Docs » Autodocs » audio.device » CMD_READ
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.
mn_ReplyPort- pointer to message port that receives I/O request after if the quick flag (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
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