CMD_READ

normal I/O entry point

CMD_READ is a standard command for a single audio channel (io_Unit). If the allocation key (ioa_AllocKey) is correct, CMD_READ returns a pointer (io_Data) to the I/O block currently writing (CMD_WRITE) on the selected channel; otherwise, CMD_READ returns an error (ADIOERR_NOALLOCATION). If there is no write in progress, CMD_READ returns zero. CMD_READ is synchronous and only replies (mn_ReplyPort) if the quick bit (IOF_QUICK) is clear.

io_Device

Pointer to device node, must be set by (or copied from I/O block set by) OpenDevice function

io_Unit

Bit map of channel to read (bit 0 thru 3 corresponds to channel 0 thru 3), if more then one bit is set lowest bit number channel read

io_Command

Command number for CMD_READ

io_Flags

Flags, must be cleared if not used: IOF_QUICK - (CLEAR) reply I/O request

ioa_AllocKey

Allocation key, must be set by (or copied from I/O block set by) OpenDevice function or ADCMD_ALLOCATE command

io_Unit

Bit map of channel successfully read (bit 0 thru 3 corresponds to channel 0 thru 3)

io_Error

Error number: 0 - no error ADIOERR_NOALLOCATION - allocation key (ioa_AllocKey)

does not match key for channel

ioa_Data

Pointer to I/O block for current write, zero if none is progress