STREAMS Programming Guide

stream

A kernel aggregate created by connecting STREAMS components, resulting from an application of the STREAMS mechanism. The primary components are the stream head, the driver, and zero or more pushable modules between the stream head and driver.

stream end

A stream component furthest from the user process that contains a driver.

stream head

A stream component closest to the user process. It provides the interface between the stream and the user process.

STREAMS

A kernel mechanism that provides the framework for network services and data communication. It defines interface standards for character input/output within the kernel, and between the kernel and user level. The STREAMS mechanism includes integral functions, utility routines, kernel facilities, and a set of structures.

STREAMS-based pipe

A mechanism used for bidirectional data transfer implemented using STREAMS, and sharing the properties of STREAMS-based devices.

TTY driver

A STREAMS-based device used in a terminal subsystem.

upper stream

A stream that terminates above a multiplexer. The beginning of an upper stream originates at the stream head or another multiplexer driver.

upstream

A direction of data flow going from a driver towards the stream head. Also called read-side and input side.

water mark

A limit value used in flow control. Each queue has a high-water mark and a low-water mark. The high-water mark value indicates the upper limit related to the number of bytes contained on the queue. When the queued character reaches its high-water mark, STREAMS causes another queue that attempts to send a message to this queue to become blocked. When the characters in this queue are reduced to the low-water mark value, the other queue is unblocked by STREAMS.

write queue

A message queue in a module or driver containing messages moving downstream. Associated with the write system call and output from a user process.

write side

A direction of data flow going from the stream head toward a driver. Also called downstream and output side.


	stream A kernel aggregate created by connecting STREAMS components, resulting from an application of the STREAMS mechanism. The primary components are the stream head, the driver, and zero or more pushable modules between the stream head and driver. stream end A stream component furthest from the user process that contains a driver. stream head A stream component closest to the user process. It provides the interface between the stream and the user process. STREAMS A kernel mechanism that provides the framework for network services and data communication. It defines interface standards for character input/output within the kernel, and between the kernel and user level. The STREAMS mechanism includes integral functions, utility routines, kernel facilities, and a set of structures. STREAMS-based pipe A mechanism used for bidirectional data transfer implemented using STREAMS, and sharing the properties of STREAMS-based devices. TTY driver A STREAMS-based device used in a terminal subsystem. upper stream A stream that terminates above a multiplexer. The beginning of an upper stream originates at the stream head or another multiplexer driver. upstream A direction of data flow going from a driver towards the stream head. Also called read-side and input side. water mark A limit value used in flow control. Each queue has a high-water mark and a low-water mark. The high-water mark value indicates the upper limit related to the number of bytes contained on the queue. When the queued character reaches its high-water mark, STREAMS causes another queue that attempts to send a message to this queue to become blocked. When the characters in this queue are reduced to the low-water mark value, the other queue is unblocked by STREAMS. write queue A message queue in a module or driver containing messages moving downstream. Associated with the `write` system call and output from a user process. write side A direction of data flow going from the stream head toward a driver. Also called downstream and output side.