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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