alGetFD(3dm)                                                      alGetFD(3dm)


NAME
     alGetFD - get the file descriptor for an audio port

SYNOPSIS
     #include <dmedia/audio.h>

     int alGetFD(ALport port)

PARAMETER
     port   expects the ALport structure whose file descriptor you desire.
            This structure is the returned value of an alOpenPort(3dm) call.

DESCRIPTION
     alGetFD() returns a file descriptor that you can use to construct the
     arguments to a select(2)  or poll(2) call.

     These calls are used when you want to block a process until the device
     fills or empties the audio port past a fillpoint (see the
     alSetFillPoint(3dm) manual page). At that time, select(2) and poll(2)
     return, and your code can continue processing the audio ports.  If the
     device has already filled or emptied the audio port buffer past the
     fillpoint when you make the call, control returns to your program
     immediately.

     When using select(2), an input port's file descriptor is used in a read
     fdset and an output port's file descriptor is used in a write fdset.

     When using poll(2), an input port's file descriptor is used with the
     POLLIN event flag and an output port's file descriptor is used with a
     POLLOUT event flag.

     Several AL functions implicitly change the current fillpoint value.
     Therefore, alSetFillPoint(3dm) must be called immediately before a
     select(2) or poll(2) call which uses an audio file descriptor.

DIAGNOSTICS
     Upon successful completion, alGetFD returns a valid file descriptor.
     Otherwise, alGetFD returns -1 and sets an error number which can be
     retrieved with oserror(3C).

     alGetFD can fail for the following reason:

     AL_BAD_PORT   port is either invalid or null.

SEE ALSO
     alSetFillPoint(3dm), alGetFillPoint(3dm), alOpenPort(3dm), select(2),
     poll(2), oserror(3C)


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