async(3) [plan9 man page]

ASYNC(3)						     Library Functions Manual							  ASYNC(3)

NAME

       async - framing for a serial line to Datakit

SYNOPSIS

       ctlfd = open(".../ctl", ORDWR);
       write(ctlfd, "push async", 10);

DESCRIPTION

       This is not a device, but rather a stream module (see stream(3)) that can be pushed onto a stream.  This module provides the framing neces-
       sary to treat a serial line as a Datakit trunk.	It is usually pushed onto a stream before the dkmux module.  The  frame  includes  a  CRC.
       Any received frames with an incorrect CRC are discarded.

       The format of a message upstream of the module is:

	      channel # low byte
	      channel # high byte
	      control byte (0 means none)
	      data bytes

       The format of a frame is:

	      0x7d
	      0x7d
	      channel # low byte
	      channel # high byte
	      crc low byte
	      crc high byte
	      0x7d
	      0x7d

       All control bytes in the frame are preceded by a 0x9d byte.  All 0x9d and 0x7d bytes in the data are followed by a 0x00 byte to distinguish
       them from framing or control specifiers.

SEE ALSO

       stream(3), cons(3), dk(3)

SOURCE

       /sys/src/9/port/stasync.c

																	  ASYNC(3)

PIPE(3) 						     Library Functions Manual							   PIPE(3)

NAME

       pipe - two-way interprocess communication

SYNOPSIS

       bind #| dir

       dir/data
       dir/ctl
       dir/data1
       dir/ctl1

DESCRIPTION

       An  attach(5) of this device allocates two new streams joined at the device end.  X/data and x/ctl are the data and control channels of one
       stream and x/data1 and x/ctl1 are the data and control channels of the other stream.

       Data written to one channel becomes available for reading at the other.	Write boundaries are preserved: each read terminates when the read
       buffer is full or after reading the last byte of a write, whichever comes first.

       Written data is buffered in kernel stream blocks.  The writer will block once the stream is full, typically after 32768 bytes or 16 writes.
       The writer will resume once the stream is less than half full.

       If there are multiple writers, each write is guaranteed to be available in a contiguous piece at the other end of the pipe.  If	there  are
       multiple readers, each read will return data from only one write.

       The  pipe(2)  system call performs an attach of this device and returns file descriptors to the new pipe's data and data1 files.  The files
       are open with mode ORDWR.

SEE ALSO

       pipe(2)

SOURCE

       /sys/src/9/port/devpipe.c

																	   PIPE(3)