(reader: Reader) -> int:
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length_bytes = await read_exactly(reader, SIZE_LEN_BYTES)
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return int.from_bytes(length_bytes, byteorder=BYTE_ORDER)
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def encode_msg_with_length(msg_bytes: bytes) -> bytes:
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len_prefix = len(msg_bytes).to_bytes(SIZE_LEN_BYTES, "big")
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return len_prefix + msg_bytes
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class MsgIOWriter(WriteCloser):
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write_closer: WriteCloser
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def __init__(self, write_closer: WriteCloser) -> None:
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self.write_closer = write_closer
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async def write(self, data: bytes) -> int:
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await self.write_msg(data)
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return len(data)
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async def write_msg(self, msg: bytes) -> None:
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data = encode_msg_with_length(msg)
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await self.write_closer.write(data)
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async def close(self) -> None:
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await self.write_closer.close()
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class MsgIOReader(ReadCloser):
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read_closer: ReadCloser
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next_length: Optional[int]
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def __init__(self, read_closer: ReadCloser) -> None:
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# NOTE: the following line is required to satisfy the
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# multiple inheritance but `mypy` does not like it...
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super().__init__(read_closer) # type: ignore
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self.read_closer = read_closer
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self.next_length = None
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async def read(self, n: int = None) -> bytes:
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return await self.read_msg()
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async def read_msg(self) -> bytes:
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length = await self.next_msg_len()
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data = await read_exactly(self.read_closer, length)
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if len(data) < length:
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self.next_length = length - len(data)
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else:
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self.next_length = None
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return data
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async def next_msg_len(self) -> int:
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if self.next_length is None:
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self.next_length = await read_length(self.read_closer)
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return self.next_length
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async def close(self) -> None:
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await self.read_closer.close()
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class MsgIOReadWriter(MsgIOReader, MsgIOWriter, Closer):
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def __init__(self, read_write_closer: ReadWriteCloser) -> None:
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super().__init__(cast(ReadCloser, read_write_closer))
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async def close(self) -> None:
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await self.read_closer.close()
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