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78 lines
1.7 KiB
Python
78 lines
1.7 KiB
Python
"""Various I/O and serialization utilities."""
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import io
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import struct
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def send(conn, data):
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"""Send data blob to connection socket."""
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conn.sendall(data)
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def recv(conn, size):
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"""
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Receive bytes from connection socket or stream.
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If size is struct.calcsize()-compatible format, use it to unpack the data.
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Otherwise, return the plain blob as bytes.
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"""
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try:
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fmt = size
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size = struct.calcsize(fmt)
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except TypeError:
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fmt = None
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try:
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_read = conn.recv
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except AttributeError:
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_read = conn.read
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res = io.BytesIO()
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while size > 0:
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buf = _read(size)
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if not buf:
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raise EOFError
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size = size - len(buf)
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res.write(buf)
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res = res.getvalue()
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if fmt:
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return struct.unpack(fmt, res)
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else:
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return res
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def read_frame(conn):
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"""Read size-prefixed frame from connection."""
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size, = recv(conn, '>L')
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return recv(conn, size)
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def bytes2num(s):
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"""Convert MSB-first bytes to an unsigned integer."""
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res = 0
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for i, c in enumerate(reversed(bytearray(s))):
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res += c << (i * 8)
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return res
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def num2bytes(value, size):
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"""Convert an unsigned integer to MSB-first bytes with specified size."""
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res = []
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for _ in range(size):
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res.append(value & 0xFF)
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value = value >> 8
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assert value == 0
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return bytearray(list(reversed(res)))
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def pack(fmt, *args):
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"""Serialize MSB-first message."""
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return struct.pack('>' + fmt, *args)
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def frame(*msgs):
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"""Serialize MSB-first length-prefixed frame."""
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res = io.BytesIO()
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for msg in msgs:
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res.write(msg)
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msg = res.getvalue()
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return pack('L', len(msg)) + msg
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