Instead of transmitting the read command with either DoIO() or SendIO(), you might elect to use the low level BeginIO() interface to a device. BeginIO() works much like SendIO(), i.e., asynchronously, except it gives you control over the quick I/O bit (IOB_QUICK) in the io_Flags field. Quick I/O saves the overhead of a reply message, and perhaps the overhead of a task switch. If a quick I/O request is actually completed quickly, the entire command will execute in the context of the caller. See the "Exec: Device Input/Output" chapter of the Amiga ROM Kernel Reference Manual: Libraries for more detailed information on quick I/O. The device will determine if a quick I/O request will be handled quickly. Most non-I/O commands will execute quickly; read and write commands may or may not finish quickly. SerialIO.IOSer.io_Flags |= IOF_QUICK; /* Set QuickIO Flag */ BeginIO((struct IORequest *)SerialIO); if (SerialIO->IOSer.io_Flags & IOF_QUICK ) /* If flag is still set, I/O was synchronous and is now finished. * The IORequest was NOT appended a reply port. There is no * need to remove or WaitIO() for the message. */ printf("QuickIO\n"); else /* The device cleared the QuickIO bit. QuickIO could not happen * for some reason; the device processed the command normally. * In this case BeginIO() acted exactly like SendIO(). */ printf("Regular I/O\n"); WaitIO(SerialIO); The way you read from the device depends on your need for processing speed. Generally the BeginIO() route provides the lowest system overhead when quick I/O is possible. However, if quick I/O does not work, the same reply message overhead still exists.
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