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WaitPort -- wait for a given port to be non-empty
message = WaitPort(port)
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struct Message *WaitPort(struct MsgPort *);
This function waits for the given port to become non-empty. If
necessary, the Wait() function will be called to wait for the port
signal. If a message is already present at the port, this function
will return immediately. The return value is always a pointer to
the first message queued (but it is not removed from the queue).
CAUTION
More than one message may be at the port when this returns. It is
proper to call the GetMsg() function in a loop until all messages
have been handled, then wait for more to arrive.
To wait for more than one port, combine the signal bits from each
port into one call to the Wait() function, then use a GetMsg() loop
to collect any and all messages. It is possible to get a signal
for a port WITHOUT a message showing up. Plan for this.
port - a pointer to the message port
message - a pointer to the first available message
GetMsg()
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