Class Connection

Lib/multiprocessing/connection.py:381–459

Connection class based on an arbitrary file descriptor (Unix only), or a socket handle (Windows).

class Connection(_ConnectionBase):
    """
    Connection class based on an arbitrary file descriptor (Unix only), or
    a socket handle (Windows).
    """

    if _winapi:
        def _close(self, _close=_multiprocessing.closesocket):
            _close(self._handle)
        _write = _multiprocessing.send
        _read = _multiprocessing.recv
    else:
        def _close(self, _close=os.close):
            _close(self._handle)
        _write = os.write
        _read = os.read

    def _send(self, buf, write=_write):
        remaining = len(buf)
        while True:
            n = write(self._handle, buf)
            remaining -= n
            if remaining == 0:
                break
            buf = buf[n:]

    def _recv(self, size, read=_read):
        buf = io.BytesIO()
        handle = self._handle
        remaining = size
        while remaining > 0:
            to_read = min(BUFSIZE, remaining)
            chunk = read(handle, to_read)
            n = len(chunk)
            if n == 0:
                if remaining == size:
                    raise EOFError
                else:
                    raise OSError("got end of file during message")
            buf.write(chunk)
            remaining -= n
        return buf

    def _send_bytes(self, buf):
        n = len(buf)
        if n > 0x7fffffff:
            pre_header = struct.pack("!i", -1)
            header = struct.pack("!Q", n)
            self._send(pre_header)
            self._send(header)
            self._send(buf)
        else:
            # For wire compatibility with 3.7 and lower
            header = struct.pack("!i", n)
            if n > 16384:
                # The payload is large so Nagle's algorithm won't be triggered
                # and we'd better avoid the cost of concatenation.
                self._send(header)